I'm planning my engine atm, and I was about to put in my order for the RPW Stage 1 Decompression headgasket. Then I read down near the bottom of their listing that I would need to run and aftermarket cam gear/shaft due to the differences in thickness. Ii this true? I was hoping to stick with my stock cam until I push over 10psi. Any help?

 

i dont think you need the decompression gasket either until you are over 10psi.

 

I don't think that is necessary for our cars. It's made like that to ensure the proper valve/piston clearance. There shouldn't be any problems but the best thing is to contact Mitsiman. He is on this forum and he works for RPW.

 

One of the decompression gaskets is thick enough that you need a different timing gear itself. Because it throws timing off. Mitsuman is who you need to talk to.

ROAD/RACE

 

Could it be detrimental to performance below 10psi? I need to buy a new head gasket anyways, figured why not get one now and be safer. I however will not get one if the camshaft deal hold true.

 

i certainly dont think it would be bad... especially if you are at 9psi now anyway, so it would be better for your engine. You will have to talk to mitsuman about the specifics on the cam gear and camshaft.

 

ya i also would like to know about this decompresion gasket i keep hearin about

 

Mitsiman Pm'ed me back, heres the answer:

You only need the camsahft gear if you run the 1.50 or 2.20mm thick gasket. If you use the 1.10mm thick gasket there is no need for the gear. So i guess that would also mean no need for the camshaft, woohoo

 

Cool... give us a write up when you get it installed. Doing it yourself or at a shop?

 

Better clarify there - the reference to the need for a vernier camshaft gear is only in relation to the thickness of the head gasket. The 1.5 / 2.2mm units will retard the camshaft timing due to the extra height of the cylinder head and slightly put out your injection timing. The cam gear is necessary to correct this.

With the 1.10mm head gasket, this is not necessary although there is a slight change in camshaft timing it is not enough to justify the need to do a camshaft gear. And with this gasket, 14 psi is easily acheivable with no problems.

Camshaft is a different story - the turbo grind profiles, will improve the car regardless of which amount of boost you run. Stage 1 cams will handle 3 psi up to 20 psi easily. Obviously if you are pushign more than say 12 psi a stage 2 is recomended for its greater efficiency in the higher boost ranges.

Again whilst a stage 1 does not necessarily need a vernier camshaft gear, we did a customers car recently where we put one on, tried it on a dyno and picked up an extra 5hp at the wheels with playing with the camshaft timing. So its a case of money V gains and how far you want to go and this was on a n/a car. On a turbo car the gains could be higher again.

I hope that helps.

 

were the gains you achieved in the top end range?

If i'm going for a streetable car, wanting low-mid range torque I would be better off with the stock profiles, correct?

I guess dropping comression with the gasket is kind of defeating my low-mid range goal, however I'm willing to sacrifice a bit of power for reliability/streetability. Only pushing 9 psi would I see any noticble increase in lag?, weaker low end??

 

No in fact due to a turbo camshaft running very low valve overlaps, less than factory stock, they tend to have more low down rpm torque and more fuel effficient because they depend upon forced air pushing through the engine to produce horsepower.

Typically a stage 1 turbo camshaft will produce very smooth idle, some woudl even say beteter than stock, very good economy and throttle response. Once that turbo starts pushing air through - the camshaft really starts to do its job. Better tuning, less fuel going out the exhaust - all is good.

 

I thought so. You got your answer now.

ROAD/RACE