Supercharger Performance and Engine Performance Parts

Posts Tagged ‘Power Calculator’

I had a question over email the other day about an E85 converted, supercharged BMW 3-Series. After answering the question, I thought it would be helpful and interesting to demonstrate to all my readers here and followers (on facebook and twitter) the advantage of using E85 on a supercharged set-up and the possibilities it opens up during your build up.

As an introduction, E85 is an alcoholic fuel that is 85% Ethanol and 15% Gasoline. E85 is a high octane fuel with an Octane rating of around 102 Octane points which, when compared to gasoline and it’s 92 Octane points rating, has an additional 10 points of Octane.

The advantage of using a higher octane fuel is that the in-cylinder flame front travel rate of a higher octane mixture is slower than that of a lower octane mixture. If you had watched my video series on tuning your timing and timing trends (here), then you may remember that the flame front travel speed is affected by many factors including mixture density and in cylinder pressure.

Having a higher octane mixture, slows down the burn rate. This means that we can increase our boost level, our compression ratio, or our timing advance and return the mixture to a normal burn rate similar to that of gasoline, having a similar level of ’safety’ in the cylinder, a similar mixture volatility, but albeit at a higher power level.

To put some exact figures to this phenomenon, switching from 92 Octane premium gasoline to 102 Octane E85 allows you ONE of the following options:

• Increasing your boost level by 6psi of boost above your gasoline maximum boost level.
• Increasing your static compression ratio by 2.5 compression points above your gasoline maximum safe compression level.
• Increasing your timing advance by 13 degrees of timing above what you would use for a gasoline tune.

(Or some combination of the three such as a 3psi boost increase with a 1 point compression hike, resulting in a similar overall increase in compression pressure and flame front travel speed).

Now the advantage of this high octane feature of E85 is that it allows you to build a more aggressive set-up, to reach a higher power goal, while having a similar margin of safety to that of gasoline. The real world benefit of this kind of set-up, is that you have two new possibilities opening up for you in your power build:

1. You can now reach higher power goals, on E85 at the same red-line, and with the same static compression ratio, by being able to run more boost on the same motor, safely.
2. You can now build high compression supercharged set-ups, because you will no longer need to take apart your engine to replace your pistons, to lower your compression ratio, or severely retard your timing to be able to boost a factory high compression motor.

The second interesting fact about E85 ethanol based fuels is that it reaches stoichiometry at an air:fuel ratio of 9.7:1 compared to an air:fuel ratio of 14.7:1 for gasoline.

By dividing those two figures into each-other it becomes apparent that an engine running on E85 needs 48% more fuel flow compared to the exact same engine running on Gasoline. For example, a 400hp 6 cylinder engine will require about 400cc/min injectors for a gasoline setup, but it would need almost 600cc/min injectors to be converted to Ethanol.

The advantage of this information, is that a car that is built to run on E85, has enough injector to also run on gasoline. The benefit of this kind of set-up is that having a dual-map ECU, with large injectors designed for E85, can be ‘detuned’ to reduce it’s injector duty cycle by 48% to run on gasoline. This is essentially how ‘flex fuel’ cars are mapped to run on either fuel, namely because their factory fuel system is oversized (for gasoline) allowing them to run either E85 or Gasoline.

The third interesting fact about E85 is that it has a LOWER energy output than gasoline.

E85 has can produce 25.2 Mega Joules of Energy per Liter of fuel, while Gasoline can produce a more potent 33.7 Mega Joules of Energy per Liter.

Your first thought, might be that gasoline is thus able to produce about 30% more horsepower on the same engine (because gasoline is a more potent fuel chemically speaking), however when you factor in that we are injecting 48% more fuel with E85 to reach a complete combustion and stoichiometery, then the net result of those two figures is that E85 has the potential to deliver 11% more horsepower on the same exact engine, when compared to Gaslone.

This 11% boost in power, is based on a straight gasoline to E85 conversion. More power can be found using E85 by taking advantage of the higher octane rating and tuning specifically for E85 or adding more boost and compression into the mix.

The advantage of this 11% power boost is that you can make more power with the same amount of airflow. The benefit here, is that if you have an engine that is maxed out at say 450hp because that is the maximum amount of air your supercharger can flow, you can add in another 11% (or 50hp!) by converting from gasoline to E85, without having to upgrade your airflow side of the equation (blower included).

So to illustrate how you can use the Power calculator to plan your E85 fuel conversion, I have prepared a short video showing the process. This video includes 3 main differences from using the calculator for a gasoline setup as follows:

1. The target power level you enter into the power calculator should be 11% lower than your actual power level. For example, if you are shooting for 450hp, then entering a target of 450/1.11 = 405hp will give you the right airflow side of the equation, including your intake, exhaust, and supercharger systems.
2. Once the calculator has given you the results of your airflow side of your build-up as described in step #1, you can add 2.5points of compression ratio to your maximum safe compression level. That is to say, that if the calculator recommends an 8:1 compression level as the maximum static compression ratio, then on E85, you can run up to 8+2.5 = 10.5:1 points of static compression and still have a safe set-up.This makes E85 an amazing option for supercharging cars that come from the factory with a higher compression ratio such as 10.5:1 or higher because E85 will allow you to boost this engine WITHOUT the need to take the engine apart and lower the compression ratio.
3. To calculate your fuel demands on E85, you need to inflate your power target by 48% as we explained earlier. So shooting for the same 450hp target, we should enter a target of 405*1.48 = 600hp to the calculator to give us the correct injector, fuel pump, and fuel line sizing for an E85 build-up.

(If you are reading this on an external site such as facebook, please visit our site to see the complete article)

Example application:

A great example of an Ethanol conversion is the new Tri-Fuel Lotus Exige. The exige is a true Tri-Fuel care capable of running on Gasoline, Ethanol, or methanol.

The only modifications performed to the car as per the official lotus press release are:

• Sensors to detect alcohol content
• Slightly modified software for engine management controls/ECU’s over ethanol/gasoline and flex fuel
• Fuel lines compatible with alcohol
• Higher flow rate fuel pump and injectors
• Fuel tank material, compatible with alcohol

Making no changes to the airflow side of the engine, lotus is able to coax out an extra 51 hp or 19% more power from the same power plant simply by switching to an 11% more potent fuel mixture (as we mentioned earlier) coupled with another 8% coaxed through an alcohol specific tune with more aggressive mapping to take advantage of the higher octane and slower burn rate properties of alcoholic fuels.

Use the power calculator to design your E85 conversion

Technorati Tags: E85 Conversion, Power Calculator, supercharger performance

Update:

The article below was written for an older version (version 3.1) of the header calculator. Since then, in version 3.3 and above, the power calculator is able to do all forms of header calculations, including:

• Primary and secondary pipe lengths and diameters
• Shorty, tri-y, and long tube header designs
• Targeting a specific rpm range for your long tube or tri-y design for maximum launch power or best street cruising

The first part of the video below is still informational because it goes through the concept and theory of a 4-2-1 header and why it is benifitial on street applications. Part 2 of the video which covers using the old version of the header calculator is now obselete I’m afraid.

Be sure to checkout the link at the bottom of this page to the free trial of the power calculator where you can calculate the dimensions for your intake, shorty header and exhaust for FREE

Watch the videos here:

Part 1 -- Theory

Part 2 -- Calculations

The procedure:

Steps for doing a 4-2-1 (using my 1.8 liter , 160 hp @ 5800, 6200 rpm redline, Mercedes) …

So i setup my target power and everything normally (230hp) and I run a normal calculation and I get:

13psi of boost
1.52″ primary diameter
15.03″ primary length
Collector 2.36″

(I happen to know that these are almost exactly the dimensions of the kleemann shorty header for my car which dynos +13whp untuned on the car)

Now I want to redo this calculation for a the 2-1 section

I go back to my inputs and i select ‘true dual’ exhaust and re-run the calculations

This gives me a cutout and midpipe diameter of 2X 1.67″

So that will be the diameter of my 2-1 section

So we go 1.52″ to 1.67″ to 2.36″ 4-2-1 … that’s the diameters.

To find the length of the secondaries … we have to redo the calculation for our second rpm peak… for example my car could really use a boost at 2500 rpms… as the automatic (when not in manual mode) keeps the rpms below 3000 for fuel economy and the car is a but sluggish unless you keep the rpms above 3200.

So with my target as 2500 rpms I go back and change my redline to 2500 rpms

I click calculate and get a huge figure 54psi of boost, but i know i’m really going to run 13psi (from the first calculation) so i need to reduce my target hp number till i get 13psi again

So i go back and reduce my target horsepower and calculate (it takes a couple of trials) till i get 13psi again… the target hp is around 95hp (with the redline set at 2500 rpms).

This gives me the following header numbers:

Header primary diameter = 0.84 inches << ignore this
Header primary length = 29.51 inches << This is what we’re looking for
Cutout & midpipe & collector diameter = 2 x 1.07 inches << ignore this
Cat-Back diameter = 2 x 1.0 inches << ignore this

So now we know the total length for a header tuned for 2500 rpms is 29.5″ and the total length for 6200 rpms is 15.03″ That means your 4-2-1 is 4X 1.52″ to 2X 1.67″ to 1X 2.36″ --> 2.25″ catback
primary=15″ long
secondary= total length -- primary = 29.5″-15″ = 14.5″

And that’s your 4-2-1

So you see if you already know your target power and your 2 target rpm peaks you can design your own header like this.
If you already have a header, you can work it backwards… it will just take some trial and error with the numbers till you figure out originally what the header was designed for.

Results

Technorati Tags: 4-2-1, header calculator, header design, Power Calculator, supercharger performance, tri-y

Transcript:

Hi , it’s Haitham again and this is another one of our.. how-to videos around the Power calculator on Supercharger Performance .com

What I’m going to talk about today…
is timing advance and tuning your ignition curve.

First we’re going to talk about some of the underlying concepts of ignition timing and timing advance

Then we’re going to look at some simulated timing curves

Then we’re going to summarize with some insights on how you can use this information to increase your horsepower by advancing or retarding timing, in the right places to gain more power.

First of all, let’s look at a 4 stroke engine animation …

This is top dead center… when the piston is all the way up the bore
This is bottom dead center … when the piston is all way down the bore.

Usually when when we talk about timing advance, we talk about ‘B.. T.. D.. C.. ‘ or before top dead center.

Usually the spark plug ignites the mixture before the piston reaches top dead center in the compression stroke.

Now the reason why we fire the plug ‘early’…
is that the mixture of air and fuel (and possibly water, methanol, or nitrous) takes some time burn…
and so the flame front takes some time to travel outwards and consume all of the air inside this top volume (comprised of the cylinder head volume, and the piston surface volume if the piston is dished)…

once the flame has consumed a large portion of the air fuel mixture… this flame, trapped between the piston and the cylinder head, creates ‘peak cylinder pressure’ and it is this cylinder pressure and expanding flame that pushes down on the piston making it rotate.

Now the trick here is that you have to synchronize the piston rotation, with the flame front burn rate so that you can hit the piston with peak cylinder pressure just after it cross top dead center and thus deliver ALL the force of the combustion into the rotation of the engine.

If you advance timing too much, you catch the piston on it’s way up and slow down it’s movement losing power
If you retard the timing too much, the piston outruns the flame front and very little power is transfered from the combustion into rotation

So there is a ‘perfect’ timing setting based on these two things:

piston speed: which is affected by rpm, and by Rod/Stroke ratio
flame front travel speed: which is affected by factors like mixture density, fuel to alcohol ratio, compression ratio…etc

Now let’s talk a little bit about the two main factors affecting timing advance:

The first is RPM. As RPM increases, the piston speed increases.

The thing is that the piston speed increases linearly with RPM … but the flame front travel speed only increases slightly with RPM due to more turbulance in the cylinder and a better mixture of air and fuel which allows the ‘fractal’ moving flame front to travel faster.

So going from 700 rpms to 7000 rpms, the piston increases it’s speed by a factor of 10, but the flame front only increases it’s speed by about a factor of 3.

So in a sense the piston is OUTrunning the flame front, and to re-synchronize the mixture so that we can catch the piston at top dead center we need to further advance the ignition timing.

To make up for this effect, the timing advance at 7000 rpms needs to be about 3 times the timing advance at idle and that’s how ‘mechanical timing’ came to be starting with a base timing of something like 10 degrees BTDC and growing out to 32 BTDC near redline if we’re talking for example about a large bore engine).

The second factor is mixture density. Which is typically measured by the car’s ECU with RPM, Flow and temperature sensors… But for this example we’re going to measure it in terms of volumetric efficiency since we can calculate that figure.

As the mixture increases in density, then so does the number of air and fuel molecules available for the flame front to expand outwards. This denser mixture allows the flame front to travel faster, as is typically the case with forced induction engines such as turbocharged and supercharged vehicles that cram more air and fuel into the cylinder.

If we leave this mixture alone at stock timing, then the air fuel mixture will out-accelerate the piston and catch it BEFORE top dead center which slows the engine rotation and exerts power rather than making it.

So as mixture density increases we retard timing to catch the piston once again just as it crosses top dead center. As the mixture density decreases, we advance timing to prevent the piston from outrunning the now slower moving… & less-dense mixture.

Of course there are other things that affect flame front travel speed besides mixture density…

such as:
octane rating (higher octane fuels burn slower)
the presence of burn accelerators such as nitrous oxide and oxygenated alcoholic fuels like ethanol and methanol,
or the presence of flame retardants such as water injection and high humidity.

Now that we have a basic understanding of timing curves, let me show you some simulated timing curves based on the 5.7 liter LS1 engine.

Now let’s talk about the advantages of knowing this information…

Dyno time
Different VE curves for modified cars
Not leaving any power on the table (nitrous or superchargers)

____________________________________________

The Apexi S-ITC is an older generation piggy back controller. The S-ITC stands for Super Ignition Timing Controller, and had a +/-15 degree advance/retard setting adjustable at 5 RPM points between idle and 7000 rpms.

At the time when this box was released, most timing controllers were either basic boost based retards such as the MSD BTM (boost timing master) or a fixed single externally triggered retard box for nitrous activation…etc

So, at the time, this product was much more advanced than the cruder forms of ignition tuning available by competitors. However, this product sold very poorly and was quickly discontinued.

The primary reason for the product’s failure was not the product itself, but rather lack of information in the general community about proper ignition tuning and the power potential that was being left on the table with un-tuned cars.

I hope that this how-to video here gives you a better idea about ignition tuning (since very few people actually discuss this aspect of supercharger performance and engine tuning in general). Even though the tools have changed over the years (and now we have full 16 X 16 timing maps that are 100% tunable to your desired timing), the basic theory remains the same, and the thirst in this community for this information is still there.

Technorati Tags: Power Calculator, supercharger performance, Tuning Timing

A friend of mine is building an intake manifold for a naturally aspirated Toyota Celica. The car is equipped with a 2.2 liter 4 cylinder engine that generates around 135hp @ 5500 with 6200 rpm redline. With a lot of modifications, the engine can achieve 180 crank hp @ 6200 rpms and turbocharged and supercharged versions of the same car have broken the 320 wheel hp mark @ 21psi of boost @ 6200rpms.

Now that we have our parameters defined:

Displacement: 2200 cc

Peak RPM: 6200 RPMs

Target hp: 180 hp corresponding to about 270 CFM of flow

Number of runners: 4

Number of throttle bodies: 1

Plugging these parameters into my power calculator I get the following dimensions for the intake manifold that I would build. For comparison here, we have the dimensions chosen by Mr. Turrani for his application.

In general, when doing research for the power calculator, I found that typically intake manifolds have a volume that is 50 to 80% the displacement of engine. Obviously proper intake manifold design is much more involved than that as dynamic fluid flow modeling shows us that sometimes very large yet appropriately designed intake manifold shapes can maintain peak velocity while still having a decently sized plenum volume to promote top end power.

The compromise in plenum volume is as follows:

A larger volume leaves more available air to the engine within its reach, and so long as this air can be replenished in time through the intake system, then the engine never has to work hard to get intake air because there’s always enough of it sitting there in the larger plenum.

As the plenum volume gets smaller, it becomes easier for the engine to rapidly consume all of the air in the plenum and thus it would have to spend a lot of effort (after the initial draw of air) trying to suck air in all the way through the entire intake system to stay alive.

The problem with a larger plenum is that it hurts throttle response. Throttle response is very much affected by throttle pressure (or in other words how fast the engine can consume all the air in the plenum and create a significant amount of vacuum in the manifold to draw in fresh air). The smaller the plenum (or smaller the runners), the higher the gas velocity, the faster the pressure drop, the sooner the new air rushes in, the faster the throttle response.

This usually leads to an oddball design by most OEM’s of an oversized plenum wit h a smaller throttle body and runners to try to boost gas velocity, or an undersized plenum (that will be consumed faster for better response) but with a larger throttle body that will not bottle neck the engine as it tries to pull in more air from the outside to stay alive at higher flow demands at higher rpms.

Either way, shifting peak power from 5500 to 6200 has a potential increase of 12% especially coupled with a properly designed exhaust manifold, appropriate camshafts, and a proper tune (all of which Mr. Turrani already has on his car).

As far as superchargers are concerned, intake manifolds have lower diameter requirements for the throttle body and the intake runners because the air is compressed. At the same time, runner length and resonance calculations are not much affected because air in the manifold travels at the speed of sound, and the speed of sound is not drastically affected by a slight increase in temperature and a boost in pressure.

One thing to note is that with something like a roots or screw style supercharger, engine vacuum is not alone responsible for throttle response. As the air is being both sucked in (by the piston stroke) and shoved in (by the supercharger rotation) it becomes easier and faster to fill a larger volume plenum manifold. This allows for an oversized manifold for higher rpm volumetric effeciency while relying on the screw supercharger to take care of the gas velocity, and throttle response.

Technorati Tags: manifold tuning, Power Calculator, supercharger performance, throttle pressure, Throttle response

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