When fitting C20LET Pistons for a Zetec Turbo, what compression do they give you?

Thanks

 

I belive on a standard engine its about 7.4:1, but obviously going to need checking on your engien depending on if its been skimmed and to check the deck height in the block at TDC etc.

 

ive never built one,, but i thought it was around the 9:1 area

 

Thats using the N/A pistons i believe mate.

But ive not built one either, im just going from what ive seen on forums.

 

i didnt think it was as low as the 7's - but i haven't built one either

 

Its definately 7.something

They are very low CR in that engine.

 

I have used the N/A forged XE pistons in my ZT and have a CR of 8.1:1 if that is any help.

Most of the extra chamber volume is acieved by a lower deck height on the pistons. Not ideal but it will work for what i want from that lump.

 

The LET ones plus skimming the bollocks out of the block to get a decent deck height are the route i would go down personally if trying to build one on a budget to that CR.

 

Essentially mate yes.


Basically its all about managing peak cylinder pressures.

If you run lots of boost and lots of CR, then cylinder pressure sky rocket and you risk detonation, to combat this you have to retard the timing and that then loses you power.

Its very application specific though, if you are using 108ron fuel you can run high boost and high CR at the same time easily.

Also at higher RPM, because the cylinders fill less effeciently, you can run more boost without needing to lower the CR.

My own LET engine im building is very much like that, 8.2:1 compression and 8500rpm

Where as a cossie tuner going for 500bhp would normally use 7.2:1 and a lower rpm range.

 

I know what you are saying, but the N/A pistons came up at hardly and cost and bloody good nick.

These days i wouldn't even bother with the XE/LET pistons as you have to mod the rods as well. I would just get another custom set from the states.

 

Well with stock rods you have to convert them to fully floating operation.

Depends if your rods were bespoke made for those pistons or are just of the shelf zetec items? They will aready be designed for a fully floatng gudgeon pin but you may need to get the little ends reamed out a few thou to fit the slightly larger LET gudgeon pin.

 

Got a set off XE and Let Pistons here if any body interested? cheap.
Also a Set of .5mm oversize Mahle let pistons, brand new in box.

 

chris S you have pm mate