I was under the impression that flashes are specific to the octane. Ie different flash for 91, 93, 100 etc.

Do you use the same flash for any octane you put in?

 

I'm NorCal. More specific please!

 

ive ran 87 on my car on several occasions just to see if there was a difference, my car is modded and all. not a single issue. nothing.
my ecu is flashed for 93 octane.
car still boosted and held boost at 1.2-1.3 bar no problem.

 

you can run higher octane than what your flash is for but you should not go the reverse like Steve below did.


didn't you have engine failure once? hmmm

doing stuff like running 87 octane with 1.3 bar will sure get you a new motor. That's like turning up an EBC without adding more octane. Definitely not recommended.

 

muker i bought gas there about a month ago it's just over the hill from the sharkwerks.. across the freeway fron sunol golf course,,,,

stop at sharkwerks get a tune go to sunol buy gas does it get any better?? guess you should get the 100 oct before the tune..

 

I disagree. Programming (decent programming) will compensate for lower octane, sense incipient knock and pull timing.

Dr. F. I did already- post 11. A few miles north of PA.

 

nope it wasnt engine failure
we thought it was a lifter, but in fact it was an exhaust issue

 

What kind of issue?

 

nothing major at all. metal was rubbing against metal from one of the clamps that goes on the cat bypass.

 

caused by low oct gas no doubt.... ok i guess not

 

Really? So you think your ECU can pull timing fast enough at WOT 6000 rpm's to save your engine? you willing to stake your 30k engine on that one? you willing to stake your engine on your O2's giving the correct reading under extreme conditions?

and even under normal conditions, why would anyone want their ecu to pull timing and give them less power, which is what happens? to compensate for their stingy wallet? I don't get it. People buy a high end performance car and stick crap fuel in it? why?

I know of one car that ran 100 octane file with 91-93 pump gas and raced. He had serious engine issues. He's on this board. And he didn't even have an EBC which overrides safety controls.

 

I don't code DMEs, so I do not feel totally versed in this issue. BUT, I've discussed this issue with two people on two different models who HAVE,

Timing can be pulled VERY quickly. VERY. Once a functioning knock sensor gets the slight vibrations telling it there is a hint of pre- detonation, the timing is pulled. Within one engine rev.

If things are really bad, the injector duty cycle is bumped up to add gas and cool the charge, and the boost is bleed down...(or if you have an external BC, the motor is stuck dealing with overboost, Say "boom'?) This is all done in small increments and based on the degree of the issues detected.

Having said that, I agree one should not use crappy gas, and one should not risk an engine....fine, lets get past that. The truth is that driving around more than 20 miles from your home garage with a barrel of 109, you may find your tank octane fluctuating based on the need to re-fuel. You need to be able to deal with this rationally.

I am not talking about buying regular 87 gas and letting the engine deal with it so as not to pay those 'high prices' of "super" at 91!

I TOTALLY agree that once you load a tune with a designed octane above stock (ie a 100 octane tune) you do not want to use 91 or even 93. There is a range over which the DME can accommodate octane variation, and 100 down to 91 likely over-reaches that range. I have a 100 file and only load it when I know I will have 100 octane in the tank for the whole time.

A

 

I agree, I have been looking up stuff on the internet and I am shocked at how many hiperf car people are using 87 craptane. The general consensus is that the 87 is faster burning fuel so puts out more energy. WTF.

I have a 91 file and I run 91 with a few extra gallons of 100 for safety measure mainly to compensate for a bad batch of fuel which I have had before. I have never run 87, nor will I. But if you are not boosting I guess it is ok.

 

My EPL tune is specific to 91 octane and my elevation. Of course elevation really helps the octane issue quite a bit.

 

My car has a custom tune for VP MS 109. I can not run a lower octane gas with this race gas file. As it has been stated above, never run 91 with a race gas tune. You must have a race file to get the performance out of a higher octane gas.