Going to try and order the bits I need this week. When ordering the Wiseco Pistons what compression ratio should I go for?

 

I tried researching on here and its either lower Comp and loads of loag or risk of det if I go higher.

 

What have people gone for in the past please?

 

Thanks,

 

Ant

People buy the pistons dependant upon size mate and the most common being 87.5mm as the stock bore size is 87mm. 88mm is purchased if the bore are damaged and require a full rebore.

If your buying from a supplier of 300zx parts, that's all the info you need to know.

cheers

smithy

Im going for the 87.5 mm, but from Z1 they are asking about the Compression Ratio as well.

 

I'm also installing the GT28r tubs and larger injecters etc. Would this affect my choice regards to the CR?

 

Cheers,

 

Ant

Gotcha, bloody yanks, lol

Only difference is between the TT and N/A compression wise, though wiseco will to order do a custom one. Never ever knowm anyone to get a custom compression set and i sold em for years :)

So standard 8.5:1 fella. assuming your a TT that is!

smithy

Yep, stick to the standard 8.5:1 ratio.

Gotcha, bloody yanks, lol

Only difference is between the TT and N/A compression wise, though wiseco will to order do a custom one. Never ever knowm anyone to get a custom compression set and i sold em for years :)

So standard 8.5:1 fella. assuming your a TT that is!

smithy

 

Sorry Smithy just to confirm. With my rebuild with bigger tubs, injectors etc... Standard 8.5:1 woudl be fine?

 

Just on a side note, what sort of circumstances would you require to go with custom CR?

 

Cheers again,

 

Ant

Completly and utterly yes mate.

Major major BIG builds would require a custom CR for like massive boost and like i've said, in all the years i've dealt in Zeds,(10 ) i ain't heard a single one in the UK who's done it!

HTH

Smithy

Completly and utterly yes mate.

Major major BIG builds would require a custom CR for like massive boost and like i've said, in all the years i've dealt in Zeds,(10 ) i ain't heard a single one in the UK who's done it!

HTH

Smithy

 

Excellent. Thanks again Smithy.

 

Ant

Go for 8:1

nows a good time to do it will help with reducing the risk of det.

and allow you to run higher boost.

daz.

Go for 8:1

nows a good time to do it will help with reducing the risk of det.

and allow you to run higher boost.

daz.

 

Sacrifices off-boost power and spoolup and not needed unless your looking at really hight boost , ~30psi, which nobody runs....and even then I would alter CR with the Headgasket not the pistons.

 

Custom Piston CR ratios more suited for those looking at High NA Builds and want to raise CR.

Edited March 31, 200916 yr by Yowser

No it does'nt

you wont notice the difference in that way with correct set up.

Yes it does ;)

 

If anything I would personally go the other way...raise the compression and run a little less boost. But in reality stick to the stock Compression. There is no need to lower it for the boost levels being ran.

Edited March 31, 200916 yr by Yowser

I disagree.

If you want room to improve things later on then its a good choice to fit 8's it will give you more scope and reliabilty for the future.

If your not sure speak to a pro.

:)

daz.

...except your never going to run GT28r's over 25psi, and stock CR is fine for that sort of boost (with proper tuning). Therefore you would be making sacrifices for no gain.

Edited March 31, 200916 yr by Yowser

you dont need to run really high boost to gain the benifits from lower comp pistons.

you dont need to run really high boost to gain the benifits from lower comp pistons.

 

If your not running more boost with lower compression then whats the point.

 

A higher compression engine will make more power than a Lower compression engine at the same boost level.

 

Lower compression allows you to run more boost, while sacrificing off-boost and same boost power, lag and to more extreme levels, driveablity.

 

Btw - A 8:1 ratio with 22psi is the same effective compression ratio as a 8:5:1 at 20psi, which is around 20:1 (not correcting for altitude).

Edited March 31, 200916 yr by Yowser

surely the lower the compression the less stress on the engine so the better the reliability???

Well Ant, you certainly got some responces there eh :D

 

Certainly the likes of Cossies who run silly high levels of boost, a lower CR is best suited.

The highest boost i've come across is Mac's at around 30psi.

The average boost level for a 450-600bhp Zed is around 20-23psi.

Your spec is nothing out of the ordinary and in fact as the cost of these cars fall, more people are now doing bigger rebuilds.

Z1 were the company who commissioned Wiseco to do pistons for the Zed and they are probably the most used brand anywhere now.

Off late and to special order of around 3 months, Wiseco for Z1, will do a custom CR for the mega mega high power builds that some are trying to attain in the US.

The 2 top engine builders in the whole of America, Mike smith and Kyle puckett do not use a lower CR piston unless customer specified and even then rarely needed.

None of the other top branded piston manufactures use a custom CR because it's not required.

So finally in short, you will not see any benefit at your desired level or even any other possible level for using a custom CR piston.

Good luck bud.

Cheers

Smithy

I was not expecting anymore responses after my last post :D

 

I'm glad there was a bit of a disscussion regarding lowering the CR just to see what other peoples opinions are.

 

Thanks again,

 

Ant