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Discussion Starter #1
As some may know, I plan to put on a thin head gasket on this winter. I was wondering if anybody had their head skimmed also. I'm toying with the idea of having a tuner bump up my compression to the highest ratio 93 octane will allow. I'm wondering if anyone has done this on a street ridden ZX10R? Is their more comp. to be had beyond the thin head gasket for 93 octane?
 

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There is more compression available with skimming the cylinder and the head, but be very careful as you are getting pretty close to as much as you can handle with the thin gasket and pump gas. if you start getting into milling the head or cylinder, you will start getting in to detonation problems on pump gas.
 

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an the bigger problem comes in if you leave yourself no window for octane tolerance...meaning the pump might say 93 but be 91.5 and if your are running that close to the line...you are all done
 

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I agree all it takes is one wrong stop and a tank of some bad gas, and your looking at some decent damage.
 

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Discussion Starter #7
I was thinking since I'll have the head off. I'll get everything done at once. The ZX6RR has a ratio of 13.5:1. So i figure that should be a safe ratio for pump gas. If thin gasket doesn't go that high, then i want a head skim to reach that number. I'm thinking of having the cams dialed in also since the top will be off. May be some porting if needed.
 

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SP8, good luck and let us know how it goes down. I've read many a person who has done this and said it was not worth the time, money or effort.
 

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SP8 said:
I was thinking since I'll have the head off. I'll get everything done at once. The ZX6RR has a ratio of 13.5:1. So i figure that should be a safe ratio for pump gas.


This is very dangerous logic ... Detonation happens when air/fuel mixture reaches ignition conditions before the normal flame front burns it. Larger bore diameter favors more detonation; slower-running engine favors more detonation; and there can be differences in combustion chamber design or the temperature that various components operate at which can affect it. The 600 engine, with a smaller bore and which spins faster, would be less prone to detonation and could tolerate more compression. Also, cam timing makes a difference. Cams that favor top-end performance, with late intake valve closing, act against detonation at low RPM simply by letting some of the mixture back out of the cylinders, thus "effective" compression ratio is lower. The 6RR engine has more radical cams than the 6R, if I remember right.

Put it this way - You can get away with 13-ish:1 compression and pump gas on an engine with 250cc per cylinder (1-litre 4-cyl), but you can not get away with it with an engine having 500cc per cylinder that spins slower (2-litre 4-cyl car engine - 13:1 is unheard-of for normal car engines).

It has been reported that the thin head gasket doesn't cause trouble (in the short term). It has been reported that 4 degrees ignition advance doesn't cause trouble (in the short term). There is no guarantee that doing *both* will not cause trouble. It might work, it might not. Sooner or later, there is a limit. And, what works in the short term might not work under all conditions, or it might work but shorten the engine life, we don't really know.

SP8 said:
I'm thinking of having the cams dialed in also since the top will be off. May be some porting if needed.
Cam timing - Good idea. Porting - probably not, these engines already have machined ports from the factory.
 

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Go faster- Well put. For comparison sake based on GoFaster's statement, superbikes are not running much more than 13.7:1 right now because they simply cannot make power beyond that with the most exotic race fuels available in the world. For a street bike, I would definitely not go any more than 12, maybe 12.5:1 as the quality of pump gaas varies so much and you are really getting into potentially grave consequences. Having seen people melt pistons because they ran poor quality gas on a race weekend I can assure you it is not a fun proposition. My $.02

Oh Yeah, these ports are ported very well from the factory. I can assure you there isnt much to gain there
 

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If you decide to install the thinner head gasket AND machine the head, ensure you or the mechanic checks the valve to piston clearance. Detonation will be the least of your worries if one (or more) of those valves kiss a piston.

I would just do the head gasket, but that's just me.
 

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The gasket would be good but I would not mess with the head. There is about a 3% increase for 1 compression point. If you are only going to up it .5 with a gasket and another .5 with milling. you are only looking at 5 horse+/-. Like was said before p/v clearance is important. You only want to add timing if you can pick up torque. More timing compensates for inefficient combustion chambers. There is alot 2 or 3 to be gained in the oil you run. On the street I run 20w-50 but on the dyno i run (something different).
 
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