Higher Compression ECU Questions
03-31-2002, 09:29 AM
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Higher Compression ECU Questions
I'm thinking of bumping up my compression with a hi-comp head-gasket. Does anyone have an idea as to how the ECU will react to the higher-compression, if it even will?
Thanks in advance for any info you can provide!
Thanks in advance for any info you can provide!
03-31-2002, 04:11 PM
#2
Well, the ECU knows nothing about compression really, but it will sense the detonation that could be caused by this change (thru the knock sensor) and retard the timing to compensate, thus negating any supposed advantage that the higher compression gave you. (Unless you run really, really good unleaded and maybe even 100 octane racing unleaded would be needed).
Also, when considering a head gasket change, you have to think about some things. Is piston to head clearance going to be sufficient with a thinner gasket? How about piston to valve clearance? Both of these clearances will diminish because the head is moving down in relation to the block. Also, "quench" or "squish" will be slightly affected, maybe for the better but maybe not. Only a dyno session will tell.
How thin is this head gasket?
BTW, does anyone know, is the JDM F20C compression higher because of pistons or head gasket? I'd bet it's a piston change which would make me be very careful if considering a head gasket change. Or put another way, why would Honda choose to up compression with pistons (expensive option) vs. a head gasket?? The head gasket thickness, and hence the quench area, has probably been optimized on the F20C and a change either way on the head gasket (thinner or thicker) may prove detrimental.
Jim
Illusion Motorsport
Also, when considering a head gasket change, you have to think about some things. Is piston to head clearance going to be sufficient with a thinner gasket? How about piston to valve clearance? Both of these clearances will diminish because the head is moving down in relation to the block. Also, "quench" or "squish" will be slightly affected, maybe for the better but maybe not. Only a dyno session will tell.
How thin is this head gasket?
BTW, does anyone know, is the JDM F20C compression higher because of pistons or head gasket? I'd bet it's a piston change which would make me be very careful if considering a head gasket change. Or put another way, why would Honda choose to up compression with pistons (expensive option) vs. a head gasket?? The head gasket thickness, and hence the quench area, has probably been optimized on the F20C and a change either way on the head gasket (thinner or thicker) may prove detrimental.
Jim
Illusion Motorsport
03-31-2002, 04:24 PM
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Originally posted by 00BLACKS2K
Well, the ECU knows nothing about compression really, but it will sense the detonation that could be caused by this change (thru the knock sensor) and retard the timing to compensate, thus negating any supposed advantage that the higher compression gave you. (Unless you run really, really good unleaded and maybe even 100 octane racing unleaded would be needed).
Also, when considering a head gasket change, you have to think about some things. Is piston to head clearance going to be sufficient with a thinner gasket? How about piston to valve clearance? Both of these clearances will diminish because the head is moving down in relation to the block. Also, "quench" or "squish" will be slightly affected, maybe for the better but maybe not. Only a dyno session will tell.
How thin is this head gasket?
BTW, does anyone know, is the JDM F20C compression higher because of pistons or head gasket? I'd bet it's a piston change which would make me be very careful if considering a head gasket change. Or put another way, why would Honda choose to up compression with pistons (expensive option) vs. a head gasket?? The head gasket thickness, and hence the quench area, has probably been optimized on the F20C and a change either way on the head gasket (thinner or thicker) may prove detrimental.
Jim
Illusion Motorsport
Well, the ECU knows nothing about compression really, but it will sense the detonation that could be caused by this change (thru the knock sensor) and retard the timing to compensate, thus negating any supposed advantage that the higher compression gave you. (Unless you run really, really good unleaded and maybe even 100 octane racing unleaded would be needed).
Also, when considering a head gasket change, you have to think about some things. Is piston to head clearance going to be sufficient with a thinner gasket? How about piston to valve clearance? Both of these clearances will diminish because the head is moving down in relation to the block. Also, "quench" or "squish" will be slightly affected, maybe for the better but maybe not. Only a dyno session will tell.
How thin is this head gasket?
BTW, does anyone know, is the JDM F20C compression higher because of pistons or head gasket? I'd bet it's a piston change which would make me be very careful if considering a head gasket change. Or put another way, why would Honda choose to up compression with pistons (expensive option) vs. a head gasket?? The head gasket thickness, and hence the quench area, has probably been optimized on the F20C and a change either way on the head gasket (thinner or thicker) may prove detrimental.
Jim
Illusion Motorsport
The head gasket I'm considering is the Spoon one which is advertised to be 0.45mm thinner than the stock head gasket. They go on to say that "seal nature and durability are also more than standards." (www.spoon-sports.com)
We can get 94 octane pump gas in Vancouver -- do you think that's sufficient given the mild compression bump the gasket produces?
04-01-2002, 05:21 AM
#4
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Your 94 octane might be enough. It should also only be a problem in hot weather. I would recommend some cooling mods (heat shield, insulation, lower temp t-stat and switch) to go with this to help reduce the chance of detonation (improve your resistance/immunity to it).
As for the JDM mill... I believe it's the pistons. That's pretty traditional with Hondas in Japan.
The Spoon gasket should not cause any problems as it's advertised to work with USDM models to increase compression (without other work) and I believe a few people here are already running it.
As for the JDM mill... I believe it's the pistons. That's pretty traditional with Hondas in Japan.
The Spoon gasket should not cause any problems as it's advertised to work with USDM models to increase compression (without other work) and I believe a few people here are already running it.
04-01-2002, 08:23 AM
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By moving the head lower in relation to the crankshaft, you are reducing the effective length of the timing chain, which will retard the cams. On the B series engines it is 1 degree for every .012" reduction in gasket height.
Adjustable gears could compensate for this, when they get made.
Adjustable gears could compensate for this, when they get made.
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04-01-2002, 11:37 AM
#8
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.45mm is about .0177" which isn't much. Assuming the ratio is the same that would be about one degree of change. That sounds like a lot to me, though... but I suspect won't impact performance much, all things considered. The negative effects of retarding the cams will probably be overpowered by the positive effect of bumping the compression that much.
