mycrx

is it just me or should 18psi on a sc61 put out more then that.

baldur

Given that your engine runs with the ideal peak pressure point and no detonation under all circumstances and the airflow is the same, the power lost by going from 10:1 to 8:1 is 6.175%
But, if your engine doesn't have the fuel required to run at the optimum peak pressure point... then your efficiency is out the window.

If you go from 10 to 9 the theoretical drop in efficiency is 2.847%
If you go from 10 to 7.5 the theoretical drop in efficiency is 8.066%
Go from 10:1 to 14:1 and gain 8.329%

Bottom line is, run the compression ratio as high as you can get away with using the fuel you have. This means the engine running at the ideal peak pressure point at all revs and no detonation. Run the compression ratio too high and you have to get a better fuel or sacrifice the efficiency gained in running high compression ratio by running unoptimal spark timing.

granth91

I'd say so. My tuner made 303whp on 16psi with a .57 trim t3/t4 on stock block LS

B16CRXT

i ran 12 psi with a .48/.60 just fine. You should be really good with that big *** intercooler. mine is tiny. my compression is low in cylinder 1 now----> Shoulda spent teh extra money on pcv system/catch can.

Loserkidwac

It might have been more I don't really remeber but he was around 300whp on a stock block

Found the link it was 15psi on pump gas, my bad but still impressive look at some of ther other dynos there some of them are awesome

http://forums.evans-tuning.com/viewtopic.php?t=2489

AMkrew

Something I was reading the other day: When you have a motor that is very resistant to detonation, like hondas, this is done by the way the combustion chamber is shaped when the piston is at tdc. Within 30 degrees btdc, usually, the fire time starts and the flame front begins. This flame travels around the chamber and burns quicker out in the open (the pentroof style chamber has most of the volume dead center in the chamber), and slower in the confined areas (like on the quench pad areas on the intake and exhaust sides of the chamber).

Now quench, as it was explained to me, is when the piston comes uber close to the combustion chamber roof(reccomended static quench distance is .040" for most applications), and "squishes" turbulent a/f mixture toward the open areas. This ALWAYS has good results. The turbulence, somehow, has a great affect on the travel of the flame during combustion, and also has a cooling effect on the quench area, thereby cooling the chamber(take THAT, detonation). I must say, though, that the honda clearances are most likely nowhere near this (haven't actually been able to measure it yet) and we could potentially have a greater resistance to detonation if this was implemented in a motor.

When a thicker head gasket is used, the "quench" areas on either side of the chamber are ------ further apart at tdc, thereby negating the affects of the "close collision" of the slug to the chamber. The moral of the story is that yes, you may be able to run more boost, but your power output may be lower than you could have while bennefitting from these quench pads, due to the timing issue. Efficiency to resist detonation is lost when the quench is eliminated, as baldur said(i think ).

BTW I think I was reading a silvolite/Keith Black piston installation instruction manual from the SBC I'm putting together at work. That thing had some seemingly good info! Also, My boss said that this info might not be pertenent to turbo'd hondas :1

-josh-