I was wondering what octane fuel you guys recomend for the car in sig
I compression ratio is 13.6:1
I am running 110 unleaded right now but would like some other thoughts

thanks
Dave

 

You have to base fuel selection on the dynamic compression ratio (DCR), not the static compression ratio. Have you calculated your DCR? Part of tuning an engine like that would be to try various combinations of octane, ignition advance and A/F ratio to find the one that optimizes power.

 

we didnt try other octane fuel but I think ther airfuel is a touch rich but very flat curve and 34 degrees timing seems to make the most power

as far as dcr I have no idea

 

Why did you start with 110 unleaded? What 110 unleaded are you running.... I couldn't find anything over 104, until a couple weeks ago when someone posted a link to an obscure source of 110. Why are you using unleaded? Did it show signs of incipient detonation on the plug insulators when you advanced the timing with the 110? Air race fuel is typically highly leaded.

There are online calculators available for DCR.

 

I am using unleaded due to the o2 sensors I am still using

http://www.proracingfuels.com/Product_MARK3.html
they have 114 unleaded too

http://www.proracingfuels.com/Product_MARK5.html

 

Since your car was tuned on the 110 I'de keep running that fuel.

 

Put a small amount of 92 in it and see if it rattles. If your DCR is 9.0 or lower it shouldn't.

 

How much RWHP does it make?


David

 

how much is a small amout.If I put a 5 gallon pail of 110 how much 92?

451 rwhp@7400 with the A3

 

Run your tank down to close to running out. Then put 5 gal of 92 in it.

 

then if it does ping just add a 5 gallon pail of 110 and a octane boost?

 

 

I use the Torco accellerator and mix it to 104 and have had no problem at all, of course I only have 12.0 cr.

Randy

 

I was actuall thinking of using a 50/50 mix of 94 and 110 anyway or 50/50 114 and 94

the 110 is expensive here 18 bucks a gallon

 

That won't tell ya if it will run on 92. Isn't that what ya wanted to know?