fiestaturbo.com

[Chetski]

Hello! i dont really post on here very often but seeing as you all seem to know alot more than i do about engines can someone fill me in on compression ratios?


I own a 2002 fiesta zetec-s modd'd with a T25 turbo an other bits. I want to run more boost as im only on about half a bar max. As the zetec-s is a "high compression" engine as standard what would i need to do to change it?

Do i need to raise or lower the compression ratio to get more power?

What is it at standard an what should it be if i moddified it?

i dont want to bore the engine as its alloy with a special coating im told it would seriously damage the valves; so would i need to use a thick head head gasket to lift the head up slightly if so is this reliable or just a bodge job way of doing it?

where can i get uprated pistons from an what spec would they need to be?

would the care be reliable if i change the compession ratio, i dont want to have a rebuild every 5k miles!

Thanks Chetski

[snake]

Hello! i dont really post on here very often but seeing as you all seem to know alot more than i do about engines can someone fill me in on compression ratios?


I own a 2002 fiesta zetec-s modd'd with a T25 turbo an other bits. I want to run more boost as im only on about half a bar max. As the zetec-s is a "high compression" engine as standard what would i need to do to change it? depends on boost u want to run, low comp pistons may be available, but they will end up with thin crowns, not wot u want for turbo application, best bet if your serious is custom pistons and stell short rods made to spec. pistons u have at the mo aint forged and cannot run high boost, esp with comp ratio u are runnin

Do i need to raise or lower the compression ratio to get more power?
lower compression to run more boost

What is it at standard an what should it be if i moddified it?
standard is 10.5-1 i think, mite be 10-1, wot comp ratio u want depends on how much boost u want to run, and how much u are prepared to spend-ie intake coolers, fueling, mappable chip

i dont want to bore the engine as its alloy with a special coating im told it would seriously damage the valves; so would i need to use a thick head head gasket to lift the head up slightly if so is this reliable or just a bodge job way of doing it? think head gasket, spacer plates are bodges, urm how can boring the cylinder slightly damage the valves lol, but yeah stick to the bore.

where can i get uprated pistons from an what spec would they need to be?
depends on wot power u want and boost u want, quite a few companies out their who do this, rods i can get made to spec

would the care be reliable if i change the compession ratio, i dont want to have a rebuild every 5k miles!
only as reliable as the person who builds the engine

Thanks Chetski

[Chetski]

snake - whats the point your tryin to make?

[AdrianFRST]

Not sure if you missed it, I did at first thinking he had just quoted your message, but if you look closely he's answered your questions.

A very lazy way of replying!!

I've made his answers bold now.

[Chetski]

oohhh right, cheers!

[snake]

lol, oopsy yeah was bein lazy

[Chris_H]

Why do you want more boost? To show off a swinging needle to your mates?

Lower the CR to enable more power on a turbo but at a cost.

If by bore the engine I assume you don't mean reading it newspaper article but to increase the capacity you will only serve to increase the CR if you retain similar piston design and standard CC volume.

Thicker head gaskets, spacer plates are a bodge, yes they will enable you to run more boost and may give you a higher output, but the squish area will be opened right up making the car less driveable.

Proper way to lower the CR is to enlarge the combustion chamber, few ways you can do this, you can open up the chamber in the head which on pent roof 4 valve chambers isn't easy or dish the piston.

Piston spec, well it will need to be a dished piston (not a standard one skimmed) this allows you to retain a nice squish area, you also want the top ring to be further down the piston.

[Chetski]

Chris_H

you seem to know what your talking about, i was wondering where i could get more information about it an any places you know off whos good at this kinda stuff?

much appreciated!