Some interesting race gas info....
11-13-2010, 01:51 AM
#1
MBWorld Fanatic!
Thread Starter
Some interesting race gas info....
This was taken from a thread on 6speedonline. I thought it was very interesting and would like to get some feedback from the board on their thoughts.
Race Gas Stoich Rating Tuning Considerations
Well I have seen questions from time to time about adding race gas without tuning which can be a very expensive experiment. I am going to explain how stoich effects AFR. Hopefully in simple format.
I am not going to get into MAF transfer functions or other tuning functions.This is just about fuel.
First lets define a few terms:
AFR: Air Fuel Ratio
Stoich Rating: In simple terms is the AFR to have chemically complete combustion that is neither rich or lean. For Example most pump gasoline is about 14.64 to 1. Which means 14.7 parts of air to 1 part of fuel.
Lambda: Is a term that is utilized when tuning. In basic terms think of it as an adjustment to your stoich rating when tuning AFR. For example with pump gas tuning .80 lambda, 14.7 x .80 = 11.76 AFR target.
Lets assume your car blower car has a nice tune that gives a perfect 11.8 AFR under WOT with pump gas.
So now it is race day. We add some timing to our tune, drain the fuel tank, and fill up with some high octane unleaded VP109.
We go for a blast down the 1/4 mile while datalogging and see the A/F is reading 12.8 then make a quick trip to the bathroom only to find out they are out of toilet paper.
There are a few factors here to consider.
The stoich rating of VP109 is 13.41.
Most wideband A/F modules are calibrated to 14.7 pump gas stoich.
So this is the formula to determine the true A/F for the run.
AFR/Wideband Stoich x Race Gas Stoich
12.8/14.7*13.41= 11.7 AFR on Race Gas
So you may think 11.7 sounds safe but we must remember the VP109 stoich is 13.41. So 11.7 AFR = .87 lambda. For the most part a safe lambda value is .80 to .82 for a forced induction mustang. I prefer .80
So we take VP109 stoich of 13.41 x .80 lambda = 10.73 AFR
This is the AFR (10.73) I am tuning for.
Keep in mind this is not what will display on your wide band as it is programmed to 14.7 stoich. You must convert the AFR.
AFR/Race Gas Stoich*Wide Band Stoich
10.73/13.41*14.7 = 11.76 AFR is what I want to see on my wideband when running VP109.
Just to reiterate 11.7 on the AFR display with VP 109 is really a 10.7 AFR.
Ok so hopefully you are not totally confused.
There is a simple solution to all of this madness. The SCT Advantage software has a Scalar for Stoichiometric Air Fuel Ratio. You simply enter the correct value for the fuel you are using and all lambda fuel calculations will be based on this value. Then just do the first formula conversion to determine what you should be reading on the AFR display. Some AFR modules may be able to be programed to the correct stoich.
Or leave the stoich in the tune and wideband at 14.64 and calcualte what AFR you need to read on the wideband for the fuel that is used. (This is how I did it in the past, but I find it easier to change the stoich scalar)
This is why you have to exercise caution when mixing race gas and pump gas as you do not know the true stoich of the mixture. The leaded race fuels have a stoich that is closest to pump gas. I always drain my tank before putting in the race gas. When I mixed fuels in the past I didn't notice a drastic change in AFR, but when I have 100% unleaded race gas it really leans out with a 14.64 stoich scalar in the tune.
The other caution is the winter (oxgenated) gas we get in Arizona. I noticed the car leaned out in the winter when it was tuned on the better summer blend. A 14.1 stoich scalar works for the AZ winter gas if your initial tune was based on the summer blend.
Race Gas Stoich Ratings
Sunoco MO2X UL – 14.5
Sunoco 260 GTX – 14.4
Sunoco 260 GT – 13.9
Sunoco 260 GT Plus – 13.7
Sunoco Standard – 14.8
Sunoco Supreme – 14.9
Sunoco MO2X – 14.5
Sunoco HCR Plus – 14.8
Sunoco Maximal – 15.0
Sunoco MaxNOS – 14.9
Turbo Blue Unleaded (100 octane) -13.9
Turbo Blue Unleaded Plus (104 octane) - 13.7
Turbo Blue 110 - 14.7
Turbo Blue Advantage - 14.9
Turbo Blue Extreme - 15.0
VP Street Blaze 100 - 14.16
VP C10 -14.53
VP C16 - 14.77
VP 110 - 15.09
VP MS109 - 13.41
Well I have seen questions from time to time about adding race gas without tuning which can be a very expensive experiment. I am going to explain how stoich effects AFR. Hopefully in simple format.
I am not going to get into MAF transfer functions or other tuning functions.This is just about fuel.
First lets define a few terms:
AFR: Air Fuel Ratio
Stoich Rating: In simple terms is the AFR to have chemically complete combustion that is neither rich or lean. For Example most pump gasoline is about 14.64 to 1. Which means 14.7 parts of air to 1 part of fuel.
Lambda: Is a term that is utilized when tuning. In basic terms think of it as an adjustment to your stoich rating when tuning AFR. For example with pump gas tuning .80 lambda, 14.7 x .80 = 11.76 AFR target.
Lets assume your car blower car has a nice tune that gives a perfect 11.8 AFR under WOT with pump gas.
So now it is race day. We add some timing to our tune, drain the fuel tank, and fill up with some high octane unleaded VP109.
We go for a blast down the 1/4 mile while datalogging and see the A/F is reading 12.8 then make a quick trip to the bathroom only to find out they are out of toilet paper.
There are a few factors here to consider.
The stoich rating of VP109 is 13.41.
Most wideband A/F modules are calibrated to 14.7 pump gas stoich.
So this is the formula to determine the true A/F for the run.
AFR/Wideband Stoich x Race Gas Stoich
12.8/14.7*13.41= 11.7 AFR on Race Gas
So you may think 11.7 sounds safe but we must remember the VP109 stoich is 13.41. So 11.7 AFR = .87 lambda. For the most part a safe lambda value is .80 to .82 for a forced induction mustang. I prefer .80
So we take VP109 stoich of 13.41 x .80 lambda = 10.73 AFR
This is the AFR (10.73) I am tuning for.
Keep in mind this is not what will display on your wide band as it is programmed to 14.7 stoich. You must convert the AFR.
AFR/Race Gas Stoich*Wide Band Stoich
10.73/13.41*14.7 = 11.76 AFR is what I want to see on my wideband when running VP109.
Just to reiterate 11.7 on the AFR display with VP 109 is really a 10.7 AFR.
Ok so hopefully you are not totally confused.
There is a simple solution to all of this madness. The SCT Advantage software has a Scalar for Stoichiometric Air Fuel Ratio. You simply enter the correct value for the fuel you are using and all lambda fuel calculations will be based on this value. Then just do the first formula conversion to determine what you should be reading on the AFR display. Some AFR modules may be able to be programed to the correct stoich.
Or leave the stoich in the tune and wideband at 14.64 and calcualte what AFR you need to read on the wideband for the fuel that is used. (This is how I did it in the past, but I find it easier to change the stoich scalar)
This is why you have to exercise caution when mixing race gas and pump gas as you do not know the true stoich of the mixture. The leaded race fuels have a stoich that is closest to pump gas. I always drain my tank before putting in the race gas. When I mixed fuels in the past I didn't notice a drastic change in AFR, but when I have 100% unleaded race gas it really leans out with a 14.64 stoich scalar in the tune.
The other caution is the winter (oxgenated) gas we get in Arizona. I noticed the car leaned out in the winter when it was tuned on the better summer blend. A 14.1 stoich scalar works for the AZ winter gas if your initial tune was based on the summer blend.
Race Gas Stoich Ratings
Sunoco MO2X UL – 14.5
Sunoco 260 GTX – 14.4
Sunoco 260 GT – 13.9
Sunoco 260 GT Plus – 13.7
Sunoco Standard – 14.8
Sunoco Supreme – 14.9
Sunoco MO2X – 14.5
Sunoco HCR Plus – 14.8
Sunoco Maximal – 15.0
Sunoco MaxNOS – 14.9
Turbo Blue Unleaded (100 octane) -13.9
Turbo Blue Unleaded Plus (104 octane) - 13.7
Turbo Blue 110 - 14.7
Turbo Blue Advantage - 14.9
Turbo Blue Extreme - 15.0
VP Street Blaze 100 - 14.16
VP C10 -14.53
VP C16 - 14.77
VP 110 - 15.09
VP MS109 - 13.41
11-13-2010, 03:13 AM
#2
Super Moderator
I ARE OF THE CONFUSED? 
So is it sayin to watch out for the blend of regular pump and race fuel because it'll throw off your true AFR readings???
I'm only plannin on throwin in 3-5 gallons of VP109 along with at least 5 gallons of regular pump 91 for my runs. Will that be okay? Is there something I'm missin?
So is it sayin to watch out for the blend of regular pump and race fuel because it'll throw off your true AFR readings???
I'm only plannin on throwin in 3-5 gallons of VP109 along with at least 5 gallons of regular pump 91 for my runs. Will that be okay? Is there something I'm missin?
11-13-2010, 09:45 AM
#5
MBWorld Fanatic!
I had great results with 5 gallons 93 and 3 gallons 104.I never run full race gas,just a little to help with any knock that might occur.
You must have a real race gas map to take advantage of pure 109 and that's what I planned on doing with that speedriven box that they have.
You must have a real race gas map to take advantage of pure 109 and that's what I planned on doing with that speedriven box that they have.
11-13-2010, 10:12 AM
#6
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2004 E55 AMG
I ARE OF THE CONFUSED?
So is it sayin to watch out for the blend of regular pump and race fuel because it'll throw off your true AFR readings???
I'm only plannin on throwin in 3-5 gallons of VP109 along with at least 5 gallons of regular pump 91 for my runs. Will that be okay? Is there something I'm missin?
So is it sayin to watch out for the blend of regular pump and race fuel because it'll throw off your true AFR readings???
I'm only plannin on throwin in 3-5 gallons of VP109 along with at least 5 gallons of regular pump 91 for my runs. Will that be okay? Is there something I'm missin?
He's saying that different fuels will produce different AFR's. These different AFR's will not be displayed properly on a standard AF gauge that is calibrated for 93 Octane at ~14.7 to 1. If you have a tune that's right on the edge and you switch fuels ou could run into trouble. Think of it like filling your tank with E85, which requires about 35% more fuel, only not nearly as dramatic a difference.
I think what the author was really getting at(since any Redneck can buy software for $200 and try to tune a Mustang) is that you must do a conversion so you know what the indicated AFR should be on the wideband while you're tuning. An indicated 12.3 AFR could actually be 12.9 for instance.
11-13-2010, 10:44 AM
#7
MBWorld Fanatic!
Thread Starter
I had great results with 5 gallons 93 and 3 gallons 104.I never run full race gas,just a little to help with any knock that might occur.
You must have a real race gas map to take advantage of pure 109 and that's what I planned on doing with that speedriven box that they have.
You must have a real race gas map to take advantage of pure 109 and that's what I planned on doing with that speedriven box that they have.
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11-13-2010, 10:54 AM
#8
MBWorld Fanatic!
My Ecu is going back to kleeman now to take some fuel out and I hate the down time.
11-13-2010, 11:03 AM
#9
MBWorld Fanatic!
Thread Starter
I'm pretty sure Kleeman won't like the idea of file sharing. Most likely in your situation the best thing would be to leave only 1 tune in your into Kleeman comes out with something comparable. Kleeman is a great company with awesome support but the idea of sending the ECU back and forth sucks.
11-13-2010, 11:07 AM
#10
Super Member
Very interesting find..So if running a little rich, mixing say 93/100 octane will only make matters worst in terms of power..you'll just be running pig rich
I ran on 1/2 tank 93 last time out and my AFR's at wot were low 11's even high 10's...adding race gas would hurt me I'm guessing specially when running meth..i would think is either use meth or race gas
will log a couple of Meth/No meth Race/No Race gas runs next week to see which one benefits the most..
I ran on 1/2 tank 93 last time out and my AFR's at wot were low 11's even high 10's...adding race gas would hurt me I'm guessing specially when running meth..i would think is either use meth or race gas
will log a couple of Meth/No meth Race/No Race gas runs next week to see which one benefits the most..
11-13-2010, 11:10 AM
#11
MBWorld Fanatic!
The way I am interpreting the post is that the AFR's will appear leaner on some data loggers when using race gas. The actual AFR's will be richer (provided nothing was done to adjust for the differing stoich rating). I don't think using a mix of race gas is dangerous at all. It is just harder to adjust the AFR readings to come up with a true conversion.
Tom
Tom
