Shaving heads

spetz · Post by **spetz** » Wed Jul 05, 2006 3:24 pm

How much is it safe to shave off the MIVEC heads?

I had 20 thou taken off, thinking about bumping it to 40 thou

PS. What is that in mm?

bobz · Post by **bobz** » Wed Jul 05, 2006 4:49 pm

Detonation city unless you run good petrol and might have to think about retarding the ignition.....

40 thou will give you 12:1+ compression?

BobZ

spetz · Post by **spetz** » Wed Jul 05, 2006 6:11 pm

Can't be that much?

I got 20 thou done, and according to the engine builder, it will be closer to 11:1 now

Honda's run up to 13:1 CR on street cars?

But yeah, maybe leave it at 20 thou then just in case

bobz · Post by **bobz** » Thu Jul 06, 2006 1:55 am

spetz wrote:Can't be that much?

I got 20 thou done, and according to the engine builder, it will be closer to 11:1 now

Honda's run up to 13:1 CR on street cars?

But yeah, maybe leave it at 20 thou then just in case

Which ones in Aus?

BobZ

Post by **Bennoz** » Thu Jul 06, 2006 10:32 am

13:1!! Hope they run Av-gas....

spetz · Post by **spetz** » Fri Jul 07, 2006 2:26 am

Maybe not as far as 13:1 but 12-12.5:1 they do run

On normal petrol

THough apparently honda heads have water running through them and can handle more heat?

bobz · Post by **bobz** » Fri Jul 07, 2006 11:53 am

12.5:1 is reaching the limit of 98 petrol.

Also those engines have a very sophisticated any knock system that can retard the timing to redicules levels to stop detonation.

All water cooled engines have coolant passages in the head, thats where most of the heat is. Too high a compression has nothing to do with too much heat its all about detonation or pre ignition, where the mixture starts to burn prior to the piston reaching TDC and trying to push the piston down as the crank is still pushing the piston up. Not a pretty outcome.

BobZ

spetz · Post by **spetz** » Fri Jul 07, 2006 2:59 pm

I could imagine

How come then, the 6A12 has 10:1 CR?
The 4G92 has 11:1

I thought 10:1 was still fairly low for an everyday street car (as far as high performance NA goes?)

bigpitty1 · Post by **bigpitty1** » Fri Jul 07, 2006 6:27 pm

you could just bump the compression ratio up to around 15:1 and then you could make your fto run on diesel

spetz · Post by **spetz** » Fri Jul 07, 2006 8:01 pm

Yes!
I could!!

But believe it or not, I wont!

Post by **Bennoz** » Fri Jul 07, 2006 8:13 pm

lol! but then you'd lose your nice iridium plugs & be off buying glow plugs!

spetz · Post by **spetz** » Sat Jul 08, 2006 1:29 am

That would probably be the last reason not to do a diesel conversion that I would be worried about