Hi,

I'm building the 2.1 stroker from Enginetuner. It's coming along great. But I'm struggling with the compression ratio. According to the Wiseco spec list (http://www.wiseco.com/Catalogs/Sport...baruToyota.pdf) they use a 1.37mm gasket to get a 8,5:1 ratio.

When I put this in a calculator http://www.zealautowerks.com/ (already filled in) I get a ratio of 8.16. If I change the head gasket size to say .78mm (cosworth) the ratio goes to 8.51. This looks better.

Also I don't know the exact amount of decked surface but it has been milled close to 0. So the 0.2 is an estimate for the deck and head.

Am I on the right track? Or did I do something wrong? Please advise.
Also it's a CDB with STI V5/6 heads. What volume are they? I used 49cc.

 

I'd say give us a call?
01752 345880

 

Hanging on the phone as we speak

 

what did you go for in the end? whats the best compression ration for a 2.1? is 8.5 to 1 the safest to go for?

Thanks

 

no such thing as 'best compression ratio' depends on a lot of other things, what turbo and how much boost your going to run, fuel your using etc. Speak to your engine builder

 

ok i will do when they are back open on the third.. what are peoples opinions on here?

will be 2.1 with a built head on a gt30 turbo and i'd like 2 bar boost. v power will be main fuel with a 20% meth map for a lil more when im bored. a q16 map would be good just for drags.

cheers

Eddy

 

8.2:1 to 8.6:1 would work well if main fuel is vpower, and still see nice gain on meth.

However the wanting to run 2bar boost kind of dictates a compression ratio but is kind of the wrong way around. Ie. the boost level should be dictated at mapping time and the compression ratio, cams and fuel will influence that decision.
It might for example produce more power at 1.8bar than 2bar.

Simon

 

thanks for that simon, that makes sense.. my cams are:

Inlet 277 11.0mm lift
Exhaust 268 10.2mm lift

if that will make a difference to recommended cr?

Eddy

 

Wouldn't disagree with any of that
Always go at it from underneath, seen too many cars in the past wound up to 2 bar when they actually produce more power at much lower boost with proper timing and fueling. That said when they are sorted properly, you can sometimes find more power from turning the boost back up

As mentioned we do favour around 8.2- 8.6:1, however what you end up with will be decided by many things.
Block height, piston protrusion (Which often isn't equal due to the line boring for the crank in the block), volume of the head chambers due to surfacing current or previous and head gasket thickness.

From the sounds of it, we are building one similar to yours now Eggy, an all Cosworth 2.1 motor with ported big valve heads and Cosworth 272 cams using a Billet 30R.

Martyn

 

Thanks for that guys, cleared a lot of things up

 

is that mine