Compression Ratios

[ORIGIN]

Hey guys ive been doing alot of research into the RB30DET build and i was chatting to my mate about it, who owns a honda integra dc5 type R. As he is planning to turbo it we go to talking about compression ratios, as i am planning to go with a 8.5:1 ratio i asked him what he was going to do. He reckons he can have a ratio of 10:1 and still run 25psi through a gt35r, at first i didnt belive him but then i did some research and found that the guys in the states are actually doing this on PUMP fuel (93 octane for them) and i was wondering how or am i missunder standing something?

[Guilt-Toy]

The guys in the states must be using rocket fuel or something. sure anything can be done if tuned correctly but man thats one damn potential explosion your mate is going to have there... My rb30det uses around 7.8:1 and i am running 30psi happily with around 500rwhp.

Engines with less compression are more forgivable on user errors

Hey guys ive been doing alot of research into the RB30DET build and i was chatting to my mate about it, who owns a honda integra dc5 type R. As he is planning to turbo it we go to talking about compression ratios, as i am planning to go with a 8.5:1 ratio i asked him what he was going to do. He reckons he can have a ratio of 10:1 and still run 25psi through a gt35r, at first i didnt belive him but then i did some research and found that the guys in the states are actually doing this on PUMP fuel (93 octane for them) and i was wondering how or am i missunder standing something?

[kiwi32]

10:1 compression and 25psi will make a very big bang on 93 octane. that would probably need methanol to live past startup. My rb30det runs 8:1 an 15psi and requires atleast 95 octane to run nicely.

[Piggaz]

My car (RB 26 stroked to a 2.8) runs about 9.0:1 comp running about 25 PSI through Twin GT RS's. Never pings, VERY snappy and responsive.

[Warpspeed]

Sure it would be possible with suitable valve timing and sufficient intercooling, and a low enough exhaust back pressure.

People say 10:1 CR Oooooh that can never work, but if the intake valve does not close until the piston is half way up the bore, then it is really only 5:1 compression ratio isn't it ?

Have a real close look at the specifications of a Mazda Miller Cycle engine.

Factory compression 10.2:1 supercharged to 17psi, and it runs on crapy 93 octane.

This is a mass produced factory engine, with full warranty, that can be thrashed by idiots in tropical mid summer heat without any reliability problems at all.

http://www.mazda.com.au/articleZone5.aspx?articleZoneID=3817

[srf]

Remember.

America use Ron+Mon/2 as an octane rating as apposed to just Ron.