I've been wanting to run my car on higher octane fuels to increase the boost and timing at the strip. Last weekend I was in San Antonio racetrack and the gas light was on and I pumped 4 gallons of Torco brand 108 in my Evo but it knocked more than the 93 octane Shell that was in the car prevously. I didnt even get a chance to raise the boost or timing because immediatly after putting in the 4 gallons it started knocking > 4 counts of knock all over the map that was running knock free on 93.

So, any ideas here? I wanted to try some C16 but they were out so I got the highest octane unleaded instead.

 

you need to raise the boost.... If mix is too rich ill cause the same affects with knock as being too lean...

28 pounds would have cured your problem

 

ok, I'll try again.. thanks. I just thought maybe I had some old fuel or something and that's why it was knocking like crazy.

 

if you're self tuned you should have known the effects of higher octane fuel on your current tune. make sure to adjust your maps and boost accordingly for the slower burning fuel.

 

nice to know this, still learning myself.

 

Well the thing is that it did not richen me up any, I have a wideband and was prepared to modify the map at the track. Still 12.5 at peak torque to 11.1 by redline. Also, everything I've read pretty much says that additional octane only prevents detonation. It does not necessarily speed up or slow down the burn rate.

IMO There is no reason why adding 4 gallons of 108 should have caused substantial knock when it wasnt knocking on 93. In fact I see often when people are experiencing knock it's suggested to put race gas in to see if it's false knock or real knock. Next time I'll experiment a little though.. but I'll tell you if it's knocking I think it's unlikely that added boost and timing are going to reduce the knock counts.

 

Going from pump gas to race gas shouldn't richen you up especially with the specific gravity change on most race fuels.

I can tell you that unleaded fuel goes bad faster than leaded fuel. Back in the day I would run street blaze 104 and that crap wouldn't last for more than a month in a 5 gallon container. It also didn't even come close to performing like 110 leaded does. My 110 leaded turbo blue will stay in tip top shape for months in the same container.

Odds are you got bad race fuel. I suggest running the leaded stuff. No need for C16 unless you run crazy boost. Just get the middle of the road 110 leaded and you'll be fine at high boost and +3* timing. Don't let the P[]ssies on this forum scare you into thinking it will instantly kill your O2 sensor. I ran well over 100 gallons through my 03 and run it 24/7 in my 06 (50/50 mix). I lost track of then number of gallons I ran through my DSM and never had a problem.

The 110 normally sells for $5/gallon. If you mix it 50/50 with 93 you get 100+ octane for $4/gallon. You can't beat that.

 

Thanks Jeff, What your saying makes perfect sense. I'm guessing that the 108 unleaded had lost it's octane or something for it to knock nasty like it was. I'll give the leaded a try next time for sure. I just want to up the boost from 24psi to around 28psi and I'll add 3* of timing and log that.

 

For some reason I am weary about getting race fuel out of a pump from the ground. When I get my fuel its usually in a sealed container

You running the stock turbo? IMO I think c16 is too much on the stock turbo. I am a fan of the VP c12 leaded on the stocker