Is that a bad thing when boosting?

thanks.
-S

 

I'm running a 84.5mm bore and a 81mm combustion chamber. It will cause the engine to detonate easier, but to counteract this i have to bump my timing curves down a bit. Its a 150.00 dollar option from Portflow. I would recommend you doing it, i just did this on my all motor engine with a 86mm bore.


[Modified by boosted hybrid, 12:51 PM 2/15/2003]

 

Hmmm, I did not know this. Could be the reason I seem to be having mild det. problems with my setup. Even when the A/F ratio is spot on at 11.7~12.0, I get "popping" out of the exhaust. I'm running the same 84.5mm bore/81mm head setup. I'm only running 8.8:1 compression tho..


[Modified by Speed PHreak, 2:10 PM 2/15/2003]

 

Well in my case, the head would be bigger than the bore. I am looking at buying a head that has already been opened up to 84.5 while my bore on the block will be only 84mm.

-S

 

You will have zero problems. The .5mm is barely noticable. The 3.5mm difference on my engine is very noticeable of a lip. I wish the head was opened up, but its to late to have it done.

 

My compression ratio is around 8.8:1~9:1 with my set-up. I havent run it yet so i cannot comment on how badly the detonation will occur. Theortically the lip of the combustion chamber will get hot, letting the mixture pre-ignite. Think of it as the carbon build-up holding heat in the combustion chamber, they are associated with detonation.

 

I actually like it there. I do round it off a little bit jsut to take off any sharp edges. I would think it would help coompress everything towards the center of the chamber where it should be. I opened it up on my last motor and i didnt notice a bit of difference.