(T) Maximum Compression?

Right, after hearing that I can boost the power by changing the CR, Ive been thinking:

A. Raising the CR means charge temp is going to be higher so it will inevitably preignite - but this can be solved so is no major deal.

B. The raised temperature means a higher likelyhood of melting pistons etc...

So with this in mind, whats the highest CR I could use without making engine conditions too warm? Is 11:1 too high? I suppose If I burretted the head I could actually calculate that...or, has anyone already done it?

Do you plan to cure the pre ignition by retardign the timing?

Liam

Nope...using a higher octane fuel.

at £4.00 per litre!!, you are completely barking

Cheers

D

He probably means optimax.

Yeah...Optimax /98 RON fuel is something like that...

Wasnt thinking 110RON racing fuel... Cant source that easily let alone afford it!!

Digging up an old thread, but....

Doing the head gasket on my cinq 1.1 this week. Getting the head skimmed.

Question is - how much is enough to take off and how much *can* i take off in respect to raising the CR?

Played with the CR and squish bands in bike engines, but these car things are new...

the head has a marking on it for the max skimming allowed if thats any help

is a bit more complicated then just asking what cr you can run on an engine, there is alot more that come into play eg cam for a start, the only real way of finding out is to find out what they use on say race engine, but most the time there are rules in racing that dont allow a lot of stuff or try it and see, you can always put lots of octane booster in if it does pink which it prod will. or use avgas but your not allowed to us that on the road

You can go over this mark by at least 0.25mm. Also you can take about 0.5mm off the block or alternatively use the new metal gasket Fiat supplies now using the 886 cam.

If you are willing to pocket the pistons a bit deeper than standard you can skim even more off the head.

Only drawback is if you go over the maximum skimming marks you will get into problems with the standard belt tensioner and it would be advisable to use a vernier pulley.

also isnt the max marking the point at which the non interfierence charecteristic of the FIRE engine is at risk? as if you skim past this that could be a risk? (in theory, i dont know for sure)

Most probably. It'd seem to be the most sensible explanation IMO

DO NOT AND I MEAN DO NOT skim the head. Use the 0.6mm metal gasket from the new Grande Punto instead...

Why not?

Because metal headgasket is thinner and more durable. Fat headgaskets are more prone to failure...