416ex with 11:1 wiseco.... 91 octane gaz....

[Buffalo400]

HI
My motor is in rebuilt right now and do you think 91 octane gaz will be fine with a 11:1 87mm Wiseco piston in my 400ex?

the problem is there, in Canada, the highest octane gaz is 91 octane.... Should i buy octane booster to prevent motor pinking.....

thanks!

[GPracer2500]

I'm in the same boat--91 is as good as it gets at the pump. I'm running 10.8:1 and I get some detonation under very high load, high temperature, low elevation conditions. I tried an octane booster and wasn't impressed with the performance of that particular product--it didn't help.

If your running a aftermarket CDI or timing timing key than the problem will definitely be worse.

Mixing 1 gallon of race gas to 4 gallons of pump gas (or some similar ratio) will probably get the job done. But try it out with straight pump gas and see what happens. A little mild detonation here and there isn't going to destroy your engine. It's not good for it (hurts power and builds up heat) but it won't kill it in a hurry. Heavy detonation that won't go away IS cause for immediate concern.

If you run in cool temps and/or higher elevations than you may get away with little or no detonation--you'll have to test and see.

Note: the reason elevation makes a differance is because the less dense air of higher elevations affects the dynamic compression of the engine. Take a compression reading at 500ft and one at 5000ft. You'll have more compression at the lower elevation. In some cities that are at high elevation, the lowest grade of pump gas is 85, not 87 (Colorado Springs, CO is an example--around 6000ft). This is because everyone's engine is producing less compression at that elevation so the octane requirements are not as demanding.

[Buffalo400]

ok, Thanks... So, I will try with octane booster and see what happen..... Also, I will try to find some cheap race gaz....

What do you think about air plane gaz?

thanks

[GPracer2500]

Originally posted by Buffalo400
ok, Thanks... So, I will try with octane booster and see what happen..... Also, I will try to find some cheap race gaz....

What do you think about air plane gaz?

thanks

100LL mixed 50/50 with 91 pump would most likely be a good idea. I'd rather do that then use most octane boosting products (I *think* there ARE a few good ones but lots of bad ones). Plus the av fuel has the added benefit of being leaded.