fiestaturbo.com

[FezzR]

just generally interested on the subject of low compression engines

how they are achived
advantages
disadvantages

whatever you can tell me really to fulfil my lust for knowledge

[Fezzy Turbo]

Low Compression : A basic guide........

Is achieved by increasing the amount space between the piston crown and cylinder head, (where the valves are).
This is done by using lower compression pistons, which are typically forged items from the likes of Mahle, that will also have connecting rods. This will allow more air/fuel mixture to be put into the cylinder, which is very effective for turbo charged cars. Increasing the boost pressure and fuel pressure will then = more power. But increasing boost pressure will only give so much power and is not ever increasing.

Some dodgy ways of lowering compression :

skimming pistons (weakens the crown strength)
Double head gaskets (increases gap between head and block, putting strain on head bolts)

Lowering compression should be done properly first time.

[stu@mdevelopments]

Hi,
Contrary to popular belief we do not generally decompress an engine to fit more air in the cylinders as we could simply increase the boost if this were the case.

The reality.....
When air and fuel is compressed we reach its flash point as compression of any gas/liquid will heat it substantially and all flammable substances have a flash point where they will spontaniously combust.

If we have a condition where we have detonation or much worse.. pre-ignition, we must remove some of the temperature caused by the compression that is causing the explosion in the cylinders.

Its not all temperature related as in some engines we are simply compressing too much gas for the rods to cope and again in this case, we must lower the pressure but to alleviate the pressure on the connecting rod for this scenario.

Low comp = less power for any given cylinder mixture and requires more
ignition timing to light the gas at the correct point due to lower compression of any gas = a slower burn rate.

This is a VERY basic explanation but hopefully it will go some way to satisfying your search for knowledge.

Best Regards,
Stu

[FezzR]

This is a VERY basic explanation

i wont ask again then!
i think ill stick to the basics for a while longer
cheers ppl