what the pros and cons reason is........


We race Saxo VTR in our championship were not allowed to put any aftermarket internals in the engine but can skim heads and use different Engine managment.

Now i always thought if you can get away with it get as much Higher Compression as you can safetly do.

been speaking to engine builder and they said the best way is to use a non skimmed head ie std thinkness??? why would this be?
do you lose torque?

 

IIRC raising the compression will normally boost performance but you need to run higher octane petrol otherwise you'll get detonation. With lower octane fuel the combustion temps will go through the roof and destroy the exhaust valves

 

we use 99 ron! but just cant see why the builder says the standard thickness head is better

 

maybe he thinks that decking the block is better.
whatever his reasons are, ask him.
IMO to get more power out you need to up compression and alter fuelling. this however could cause issues with rods not being handle the extra stresses that could result in raised compression.

 

be careful my mate raised the compression to much on his 1700 crossflow and it had to be retarded on 99 petrol, needed race fuel to run properly which it wasnt intended for !

 

As indicated raise cr can give more power, but depending on head/piston design etc could vary from one type to another, raise it too much though for the type and you will have to knock back the timing losing power.
tabetha

 

Are you permited to use power pour(fuel additive)? If so then whack the compression right up then starting ramming in big ignition..... and prepare yourself for a few rebuilds during the season.

 

If your head / combustion chamber are not designed appropriately, and you thus end up having to pull back timing, you will use more fuel than you would in an engine running a lower CR but more advance. So same power (or maybe even less), but more weight = bad. Speak to a pug engine builder about it maybe?