240 Psi Combustion Pressure

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steelbuster

Senior Member
Just bought a JDM B16 SiR motor. checked the clyinders with a compression gauge.They are all at 235psi to 240 psi !! what the h#$%..... did it again with same result. checked gauge on another engine..gauge OK.. The pressure specs on this motor are 185 psi new I think. What gives? We used to run 14/1 compression methanol Sprint Cars and I don't remember seeing any thing that high.
 
Originally posted by steelbuster@Apr 22 2003, 10:55 PM
Just bought a JDM B16 SiR motor. checked the clyinders with a compression gauge.They are all at 235psi to 240 psi !! what the h#$%..... did it again with same result. checked gauge on another engine..gauge OK.. The pressure specs on this motor are 185 psi new I think. What gives? We used to run 14/1 compression methanol Sprint Cars and I don't remember seeing any thing that high.
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thats exactly what mine is also... but the reference to 185 psi is at operating temperature which makes massive difference. so i am guessing you did the compression test on a cold engine correct? and as long as the cylinders are within +- 20psi of each other your grrrrreat!
 
Thanks a bunch. I had visions of some head shaved-piston stuffed-detonating monster,,,,,I guess I should have thought about the spec conditions a little more. I'm doing this for my boy while he's in Iraq and it's been a while since my hotrodding days. ;)
 
just to give you a little insight. I did an ls/vtec with integra type r pistons, .20 bore, and a little bit thicker head gasket and i got 270 psi out of all of mine. man i did not expect to see that. Not when my Ls non vtec was at 185 on each. :lol:
 
Thanks DA,, It will be interesting to see what it is after I get it running again. I usd to have a formula for computing pressure but I've lost it. It was very complicated and was dependant on cranking speed, cam timing, valve overlap, ect,ect...easier to just stick the gauge in the hole :p

Did you have any enough piston to valve clearence with the typr r pistons? what Cam did you use? That might be my next project
 
i have zero clearance issues. not even when i retard the timing a bunch or advance it. the only thing is if i use regular 93 octane gas it pings like a S.O.B. i have to kinda mix the 110 leaded with a little 93 and that does the trick. it gets kinda expensive running on just 110 octane. i just have my b16 cams in it now. im going to upgrade to civic type r cams soon. but right now im building my transmission. I had to do a clutch (mine was slipping at the track), phantom grip LSD and a 93 GSR trans. that should really get me going i hope. Well good luck with your project :spin:
 
DA, retard the timing a little. You should be able to get that to stop pinging and run within 5-7 HP maximum with the timing pulled out of it on pump gas.

We've got a 12.8:1 compression 2.0L GSR that runs around town with 93 octane in it, and he had to pull some timing on the dyno. He only picked up like 5 hp at the wheels by dumping in 116 octane race gas and advancing the timing to near detonation levels from his "street tune".

Just a first hand FYI I thought you might like to hear.
 
Originally posted by SiR Kid@Apr 27 2003, 01:20 AM
DA, retard the timing a little. You should be able to get that to stop pinging and run within 5-7 HP maximum with the timing pulled out of it on pump gas.

We've got a 12.8:1 compression 2.0L GSR that runs around town with 93 octane in it, and he had to pull some timing on the dyno. He only picked up like 5 hp at the wheels by dumping in 116 octane race gas and advancing the timing to near detonation levels from his "street tune".

Just a first hand FYI I thought you might like to hear.
Click to expand...

thanx Sirkid i will try baxking it up more. but man that smell of 110 burning in your engine is addicting. :lol:
 
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