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I've tired various octane boosters to stop pre-detonation on non computer controlled carbureted cars, it didn't even reduce the detonation.
5 gal of 91 to 1 gal of leaded 111 fuel which I have plenty in my garage stopped the pinging even on a 100F day. 5 to 1 gal of 111 should yield in the neighborhood of 94 oct. Old cars are primitive, air fuel ratio will vary a bid depending on ambinet temperature but timing is on a set curve, remains unchanged. Variable is the fuel, if I can achive 94 octane by blending race fuel vs two bottles of booster in the tank won't do anything what does that tell us?
On my GT3 I prefer to blend 5 gal of 100, having said that if there is non available I rather drive on our crappy 91.
I just want to clarify that you're suggesting using 100 unleaded. Not leaded...
I agree that the GT3 should not detonate on 91 octane, even under extreme conditions. But the way the GT3 ensures its survival under those conditions is to retard the ignition timing (safe for the car, but you lose some power and throttle response). So ideally, adding a little race fuel should theoretically be a benefit.
After reading this thread, I started looking. There are stations that sell the fuel from the pump and many places that sell them in 5 or 55 gallon drums. For this round, I mixed 5 gallons of 100 octane with 17 gallons of 91. I really think I can tell the difference, do I? That 5 gallon drum cost me $72.
I think someone may have posted this already, but this site lists all the CA stations that sell race fuel.
Most could not detect the faint noise of knock in a modern car like the GT3. ECU intervenes prior to loud, real knock.
Just because you can't hear a pronounced pinging, doesn't mean it's running "well" on 91. No high compression NA, or high performance turbo engine will run CA 91 octane without being forced to retard timing due to knock. I blend 91 and 100 in my GT3 whenever possible. When I'm forced to run straight 91 octane, there's a measurable difference in output, as well as consistency of power delivery.
It's just too bad that with Posrche you can't log knock strategy.
Last year I spoke with their tech department a while back, and they told me that in addition to boosting octane by up to 30 points, this formula also includes a detergent to keep combustion chambers clean, which reduces OR (Octane Requirement) so this provides additional benefit. I've used it with 91 octane fuel ever since, with great results.
Yesterday I put in 5 gallons of 100 octane and 15 gallons of 91 octane, which almost filled the tank on my .2 GT3 Touring. Within 3 miles, the minor detonation I was experiencing on initial throttle tip in was eliminated. This was on a mid 80 degree day, so I'm pretty happy with the results. The 100 octane was $7.75/gallon, and the 91 octane was $3.79/gallon, for a total of $95.81 to (almost) fill the tank. I didn't notice any improvement in performance, but I'm still breaking my car in, plus didn't have an area to open it up. Hopefully will this weekend.
I just want to clarify that you're suggesting using 100 unleaded. Not leaded...
You shouldn't use Leaded, unless you get rid of the cats first with Dundon Race Headers or similar. Even then, Lead is pretty nasty stuff (officially, there is no amount small enough in your body that is not a health risk)...
03-30-2018, 10:15 PM
