Interesting thread by Eric Brooks...

This was on the other forum but I found Eric's post very interesting. Makes you wonder if a lot of tuners are running lean on the race gas tunes. It certainly makes me re-think what is the 'right' a/f range to shoot for with a specific set-up. I'm beginning to wonder if the fact Greg has been been tuning my car to 10.x for awhile now is the reason it's still in such good shape...

Ever wonder if your airfuel will change with race gas? The answer is yes....

Real gasoline has various different stoich points due to the blend, how much ethanol is in it, etc. It is somewhere between 14.1 and 14.7 though.

Finding the information on race gas isn't easy. It is not posted anywhere on the internet that I have found. VP does not publish it, nor does Sunoco (TurboBlue)

Several weeks ago I got in touch with the chemist at VP and got all the stoich points of their fuels. Last week I got in touch with a Sunoco chemist and got the data from him as well.

When I asked the guy from Sunoco why they don't publish the information on the TurboBlue website he said -

Quote:
Eric - you're right, stoichiometry is important. Fact is many people have no idea what it is - kudos to you for knowing. Unfortunately many folks we talk to think the stoichiometric air/fuel ratio is where they should set their fuel system at wide open throttle. So we are torn about posting or not posting stoichiometry data because of that potential problem.
Shocking right? Especially when you see how different the fuels are...

Here is a list of the ones I have gathered.

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): 13.9:1
Turbo Blue Unleaded Plus (104 octane): 13.7:1
Turbo Blue 110: 14.7:1
Turbo Blue Advantage: 14.9:1
Turbo Blue Extreme: 15.0:1


VP Street Blaze 100 = 14.16
VP C10 = 14.53
VP 110 = 15.09
VP C16 = 14.77
VP MS109 = 13.41

Back to pump gas.... While I had the Sunoco guy's ear, I tried to get an answer about the stoich of their fuel and to find out how much actual Ethanol is in it, when the label says up to 10%...

Here are his comments...

Quote:
I know plenty about pump gas, enough to say that there is no useful stoichiometry data on pump gas. Composition varies WAY too much, regardless of brand/refinery/etc... especially on the lower octane grades.

But I can tell you that Sunoco 94, which is very hard to find these days, will contain some ethanol. Per the first sentence, it will depend on the blend though. I would go out on a limb and say it is nearly 10% most of the time (keep in mind 10% is the max allowed by law).

Street gas blends change all the time thanks to environmental requirements (fed/state/local), seasonal adjustments, and price pressures.

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here is a link to the entire thread...

http://www.modularfords.com/forums/showthread.php?t=132632

That is an awesome post by Eric.....And that is a lot of valuable info right there....

Thanks for posting that

I actually talked to my tuner about this, with my setup running 93 pump gas and at the track adding 100 octane 50/50 mix I would be actually leaning out the car.

Good find CK

I'll tell you, the two previous motors I lost I was running around 11.8 peaking at 12.x and now I'm convinced I was running very lean on those set-ups with C16...

The new motor got torn down and looked awesome, but, like I said, Greg has been tuning it in the 10.x range since day one. I remember John Mihovetz said once you break into bigger HP numbers, '10' is actually the number to shoot for and anything above was lean. Eric's post made me realize exactly why...

This thread seems Sticky worthy.......

E.brooks knows his shit when it comes to tuning.i have 1 of his mail order tunes and my car feels like it did when i use to have nitrous.

Sometimes it is better to think in terms of Lambda instead. If your wideband reads 11.5 on your 93 octane street tune and on your Race tune with GT260 Plus reads 11.5, those are NOT the same air fuel ratios. All widebands actually read in terms of lambda and then apply the Stoich for regular gasoline and then display that on your wideband. That 11.5 on your street tune is 11.5/14.64=0.785 Lambda. Now that same 11.5 reading on the gauge when running GT260 Plus is actually 10.75 since Stoich for this fuel is 13.7 (13.7*.0785).

Just like when tuning my car on E85, we still read the wideband on the dyno in gasoline terms. Even though Stoich of E85 is 9.85, tuning car for 11.5 (.785 lambda) works out just fine because it is actually around 7.7 AFR.

I guess what I am trying to get at is that as long as your tuner is properly adjusting your tune for the different Stoich points for your particular race fuel of choice then you should be ok. What can be dangerous is just running race fuel and not being mindful of the changes in air fuel that will happen without adjusting the tune.

Great info!

I'm surprised at how many of you are shocked by this. We tuned my car last year on Shell 93 octane pump fuel. However, after sampling the Shell pumps, Exxon pumps, and Chevron pumps once per week for four straight weeks (12 samples) we had the gasoline analyzed at the Exxon Research facility here in Baytown. I went to high school with the lab manager. The differences were beyond scary. Anyone trying to consistently tune a modern fuel injected car (n/a or power adder) will end up committing suicide if they attempt to duplicate the results from one brand to another or even the same brand from week to week.

That's why we ran the car exclusively on VP Streetblaze the entire season. Yes, it bumped the A/F down a bit (from 11.5:1 to 11.25:1) but it didn't hurt the performance nor did it hurt an engine. Only my idiot first born child could hurt the engine. Mark is correct about what Mihovetz said. Take a look at his car when it leaves the starting line. That isn't clutch dust you're seeing. It's fat and happy. A "10.anything" A/F ratio will ensure the engine will not hurt itself. While you might lose a few horsepower over an 11.8:1 or 12.0:1 is it really worth it in the long run? We held one thing as an absolute when tuning my engine: nothing higher than 11.5:1 air/fuel ratio.....and Doug locked it in.

Had that retard kid of mine not gone joyriding in my car I'm sure the original engine would still be in the car and running fine.

Eric is absolutely sick in the head. I love him. This is some great info, from a great tuner! We need to all be up on this as much as possible, as stoich points are more important now than ever!

Chris

I missed that post,thanks!

US-1 said:

I'm surprised at how many of you are shocked by this.

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+1...

... but then again, I have a degree in Chemical Engineering.

Comes in handy doesn't it, Don?

US-1 said:

Had that retard kid of mine not gone joyriding in my car I'm sure the original engine would still be in the car and running fine.

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Ok guys, so when I get the car tuned this sat should I keep my wideband on the stoich diplay for my own reassurance? I run nothing but shell 93 and never change. I would also state (from reading all this info) that a safe tune would be 11.25? I realize I'm not running 20lbs of boost but shit between the threads on timming and rods bending with boost spike and now more fuel info I might as well as throw some c4 on the intake and walk away.

You don't have to read it in lambda unless you want to. The setting on your wideband doesn't matter as if the car starts to go leaner or richer the wideband just multiplies that lambda by 14.64 and displays the output. That is why I was saying that on my car with E85 I still read it in terms of gasoline stoich because lambda is lambda regardless of the fuel and I am used to reading it converted in terms for the stoich of gasoline.

slammed 06 said:

Ok guys, so when I get the car tuned this sat should I keep my wideband on the stoich diplay for my own reassurance? I run nothing but shell 93 and never change. I would also state (from reading all this info) that a safe tune would be 11.25? I realize I'm not running 20lbs of boost but shit between the threads on timming and rods bending with boost spike and now more fuel info I might as well as throw some c4 on the intake and walk away.

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You should be fine at 11.5:1 as well. As I stated, mine was at that setting and never so much as blinked. Damn car was flawless at every event we attended....right up until the retard entered the picture.

You can, however, discuss this thread with your tuner to be sure that you both are on the same page.

Thanks guys.

don_w said:

+1...

... but then again, I have a degree in Chemical Engineering.

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really ???

wow



& great input by Eric as usual, thanks for posting this...

don_w said:

+1...

... but then again, I have a degree in Chemical Engineering.

Click to expand...

US-1 said:

Comes in handy doesn't it, Don?

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But it doesn't help me one damn bit when it comes to electrical problems... I fuggin hate electrical and wiring issues. Grrrrrr....

oman_cobra said:

really ???

wow

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Yes, really... a B.S. in Chemical Engineering from Arizona State University.