Hello,

 

I've completly rebuilt my engine with wiseco 87.5mm forged piston.

My compression are now 9.5:1

 

As I will change the turbo for big Greddy or HKS, I've been told i need to lower the compression ratio.

Is that right?

Why?

And how can I do this?

 

Thank you

are you sure its 9.5:1??

 

Wisecos are 8.5:1 for a TT engine IIRC?

 

you need a lower compression ratio to run higher boost pressures.

A higher compression ratio will give more power at 0 or low boost pressures, but the benefits soon become outwieghed by the power gains at higher boost levels.

 

HTH

but how to reduce the compression ratio?

I took my self the compresio with hot engine.

one off head gaskets to lower comp level

you mean a thicker one?

if you can get them for the zx

I dont know if you can so you might have to get them made up

metal head gasket. I have a tomei 1.6mm, but that is more to do with my bore size

or you can get the heads polished/ported and the compression dropped at the same time

There is something wrong here.

If I go with a thicker head gasket, this mean i will increase the distance between pistons and head.

And if I go with polished head, so I will decrease distance between head and pistons...

 

Which one is the good? I would bet on the metal head gasket :d

There is something wrong here.

If I go with a thicker head gasket, this mean i will increase the distance between pistons and head.

And if I go with polished head, so I will decrease distance between head and pistons...

 

Which one is the good? I would bet on the metal head gasket :d

i dont think he meant the flat surface more like the dome area

The gasket is the easier route as doing the head will mean a bit of valve work as well if you are gonna change the compression area that way

>> My compression are now 9.5:1

>> I took my self the compresio with hot engine.

 

How did you measure your compression ration ?

since this is quite complicated and involves measuring/calculating the total volume of the cylinder and combustion chamber above the piston at BDC, divided by the combustion chamber volume above the piston at TDC.

For this you need to have the engine apart, so I'm not sure how you were able to do this "with hot engine" ?

hope this helps

Thicker head gaskets aren't always a good way to go. Although you decrease the compression you also increase the squish clearence and can sometimes end up with a worse detonation problem.

OK, finaly I just connect like a pressure reader into the hole of each sparks plug and record a value.

But from TTnet, they said this is wrong and also Wiseco forged piston are 8.5:1

so finaly, there is no problem, I can boost up :D

you also increase the squish clearence and can sometimes end up with a worse detonation problem.

 

will changing plug size make any differance? as if you go for a thicker gasket and your increasing the gap between each spark,thus decreasing the chance of detonation

will changing plug size make any differance? as if you go for a thicker gasket and your increasing the gap between each spark,thus decreasing the chance of detonation

 

Sorry, don't quite understand what you mean?

Sorry, don't quite understand what you mean?

 

if your going for a thicker HG! as you say your increasing the chance of det

 

but if you change the plug for a differant type,surely you can overcome the problem or at least reduce it

 

does that make sense :D

A colder plug will help only to the point where it is no longer a hot spot in the chamber, after that it just makes cold running a pig.

You can't do much with no squish, it just messes up the way the combustion proceeds in the chamber. If you can imagine the squish area is used to drive all the mixture towards the centre of the chamber, it completely changes the way the combustion happens.

A colder plug will help only to the point where it is no longer a hot spot in the chamber, after that it just makes cold running a pig.

You can't do much with no squish, it just messes up the way the combustion proceeds in the chamber. If you can imagine the squish area is used to drive all the mixture towards the centre of the chamber, it completely changes the way the combustion happens.

 

cool[no pun intended] :D