just curious how many of you run race gas? and how long it usually takes for the porsche IST system to change tunes automatically when running race gas.
thanks in advance

 

In a stock car, using race gas won't make any difference. Even in very hot climates you probably won't see much (if any) power increase.

If you're talking about an aftermarket tune which can advance timing enough to make an increase in power, then I would say the ECU corrects it pretty much as soon as it notices less knock.

Sometimes the best thing to do is disconnect the battery to clear the saved (for lack of a better term) "timing data".

 

Jesus Christ!!! If you can kill a mezger engine, than its with this method. With race gas and high octan lebel the gas air mixture will run lean instead of rich which means the engine gets way too hot. The Ecu must be optimized for race gas, orherwise you can soon say goodbye to your engine.

 

the car has been modified with hydrid K24/26 turbos, intercooler, pump, injectors...etc etc..The tuner informed me that the ECU will adjust automatically he also has recommended running race gas if I am going to be racing it.. this is what prompted my question. currently hitting an easy 1.3 bar on pump gas and sometimes seeing 1.4 bar depending on conditions...

 

Phew. Thats good news, cause its a must to have different gas pump and injectors when running low energy gasoline with high octane. But if i were you i would check the lambda data.
Well my knowledge comes from the E 85 here in Europe. Race gas has how much octane 120?
I would be cautious.

 

Thanks for the info I appreciate it. The race gas here is between 110 octane and 116... I have already tried a 110 mixed 50/50 with 91 octane. but it was throwing an O2 sensor code on both banks. A friend of mine suggested it was probably due to the race gas being leaded and that the Porsche o2 sensors don't like the lead in fuels... unfortunately I am from Canada and we do not have E85 here.. next year I would like to try some unleaded race gas, but just want to make sure the car and tune will do what it needs to do.

 

Do you have a cat-less exhaust?

 

no I don't think so. is the cat immediately after the turbo?.. sorry still new to Porsche haha trying to figure everything out.
it is a Tubi titanium turbo back exhaust I believe.

 

If you used leaded gasoline the O2 sensors are probably not in good shape. The front sensors are wide band used to more precisely fuel the engine.

I would be sure the tank is empty of any leaded gasoline and replace the #1 sensors at least, if not the #2 sensors too. Also, I suspect the converters could be poisoned but change the sensors first and see if they flag converters problems.

The DME will adapt to the higher octane fuel immediately. It adjusts constantly as you are driving the car adjusting timing and fueling to suit the immediate needs of the engine while attempting to meet the torque demands signaled by the e-Gas system.

There can be some benefit to running (unleaded!) race gas even if the octane rating is quite a bit above the nominal octane needs of the engine.

For one thing an engine's octane requirement can go up over time. Thus if the engine nominally required 93 octane it could after time require 94 or more to use max advance.

Additionally race fuel has different burning characteristics which can bring with them improved performance over and beyond what benefit there is from the timing being optimum.

My advice would be at the track to try a tank of (unleaded!) race gas and see how the engine performs. Then try a tank of say just 93 or whatever octane of fuel your engine is tuned for to see how the engine performs.

If you notice any positive difference with race fuel compared to 93 octane then use the race fuel if the increase in performance is worth the added cost. We're taking track only here. If you do not notice any increase with race fuel over street fuel then at least you know. I'd still use some race fuel to bump up the octane a point or two just to give the engine some extra margin against detonation on the track.

 

Very helpful thank you. I am no longer getting any engine codes and the Wideband is still reading as it always did (the car has a Brockview engineering engine monitor installed) should I still consider swapping out the 02 sensors? the most I put into the car was a 50/50 mix with unleaded pump gas. I guess the key is to get unleaded for my next attempt haha

 

This is just bad information. Higher octane gas will not lean out your engine. The gas is simply harder to ignite, reducing the chance for detonation. Interestingly a lot of people think their car will be faster on say 114 octane race gas, but because the ignition system isn't sufficient to ignite the higher octane fuel, the engine will misfire badly causing a big loss in power.

In high temperature weather, even a stock car will probably make more power with 100 octane unleaded (US rating not European). Our 93 octane will usually cause enough knock (detonation) on hot days for the stock ECU to pull some timing. The higher octane will reduce the knock therefore maintaining optimum timing and maintaining a higher power level.

I guess you could say the higher octane fuel doesn't actually give you more power on a stock car, it simply stops your car from losing power due to timing retardation.

You don't need a tune to run higher octane fuel, but your engine will not optimize the higher octane fuel without a tune.

Later, Steve

 

This is true. One caveat is oxygenated unleaded race gas might run a bit lean if not tuned for it, AFAIK. But "regular" 100 or 105 octane unleaded race gas won't hurt and might help.

 

^^ This is A+ info ^^

the only downside to higher octane is most engines may actually produce less power because of ignition angle and the requirement to burn quicker/better on the higher octane

you will not BLOW an engine on it though, quite the contrary

Also, I have been doing a lot of RD on E85 down to E20 etc... if anyone wants a nice paper done by a racing team on the joys of even moderate quality Ethanol please feel free to PM me........ sadly I saved it on one of my other pc's which I destroyed in a fit of rage today because I covered my stock shorts too early

 

The octane is just one thing. The important thing is how much air you need for the gas to get the right mixture. You need to know, if your engine runs the way it was build for or not. Rich mixture or lean mixture, means if the lambda is bigger than 1 or lower. The turbo engines run at full throttle a very rich mixture of around 0,85 lambda, means air insufficieny. If you change the gas to high octane (means lower energie), you need more gas per combustion to get the rich lambda data of 0,85; thats what the ECU wants. With the stock pump and the stock injectors you reach the conveying capacity of the gas.
So the engine and ECU want more gasoline per combustion but the fuel system cannot deliver it. Thats the killer. The lambda will get up to lambda 1,00. Thats good for an aspirated engine not for the turbo engine.

Albertaporsche has already an adapted fuelsystem, cause his turbochargers can get so much air inside the engine that the stock fuelsystem cannot deliver the right amount of gas for the lambda 0,85. So in his case it can work without a problem to use race gas.
In a not fuelsystem modded turbo its highly dangerous.

So take care with these special gasoline typs. The normal ones are not a problem.

 

I think I understand.. and thanks to all who responded... not gonna lie though not sure what you mean by "lambda"...Any other car I have ever owned never would auto tune to the octane level that is another reason I am asking the question.. completely blows my mind..