Compression ratios

[Jazz9]

Hello, im looking to find what compression ratio a gze block with wisco pistons would be. This is all the info i have - with 300odd deg cams and a few other bits it made 126hp atw ....



Glen

i found some more specs

4AGZ steel crank, 4AGZ steel rod's, Wiseco forged Pistons, balanced, blue printed, ported 4Age head, ARP head studs, Copper head gasket, stainless steel valves, billet cam's, ARP Rod bolts, ARP main stud kit, EMS Stinger after market computer

[nanes]

hey mate,

your actual compression ratio is the relationship between the total volome of the cylinder, head gasket and cumbustion chamber with the piston on Bottom Dead Centre, and the volume of space between piston crown, head gasket and cumbustion chamber at top dead centre.

formula:<div align="center"> comp ratio = cylinder volume + cumbustion chamber volume (including hg)
cumbustion chamber volume</div>


so we know that your cylinder volume is 400cc,

and i think the cumbustion chamber of a 4age head is 39cc but i could be very wrong and if whoever ported your head modified the cumbustion chamber than the volume may have changed anyway.

so we dont know the actual volume of your cumbustion chamber, we dont know the volume above the piston crown at tdc and we dont know the thickness of the copper headgasket it uses,

so unless you can open your engine and measure all of these things acuratley than no one on here is going to be able to tell you exactly what your compression ratio is.

to measure your cumbustion chamber volume you need to use a burette and cover the chamber with glass or clear perspex that has a hole drilled into it, then fill the chamber with liquid paraffin (kerosene). measure the amount of liquid it takes to completley fill the chamber and that is you volume,

same thing for volume above piston, but you need to seal around the piston with grease, also do this with a compressed (used) head gasket to take that space into account.

although this may not help you to know your comp ratio immediatley, i hope you can understand and when you deide to rebuild your engine you will know how to work out your comp ratio.

thanks
James

[Jazz9]

Thanks for the quick reply - I didn't think it would be easy to find the compression ratio......

I think the wisecos are 10.5:1 - I might just pull the current HG out - measure it and then put a thin TRD one in.... That should bring it up a bit!

What do you guys think of 126hp @ 7800 at the wheels ? what is needed for much more ? it started to drop off power past 8000 or so - might get the dyno graph up soon


Glen

[biggo]

126jp at 7800 is piss poor, youd have more luck with a standard gze, unless its a ge?

my 20v made 122hp at teh wheels at 8000 but it was still making power

either find out why its ghey or go to another dyno

[rthy]

duno figures cant be directly compared, theres one near me that a fully tuned 20v will read 75kw when at other places they are known to get 90kwatw

[nanes]

yeah exactly what sam said,

if your using dyno figures as bragging rights or to compare against cars tuned on seperate dyno's on seperate days, then your missing the point.

to get any use out of dyno tuning you need to use the same dyno each time you make a change to compare improvements you have made to your car not to compare how much kw you have compared to your mate

dyno's are designed for tuning,

dyno's are not consistant between workshops,

environmental variables are also inconsistant between dyno runs.

thanks

[rthy]

well said james

[Jazz9]

This is a NA car --- not gze or gte

hmm, I was thinking that it was a bit low for the almost 300deg cams - i wonder what is stopping it making more power ---

Why would it not make more power over 8000 ? is it compression ratio too low?

Glen