103 Race fuel and poor performance

[Schulmann]

I had an issue this week-end during a drag race.

Our drag race was scheduled on a track where the closest gaz station is 150mi away. Since I had to transport my fuel, I have decide to buy race fuel at home and packed up everything in my trunk. I bought 103 race fuel. Usually for a race I run my Viper on 96 oct fuel with the 6.5lb pulley.


I had good times on my street tires, consistantly 1.70/11.5/130 but I only did 5 runs because I had to leave for an emergency. Only in the evening I relized that my Viper was severly under performing by 22% above 3500rpm ! My acceleration was only 300rpm/s in 4th gear and I only had 7.5psi boost. With 96 oct fuel I make 380 rpm/s and 9psi boost in 4th gear.

My ignition was only advanced 4 degrees and I was pushing too much W/M.

Likely the fuel played an important role too.

If I use 103 oct fuel instead of 96 oct how much more advance should I give ?
is there a formula ?!

Can a too high octane fuel cause a car severly under performe ?

There is also a limit for the ignition advance.
Maybe next time I should stick to the 96 oct fuel.

 

[Kenny]

First thing, are you sure the 103 was unleaded? If it was leaded, you need to change your O2 sensors because they're toast.

 

[Longhorn94]

Kenny: check your ***. Thanks!

Jason

 

[BIGBADCJ]

Sounds like you got some leaded gas....been there done that....try it again with unleaded.

 

[klamathpro]

Leaded fuel and boost don't go well together from experience. You can do 50/50 of leaded if needed and your problems should go away. My TT Stealth had the same problem as you when I ran straight 110 leaded. Going 50/50 fixed the problem (after 2000 miles of never knowing the cause). And as far as the O2s, I have to disagree, it will eventually foul them up, but it's unlikely that 5 runs fouled them up that fast. I ran 2000 miles on straight leaded with no O2 issues. But.... if you have cats, leaded is very bad for them and can clog them up quickly and kill your performance.

 

[Schulmann]

Fuel was 100% unleaded, poored from a sealed tank.
It was a good try.

I think I had too much W/M and not enough advance.


My O2 Sensors are seems to be in good shape.

 

[Russ M]

While leaded gas is not good for your o2 sensors it will not destroy them in one or even several uses. Dyno's that use wide band o2 sensors change them out around 100 or so sessions, depending on how many pulls each session is.

There is no formula for adding timing, to it is something that should be tuned on a dyno to determine how much you can get away with.

Sounds like your problem is super charger related, fuel/timing cant effect how much pressure you are supposed to have at a certain rpm. Most likely belt slippage is your problem, and it is very common on most blower units.

 

[Schulmann]

I don't think that I have a belt slip.
I have achieved 35% more torque on a 6 rib belt, now I am running with a 7 rib belt.

Definitely my issue is too much methanol along with unsufficent ignition advance.

My question was really related to the 103 octan fuel to know how much it can degrade the performance.

Good try guys but, I need advise on this 103 fuel. Likely it is too strong for my 6.5 pulley.

 

[Russ M]

There are people that know alot more about fuels than I do. However I will tell you my experience with different fuels.

The 103 octane you are using may be a much lower btu than the 96 octane you were using, which would result in higher power being made with the 96 octane. But the difference in power would be very minimal unless there is a very big difference.

To give you an example a long time ago a friend of mine(owner of AEM) bought all of TMS's(Toyota Motor sports) remaining cans of ELF race fuel about 20 55gal drums. He then proceded to use the stuff in every car he owned and tunned. The fuel produced about 20%+ more power than normal 116octane fuels. But it was the fuel TRD was using in their GTP program and he had a feeling that stuff would be amazing.

On my car I use buy Richmond race fuel which was 96 or 98 octane, and it was one of those fuels as well. It had a very high btu, when compared to say VP race fuel. And it was a great fuel for low boost, but just not enough octane for anything more than say 15psi with 8:1 compression.

Hope this helps, or at least leads you in the right direction.

 

[Tom F&L GoR]

If the 103 was really lower btu and the fuel system wasn't making up for it by delivering more gallons, then the engine would be knocking. Was it running lean?

I call [******] on 20%+ more power difference between 116 octane fuels.

It depends on the fuel, but frequently higher octane fuels are much less volatile than pump gas, which is adjusted about every 3-6 weeks for the predicted local ambient temperatures (a fun fact the oil companies deal with provide good starting performance.) Without a volatile component race gas can make cars hard to start. (I saw a Viper at 50F that barely started and would die without revving it. Had to play with the gas pedal for 3-4 minutes until it would stay running.)

Did it start harder and was driveability otherwise different?

 

[Russ M]

Tom,

I dont know what octane the Elf fuel was, or even what was in it. What I do know is it took a considerable amount of tunning to get the stuff to run properly, and it did deliver the power.

There was a reason GTP and F1 made it illegal to use.

 

[Tom F&L GoR]

F1 has rules about the race fuel having to have components that are found in pump gasoline, in order to keep it less expensive and like the "real world." Of course, that meant the oil company sponsors simply dissected pump gas into it's thousands of components and rebuilt it with a different recipe to optimize for power. Testing at Cosworth in an F1 engine - the difference between good and average is perhaps 10 HP. I'd believe the above claim if it were 20 HP, but not 20%. Some would be due to the fuel itself and some due to tuning for the fuel's unusual characteristics.

 

[Paul Hawker]

I believe the reason that higher octane fuel reduces knock is that it burns slower.
If your Viper is tuned for pump gas, maybe the reason for reduced power is that the fuel takes longer to burn in the cyl.
I have seen Vipers running high octane at the track shooting out flames from their pipes. Unburnt fuel?

 

[EllowViper]

Our University vehicle performance team entered a high mileage competition where the fuel all the competitors used was 100 octane test fuel provided by SAE in sealed 5 gallon cans. Not to get into the details of the competition or the power plant used, but to get the potential/benefit out of the high octane fuel, we fabricated the exhaust to enclose the intake runner (post carburetor) to super heat the incoming air charge. Like has been discussed, high octane fuel is not that volatile and for our team to get our evaluated 4th place 1400 MPG, we had to superheat the intake (post Mikuni Carburetor) and tune from there. Pretty neat thinking back on this. High octane is not necessarilly the answer in an of itself.