2TG/3T hybrid Wiseco pistons.

[Michael Yount]

I'm sorry but I don't understand what you mean. What "hits first to each other?"

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I think what he's getting at is that due to the hemispherical chamber, you have to take care that the valves don't hit each other - and that occurrence may be more likely than contact with a piston.

[J-M kujala]

Yes, thats what i mean!

[J-M kujala]

another question about these pistons. The specs that wiseco gives states that the piston dome volume is 20.6cc and combustion chamber volume is 63cc. I assume these are based on the 3TC head and NOT the 2TG head , seeing as the 2TG head has a lesser piston head volume and subsequent lower combustion chamber, wouldn't these pistons result in a much higher compression ratio than the 10.5:1 it claims?

Advertised compratio is not matching correctly even with 3TC head.. its only advertised! Like you see 87-89 all same addvertised comp, but details are the same.

Use 20.6cc in youre calculation + 60cc (with most 2TG heads) + add headgasket thickness/diameter cc to the combustion chamber.

I have measure that 20.6cc is correct value for these pistons!

[ToyTA22]

another question about these pistons. The specs that wiseco gives states that the piston dome volume is 20.6cc and combustion chamber volume is 63cc. I assume these are based on the 3TC head and NOT the 2TG head , seeing as the 2TG head has a lesser piston head volume and subsequent lower combustion chamber, wouldn't these pistons result in a much higher compression ratio than the 10.5:1 it claims?

Just looking in my FIA- TA23 Group 1/A Homologation papers shows for 2TG; item 139: Compression ratio 9.8:1, item 140: Volume of combustion chamber( my comment, includes piston dome volume) 45.1cc, item 140b: Volume of combustion chamber in head 69.7cc. Item 141: Thickness of head gasket inter tightened 1.10mm. I out of memory think the standard gasket I.D is 89mm. I would have to calculate the ratio later.

[RA21Dragon]

Advertised compratio is not matching correctly even with 3TC head.. its only advertised! Like you see 87-89 all same addvertised comp, but details are the same.

Use 20.6cc in youre calculation + 60cc (with most 2TG heads) + add headgasket thickness/diameter cc to the combustion chamber.

I have measure that 20.6cc is correct value for these pistons!

Just looking in my FIA- TA23 Group 1/A Homologation papers shows for 2TG; item 139: Compression ratio 9.8:1, item 140: Volume of combustion chamber( my comment, includes piston dome volume) 45.1cc, item 140b: Volume of combustion chamber in head 69.7cc. Item 141: Thickness of head gasket inter tightened 1.10mm. I out of memory think the standard gasket I.D is 89mm. I would have to calculate the ratio later.

Thank you both for responding. It is greatly appreciated! :thumbsup:

Per J-M Kujala's figures and a cometic 1.5mm 87mm bore gasket the CR I get is ~10.6:1 (and thanks for clarifying the valve clearance issue. You've been very helpful! thanks)

Per ToyTA22's figures (extrapolated the piston dome cc by subtracting the 45.1cc from the total 69.7cc chamber volume did i do that right? ) with the same HG I get 9.58:1

Either one works for me. I was just worried about the potential pre-detonation of a crazy high CR than 10.x:1 that I expected.

Let me know if my maths are off. I used this CR calculator: http://www.csgnetwork.com/compcalc.html

[Michael Yount]

Yes, thats what i mean!

Salute! Every now and then even a blind squirrel finds a nut. Sometimes I guess the right answer....