Race fuel, Few questions?

[ShelbyGT350]

Dumb question

My local independent gas station sells Sunoco 95 and 100 octane race gas (at $7.50/gal and $8.50/gal respectively). If I put say a 1/2 tank of that stuff in my tank and drive it on the street, is it going to screw up my engine or just give it extra "oomph"?

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[Tommy V]

A tuner should share a bit of info on this

Unfortunately u will not get alot of feedback on how much the pcm can compensate for different fuels/boost ect,i do alot of data logging and my own researcs the last diagnostic class i went to i found out that when the flexfuel strategy is turned on the pcm can adjust close to 30% correction for a/f,that is quite a bit and probably why their are some tuners out their that will run e85 without a fuel system.You do have to know what your doing if tryin that though.

 

[v8ter]

I would love to, but frankly, I am buried in files to get out today.

If you want to really read up on this stuff, (and not just internet gossip)
There are a lot of engineering white papers that will dive into great detail about it. Covering topics like MBT, Flame speed, Detonation, Octane, and AFR for peak TQ production.

Just a topic on the debate between the relationship of timing advance vs. AFR and effect on EGT's is a great place to start.

No, what I meant is how safe it is to add 50/50 93 / ms109 to a empty tank with retuning for it? And if I added 100% ms109 to the same tune does the pcm detect this and puts the afr richer or ?

 

[Fivepointstevo]

No, what I meant is how safe it is to add 50/50 93 / ms109 to a empty tank with retuning for it? And if I added 100% ms109 to the same tune does the pcm detect this and puts the afr richer or ?

Hey just little input I know what your asking. My buddy went to a dyno session with MS109 the car wouldn't put in the proper timing so to make a long story short run purely race gas for whatever gas your car is tuned on because the oxygen content and stoich is very specific we had Sunoco race gas and MS109 mixed and the car but the car wouldn't make power down 3 degrees of timing after that we put in another pail of ms109 and the car picked a lot of power so run what the car is tuned for yes it "will run" but not to its potential.i only mix pump gas with race gas on the drive home from the track (because I'm not racing) and the car still runs fine but the fuel trims are lil wacky because the two fuels have very different stoichs and one being oxygenated and one being not. Hope this help sorry this is a lil long winded LoL

 

[mdnt]

in most cases the "street" race fuels will be close enough on lambda to not have ratio problems.
FYI lambda is the ratio of actual air fuel ratio to stoichiometric air fuel ratio , and not all fuels have same stoich
e85 usually 9.6 to 9.8 stoich
pump usually 14.7
the 91 oct we have here is a e10 blend with roughly a 14.1 stoich
This is the reason that some tuners are able to tune cars so well but only in the local area to them. its also a reason that some MPG numbers are all over the board depending on what fuels you have available
MS109 is 13.1 stoich

Now to add more fire into the thread not all high octane have the same Burn or BTUs, different suppliers additives will have different MBT numbers.
I went from VP to Torco in my foxbody and a few adjustments were needed.

https://vpracingfuels.com/master-fuel-table/
http://torcoracefuel.net/pro-fuels.html

 

[v8ter]

in most cases the "street" race fuels will be close enough on lambda to not have ratio problems.
FYI lambda is the ratio of actual air fuel ratio to stoichiometric air fuel ratio , and not all fuels have same stoich
e85 usually 9.6 to 9.8 stoich
pump usually 14.7
the 91 oct we have here is a e10 blend with roughly a 14.1 stoich
This is the reason that some tuners are able to tune cars so well but only in the local area to them. its also a reason that some MPG numbers are all over the board depending on what fuels you have available
MS109 is 13.1 stoich

Now to add more fire into the thread not all high octane have the same Burn or BTUs, different suppliers additives will have different MBT numbers.
I went from VP to Torco in my foxbody and a few adjustments were needed.

https://vpracingfuels.com/master-fuel-table/
http://torcoracefuel.net/pro-fuels.html

So lets say I want pulley down and prevent knock, is there a fuel I can mix 50/50 for this ?

 

[TooSoonJunior]

Stating race fuel in general has the same stoich as pump gas is straight false. One of the most popular race gases is MS109, which has a lower stoich of 13.4. Most people mix it and don't notice the slightly leaner AFR without a retune, but anyone who empties their tank and runs straight MS109 WILL run dangerously lean.

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