BlackOperative

Oh and thats why I blew mine at 7psi.... The stock gasket will not hold anything close to 18psi, at least not for very long.... maybe a few times under boost??? A decompression gasket designed for a turboed car WILL hold up better than the stock one..... if you are boosting over 18psi on a 4G94, good luck with that, as the temps entering the engine will destroy it anyway. If outside air is 70 degrees, and you boost it at 7psi, intake temperature into the engine will be 280 degrees..... 18psi, well there you go. A decompression gasket made for an engine that has been turboed is going to hold up better than the stock one, as the stock one is of course not designed to hold boost. The RPW gasket is NOT a compsite, but a steel head gasket layered with graphite. But I definitely agree about the ARP head studs, good idea to put them in REGARDLESS of boost levels. But the stock gasket... not a chance over 18psi. We arent here to discuss how much boost the stock gasket will hold, we here to try and help this guy get runnin without smoke lol. i would check the seal as i said before. test it by takeing the coolant lines off.

sykou

iTrader: (19)

checked my oil return line and guess what... Whitish brown milky looking paste... Guessing its the coolant seal in the turbo leaking thru to the oil passages.... Disconnected the coolant lines and so far no white smoke, and the return line has no milky residue on it. Also switched oil to Amsoil 0W30 Signature series. I have to say it runs the best that it ever has. the oil i used to change at 1500 miles looked like shoyu. But the amsoil oil stays cleaner for a longer time.... Using the amsoil filter btw....

senate6268

iTrader: (20)

As per RPW, when their steel head gasket shim is used in conjunction with a MLS (Multi Layered Shim) head gasket, this provides the strongest possible setup.

BlackOperative

Yeah but double gasketing is never a good idea... I blew my head gasket a while ago and I'm still trying to find a good one peice MultiLayeredSteel Decomp, but am having zero luck. I don't want to buy the shim by RPW because I'm not sure how well it seals. I'm not going to buy the graphite steel one by RPW because it isn't going to last as long as the stock MLS..... Sure it seals a hell of a lot better, but I just don't want to take the chance. Not sure what I'm going to do...... anyways glad you found the problem and that it isnt a head gasket, hope I helped a little.

sykou

iTrader: (19)

wait the rpw decom gasket is a steel with composite lining right? So your looking for a decomp gasket in a mls form just like stock form... As per the rpw site their decomp gasket is tested to hold till 18 psi.. So as long as you dont boost higher than that wouldn't that be a good choice?

cincy

please just keep your compression, its a good thing. Plus, the small amount a gasket can lower the c/r wont be worth the risk. Not to mention the powerband is better with the higher compression

BlackOperative

Yeah but even 9:1 over 9.5:1 has a huge effect on the temp in the cylinder.... so you can put more air in but still keep to around the same temp you had before. .5 does make a difference, and if you find a MLS that is a bit thicker, there is zero risk of doing anything to the motor. Just look at the older Ford Probes.... The engine came from the factory with a relatively thick head gasket, I say reletively, not extremely. Just by putting a thinner head gasket in, you will gain around 40 horsepower, and thats proven. In our case, we arent relying on the absence of pressure to get air and fuel in, we are forcing it in, and the lower the CR the more air and fuel we can get in to make more power. Sure, you are taking away comp., but the 2psi you can SAFELY gain may give another 10-15hp........ 10-15hp I am willing to pay just a bit more for, plus that is true the powerband will suffer, but not if you give it more boost, I will just lose a little down low, but I'm alright with that. I just need to know what anyone else uses because I havent founda good MLS Decomp yet, probably isnt one. I'm not dead set on getting one, but if I have the head off and I have the chance to get one, why not?? Right now its lookin like the OEM, I really don't want to double a gasket by using the shim from RPW, just not a good idea at all.

BlackOperative

Well as time goes by that graphite can wear away, leaving you more prone to leakage. The good side is that it seals a hell of a lot better than an MLS, but doesnt last as long.... The best gaskets are really the copper ones, but they are a bit spendy and need to be custom made for our cars. I don't know yet what im gonna do, most likey OEM again.......

cincy

higher compression = lower cyl temps = more efficient = better mpg and combustion = faster spool up

With lowering compression, you are taking away NA power which lowers what you gain with Xpsi. By increasing the psi, you are just regaining the power you have just given up and shorting the powerband

doctorjon

Exactly! Thats why higher compression cars make more hp with lower PSI.

BlackOperative

Well not exactly.... Lower CR equals lower cylinder temps.... The more heat you make, the more power, but the more prone to pre-ignition. If you increase the compression ratio you are increasing the heat in the cylinders, making more power. But with forced induction you can put more air and fuel to be burned when decreasing the CR... You are right that MPG will go down, but not by much, and thats not anything im worried about. With another 3psi you can safely put into each cylinder by lessening compression, you will gain more HP yet keep temps down. Just not sure yet what Im going to do.

cincy

The knock will be reduced with timing. A higher compression car will have a much longer powerband then dependent on boost alone. A good tune is all you need. Plenty of honda guys still making crap loads of power on pump with 11:1 c/r. Sticking with 9.5:1 is nothing. Thats what the 1.8T in my TT comes with stock and its not Direct fuel injection like the new 2.0T FSI which run over 10:1 stock.

Its all in how you want and feel safe. You wont have issues with 9.5:1, but if you want the added safety of lower, thats your choice. Just dont go below 9:1 or it will be a slug off boost.

BlackOperative

Actually a car that is NA running a very high CR will act the same as a turbo.... your entire powerband will be concentrated at higher RPMs. Timing will only help to a certain point..... you do not want to REDUCE knock, you don't want it at all. It doesn't matter what the stock CR is, if the motor was designed to run at 9.5:1, some engine builders will say it is NECESSARY to lower CR when turboeing a Naturally aspirated car. Direct Injection is not the answer to all problems associated with a higher compression, It just helps control the problem. 9.5:1 is reletively high compression compared to the muscle cars from the past. It's not that I will feel safer, I just want to add more air and fuel without melting the engine, as a higher CR equals higher cylinder temps. I bought the 1.00mm shim from RPW and a stock MLS with ARP head studs. I'll be running 11psi.

BlackOperative

Also, the amount of timing required to get rid of knock at 11psi@9.5:1 compared to 9.0:1, is not worth it. You would have to retard it so much that you will LOSE as much or more power than you will by installing a Decomp.

cincy

Do what you like. You wont be running a large enough turbo to notice either way nor spinning the motor high either. If/when you run a turbo with some lag, you will will understand why compression is worth it when your not a complete slug off boost.