I will be headed to the Texas mile in October and plan to attend a few drag strips this summer. Since there is no tune for our F is there any benefits of using a higher octane racing gas?? Or will it just make the car perform worse??

Thanks,
Hayden

 

A few of us tried it at the strip and no improvement. Some guys claim that it was actually slower. The guys running NOS see improvement though. So just run 93 octane.

 

Because this 5.0 F engine is direct injected higher octane fuel will likely have no benefit.

Remember:

1. Direct injected engines don't need to worry to much about pre-ignition.
2. Even though the motor is close to 12 to 1 compression, 91 octane is plenty. More octane won't help and might actually slow the car. It might even run fine on 87 octane, although I probably would let someone else try that. The 06 LS 460's had an even higher compression direct injected engine and all Toyota said was that they did not recommend 87 octane fuel.
3. Gasoline is all about BTU's. Lower the octane, usually the more BTU's. More BTU's means more power.
4. Direct injected engines are a big deal. We've needed them for many years. Better fuel economy, more power and more efficient in every way. Way cool and one of the reasons I want one.

 

Actually, the reason High Octane fuel does not make a difference on these engines is because they are tuned so conservatively from the factory that they arn't even at the limit of pump fuel yet. Even with their adaptive learning the ignition (max allowed advance) is still way conservative and well withing the means of 93 octane. I've done pretty extensive dyno testing with the stock ECU and with the ProEFI EMS controlling the engine. The biggest performance gain you will get with the stock ECU is from keeping the airtemps as cool as possible. The stock ECU gets VERY aggressive with ignition retard when the air temps start to creep up. I'm talking 30-50HP losses from mild rises in air temp. So, no, running race gas will not help much.. U may pickup a little power from an oxygenated fuel such as Q16 or MS109 just purely from the oxygenation but thats about it..

And I agree the way the engine is tuned from the factory it probably would run on 89 octane without any issues lol..

DI is definitely benificial in this situation but its not a magic solution to det/knock.. These motors are just super de-tuned. You can still get knock/det with DI, and the ISF still uses port injection for a large portion of the rev range during WOT therefore negating the benifits of DI in those situations.

 

interesting i just though runing with 100 octane would benefit in some way!!! and the car could be slower??? wao

 

It will run on 87. It says so right in the owner's manual. I don't think flogging it with 87 or even 89 is prudent, it get's plenty hot with 93 octane on a hot day, and it's bound to run hotter with retarded ignition timing (underhood temps do impact the IAT sensor). I could tell you a long story about my Supra not liking any fuel less than 93 octane and losing 33% of its normal fuel economy on 91 octane, but that's a whole different engine.

Also, DI has some big benefits for removing heat from the combustion chamber which allows higher static compression, but it's not like you can run 14.5:1 because you've got DI. Detonation resistance is a whole lot more dependent on the squish in the combustion chamber and always has been.

 

I run MS109 with nitrous when jetting from 125-150hp for the detonation protection of higher oct. I'm not trying to make more power with fuel (if it does great), i want to be able to run a larger nitrous shot which does make more power, safely. So if i don't have a computer to retard timing, race gas is cheap insurance with large nitrous shot or high boost in my experience.
I run 93oct with 75-100 shot and daily. Ive driven around with MS109 and notice no difference in drivability. Gain or loss.

 

Yeah, if your spraying it, its always a good idea to run some sort of racegas for insurance.