Is race gas hurting my times?

[1HUBCAP]

We ran a best 1/8th time and mph last weekend:

[email protected] w/1.57 60..

Setup is a 2.3 TVS with 82mm pulley,VMP tune,bassani catback,big and little race stars w/ 26x10 slicks.A6 with stock gears and converter.

This car is erradict.. It will run from 101 to 104,and mostly 7.0 with the lone 6.86.

The mph can be up to 103.5,and still run 7.0..We changed launch from trying to get it on the converter to just straight matting it from a dead stop. Tire psi was at 11.5 and the car was moving around pretty badly.When we dropped the air to 10,it drove nice and straight but slowed. I am thinking it bogs out of the hole when at 10 psi? We put 3 gallons of unleaded 109 VP in it after the 6.86 pass,and it slowed to 7.01@101. Should i just keep straight 93 in it? (we have a 93 tune),should i have taller tires? I am confused on why it will run 7.0's no matter the mph,except for the one pass in the 6's..

One other thing i have noticed is that at the beginning of the night the trans will shift lazy,but towards the end of the night it will get rubber in 1-2,2-3..:??:

 

[slagburn]

10psi seems awful low, I run a stiff sidewall 28 at 14-15.
Do you log your runs? The KS could be picking something up and holding the timing back. How many degrees of timing are you seeing?

 

[1HUBCAP]

10psi seems awful low, I run a stiff sidewall 28 at 14-15.
Do you log your runs? The KS could be picking something up and holding the timing back. How many degrees of timing are you seeing?

Embarrasingly no,i have not.That would make sense. If we have the tires set at a higher psi,it is all over the place,i don't really understand that. It was suggested on here before that i need a taller tire.I would be interested to know why the KS would see knock if i have a splash of the good stuff in it for good measure. I only do that for a safety net.

 

[slagburn]

It can't hurt to log and see what your PCM is seeing. Maf and load play a big part in shift scheduling and firmness, see what they look like during a pass.

Make sure the race fuel you're adding in has a similar stoich point to your pump gas, lots of race fuels have a different stoich and you could be chasing your tail.

 

[1HUBCAP]

It can't hurt to log and see what your PCM is seeing. Maf and load play a big part in shift scheduling and firmness, see what they look like during a pass.

Make sure the race fuel you're adding in has a similar stoich point to your pump gas, lots of race fuels have a different stoich and you could be chasing your tail.

Please forgive my ignorance.. Can you explain about "stoich" points? I have heard that mentioned,but honestly do not really understand it.

 

[CPRsm]

If you add race gas without bumping timing your car will slow. It just causes lower cyl pressures and less power. Slicks w low tire pressure cause more roling resistance also. A dead hook is not always a good thing. A little tire speed helps things along.

 

[stang8psi]

could be seeing some heat soak also!

 

[1HUBCAP]

Ok,reading is fundamental... Done some research on stoich points,and that makes sense. Also what you are saying about timing. I have to remember that these cars are light years ahead in technology than i am used too,so i just figured that more octane,the safer i would be. I always cool the car down between runs,i never hot lap a boosted car. I have a set of 275 60 Drag radials i believe i will try. Straight BP 93 and these drag radials may be the ticket?

 

[slagburn]

I bet you'll pick up some with radials, slicks work great on a manual but the rolling resistance isn't helping.

 

[corepwn]

The tire height isn't causing your issue. I also don't necessarily believe that adding a few gallons of race gas is dropping you 3mph.

Post your slips if you have them please. I'd be interested in seeing the differences in 60'.

 

[vfast]

the race gas has a slower flame rate than 93

 

[SILV03MustangGT]

If you add race gas without bumping timing your car will slow. It just causes lower cyl pressures and less power. Slicks w low tire pressure cause more roling resistance also. A dead hook is not always a good thing. A little tire speed helps things along.

Thats wierd, I have the knock sensors active in my TVS tune (the roush base tune disables them) and I run 104 or 105 when im at the track i picked up 2mph over my previous best, same 60 ft and worse DA. I logged the runs and Shaun said the tune was looking really good.


OP what tune are you running and are you running a radial tire out front with a bias ply outback? that could be your wandering issue your having. I dont think it would be heatsoak, ive done multiple back to back runs in my car in hot weather and the car was very consistent time and trap wise.

 

[01bluesnake]

A lot of good info in this thread. Yes, not tuning for race gas will not help as the burn rate does slow much more than 93. Depending how the tune is set up, the car may be able to take advantage of a higher octane fuel and add more timing thus getting some more power. If the timing in the tune is only allowed to go as high as it was tuned regardless of knock, it will not be any benefit running a high octane fuel and can actually hurt more than help. Also the tire pressure seems very low and can cause wondering up top and slow ET as mentioned from increased rolling resistance. Think of driving on a flat vs a tire with air, the lower the harder it is to move. I recommend getting the car on a two step at the line, and increase tire pressure. You want to go as high as possible without hurting your '60.

 

[1HUBCAP]

I have hoosier fronts,the radial type 17" skinny.I find it strange that the car wanders around when the tires have more air,and it doesn't when i have 10 in them.:shrug:

I can tell you the time slips are all 7.03 down to 7.01 at 101 to 103.5 with 60's in the 1.63-1.62 range. The one lone 6 second slip had a 1.57 60,104.7 mph and 6.86 e.t..

It runs its best when it wanders around...

 

[Bad Intention]

On my best 3 passes. Car had allot of sway. Was running 12psi in my slicks.

 

[01bluesnake]

I have hoosier fronts,the radial type 17" skinny.I find it strange that the car wanders around when the tires have more air,and it doesn't when i have 10 in them.:shrug:

I can tell you the time slips are all 7.03 down to 7.01 at 101 to 103.5 with 60's in the 1.63-1.62 range. The one lone 6 second slip had a 1.57 60,104.7 mph and 6.86 e.t..

It runs its best when it wanders around...

Radial fronts will cause a little more wander than a bias ply. I run 18" M/T SR radials at 51psi, car up top is a lot more loose than i like or use to with slicks out back. More pressure will help from keeping it do that, will also help ET. The one good run may of been a sweet spot the car left at. Did you stay in the same lanes, or switch up?

 

[01bluesnake]

On my best 3 passes. Car had allot of sway. Was running 12psi in my slicks.

I was at 13.5-14 psi through out my runs. Even with me having stiff side wall tires mine swayed pretty bad. Thankfully im use to cars with slicks, just dont like the feeling. I may eventually try a bias ply up front since i wont DD the RT-s wheels anymore with slicks out back.

 

[sambandit]

You CANNOT and SHOULD NOT run a mix of fuel unless you are tuned for it. Stoich is totally different for different fuels and completely messes with your tune. This isn't like the old days. Cars are tuned for very specific fuel and very specific A/F ratios now.

 

[corepwn]

People say race gas burns slower and makes less power if you do not tune for it by adding timing, but I’ve tested that on the dyno and never seen it.

Like I explained OP, I don't think it's your issue.