Different Theory on Fuel Tuning...
11-11-04, 04:25 PM
#1
Different Theory on Fuel Tuning...
I was watching this video produced by Innovate Motorsports with this guy from EFI University. Video 1.
He was talking about the standard tuning convention of using rich AFR to cool the charge in order to prevent the probability of knock. This is basically what we do, running 11's or sometimes richer under high boost. He goes on to describe the theory in the vid.
Now, he's saying that this theory is basically wrong.
That a better way would be to run an optimum fuel mixture for power (which I think is 12.5 or so for gasoline), and running more ignition timing retard. This should make more power and still guard against knock.
Can any of the many people more knowledgeable than me shed some light on this? Most of the RX-7's I've seen tuned, including my own, have been done in a fairly conventional manner: low to mid 11 AFR, timing at around 15 degrees etc.
He was talking about the standard tuning convention of using rich AFR to cool the charge in order to prevent the probability of knock. This is basically what we do, running 11's or sometimes richer under high boost. He goes on to describe the theory in the vid.
Now, he's saying that this theory is basically wrong.
That a better way would be to run an optimum fuel mixture for power (which I think is 12.5 or so for gasoline), and running more ignition timing retard. This should make more power and still guard against knock.
Can any of the many people more knowledgeable than me shed some light on this? Most of the RX-7's I've seen tuned, including my own, have been done in a fairly conventional manner: low to mid 11 AFR, timing at around 15 degrees etc.
11-11-04, 04:54 PM
#2
Lives on the Forum
have not seen the video but there has always been an argument on this subject on getting the most power and retaining the reliability of the motor with n/a engines. it is not as groundbreaking of a newsflash as you may believe. there are the school of people who would argue that less advance and lower octane fuel is "the way to go" and other that believe that an increased spark advance and higher octane fuel is the "best way". now consider heat and lean conditions in an "advanced" setting throwing a turbo into the mix on a fragile motor amplifying these conditions....
11-11-04, 06:42 PM
#3
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at some point you cant retard any more because the a/f mix is burning in the exhaust. i guess volvo has done some work, basically with a big egr valve and a leaner mixture to get some fuel efficency back
from http://www.teknett.com/pwp/drmayf/injchem.htm
As a side note - Volvo recently released some SAE papers documenting the use
of cooled EGR to both reduce detonation and return to a stoic mixture under
boost in the 15 psi range - while maintaining approximately the same power
output. Notice - they reduced fuel and still get the same power output.
When you consider that EGR consists primarily of nitrogen, CO2, and water ( to
the tune of about two gallons formed from each gallon of water burned ), you
might draw the conclusion that it also was not "inert". They peaked their
tests at about 18% cooled EGR - which would work out to about 36% water
injection and got about the same results under similar conditions that the
early NACA research got."
from http://www.teknett.com/pwp/drmayf/injchem.htm
As a side note - Volvo recently released some SAE papers documenting the use
of cooled EGR to both reduce detonation and return to a stoic mixture under
boost in the 15 psi range - while maintaining approximately the same power
output. Notice - they reduced fuel and still get the same power output.
When you consider that EGR consists primarily of nitrogen, CO2, and water ( to
the tune of about two gallons formed from each gallon of water burned ), you
might draw the conclusion that it also was not "inert". They peaked their
tests at about 18% cooled EGR - which would work out to about 36% water
injection and got about the same results under similar conditions that the
early NACA research got."
11-11-04, 09:26 PM
#4
Ben Strader is talking about piston motors. Rotary's, although many theories are still valid,
are still a different breed. Due to the amount of time it takes a rotary to complete combustion we need to run richer a/f and colder spark plugs.
Ben is a good friend of mine and he is very knowledgable and what he's saying is true.
He has a lot of experience with cylinder pressure tuning on piston motors
He's basically saying you don't want to avoid knock by running overly rich
Instead use the right amount of ignition timing and proper a/f and you'll have a much happier motor.
Running very rich doesn't prevent knock from the extra cooling it's actually due to slowing down the burn and so what happens is peak cylinder pressure is happening after TDC.
You generally want your peak cylinder pressure to occur at about 15~20 degrees after TDC.
If your ignition advance is to early your peak pressure will occur at TDC or sooner and this causes Knock.
Hopefully soon tools for pressure testing become much cheaper and more of us could get our hands on them. Right now i've looked into a few and unless your willing to spend 20k+
it's a bit out of reach for now. Formula One has been using these methods for quite some time already.
This will change soon and we will see alot more of Ion Sensing.
Many OEM cars will be fitted with them.
New Autronic Ecu's (later SM4/SM5) will actually come fitted with them as well.
This will enable individual cylinder knock control.
are still a different breed. Due to the amount of time it takes a rotary to complete combustion we need to run richer a/f and colder spark plugs.
Ben is a good friend of mine and he is very knowledgable and what he's saying is true.
He has a lot of experience with cylinder pressure tuning on piston motors
He's basically saying you don't want to avoid knock by running overly rich
Instead use the right amount of ignition timing and proper a/f and you'll have a much happier motor.
Running very rich doesn't prevent knock from the extra cooling it's actually due to slowing down the burn and so what happens is peak cylinder pressure is happening after TDC.
You generally want your peak cylinder pressure to occur at about 15~20 degrees after TDC.
If your ignition advance is to early your peak pressure will occur at TDC or sooner and this causes Knock.
Hopefully soon tools for pressure testing become much cheaper and more of us could get our hands on them. Right now i've looked into a few and unless your willing to spend 20k+
it's a bit out of reach for now. Formula One has been using these methods for quite some time already.
This will change soon and we will see alot more of Ion Sensing.
Many OEM cars will be fitted with them.
New Autronic Ecu's (later SM4/SM5) will actually come fitted with them as well.
This will enable individual cylinder knock control.
11-11-04, 11:24 PM
#5
11-12-04, 01:17 AM
#6
Originally Posted by enzo250
Ben Strader is talking about piston motors. Rotary's, although many theories are still valid,
are still a different breed. Due to the amount of time it takes a rotary to complete combustion we need to run richer a/f and colder spark plugs.
Ben is a good friend of mine and he is very knowledgable and what he's saying is true.
He has a lot of experience with cylinder pressure tuning on piston motors
He's basically saying you don't want to avoid knock by running overly rich
Instead use the right amount of ignition timing and proper a/f and you'll have a much happier motor.
Running very rich doesn't prevent knock from the extra cooling it's actually due to slowing down the burn and so what happens is peak cylinder pressure is happening after TDC.
You generally want your peak cylinder pressure to occur at about 15~20 degrees after TDC.
If your ignition advance is to early your peak pressure will occur at TDC or sooner and this causes Knock.
Hopefully soon tools for pressure testing become much cheaper and more of us could get our hands on them. Right now i've looked into a few and unless your willing to spend 20k+
it's a bit out of reach for now. Formula One has been using these methods for quite some time already.
This will change soon and we will see alot more of Ion Sensing.
Many OEM cars will be fitted with them.
New Autronic Ecu's (later SM4/SM5) will actually come fitted with them as well.
This will enable individual cylinder knock control.
are still a different breed. Due to the amount of time it takes a rotary to complete combustion we need to run richer a/f and colder spark plugs.
Ben is a good friend of mine and he is very knowledgable and what he's saying is true.
He has a lot of experience with cylinder pressure tuning on piston motors
He's basically saying you don't want to avoid knock by running overly rich
Instead use the right amount of ignition timing and proper a/f and you'll have a much happier motor.
Running very rich doesn't prevent knock from the extra cooling it's actually due to slowing down the burn and so what happens is peak cylinder pressure is happening after TDC.
You generally want your peak cylinder pressure to occur at about 15~20 degrees after TDC.
If your ignition advance is to early your peak pressure will occur at TDC or sooner and this causes Knock.
Hopefully soon tools for pressure testing become much cheaper and more of us could get our hands on them. Right now i've looked into a few and unless your willing to spend 20k+
it's a bit out of reach for now. Formula One has been using these methods for quite some time already.
This will change soon and we will see alot more of Ion Sensing.
Many OEM cars will be fitted with them.
New Autronic Ecu's (later SM4/SM5) will actually come fitted with them as well.
This will enable individual cylinder knock control.
11-13-04, 01:17 AM
#7
Banned. I got OWNED!!!
Can tell you for a fact its crap. Innovate are good friends of mine but dont take the tuning advice as told by Ben to be any sort of *guide* when tuning a rotary engine 
Richer AFR's and appropriate timing are what is needed in mega power forced induction cars, F1 turbo cars were no different either I have video of a BOSCH programing module setting mixture on a 1000bhp GP engine during a practice session and you can clearly see the AFR being set to 10.4:1 on racing gasoline.
Rotaries timing is fundamentaly different to a piston engine because of geometric and dual plug lay out ++++ you have 1/3rd more time for any given RPM *compared to piston 4 stroke* to burn the mixture hence you only require or need quite conservative timing settings.
THERMAL MELTDOWN and OVERLOAD on apex seals and turbine wheels mandate the use of quite heavy AFR's to ensure logetivity of engines and other parts, please dont feel the need to experiment with this *advice* and consult a rotary expert before you attempt to go lean and more advance route. Its not worth the marginal gains in fuel economy/efficiency...power output gains are neglidgable for the increased risks associated.
We had a NA FSAE motor bike ening on our own engine dyno and I can tell you the amounts of power variation with wildly fluctuating AFR set points and timing values makes little difference in power as recorded onthe brake, differences to EGT and combustion temps in general are far more important in turbocharged applications and minor gains in fuel efficiency are dismissed in preference to increased durability.............. this is the same wether it be a 1000bhp GP F1 engine or a highly stressed Wankel rotary turbo, dont play with lean mixtures and advanced timing unless you like the idea of reducing the life of your engine.
Richer AFR's and appropriate timing are what is needed in mega power forced induction cars, F1 turbo cars were no different either I have video of a BOSCH programing module setting mixture on a 1000bhp GP engine during a practice session and you can clearly see the AFR being set to 10.4:1 on racing gasoline.
Rotaries timing is fundamentaly different to a piston engine because of geometric and dual plug lay out ++++ you have 1/3rd more time for any given RPM *compared to piston 4 stroke* to burn the mixture hence you only require or need quite conservative timing settings.
THERMAL MELTDOWN and OVERLOAD on apex seals and turbine wheels mandate the use of quite heavy AFR's to ensure logetivity of engines and other parts, please dont feel the need to experiment with this *advice* and consult a rotary expert before you attempt to go lean and more advance route. Its not worth the marginal gains in fuel economy/efficiency...power output gains are neglidgable for the increased risks associated.
We had a NA FSAE motor bike ening on our own engine dyno and I can tell you the amounts of power variation with wildly fluctuating AFR set points and timing values makes little difference in power as recorded onthe brake, differences to EGT and combustion temps in general are far more important in turbocharged applications and minor gains in fuel efficiency are dismissed in preference to increased durability.............. this is the same wether it be a 1000bhp GP F1 engine or a highly stressed Wankel rotary turbo, dont play with lean mixtures and advanced timing unless you like the idea of reducing the life of your engine.
Last edited by RICE RACING; 11-13-04 at 06:15 AM.
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11-13-04, 11:04 AM
#8
Originally Posted by RICE RACING
Can tell you for a fact its crap. Innovate are good friends of mine but dont take the tuning advice as told by Ben to be any sort of *guide* when tuning a rotary engine
Peter your are correct. Rotaries are a different breed altogether.
Also the difference between(on a toyoto 4ag) 10.5:1 a/f and 11.5:1 a/f on my dyno was only about 8hp.
So you make you call. Me personally i would run it richer, who cares about 8hp.
Lean and mean is not what i would run in a rotary!
11-13-04, 01:18 PM
#10
Originally Posted by RICE RACING
Richer AFR's and appropriate timing are what is needed in mega power forced induction cars, F1 turbo cars were no different either I have video of a BOSCH programing module setting mixture on a 1000bhp GP engine during a practice session and you can clearly see the AFR being set to 10.4:1 on racing gasoline.
I believe the reason F1 engines(turbo era) ran that rich was to avoid pre-ignition not necessary knock/detonation. With the amount to time an F1 engine spends at WOT with those insane boost levels and insane rpm they ran they had to make sure they had a handle on heat. Running that rich would keep the spark plugs cool and prevent preignition.
I too often look at what F1 does and try to understand it because its clearly the most advanced form of racing in the world. Whatever these engineers come up with you know they have spents millions of dollars r&ding and if there wasn't a benefit to using it they won't use it.
11-13-04, 04:37 PM
#11
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What makes more sense with engines (and there is another paper by innovate that explains this well) is running slightly richer than best power and using a different liquid for the cooling/knock prevention.
I tend to favour a mixture of water, acetone and methanol.
I tend to favour a mixture of water, acetone and methanol.
11-13-04, 06:56 PM
#12
Banned. I got OWNED!!!
Originally Posted by bill Shurvinton
What makes more sense with engines (and there is another paper by innovate that explains this well) is running slightly richer than best power and using a different liquid for the cooling/knock prevention.
I tend to favour a mixture of water, acetone and methanol.
I tend to favour a mixture of water, acetone and methanol.
11-13-04, 07:10 PM
#13
Mad Man
This whole conversation is way out of my league, but also do not forget that F1 needs relatively little in the way of engine life, and is always looking to go farther on less fuel. Obvious, but though I'd mention it. Carl
11-13-04, 07:31 PM
#14
Banned. I got OWNED!!!
Originally Posted by Carl Byck
This whole conversation is way out of my league, but also do not forget that F1 needs relatively little in the way of engine life, and is always looking to go farther on less fuel. Obvious, but though I'd mention it. Carl
Even being conservative using this "little life" that F1 engineers managed to obtain over 20 years ago with much less technology than the current crop of turbo experts have at their disposal, their motors would do well over 500 1/4 mile passes !
11-13-04, 08:03 PM
#15
Senior Member
Hi Peter! Clock is now 3 am in Sweden and couldn't sleep so what to do? Go look on the RX-7 club forum of course! I am about to buy me an A/F meter which i can have when i dyno my N/A and turbo rotaries this winter. So far i've only been using egt metering but know that i am gonna build a 600 hp street port motor on race gas and a 700 hp (hopefully) methanol 13B RE engine what meter do you recommend? How rich can you measure with a 5v sond? Don't know what "ideal" afr is on a methanol turbo motor is, any suggestions?
Thanks in advance: Lars
Thanks in advance: Lars
11-13-04, 08:54 PM
#16
Originally Posted by RICE RACING
??If you call 600km *racing life* little for a 1000bhp 1.5lt gasoline 20 year old F1 engine then have a look at the current crop of *import* drag racing experts and you will see what "little" engine life is !
!I'm hoping to god that i could get one full season with my motor.
That would probably add up to be about 30~40 1/4 mile passes.
11-13-04, 09:48 PM
#19
Banned. I got OWNED!!!
Originally Posted by Lasse wankel
Hi Peter! Clock is now 3 am in Sweden and couldn't sleep so what to do? Go look on the RX-7 club forum of course! I am about to buy me an A/F meter which i can have when i dyno my N/A and turbo rotaries this winter. So far i've only been using egt metering but know that i am gonna build a 600 hp street port motor on race gas and a 700 hp (hopefully) methanol 13B RE engine what meter do you recommend? How rich can you measure with a 5v sond? Don't know what "ideal" afr is on a methanol turbo motor is, any suggestions?
Thanks in advance: Lars
Thanks in advance: Lars
I have been using an Innovate LM-1 with great sucsess and fully recomend it. PM me and I will give you a special price shipped to you and some details to your other questions
11-17-04, 07:50 PM
#22
Originally Posted by RICE RACING
THERMAL MELTDOWN and OVERLOAD on apex seals and turbine wheels mandate the use of quite heavy AFR's to ensure logetivity of engines and other parts, please dont feel the need to experiment with this *advice* and consult a rotary expert before you attempt to go lean and more advance route. Its not worth the marginal gains in fuel economy/efficiency...power output gains are neglidgable for the increased risks associated.
Does the thermal meltdown and overload include cruising afrs or just in boost? So the richer afr during postive pressure in rotaries are to help cool their apex seals correct? I know meltdown means heat and all, but I'm just trying to make things crystal clear
03-21-05, 08:56 PM
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Originally Posted by bill Shurvinton
What makes more sense with engines (and there is another paper by innovate that explains this well) is running slightly richer than best power and using a different liquid for the cooling/knock prevention.
I tend to favour a mixture of water, acetone and methanol.
I tend to favour a mixture of water, acetone and methanol.
If you replace this overfueling with vapourising a mixture of water, acetone and methanol, as you said above, then this liquid to surface cooling effect will be lost.
I realise that the method you speak of should lower intake temps dramatically but will this be enough to offset the lack of liquid to surface cooling that the overfueling offered?
PS Sorry for draggin up an old post
