how to outperform most of the mods with stock TPI concept
12-10-2007, 10:50 AM
#1
Drifting
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how to outperform most of the mods with stock TPI concept
I know this sounds crazy but I wanted to share something I am working on for quiet some time now.
Everybody knows that the stock TPI has restrictions but long tubes intake allows a fabulous venturi effect and optimize the mix velocity. Problem is that, reaching 4200 rpm, the velocity is at maximum.
The idea is here to reach a 20% more efficient combustion process by lowering the Air/fuel mixture by 20% in order for the stock TPI to go over this 4200 rpm limit and bring the venturi effect top efficiency to 5200 rpm.
After conducting many test based on fuel, I found out that more heavy the fuel is and less air you need. By lowering the 14/1 ratio to 11/1, and even 10/1, these means that you need far less air. I also use the stock injectors that are far suficient. I tought bigger was better with higher pressure ( TPIS tricks) at first but this was a big mistake and took be 1 year to find out.
So far, the best fuel I have used is the ELF competition 110 octane.
Of course I need to rescale the complete AF ratio to a safe 10.5/1 with a slitly modified timing.
When not using 110 octane fuel, I simply use a octane booster that is commonly used for competion to reach the 104 octane limit.
Doing so, the engine response is incredibly well. The seat of the pant effect is fabulous and the car is hard to handle.
While lowering by 20% the air needs, the venturi limit only appears at around 5100 rpm.
Result is an engine that is running far cooler all the time, with the benefit of the TPI system torque concept, 10% better mpg and 1000 more rpm of pure power.
The biggest problem is that I need my laptop (smalest I found) all the time to flash the ECM depending on the fuel I find on the roads, the quantity of fuel left in the tank etc etc to keep track of what is burning all the time. 2 years reasearch on this...
Result is that my stock TPI 1991 Z07 with 3.07 runs as well as a C5.
I also competed against a ZR1 and we ran identicaly.
I know this is commonly use in competition and many pros helped me here regarding the AF ratio scalling and tests . Now, I must admit that this stock GM TPI is really a fabulous piece of joy.
Anyone tried this aproach already ?
Everybody knows that the stock TPI has restrictions but long tubes intake allows a fabulous venturi effect and optimize the mix velocity. Problem is that, reaching 4200 rpm, the velocity is at maximum.
The idea is here to reach a 20% more efficient combustion process by lowering the Air/fuel mixture by 20% in order for the stock TPI to go over this 4200 rpm limit and bring the venturi effect top efficiency to 5200 rpm.
After conducting many test based on fuel, I found out that more heavy the fuel is and less air you need. By lowering the 14/1 ratio to 11/1, and even 10/1, these means that you need far less air. I also use the stock injectors that are far suficient. I tought bigger was better with higher pressure ( TPIS tricks) at first but this was a big mistake and took be 1 year to find out.
So far, the best fuel I have used is the ELF competition 110 octane.
Of course I need to rescale the complete AF ratio to a safe 10.5/1 with a slitly modified timing.
When not using 110 octane fuel, I simply use a octane booster that is commonly used for competion to reach the 104 octane limit.
Doing so, the engine response is incredibly well. The seat of the pant effect is fabulous and the car is hard to handle.
While lowering by 20% the air needs, the venturi limit only appears at around 5100 rpm.
Result is an engine that is running far cooler all the time, with the benefit of the TPI system torque concept, 10% better mpg and 1000 more rpm of pure power.
The biggest problem is that I need my laptop (smalest I found) all the time to flash the ECM depending on the fuel I find on the roads, the quantity of fuel left in the tank etc etc to keep track of what is burning all the time. 2 years reasearch on this...
Result is that my stock TPI 1991 Z07 with 3.07 runs as well as a C5.
I also competed against a ZR1 and we ran identicaly.
I know this is commonly use in competition and many pros helped me here regarding the AF ratio scalling and tests . Now, I must admit that this stock GM TPI is really a fabulous piece of joy.
Anyone tried this aproach already ?
12-10-2007, 11:06 AM
#3
Drifting
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The next step is to work on the pcmforless stock L98 curves that seems to be fabulous and obtain the best of both worlds.
I posted a thread about this pcmforless stock curves but as everybody are working on big mods , nobody really knows about.
I will need to go the empiric way and try it directly but I am not sure I will be able to twick the pcmforless ECM without going back and forth with them (means $$$).
I posted a thread about this pcmforless stock curves but as everybody are working on big mods , nobody really knows about.
I will need to go the empiric way and try it directly but I am not sure I will be able to twick the pcmforless ECM without going back and forth with them (means $$$).
12-10-2007, 11:34 AM
#4
Burning Brakes
Great theory. I hope it works for you! I would think since you are swimming in uncharted territory, having the car on the dyno to set the chip might be the best for optimization as I would think pre set curves are based on standard air/fuel ratios
12-10-2007, 01:59 PM
#5
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I admit, I don't get it. Octane is a rating for knock resistance. All else being equal, different octane gasolines don't have different oxygen requirements for the "ideal" A/F ratio. If you like putting in more liquid, try a different fuel than gasoline. Alcohol uses less air per volume of fuel. However, the greatest power output is the result of filling the cylinder with air and the appropriate amount of (for the type used) fuel.
RACE ON!!!
RACE ON!!!
12-10-2007, 02:15 PM
#6
Le Mans Master
are you saying you lowered the closed loop stoich to 10:1?
or,
are you saying you changed PE to a 10:1 AFR?
Did you use an AFRmeter or are you looking at the AFR shown in scanning software?
or,
are you saying you changed PE to a 10:1 AFR?
Did you use an AFRmeter or are you looking at the AFR shown in scanning software?
12-10-2007, 02:48 PM
#7
Le Mans Master
However, the principle you mention is how top fuel cars can make so much power, I think that stuff is somewhere around 2:1 or 3:1, so for a certain volume of air, you can use much more fuel and therefore make much more power. While nitromethane has less energy than gasoline, you use quite a bit more of it. I seem to recall hearing that for basically the same engine size and flow, you can make about 4 times the power (you use like 7 times as much fuel, but it has less energy).
But I don't see how you can take advantage of that if you are still using gasoline. I also don't quite follow why it would move the power curve up 1,000 rpm, I'd think something like that would simply move the whole curve up in magnitude, but keep the shape. But I admit that's just my guess.
12-10-2007, 03:53 PM
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I was at a magny Magny-Cours 2 years ago and 2 guys stoped at my car (she look great). We started to discuss and they were very aware about corvette.
when I started to tell them (trying to impress them on how I was "on the edge" about V8 engine (stupid me when I recall this), that the engine is great but the intake system is very restrictive I saw a smile on there faces !
They told me that they are engeneers working on C5R engines for ALMS and explained me that they were facing the same problem. I was surprised.
They explained me that ALMS regulations oblige teams to have air restriction to avoid engine to output to much power and that this is exactly the same problem as my TPI.
They them explained me that to conpensate they are working a lot on air velocity with high octane fuel and very fine tune.
This is were the story began.
Yes, more octane you have and less pre-ignition you have but high octane fuel also need less air.
It is not like moving the power curve up to 5000 rpm. It is allowing the engine to output more power with less air and less fuel. Therefore, at 5000 rpm, the engine pumps enough air for the correct fuel ratio.
when I saw them again, they helped me and plugged computers on my car to have a look at and , again, they smiled. They gave me the basis of what to work with and told me that this engine has very good potential if properly tuned with quality fuel.
They are the ones that told me to use smaller injectors and also told me that with modified high pressure ones I would obtain power that I would not believe in.
I normaly see them next january again at their facilities for them to show me what is REAL race car. (and they told me they have everything you can imagine to work on engine parts for Formula 1 and Endurance cars...may be they will work on my injectors ! ).
I cannot wait to see them again with the best work I can possibly do to my car. For sure, I will impressed them! haha Well not sure when I look at the tools and engines they are working on.
. Very very impressive work they do. but they have sooo much money.. pfff.
This work about new high octane fuel adapted to stock engines are directly coming from Le-mans series engeneers.
when I started to tell them (trying to impress them on how I was "on the edge" about V8 engine (stupid me when I recall this), that the engine is great but the intake system is very restrictive I saw a smile on there faces !
They told me that they are engeneers working on C5R engines for ALMS and explained me that they were facing the same problem. I was surprised.
They explained me that ALMS regulations oblige teams to have air restriction to avoid engine to output to much power and that this is exactly the same problem as my TPI.
They them explained me that to conpensate they are working a lot on air velocity with high octane fuel and very fine tune.
This is were the story began.
Yes, more octane you have and less pre-ignition you have but high octane fuel also need less air.
It is not like moving the power curve up to 5000 rpm. It is allowing the engine to output more power with less air and less fuel. Therefore, at 5000 rpm, the engine pumps enough air for the correct fuel ratio.
when I saw them again, they helped me and plugged computers on my car to have a look at and , again, they smiled. They gave me the basis of what to work with and told me that this engine has very good potential if properly tuned with quality fuel.
They are the ones that told me to use smaller injectors and also told me that with modified high pressure ones I would obtain power that I would not believe in.
I normaly see them next january again at their facilities for them to show me what is REAL race car. (and they told me they have everything you can imagine to work on engine parts for Formula 1 and Endurance cars...may be they will work on my injectors ! ).
I cannot wait to see them again with the best work I can possibly do to my car. For sure, I will impressed them! haha Well not sure when I look at the tools and engines they are working on.
. Very very impressive work they do. but they have sooo much money.. pfff.This work about new high octane fuel adapted to stock engines are directly coming from Le-mans series engeneers.
12-10-2007, 04:36 PM
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very interesting i have been looking at buying an intake but what I am taking away from what you are saying all i need is a great tune.
I am really waiting to see what the PCM4Less rep says to this thread
12-10-2007, 05:53 PM
#11
Burning Brakes
I think he is intimating that higher octane fuels, using more "light end" HC's needs less air to combust, that allows the gains while utilizing the stock TPI airflow. It seems that more overall fuel added at a given time, if of a higher octane rating, to the same amount of air required by a less fuel, of a lesser octane rating is how he is getting his gains. That runs somewhat counterintuitive in some ways, but seems to be what he is saying.
12-10-2007, 06:36 PM
#12
Team Owner
I think he is intimating that higher octane fuels, using more "light end" HC's needs less air to combust, that allows the gains while utilizing the stock TPI airflow. It seems that more overall fuel added at a given time, if of a higher octane rating, to the same amount of air required by a less fuel, of a lesser octane rating is how he is getting his gains. That runs somewhat counterintuitive in some ways, but seems to be what he is saying.
but I would be worried about burning up my engine doing this if it wasnt tuned just right. Sounds to me like its being forced to run lean. Also this sounds like a better setup for a race car if you have to use 104 octane 
12-10-2007, 07:24 PM
#15
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I admit, I don't get it. Octane is a rating for knock resistance. All else being equal, different octane gasolines don't have different oxygen requirements for the "ideal" A/F ratio. If you like putting in more liquid, try a different fuel than gasoline. Alcohol uses less air per volume of fuel. However, the greatest power output is the result of filling the cylinder with air and the appropriate amount of (for the type used) fuel.
RACE ON!!!
RACE ON!!!
I don't understand how you can improve the combustion process merely by richening the A/F mixture.
I don't understand how you can raise the breathing "choke" point from 4200 to 5200 just by changing the A/F ratio.
Most available gasoline fuels have reasonably small differences in BTUs per gallon. I find it difficult to believe ELF fuel is substantially different.
The 10% economy improvement does not make sense with a richened fuel mixture.
There are a couple other items that seem contradictory to me, but you get my drift. I am in no way trying to be rude or dispespectful. As I said earlier, I respect those who try to think outside the box. May I request a little more detail in your descriptions, so that we can all understand the process you are experimenting with.
Thank you, and please keep us updated.
12-10-2007, 08:08 PM
#16
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Originally Posted by frenchyoliver
Yes, more octane you have and less pre-ignition you have.
Originally Posted by frenchyoliver
but high octane fuel also need less air.
Originally Posted by frenchyoliver
It is not like moving the power curve up to 5000 rpm. It is allowing the engine to output more power with less air and less fuel. Therefore, at 5000 rpm, the engine pumps enough air for the correct fuel ratio.
when I saw them again, they helped me and plugged computers on my car to have a look at and , again, they smiled. They gave me the basis of what to work with and told me that this engine has very good potential if properly tuned with quality fuel.
They are the ones that told me to use smaller injectors and also told me that with modified high pressure ones I would obtain power that I would not believe in.
I normaly see them next january again at their facilities for them to show me what is REAL race car. (and they told me they have everything you can imagine to work on engine parts for Formula 1 and Endurance cars...may be they will work on my injectors ! ).
I cannot wait to see them again with the best work I can possibly do to my car. For sure, I will impressed them! haha Well not sure when I look at the tools and engines they are working on. . Very very impressive work they do. but they have sooo much money.. pfff.
This work about new high octane fuel adapted to stock engines are directly coming from Le-mans series engeneers.
when I saw them again, they helped me and plugged computers on my car to have a look at and , again, they smiled. They gave me the basis of what to work with and told me that this engine has very good potential if properly tuned with quality fuel.
They are the ones that told me to use smaller injectors and also told me that with modified high pressure ones I would obtain power that I would not believe in.
I normaly see them next january again at their facilities for them to show me what is REAL race car. (and they told me they have everything you can imagine to work on engine parts for Formula 1 and Endurance cars...may be they will work on my injectors ! ).
I cannot wait to see them again with the best work I can possibly do to my car. For sure, I will impressed them! haha Well not sure when I look at the tools and engines they are working on.
. Very very impressive work they do. but they have sooo much money.. pfff.This work about new high octane fuel adapted to stock engines are directly coming from Le-mans series engeneers.
These guys are pulling your chain! They are probably laughing their behinds off, seeing how you swallowed their
story, hook, line, and sinker. Chances are they are reading this and rolling on the floor. 
I have to admit, it is a little funny. It would be funnier if it weren't so sad. Then there is back up like this::
Originally Posted by xrcrx
I think he is intimating that higher octane fuels, using more "light end" HC's needs less air to combust, that allows the gains while utilizing the stock TPI airflow. It seems that more overall fuel added at a given time, if of a higher octane rating, to the same amount of air required by a less fuel, of a lesser octane rating is how he is getting his gains. That runs somewhat counterintuitive in some ways, but seems to be what he is saying.
Originally Posted by Demonic85
but I would be worried about burning up my engine doing this if it wasnt tuned just right. Sounds to me like its being forced to run lean. Also this sounds like a better setup for a race car if you have to use 104 octane
CentralCoaster seems to have the answer. Now, all I have to do is find an unported Crossfire intake manifold, add another fuel pump, and start making 700 horsepower. 800 HP, with CCs suggestion
RACE ON!!!
12-11-2007, 12:10 AM
#18
Le Mans Master
and yet another country heard from....
Last edited by mseven; 12-11-2007 at 12:38 AM.
12-11-2007, 02:03 AM
#19
Burning Brakes
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hmmm, very interesting...
so by richening the A/F ratio @ WOT and running high octane fuel (plus an increase in timing advance I take it).
you are trying to burn more of the available air and allow the engine to run out past the normal 4200rpm HP peak.
sounds possible!
after all a O2 sensor measures the "O2" left over after the combustion process, the only reason we don't try to burn it all is because normally it doesn't gain enough power to justify the extra fuel burnt (or not burnt).
but if that fuel makes power then it could be worth doing (on a restricted race car anyway)
sounds like a fine line though and I can see that ignition advance would be critical (too much and you risk pre-ignition, too little and you waste gas at a fast pace).
can't say I would rush out and try it on my vette (nor would I recommend anyone else, unless you "really" know what your doing! and I hope you do).
I can say that I have played/done something simular with my idle though (bigger cam, motor), by advancing timing I was able to get a leaner readout on the O2 sensor at idle with the same injector pulse width.
granted I am bringing in more air also to do this (vaccume increased) and it is burning more fuel at idle than absolutely nessary, but the O2 is happier and it doesn't try to lean out the idle so much that it idles like crap.
normally the thing to do is lean out the injector pulse width (or tell the ECM that you want an "idle" richer than 14.7 to 1, but the stock ECM doesn't let you do that), but since my motor wanted a richer idle thats how I got around it.
BTW, my advance is 35deg at 1000 rpm idle
so by richening the A/F ratio @ WOT and running high octane fuel (plus an increase in timing advance I take it).
you are trying to burn more of the available air and allow the engine to run out past the normal 4200rpm HP peak.
sounds possible!
after all a O2 sensor measures the "O2" left over after the combustion process, the only reason we don't try to burn it all is because normally it doesn't gain enough power to justify the extra fuel burnt (or not burnt).
but if that fuel makes power then it could be worth doing (on a restricted race car anyway)
sounds like a fine line though and I can see that ignition advance would be critical (too much and you risk pre-ignition, too little and you waste gas at a fast pace).
can't say I would rush out and try it on my vette (nor would I recommend anyone else, unless you "really" know what your doing! and I hope you do).
I can say that I have played/done something simular with my idle though (bigger cam, motor), by advancing timing I was able to get a leaner readout on the O2 sensor at idle with the same injector pulse width.
granted I am bringing in more air also to do this (vaccume increased) and it is burning more fuel at idle than absolutely nessary, but the O2 is happier and it doesn't try to lean out the idle so much that it idles like crap.
normally the thing to do is lean out the injector pulse width (or tell the ECM that you want an "idle" richer than 14.7 to 1, but the stock ECM doesn't let you do that), but since my motor wanted a richer idle thats how I got around it.
BTW, my advance is 35deg at 1000 rpm idle
Last edited by ol,RJ; 12-11-2007 at 02:06 AM.
12-11-2007, 12:02 PM
#20
Burning Brakes
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after sleeping on this one,
I can only see trying something like this (a 11 to 1 A/F ratio) at and above the point where the intake is acting like a restrictor (WOT, above 4200rpm).
in effect all that is being done is optimizing the spark and air/fuel ratio for a higher octane fuel. so the normal A/F ratio's (or close to it) should apply most everywhere else (cruise, light accel, ect.) unless your using something like E85 (or a fuel with a different stoich ratio).
all I can say is good luck and I hope you don't run into any bad gas!
I can only see trying something like this (a 11 to 1 A/F ratio) at and above the point where the intake is acting like a restrictor (WOT, above 4200rpm).
in effect all that is being done is optimizing the spark and air/fuel ratio for a higher octane fuel. so the normal A/F ratio's (or close to it) should apply most everywhere else (cruise, light accel, ect.) unless your using something like E85 (or a fuel with a different stoich ratio).
all I can say is good luck and I hope you don't run into any bad gas!