Supercharger Performance and Engine Performance Parts

Posts Tagged ‘MAF’

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