Hello everyone,

I am trying to understand and find out what compression I am currently at with my build?

ITR head No milding ITR valves
OEM head gasket

GSR fully built block sleeved and rods
GSR Crank
JE 11:1 84mm bore pistions

I know it would be 11:1 if I had a GSR head and block combo but since the the ITR head chambers are larger compared to a GSR this would lower compression...correct?
I was told I would be about 10:6 but since I am bored to 84mm this should bring me back up to 11:1 ???
I dont think me being bored to 84mm would raise my compression back to 11:1 because when JE designed the pistion they were factoring that in already, being 84mm bored.

Can someone help me understand and validate? Sorry I am slightly confused and wanted to get peoples opinion in figuring out what CR I am currently at?

I've just dynoed and made 204 WHP and 144 TQ over at Skunk2 and I was a little dissapointed and now I am thinking because I am at 10:6 CR.

 

Furthermore, what liter would I be at using a GSR crank with a 84mm Bore?

 

I would say you're probably very close on your calculations. Using a thinner headgasket and head milling would be your only way to raise compression. Ideally you'd want to have your combustion chambers cc'd to see exactly how big they are. I have a GSR head that has some deshrouding done around the valves and even with it planed .030", the chambers are still 42cc. For every layer you remove from your head gasket, you'll gain about .2 compression and the same goes for every .010" you remove from your head (roughly).

 

you're at 1.9L

 

What cams are you running? Your setup should be built around your cams, not your compression ratio.

 

Are you running stock cams? And if so what does a build like that typically make on that dyno (even tho its really not comparing apples to apples)?

 

What is it you were EXPECTING to make? A 0.5 point of compression isn't going to make that big of a difference.

There are too many variables that you haven't addressed for anyone to be able to answer your question.

Did you ask the guys at Skunk2 what similar setups make on their dyno?

On an unrelated note, if that's your engine bay you have pictured, it's a nice looking install.

 

using http://www.c-speedracing.com/howto/c...c/compcalc.php and the little information u gave i came up with 10.9/1. i have used this website on several builds before doing the cc and i have been very close (nothing beats CC everything u have)

as for ur power, who tuned it, what ecu, octane, what cams.