Posts Tagged ‘boost’

There are many great articles online on general piston design, piston ring design, and how the design of OEM and aftermarket pistons has changed over the last decade.

What we will focus on today is the choice of a proper aftermarket piston for your street engine running a significant amount of forced induction using supercharged, turbocharged, nitrous injected or a combination of these power adders.

So what we have in mind today is a daily driven motor, running in the rpm range up to about 8000 rpms with up to 18psi of boost pressure, and experience all the typical operating conditions of a daily driven motor including cold starts, short warm up durations, conventional oiling systems …etc

Before we start talking about piston design I want to first spend a minute talking about the different sections of the piston that are of interest:

The Crown: Is the top most surface of the piston which creates the moving bottom barrier in the combustion chamber. This part of the piston is in contact with incoming airflow, burnt exhaust gasses, and is part of the combustion chamber shape.

The Ring lands: Are the reliefs cut into the side profile of the piston where the piston rings sit. The ring lands are typically taller than the ring thickness which allows the rings to move and rotate in the bore. It also allows combustion pressure to contact the entire piston ring top face inside the ringland pressing it down (and out in some designs) improving ring seal.

The Skirt: The piston skirt is the extension of the side profile of piston which controls the piston movement in the bore preventing it from wobbling around and controlling the angular forces present on the piston walls from the angular rotation of the crankshaft.

The Underside: This part of the piston is exposed to the crank case and houses the wrist pin (connecting the piston to the rod) and exposed to the engine oil in 3 ways:

• Oil collected by the oil retention ring (the bottom most piston ring) is routed through holes in the side of the piston to the underside to drain back into the crank case.
• Oil sloshing around in the crankcase due to the crankshaft counterweights dipping in and out of the oil sump as well as oil forced up through the connecting rod up to lubricate the wrist pin (on forced oil pins).
• On engines equipped with oil squirters under the piston, where oil is squirted on the underside to help cool the piston mass for longevity or racing applications, which in some situations may also allow for an overall thinner crown without sacrificing the strength of the piston and while reducing the overall weight of the package.

When it comes to choosing the right pistons for your street car on boost there are five aspects to look into:

1- Construction
2- Design
3- Coatings
4- Other considerations

1- Piston Construction:

For a street driven application, you’re looking for primarily a forged piston with a high silicone content in the range of 12% to 16%. The high silicone content in the piston improves thermal management in the piston and reduces the overall expansion of the piston in the bore when heated due to boost and power.

This reduced expansion means that you will not need to use undersized pistons (that will grow to fill the bore as they heat up) and engine will not have large tolerances causing piston slap at cold starts and long warm ups in cold weather, which is ideal for street applications.

Furthermore, most modern engines come with high volumetric efficiency from the factory (for example the new mustang 5.0 engine in 2011 will come with 412hp stock compared to a much lower 165 to 205hp -depending on the actual model year for the older 1980s ford 5.0).

Having engines now producing roughly double the power that they were producing just 15 years ago, and having the potential of further doubling that power figure with nitrous injection or 15psi of supercharged boost, then care must be taken to making sure the piston ring lands are anodized for reduced micro-welding between the piston and its rings under the increased heat and pressures from forced induction.

2- Piston Design:

As mentioned earlier, the top of the piston (the crown) is both exposed to the incoming airflow, as well as constitutes the bottom of the combustion chamber.

The piston crown during the intake stroke :To take swirl one step further, certain piston manufacturers have equipped their pistons with swirl enhancing crown faces either equipped with circular grooves or dimpled impressions on the piston crown. These groves and dimples are designed to promote increased swirl in street engines and have been shown to further improve torque delivery by another 4 to 5% over stock figures. Similarly, high compression pistons that gain compression through a very sharp protrusion in the center of the piston will reduce disrupt swirl in the chamber and lower combustion efficiency, although the increase in compression (at 3 to 4% per added point of compression) can negate this loss.	high swirl engines continue to tumble the air inside the bore Dimpled top pistons and groove top pistons improve airflow swirl and tumbling Custom machined dimpled top pistons for similar effect Not all cylinder heads are hemi(spherical) heads. In this application for example a piston with a kidney shaped dish and a raised outer edge will give better results than a flat or symmetrical hemi-style piston Asymmetrical piston for a hemi head, notice the lip that goes around the entire out rim of the piston to squish air towards the central spark plug Combustion profile showing the irregular distance between the spark plug and the edges of the boundaries combustion chamber on a typical flat top piston piston cutaway showing the distance between the valve relief and the first ring land which should be maintained at 0.2" If you’ve never seen a piston machined down before … watch this video: visible here: piston crown with thermal barrier coating, side skirt with friction reduction coating, forced side relief (FSR) piston with reduced side skirts for very high rpm operation (typical on race engines and motorcycles) visible here: bottom of the piston with oil shedding coating
The piston crown during the compression stroke : This brings us to a very important point which is engine ‘squish’. The use of asymmetcrical piston crown design not only continues the swirl process initiated in the intake system, but more importantly having an asymmetrical piston crown forces the air to rapildy move towards one side of the combustion chamber, especially as the piston approaches top dead center. This squish effect near top dead center can be used for several advantages: Getting a good air and fuel mix for more efficient combustion. Moving the air and fuel mixture closer to the spark plug for easier ignition. Reducing the distance between the tip of the spark plug, and the farthest pocket of air and fuel mixture that needs to be burnt. Reducing the flame front travel distance builds cylinder pressure faster in the chamber which reduces timing advance requirements at lower rpms, but also, maintains more torque delivery to the piston as rpms increase (and as the time that the piston spends between top dead center and 17* ATDC) starts to shrink rapidly compared to flame front travel speed past a certain rpm point, as well as for engines with a shorter rod to stroke ratio with faster piston acceleration away from Top Dead Center. Reducing the probability of detonation and uneven combustion from the better air and fuel mixture and better heat distribution.
Knowing these advantages during the compression stroke to shaping the piston top, then the typical flat top pistons of late become obviously obsolete. The best piston choice is actually a D shaped ‘reverse dome’ piston which combines an asymmetrical crown design with a thicker crown height that either mirrors the combustion chamber shape (as seen look into the bottom of the cylinder head) or with a thicker out ring on hemispherical head. The whole point here is that the air fuel charge is compressed in a tighter pocket area around the spark plug location, and moved away from the far cylinder walls. Then, to maintain the same compression ratio (even with this thicker crown height) the crown area around the spark plug is dished by the right amount to bring the total volume of the combustion chamber + the piston dish to be the correct volume for the proper engine compression ratio. Furthermore, on some applications we can take this one step further by milling down the cylinder head (or using a different cylinder head casting with shallower combustion chambers) which brings the spark plug down deeper into the bore, and offsetting the loss of combustion chamber volume with further dish in the piston crown. Bringing the air and fuel pocket closer to the spark plug, and bringing the spark plug closer to the center of the combustion chamber formed between the cylinder head contours and the piston crown contours boost engine efficiency, reduces detonation probability, reduces timing advance requirements, and promotes increased efficiencies at higher rpms as described earlier.
Finally, for a forced induced motor, care must be taken that the crown thickness after all modifications to the piston crown are complete (such as enlarging the valve reliefs for oversized valves, or increasing the piston dish for a shallower cylinder head and a lower spark plug position as described earlier) is still at least 0.175” thick with a good margin of safety being around the 0.200” mark for forged aftermarket pistons. Another thing to note is that typically enlarging valve reliefs not only reduces crown thickness as a vertical measurement, but also diagonally reduces the distance between the valve relief and the primary piston ring. This is even more evident on newer high efficinecy (low emissions) engines that come from the factory with a raised primary compression piston ring (or a reduced distance / lip between the piston top and the first ring land).To summarize: When choosing an aftermarket piston for your motor, look for a reverse dome piston top (rather than a flat top or typical dish type piston) with dimpled flat surfaces for better mixture, and still having at least 0.2” material thickness throughout the entire crown of the piston. If the piston I just described does not exist, a thick piston (high compression) piston can be machined down to make the piston I’m describing by someone who knows enough about this to do it properly (or by requesting a custom style piston from the piston manufacturer themselves).
3- Piston Coatings Investing the money in getting your pistons coated has several benefits including: Increased power Reduced emissions Better response More resistance to catastrophic failure The best combination of coatings are as follows: A thermal barrier coating on the piston crown A friction reduction coating on the piston skirts An oil shedding coating on engines equipped with oil squirters in the crank case The thermal barrier coating gives a more consistent finish to the top of the piston crown. It helps reflect heat into the combustion chamber, rather than dissipating it through the piston materials and thus improves combustion speed and the completeness of the combustion process. However, this increase in combustion temps and trapping the power rather than dissipating it does require reduced timing advance, but will as stated earlier, pay back dividends on higher rpm motors or on engines with short rod/stroke ratios where piston acceleration away from TDC becomes a problem for power transfer into the pistons at higher rpms. One thing to note here is that since the thermal barrier coating improves torque delivery by accelerating the burn rate inside the engine, it can be used to boost torque output on cars with centrifugal superchargers or large turbos to give better response before the boost builds. Overall, it may seem like it’s disadvantageous to trap more heat in the chamber and that it possibly reduces the octane, boost, or timing limits of the motor but this is not true. The increased heat can be counteracted with timing reduction without power loss (since the burn rate is maintained) and the added advantages are that the thermal coating helps spread the heat out over the entire crown area of the piston, thus protecting any thin or weak spots from being pummeled to failure. Also in the rare event that you do have some minor detonation in the engine due to high load, a bad fill of gas, or some other factors, the thermal coating prevents piston pitting due to minor occurrences of detonation, and thus it prevents the creation of hot spots on the piston crown which could have become hot-beds for further detonation and a prevented runaway towards total piston failure! Seems like a fair trade off of some timing advance for increased longevity and increased high rpm efficiency. The low friction coating on the piston skirt reduces frictional losses between the piston sides and the cylinder walls. This protects the pistons from damage and scuffing on cold starts, if the engine is overheated or overboosted (and the piston expands due to heat), and during oil starvation conditions (high cornering G’s, coild oil, first crank after a rebuild). Reducing friction in the engine delivers more horsepower to the crank, improves the engine’s operation near redline, and gives the engine crisper response. One study showed that using lower profile skirts, with proper friction coating, as well as lower friction wrist pins can reduce the total engine internal friction by 40%… So, something as simple and non intrusive as coating your piston skirts is definitly worth the effort, especially on boosted street cars that need to run a full skirted piston (as opposed to naturally aspirated motorcycles that will more likely run a forced side relief piston which features a longer skirt in the primary axis of the piston motion as the connecting rod movement shoves and pulls the piston against the bore on the upwards and downwards strokes… and a short or no-skirt in the axis 90* with plane of the connecting rod’s movement). Finally, oil shedding coatings on the bottom surface of the piston help evacuate oil off of the piston faster. This helps keep the piston lighter and faster moving in its rotation, however since oil is used to cool the piston bottom and increase its longevity (especially in motors that will experience high cycles as we will explain later), then there is a debate as to weather this coating is beneficial or detrimental on different engines. Engines with oil squirters get plenty of oil volume delivered to the bottom of the piston at a constant stream of flow. These engines can do with a reduced duration for oil clinging to the bottom of the piston. On the other hand engines that rely on the crankshaft counterweights sloshing in the oil sump and indirectly sending oil up to the pistons to cool them (and up to the wrist pins to lubricate them on engines without a force-lubricated style connecting rod) could use with the oil clinging to the piston bottom for a longer duration. If you are doing a full rebuild, my recommendation would be to both coat your pistons AND install oil squirters. Otherwise, choose weather or not to use the oil shedding coating based on weather you have a dry sump, wet sump with squirters, or wet sump without squirters oiling system. 4- Other Piston Design Considerations As mentioned earlier there are other considerations to choosing your piston design which I have eluded to earlier. Even though most people judge engine life based on mileage, performance engines are more accurately judged on cycles. For example, an engine can run for 100 continuous miles at 7500 rpms in 1st gear, or at 1500 rpms in 5th gear…. the same engine could be tracked every weekend (spending a healthy portion of its life in the higher rpm ranges) or cruised on a highyway commute to and from work. Even though these two engines have the same mileage, they have lived through a different number of engine cycles. Engine cycles is what determines the amount of continuous (or accumulated) stress both on your pistons (for thermal management) as well as on your piston rings (for wear management). The advice given here is primarily for dual purpose vehicles that are both street cars but will see occasional or repeated track use. Vehicles that will be used primarily for racing, require a thicker crown for better thermal management, will probably use a lower silicone content piston (with much larger piston to bore clearances to allow for the thermal expansion of the piston after it stops slapping and warms up in the bore, and will definitely have lower ring height for the primary compression ring (which reduces the operating temperature of the ring from around 600*F to around 300*F) as well as using a thicker compression ring that is less likely to distort or fail under continuous sustained high rpm abuse (think about a car in Nascar racing that does the entire race over 5000 rpms…) These cars that are designed for ‘standing mile races’ as I like to call them or long term endurance racing will also have to be tune differently as I have a complete longevity tuning chapter in The Tuner Mastermind. However, for most street vehicles running up to around 18psi of boost, and having dual street / track duty… then follow exactly the piston recommendations detailed here and you will have a great combination of torque, efficiency, detonation resistance, and reliability.

Technorati Tags: boost, centrifugal, Octane, piston, RPM

The Lysholm / Autorotor Supercharger is a unique and very practical chager. The unit is a great compromize between a positive displacement supercharger (that creates boost pressure by over pumping and over feeding the engine with air) and a compressor (similar to a turbocharger) that compresses the air inside the supercharger housing before sending it out to the charger piping.

The unique three-five design of the twin screw chargers relies on a 3 lobe and a 5 lobe rotor intermeshed to capture the air flowing into the supercharger for inter-screw compression. The combination of an intermeshed 3 lobe and 5 lobe rotor means that the rotors inside the housing are operating at different rpms with a ratio of 5:3 to keep the rotation of the lobes (3 lobes to 5) in synchronsim. This complex design allows the rotors to capture air (in its natural volume) from the back of the blower housing, and push it foward as the screws rotate. As the air is moved forward it is captured and compressed between the intermeshed rotors as well as being pumped (in positive displacement) from the inlet port at the back of the charger housing to the outlet port near the front.

Because of this unique design, screw style chargers are able to outperform simpler rotor based chargers in two aspects:

1- The blower is able to acheive a higher pressure ratios because the compression is combined between positive displacement (overfeeding) and between direct compression of the air (inter-screw compression).

2- Since the air is compressed inside the housing, the housing is able to ingest and move more air (higher CFM ratings) for a similarly sized roots style blower.

These kinds of superchargers boast great adiabatic efficiency of up to 68% while at the same time being able to deliver that high efficiency at high boost levels of up to 18 psi. With such a high potential peak boost level, these chargers are capable of matching the top end delivered by a typical turbo system, without the lag and throttle delay disadvantages of spooling a turbo. Because of the positive displacement nature of this charger, the charger will always be able to make boost at any rpm so long as they bypass valve is closed.

Some applications for this unit include the OEM install of 1.1Liter Lysholm / IHI hybrid in the Mazda Millenia motor.

Other kits include the BBM upgrade kit for the Volkswagen Corrado. The kit replaces the G20 centrifugal supercharger with the lysholm twin screw system. As you can see in the dyno below, the twin-screw outshines the smaller centrifugal unit both in the lower rpms and in the top end and this exactly the result of the inter-rotor compression keeping flow and efficiency up to par at higher rpms while positive displacement fills out the low rpm torque.

Here is an overview of Lysholms available chargers:

Lyshom	pressure ratio	Boost	CFM	HP	effeciency	displacement (liters)
1200 AX	2.2	18	636	424	64	1.2
1600 AX	2.2	18	848	565	66	1.6
2300 AX	2.1	16	1059	706	65	2.3
2300 R	2.2	18	989	659	68	2.3
3300 AX	2.2	18	1236	824	66	3.3
3300 R	2.2	18	1236	824	66	3.3

For more Information please visit:

Lysholm

BBM

Technorati Tags: Autorotor, boost, CFM, Displacement, Lysholm, pressure ratio, Rotor, supercharger performance, VAG

The other day I had a thought about DIY modifications, possible fuel savers and other performance tricks and tips to increase gas mileage. See, although this is a performance oriented blog, as the cost of oil per barrell crosses the 70 dollars per barrell threshold once again, and as the economic depression in the USA (and thus in many other parts of the world) seems to be very much a mainstay till around 2012 according to analysts, I can’t help but think about mileage and how so many people might want performance parts for their car, but they may also NEED better fuel mileage.

Ouch. My first gas tank in the USA I paid 75c per gallon @ 1998

This got me to thinking about how we as automtive enthusiasts modify our cars for increased volumetric effeciency and higher performance in a specific rpm range of around 4000 rpms and higher. This is mainly due to the fact, that when you are racing, you spend alot of your time on the eastern half of the tachometer in the higher end of the rev range and thus it makes sense that most performance products and tips are focused towards higher rpm effeciency. However, there are some (but not all) performance modifications (and racer’s secrets quite frankly) that we as enthusiasts may use to gain that power advantage, but can be utilized to effectively boost gas mileage.

This isn’t only a theoretical debate as I’ve done this ‘accidently’ on my first car, a 1991 Toyota Celica GT back in 1999. In typical 10 year old car fashion it ran horribly when I first bought it, as indicated by my first tank of gas that was over in about 180 miles. Over the next two years I modified it and tuned it, not only increasing its performance and acceleration, but also acheiving over 32mpg (which is about 4 mpg over the factory figures, when the car was brand new, and more importantly I was doing this on a 10 year old car that was definately not babied throughout its life).

My friends and I also went out and replicated these results on a 1988 Celica GT-S, a 1996 Jeep 4.0 I6, and my friend’s moms Nissan Quest V6. My uncle also bought a 1993 Cadillac Deville that was getting double the mileage on cruise control as it was during normal driving. I recommended he change one thing on his car, he did and he got his mileage back. Then I went ahead and did a similar electrical fix (different part though) on my dad’s 1994 Cadillac Fleetwood brougham.

Anyway, enough stories of the past, let’s look at the future… I’ve sat down and brainstormed every thing you can do to boost mileage on an older car and I have come up with a hand written rough draft of performance modifications that you can do to your car to gain back it’s factory mileage and to even go beyond that by another 4+ mpg.

I am thinking of turning this draft into a fully detailed guide, but first I’d like to know that there is serious interest in this guide before I go ahead and invest time in this product….

If you are seriously intersted in a mileage booster guide please show us your interest by subscribing to this topic below.

The beauty of these kinds of modifications is that they obviously pay you back with time, so if you start out with a horribly performing car, or if you put a lot of mileage on your vehicle, then this information will end up saving you money in the long run, which is really cool.

Technorati Tags: boost, cadillac, effeciency, Jeep, Mileage, RPM, Toyota

Supercharger performance is proud to present the newly updated power calculator. The only calculator built for enthusiasts by enthusiasts…

Get your copy today !

Technorati Tags: boost, CFM, compressor map, header, Intercooler, N2O, Power Calculator, RPM, water injection

The LS1 powered Camaro Z28 is a great car, with plenty of power and great modification potential. One of the typical upgrade paths for Z28 owners is high flow heads, high lift moderate duration cams, and healthy doses of nitrous oxide. In unleashing this nitrous driven frenzy on the LS1 engine, the LS1 has proven to be a fairly robust contender in the face of a 200 horsepower shot of nitrous unleashed on the motor at 2500 RPMs, some people have even gone as far as spraying 300 shots on their stock LS1 with great success.

One of the great things about nitrous is it gives us some insight on the power of our engine. Since nitrous is typically delivered all at once in a single shot, then it usually produces huge torque figures at lower rpm ranges, and as the RPM’s rise, the torque increase from the nitrous shot drops down, as horsepower stays maintained.

The reason for this is the basic relationship between torque and horsepower.

Horsepower (hp) = Torque (ft.lbs) * RPM / 5252

By applying this math we find that a 200 horsepower shot sprayed at 2500 RPMs add about 420 ft.lbs of torque to the motor. And if we look at a dyno for a stock LS1 engine such as this one I found for a 2002 6speed SS, we find that the motor alone is making about 290 ft.lbs of torque at 2500 RPMs.

The motor on nitrous will be expected to make: 290 (motor) + 420 (nitrous) = 710 ft.lbs of torque. Quite impressive for our 5.7 L V8.

Now if you’re using 200 and 250 and 300 horsepower shots of nitrous, you will get bored fairly quickly of the amount of money and time that you waste refilling the nitrous bottle, and you may be willing to pay one time lump sum to have that power avaialbe to you ‘on tap’ rather than in the bottle.

Using our same formula and taking our 710 ft.lbs of torque up to the LS1’s redline of 6200 RPMs I find that I can fairly safely set my peak horsepower goal to be:

710 * 6200 / 5252 = 838 horsepower.

So let’s think about this for a minute, I can make 515 horsepower using a 200 shot worth of nitrous, or I can make 838 horsepower using a centrifugal supercharger setup all the while not exceeding my bottom ends’ well known, tried and true, withstand of 710 ft.lbs of torque. I think this is a very safe adventure into supercharger performance.

Looking at the stock LS1 dyno we can see that peak power is delivered early at 5200 RPMs through the use of conservative 202*/210* duration camshafts (intake/exhaust) in stock format. According to my calculator, that duration cam would typically put peak power around 4500 to 5000 RPMs which corresponds to our dyno shoot.

Before we find out how much boost we should expect to need to reach 838 horsepower we should factor in the fact that we plan on making 838hp at 6200 RPMs rather than 5200 RPMs through the use of a proper supercharger camshaft. Again using my power calculator I come up with an ideal cam configuration of 210*/244* (intake/exhaust) with a target LSA of 112 to 115 degrees. And based on our new peak power RPM we find that we will probably need 18psi of boost to make 838 hp @ 6200 RPMs (on the other hand we could make 838 hp @ 5200 on the stock camshaft at a much higher 24 psi… I personally would rather make the power with RPM at lower boost than use much 20+ PSI figures on a restricted motor).

Based on my calculator, the following falls into place for our 838 horsepower stock block LS1 build up:

Quite an impressive build we are about to take on. Now these are calculated figures. Not all of them will end up being exact as we need to source available parts that work for our target build.

Supercharger:

Procharger offers a supercharger kit for the LS1 based off of its P1SC2 supercharger (or the even larger D-1SC) which

P-1SC1 impeller...

are at least capable of delivering 1200 CFM @ up-to 32psi of boost if needed. Perfect for our requirements of 1200 CFM and 18psi.

Camshafts:

Looking around for a bit I found thunder racing’s cheater camshaft which is perfect for our application: 214* intake duration, 230* Exhaust duration, and 117* LSA. Notice in the description they say ‘responds very well to nitrous’, well high boost supercharger applications have similar cam requirements to nitrous oxide in that you neither want excessive overlap (to waste your nitrous or boost into the exhaust manifold, and at the same time your duration requirement on the intake cam is reduced (to reduce overlap and because of the compression of the air via nitrous or a supercharger means that you can ingest more air volume in a shorter duration of time). A great find.

 Thunder Racing Custom Camshaft
“CheaTR” - 214/230 .601/.575 117 LSA. Off Idle-6800 RPM Power Band. Broad power range. Works well with stock exhaust manifolds and catalytic converters. Stock like idle. Minor tuning required on automatic transmission cars.  Responds very well to nitrous.  Due to the fast ramp rate of this camshaft, the use of 1.8 rockers is not recommended.  Double valve springs and titanium retainers required for this cam.

The ideal figures we got for cold side and hot side piping are 190mm and 170mm respectively. These figures are calculated based on less than 1 horsepower loss in the intake system and less than 0.01 psi pressure drop. Now air is a compressible fluid. If it needs to go through a 90mm intake system rather than a 170mm intake system it can do so. However, there is a certain pressure required to force the air to flow through this bottle neck of a restriction and that shows up as a pressure drop.

As we said earlier we’re going to need 18psi of boost to reach our target hp goal on the motor giving the parameters given in the calculation. But if we use a 92mm throttle body costing us 18hp and 0.25psi, a 125mm intake hose (as we have calculated later on for our MAF housing), costing us another 6hp and 0.1 psi, as well as an undersized header with another 3 or 3 psi in back pressure from using 2” primaries rather than 2.4” primaries, then the overall pressure losses in the system can add up to about 4psi. What this means is that in the end, when all is said and done, we will probably make our target 838 horsepower somewhere between 18psi and 22psi because some of our parts were undersized.

For the supercharger cold-side piping, the supercharger has a 3.75” inlet which we will expand out to 125mm or a 5” intake using our new 125mm MAF housing and a 5” air filter.

For the supercharger hot-side piping, the supercharger has a 3” outlet which will take out to 3.5” using 3.5” piping into our procharger air to air intercooler and all the way into a 92mm (3.62”) throttle body.

This 92mm throttle body is the largest I could find for a bolt on LS1 throttle body and comes as part of a package with the Fuel Air Spark Technologies (F.A.S.T) LSX style intake manifold for the LS1.

This throttle body will cost us 18hp at our target power level, but we should more than make that up elsewhere. Why so? Because all these calculations are done based on a stock motor (stock intake, header, exhaust) figures. The only modification I have factored in here is Cams and boost pressure. If I were to factor in the fact that the factory motor is restricted by the factory intake, header, exhaust systems, and that it could potentially gain 3 or more psi of pressure losses by upgrading those items, and if you factor in that we in the process of installing our supercharger package are in fact upgrading those same items, then it’s safe to say that my 838 is a somewhat conservative estimate of what a Cammed LS1 can put down at 18psi of boost. However, I like to do my math conservatively and be pleasantly surprised by the results later on J.

Intercooler

The kit also comes with procharger’s twin high flow intercoolers which are each sized at 11 x 9 x 4.5 or a core volume of 445.5 cubic inches. In total we have 891 ci of intercooler cooling volume (between both intercoolers) compared to our original calculations of 1470 cubic inches. Instead I would call up procharger and try to get a larger core (to try to stay away from needing water injection for this application) … and choose something like their Air to Air core at 27.5” X 12” X 4.5” which they rate to 1300hp and should do very nicely on our 838 (or more) horsepower build. Furthermore this intercooler has 3.5” inlets and outlets which match our chosen throttle body for a good matched package.

Headers

Kooker race header with 2" primary and 3.5" collector.

This was actually pretty tough to find. There are probably many supercharged LS1 powered Camaro’s out there, but yet the only header that I could find that comes close to our requirement (2” primary, short 12” (or longer) runner length into a 3.5” collector) seems to be the Kooks race header with venture collectors. The kooks header comes with 2” primaries and 3.5” collector.

Exhaust

For the exhaust there are two options:

1-      To do a custom dual 3.5” exhaust with 3.5” X-Pipe and under car turn downs releasing the exhaust gases before the rear differential (see picture), or even using some custom 3.5” side pipes if you like.

True dual x-piped exhaust with under car exit before the bell housing.

2-      To make a custom 3.5” exhaust cutout section right after the 3.5” collector exit on our cook headers, and then from then on reduce the exhaust back down to a typical 3” exhaust and get an aftermarket single or dual 3” exhaust that will be used for normal street use. When full power is demanded, the 3.5” exhaust can be unleashed right at the headers at the flick of the switch by opening the e-cutouts and dumping the exhaust before the cat-back.

Fuel System:

According to our calculations, we need to be able to supply 350 liters per hour (lph) of fuel at a constant fuel rail pressure of about 40psi. Most typical single fuel pump upgrades use a Walbro 255 lph pump instead of the stock pump. Although this pump alone is good with the proper hotwire kit to 610 crank horsepower, it will not be enough for our target power figure. One option is to install a kenne-bell boost a pump which can increase the pump voltage from 14volts (stock with a hotwire kit) to 17 volts or 20 volts. Increasing the voltage from 14volts to 20 volts potentially gives us a 42% increase in flow making our pump capable of delivering 362lph of fuel which can meet our requirements.

Lonnie's performance fuel kit

I think for our application, I would rather cut it safe than cut it close. Who’s to say that we end up geared with our pulley system for exactly 18 psi? Who’s to say that we don’t end up making 850 horsepower with our setup when all is said and done? Who’s to say that the motor won’t want to run a one point richer air fuel ratio at that power level and so our fuel delivery requirements will actually be higher by about 8 to 10% to cover that extra point of air fuel ratio.

Instead a better approach for this application would be to use a complete fuel supply kit, including dual in-tank pumps, a hotwire kit to deliver full 14volts to the pumps, complete with new fuel feed and return lines (matched for 800hp) and some high flow fuel rails to make sure that every injector (weather it is right at the fuel feed or at the end of the fuel rail closer to the return) sees the same amount of fuel pressure, because the fuel rail is large enough that there is no significant pressure drop between injector #1 and injector #4.

One such kit is provided by lonniesperformance in conjunction with racetronix.

The kit includes

Double Pumper Kit & Complete Custom Fuel System
Camaro/Firebird ‘99up LS1 Double Pumper -- Twin High Output Fuel Pump Kit,  Wiring Harness & Hobbs Switch -- Fully Assembled & Tested - Requires your sending unit for modification

Includes -8 Supply & -6 Return lines, fuel rails, regulator, filter, & all fittings needed to connect to double pumper sending unit.
LS2 fuel rails optional.
LS7 fuel rails optional.

Fuel Injectors

Delphi 75 lbs/hour injectors

Again we can pick these up from lonnies performance. By our calculations we need 630cc/min injectors (or 63 lbs/hr injectors). It’s a good rule of thumb to have injectors that will deliver your fuel needs at around 85% duty cycle. Which means to deliver 63 lbs/hr of fuel per injector we need a fuel injector that can deliver 74 lbs/hr.

Driving larger injectors to 85% of their maximum capacity is ultimately safer than trying to extract 100% of the capacity out of a smaller injector. The reason is that an injector that is running at 100% duty cycle is more likely to fail, and any variation in power level or boost level means that you have no room to increase your fuel delivery because your injectors are maxed out.

A set of 75# (or 75 lbs/hour) Delphi injectors will do the trick for our build.

Tuning

One simple route for tuning is typically to use a matched pair of an upgraded MAF sensor and upgraded injectors. For example using a 100% larger MAF sensor or MAF housing recalibrates the performance of the factory computer around the use of injectors that are also 100% larger than stock.

This approach works well for low boost packages or normally aspirated buildups of the healthy 5.7L V8.

The largest MAF housing I could find was a 100mm MAF which is maxed out at a reading of 511 grams per second of air. If we do some calculations we find that 511 grams per second comes out to about 545 hp worth of air which is shy of our eight three eight horsepower goal. If we were to use this kind of setup on our car, the ECU would not know the difference between 600 hp and 800 hp because at both situations it would be reading full MAF voltage and giving the command to the injectors to go Full on at 100% duty cycle.

There are two reliable ways we can go about solving this problem:

1-      Upgraded MAF / Injector combo

850 horsepower / 545 hp = a mass ratio of 1.56 (or an increase in area of 56%).

TSP 100 mm MAF

To make our stock MAF sensor capable of reading 850 horsepower it is possible to transplant the sensor into a housing that has an area that is 56% larger. Doing the math we find that transplanting the sensor into a 125 mm housing can do the trick. The problem with continuing to transplant the stock sensor into a larger housing is two-fold:

As the housing gets larger, then at very low flows (such as at idle) the small amount of air flowing through the larger 4.7” pipe can get turbulent, and as it gets turbulent, then the sensor reading oscillate as the air spinning inside this 4.7” pipe hits the sensor in waves (rather than in nice laminar flow). What this does is it gives inconsistent readings to the ECU about the amount of air flowing, and results in a wandering air fuel ratio because the fuel supply itself can be oscillating based on the reading.

One of the things talked about in mechanical engineering is the flow profile of a fluid in a pipe. Obviously the walls of the pipe have some resistance to the air flow, and this wall resistance means that the air travelling in the center of our 4.7” pipe is at a higher velocity than the air travelling on the surface walls of our pipe (because this air has some frictional forces reducing its velocity). As our flow pipe gets larger then our sensor gets moved farther and farther away from center of the pipe, and thus our sensor’s reading is less accurate because it’s measuring the slower air closer to the pipe walls.

If you find that you have either of the two problems (a poor idle and wandering air fuel ratio, verified with a wandering OBD-Log of your MAF reading, or a sensor that seems to be under-reading the amount of air as you get into boost verified with comparing your required injector duty cycle to sustain your target air fuel ratios compared with the amount of air that your sensor is reporting) then one typical solution is to use some fine wire mesh to create your own MAF screen. The screen that we see common on factory sensors helps reduce this velocity profile for the air as it enters the sensor for metering and makes the air closer to laminar at that point, such that any sample of that air being metered is very similar to the velocity, density, and temperature of the rest of the air being unmetered by the sensor.

Matching our 125mm MAF, with our 75lph injectors we can then do the rest of our tuning using the factory ECU and a flash tuner.

2-      Speed density setup:

A speed density setup eliminates the MAF sensor altogether replacing it with a manifold pressure sensor, air temperature sensor, and uses both RPM and throttle position readings as well to approximate the car’s air flow requirements based on those inputs.

I prefer directly metering air myself rather than extrapolating it from pressure and some assumptions about volumetric efficiency. When you directly meter air, if you for example open your exhaust cutouts (as stated earlier in our exhaust section) and those cutouts allow your engine to breathe in more air, then that air will get metered and your ECU will know about it adding more fuel. If you use a speed density setup then when you get into situations where your motor is breathing in more air at the same (or even lower) boost pressures because of a change in volumetric efficiency then your ECU will be completely oblivious to the change.

Water Injection

Since we got cams for our setup (to reduce our peak boost requirements for our target horsepower) and since we were able to source a good sized intercooler for our power goals, we may not need water injection at all on this build. This is not by accident, but rather by design. In our calculations we came up with 12 gallons per hour of water injection (typically this figure comes in as 10 to 15% of the fuel delivery of our car).

If you have a 12 gph water/methanol injection setup and a healthy 2 gallon tank in your trunk, then you will run out of water/methanol mix in 10 minutes of full throttle time.

It quickly becomes clear that you would rather invest in some power upgrades (to lower your peak boost level and thus your peak inlet air temperatures) as well as invest in a healthy sized intercooler (again to lower your peak inlet temperatures) so that you can steer away from having to drag behind you a water/methanol tanker to keep up with your supplemental injection needs.

Spark plugs

Typically 1 step colder spark plugs are needed for every added 100hp as well as a 2-3* ignition timing retard for the same, at least that is a good starting point, and then hotter plugs or more ignition advance can be added when tuning.

The stock NGK spark plugs for the LS1 is a TR5 which is a 14mm 3/8” hex plug with 18mm reach and a projected tip, a tapered seat and is resistive for reduced EMI.

After looking NGK’s part code I think the best start would be BR10ECMIX iridium plug (or a similar BR10ECS copper plug which is cheaper). The spark plug has 1mm more reach, but is a non projected tip which we need for a high power application and is 5 heat ranges colder than stock as required by our additional 500hp. Furthermore the ‘CM’ designation means that this is a compact plug with a low profile or even side discharge ground strap so both the spark plug gap is reduced (for high boost) and the ground electrode is moved farther away from the center of the combustion chamber and reduced in size to prevent it from becoming a hot spot and an instigator for detonation.

Expected dyno:

Based on an expected boost curve and a stock LS1 dyno, I’ve created the following expected dyno for our car.

-          Blue lines are stock hp and torque.

-          Green Lines are Stock + 200 shot of n2o (peak torque at 700 ft.lbs and peak hp at 500hp).

-          Red Lines is our custom supercharged setup. If you look closely you see that I have not crossed the 700 ft.lbs line on this setup yet we are able to reach our peak power goals over 800 horsepower. Reliable, progressive power delivery from zero to redline.

LS1 stock, vs 200 shot vs 18psi + supporting mods centrifugal

 Some Procharged LS1’s on youtube …

Links to parts:

Thunder Racing (Split patter camshaft for 6800 rpm supercharger application)

Procharger (P-1SC2 supercharger kit and race intercooler)

Lonnie’s Performance (Complete fuel system solution up to 1000 hp)

Kooks headers (2” primary headers into 3.5” collector)

DMH (electric exhaust cutouts)

Burns Stainless (X-pipes and custom exhaust)

FAST (intake manifold and 92mm throttle body)

Texas Speed and Performance 100mm MAF

Clubplug (NGK spark plugs)

Technorati Tags: boost, Camara, camshaft, CFM, engine performance parts, Intercooler, kooks header, LS1, MAF, Procharger, supercharger performance, twin-pump fuel system

This is the first in a series of ’snapshots’ of a manufacturer’s superchargers that I plan on posting every so often. As you can see it’s written in simple English (in horsepower and boost) and is an easy way for people that don’t know how to read a compressor map to get a good idea of what their supercharger (or planned supercharger) is capable of.

Eaton

The Eaton TVS vortices clearly showing the 4 blade rotors and the 160* helical twist

Eaton’s first supercharger was released on the thunderbird back in 1989. Since then, Eaton has blessed the market with 5 generations of positive displacement, roots style superchargers with incremental changes between every generation and the previous.

 “The fifth generation Eaton supercharger or Gen V is the culmination of over 50 years of improvement to the original design for Roots superchargers. It features two three-lobe rotors, twisted 60 degrees and provides engine manufacturers with a proven, economical solution for adding power.”

After five successful generations of the M-Model supercharger. Eaton released a new version of their positive displacement supercharger called the TVS – Twin Vortices Series.

“The Eaton Twin Vortices Series™ or Eaton TVS™ is a patented supercharger design that features twin four-lobe rotors, twisted 160 degrees. By comparison, the original Eaton supercharger features three lobes twisted 60 degrees. The fourth lobe and added twist, when combined with redesigned air inlet and outlet ports, creates a smoother, more efficient flow of air into the engine. In addition to improved overall efficiency, the twin vortices Eaton Twin Vortices Series supercharger have improved noise and vibration characteristics as well.”

Figures in red are estimates based on relative supercharger displacement.

Visit Eaton on the web

Technorati Tags: boost, compressor map, eaton, Eaton TVS, pressure ratio

Our last articles about combining supercharger performance with turbocharger top end seems to have found some online appreciation. So, I’ve decided to write up a step by step on how to do the math for twin-charging your own car.

I’m going to start with a typical compact car engine, such as the Toyota Celica 2.2 liter 5sfe engine. The engine makes 135 hp at 5200 RPMs with a 6200 RPM redline.

For starters, every horsepower requires about 1.5 CFM of air (depending on the air density).

So 135 naturally aspirated hp requires a flow of 202 CFM at pressure ratio of 1.

The pressure ratio is the ratio of turbocharger or supercharger boost pressure divided by atmospheric pressure. Each 1 atmosphere is equal to 14.7psi of pressure… thus:

PR = (14.7 + Boost pressure)/14.7

So for a normally aspirated car: PR = (14.7 + 0) / 14.7 = 1.

Supercharger calculations:

Using 14psi as our target boost (and the maximum safe boost we’d want to extract out of a roots style supercharger) we get the following pressure ratio:

PR = (14.7+14)/14.7 = 1.95

New expected horsepower level: old HP * pressure ratio

New HP = 135 * 1.95 = 263 HP

New CFM = 227 * 1.5 = 395 CFM.

So now, we have our supercharger flow requirements, we need a supercharger able flow 395 CFM at a pressure ration of 1.95 (or 10psi).

Going through different Eaton supercharger maps I had available I find one available option:

1-      The third generation M62 or the fourth generation MP62 are capable of producing 395 CFM @ 1.95 PR @ 13,000 RPMs.

My final expected hp is going to be less than the original estimate263 for two reasons:

1-      The supercharger requires 35 hp to drive it at 13,000 rpms.

2-      The outlet temperature (if not managed through a proper intercooler) is going to be 88*C higher than the inlet temperature, and with every 13*C by rule of thumb costing us 1 hp of power, then 88*C would equate to a power loss of 7 hp.

Our final supercharged power figure (with no intercooler and no other bolt-ons) is

Final hp = (original hp * pressure ratio) – supercharger drive power – (delta T (Centigrade) / 13)

Final hp = 263 – 35 – 7 = 221 HP

Supercharger Dynograph:

14psi Eaton M62 on a Toyota 5sfe

More power can be made between 5000 and 7000 RPMs with bolt on modifications designed to shift the power peak to the right, mainly cams with longer duration, and properly designed headers.

With this graph it is clear that the power of superchargers is mimicking a 95% larger motor by providing linear boost across the entire RPM range. This makes the engine feel like a much larger engine which is great for OEM applications.

Turbocharger:

As we’ve seen in our previous calculations, it takes 35 horsepower to drive our M62 to maintain 14psi of boost on our motor. Because of this horsepower requirement, we find that with superchargers there is a point of diminishing returns when talking about higher boost and flow levels.

Now if my ultimate horsepower goal is 320 horsepower for this motor, then let’s do the math:

Pressure ratio = 320 hp / 135 hp = 2.37

Solving for boost: 2.37 = (14.7 + boost)/ 14.7

Boost = (2.37*14.7)-14.7 = 20 PSI

CFM requirement = target hp * 1.5 = 320*1.5 = 480 CFM ~= 33 lbs/min

(Some turbocharger compressor maps are graphed in CFM vs PR, some are in lbs/min vs PR, 14.47 CFM = 1 lbs/min depending on air temperature and density).

So to find a turbocharger that will give me my target HP goal, I need to find a turbocharger that has the point 480 CFM of flow at a 2.4 pressure ratio on its map.

Now I’ve done this search before so I know that the best turbo for this engine is a T3/TO4E 46 trim…

VERY IMPORTANT: Other trims of this compressor such as a 50 trim a 54 trim a 60 trim or a 60-1 trim, although they do have more CFM flow capacity, they cannot produce those CFM’s at the pressure ratio that I’m looking for. This is why you REALLY need to check your engine demand and flow requirements on your turbocharger compressor map. If your engine needs cannot be plotted on your compressor map then it’s not a proper turbo for your motor and it may never spool or create boost. A smaller turbo with a taller map (rather than a wider map) that produces less peak CFM, but at a higher pressure ratio, may be more adequate for your sized motor. Bigger is not better you really have to choose the right turbo for your application.

By starting with 2.4 PR and plotting my flow requirements at that pressure ratio on my compressor map I find that this motor is a good match for my engine, it will be fully spooled to 20 PSI by 3000 RPMs! It is also capable of supporting my peak power requirement of 480 CFM @ 2.4 pressure ratio at its peak efficiency of 76%. This means that the turbocharger outlet temperatures will be acceptable, since it is working within its peak efficiency and thus should be most power friendly.

Note: Again, I already knew this was a good turbo for this motor because I’ve been through this process before, if you’re doing this for the first time you want to plot your engine demand requirements on several different compressor maps, and compare both spool (the minimum RPM that the engine will make your peak boost at) and your compressor efficiency at peak demand to make sure that the turbo you choose will spool early and give you good power efficiently at higher rpms.

Now for the three rpm points that are not on my compressor map, I iteratively reduce my pressure ratio, recalculate my CFM flow requirement at that pressure ratio, and look to see if I can plot that point on the compressor map. Essencially I am trying to find the maximum boost that chosen turbocharger can support at that engine RPM.

Here are my results:

One thing to note here, my turbocharger can no way produce any boost for this motor below 2000 RPMs. At those lower RPMs the turbo is more a drag on the engine trying to spin itself up to its operating RPM to produce enough CFM to pressurize the engine. In a typical turbocharged application it is good to use a bi-directional bypass valve (rather than a unidirectional blow off valve) because the valve will bypass the turbocharger at lower RPMs feeding the motor directly from the intake system. This will prevent the unspooled turbo from choking the motor, and also help the motor produce more horsepower at lower RPMs which will help spool the turbocharger faster by providing more exhaust gasses to the turbines side of the turbocharger to spin it up.

As you can see the major difference between our supercharger and turbocharger is that our supercharger was able to produce boost at any rpm, but did not shine at higher RPMs where it’s efficiency and required drive power increased. On the other hand, our turbocharger is unable to produce any power boost (but rather a power drag) at lower RPM’s trying to spool up, but it shines at higher RPM reaching its peak efficiency at our power peak.

Once the turbocharger is fully spooled, the wastegate begins to open bypass the turbine restriction on the exhaust, which means there is virtually no horsepower loss driving the turbocharger at this point. As far as thermal losses are concerned, I went and factored in the turbocharger efficiency and outlet temperatures, and if the system is un-intercooled, the turbocharger is only costing us 9hp at peak power due to its outlet temperatures.

So the final HP figure = original hp * pressure ratio – temperature loss

Final HP = 135 * 2.4 – 9 = 315 hp.

Turbocharger Dyno Graph:

TO4E 46 trim @ 20psi on a 5sfe motor

As you can see the turbocharger produces a non linear power graph that is heavily weighted towards higher RPMs providing us with no power advantage at lower RPMs.

The thing to note here is that I started with a car with a low redline of 6500 RPMs and a great turbo for it. As the engine’s peak rpm gets higher and as our peak power target gets higher into 400 and 500 hp range, the choice of turbo to support those power figures will be larger, and naturally the power graph as well as the first RPM that the turbocharger will spool at will all shift to the right another couple of thousand RPMs.

The higher your HP goals, the more need there will be for twin-charging, because you will be using a larger turbocharger that takes more RPM and more exhaust gas to be able to spool and create positive boost for the motor.

Twin-charged:

Now if I overlay the two charts on top of each other we can see the potential benefit of twin-charging:

Twincharged 2.2 litre engine

As you can see, until the turbocharger has spooled, the supercharger provides us with 15 more horsepower and possibly more if the engine were not completely stock, or we had higher power aspirations and used an even larger and later spooling turbocharger.

The other advantage will not show up on a dyno chart, if you’re doing 50mph in top gear (5^th or 6^th gear) then the amount of time you spend going from 1500 to 2500 RPMs may be a very long time at such a long gear, even though it seems like a small part of the dynochart posted above compared to the 3000 RPM’s of turbo goodness above 3500, it will be a significant disadvantage during a quick passing attempt where you are left without any boost. Now being twincharged, no matter what the RPM and what the situation, when you stop the gas you will get a power boost to help you pass. If you stay in the gas (to go from a pass to a full on drag race) then the RPMs will rise, the turbocharger will come online and carry you through impressively to your redline in a flash… This is also a huge advantage on the track coming out of corners in the wrong exit gear.

Now do this for your own cars… if you need help with it leave me a comment.

You can easily find compressor maps for your chargers using google image search…

Other twin-charger articles:

The Twin-Charged Hyper Car

Twin-charged Performance

Technorati Tags: boost, compressor map, pressure ratio, Supercharger, turbocharger, twincharging