G 's 3rd gen

Hi all...... I posted recently that my motor experienced some detonation(which it did) and since had it looked at by a very respectable 3rd gen shop. The tech explained to me that when the detonation ocurred it did not destroy an apex seal but instead blew out the paper intake or turbo manifold gasket. He ensured me this (even though it idles @ 10 lbs. of vacuum a idle and rough) that this is the cause. He further explained that if it was a damaged APEX SEAL that when the throttle is held at a higher rpm there would still be some unsteady vacuum shown on the boost gauge. The car is smooth as silk when running. I am a bit weary because I cannot hear an exhaust leak in the engine compartment. I was given an estimate of $525 for the job. 25 for the metal gasket from Rx7.com and 500 labor for replacement. I know this is cheap for this but he is a friend of mine. I just wanted some info. from the experts before I do this. I was planing on saving for a new motor anyway and don't want to throw this cash away if there is engine damage..Thanks.G.....
93 montego blue w/ 60000
Pettit unlimited ECU
Greddy Profec b
3" stainless all the way
Pettit intake, powwer pulleys, AST
Autometer boost gauge
PIAA lighting
Koyo radiator
upgraded ignition,vacuum and boost hoses
cusco tower brace
Stock rims
stock intercooler, motor and turbos for now

RTS3GEN

Doesn't sound like the turbo manifold gasket, you'd definitely hear an exhaust leak if that were the case but that would only lead to poor boost, not poor vacuum(vacuum is like space, it isn't pressure). If you damaged an apex seal even slightly, the vacuum reading usually drops below 10in Hg and the idle is very rough and the car vibrates terribly. If you blew the paper gasket between the extension manifold and the engine, the vacuum would be low, about 10inHg, and poor idle quality, because the engine isn't "seeing" this air in the manifold and thus the air/fuel mixture is off. If this gasket did blow out, you may not be able to hear the air leaking in, but you can check it by spraying carb cleaner around the attachment of the extension manifold with the engine idling, if the engine idles up when you spray the carb cleaner, aha, a vacuum leak is present. At least give it a shot.
And, guys, no flames, if you have a different opinion, if you don't like my suggestion post your own!
art

G 's 3rd gen

Thanks ART!.. Thats exactly what he did but wd40 did the trick....Man that makes me feel alot better!!I think i will upgrade my fuel system just to be safe also.Thanks again! G....
P.S. Is it ok to run the car like this or can pieces of that gasket damage my turbos??

RTS3GEN

Don't drive it until you get that gasket replaced! The paper gaskets get old and brittle, if you've blown a section of it out, it's likely that other pieces can work loose and get sucked into the motor causing damage to either the apex seals or the rotor housings, or even worse, get jammed between the rotor and the side housing causing it to sieze. I would put 'er away until you can get the new, updated metal 3 piece gasket installed!!!!

Art

CantGoStraight

That's not a bad price for that job....it's a PITA to change that gasket and on 94&95 the paper one was changed to the metal one. I wouldn't drive it like that.

Flybye

It's a pita and expensive because the exhaust manifold must be removed in order to get to the bolts holding the lower intake manifold.

You know, now's a good time to get a bunch of things polished and/or ported

G 's 3rd gen

Thanks guys.....I will leave it in the garage and trialor it to get fixed. I need some info on porting my wastegate.Got any?? Thanks!! HAPPY NEW YEAR!!!!

RTS3GEN

Yeah, Just don't go too big. Make sure that the flapper has some manifold edge to seal against, other wise, the boost creep will be gone, and low boost will be a problem!
Art

G 's 3rd gen

What do you mean by low boost? Or are you joking about having a heavy foot?!G....

RTS3GEN

If you port the wastegate too much, then too much exhaust gas will just go thru the wastegate even if it is shut. With the wastegate completely shut, the turbos will make about 19-22psi, but if you remove too much material from the edges where the wastegate flapper contacts the manifold then as the wastegate tries to close to give you boost, too much exhaust will get past it and not thru the turbine side of the turbo and thus resulting in low boost!
Art

Chron

What is the purpose of porting the wastegate? I've heard a lot of people doing this, but never got the idea of it.

RTS3GEN

When the stock internal wastegate on the turbos is left alone on a higher flowing intake and exhaust, the exhaust flow becomes too much volume for the small wastegate opening to handle and it starts" backing up". And instead of bleeding thru the wg opening, it has to go somewhere, ie thru the turbine. Hence, boost creep. If you have a highly ported motor and all straight thru exhaust this creep may be severe. So, if you port the wastegate opening and smooth out the edges around the inside the flow characteristics thru the wastegate will be much improved and thus help the creep problem, either eliminating boost creep altogether or at least help it to stay within an acceptable range(1psi or so). Hope that helps you understand a little better (so long as you understand what the wastegate does and how it works to control the boost).
Art

G 's 3rd gen

Is there any numbers or figures on how much is best to port the wastegate? I noticed that most of your hardware is from Pettit so you must know some people there. I became good friends with a guy who used to work for Pettit and now has his own shop in Ft. Lauderdale. He knows just about everything there is to do with these cars. He even has experience in their Banzai projects. Although when I explained to him that we should port the wastegate he has never done this. He would try in doing so if some numbers were tossed around to better get an idea. Any where to get some info??Thanks Rt for all your intuition so far..G.

RTS3GEN

G,
There aren't any hard numbers to "throw" at you, per se. All you really need to do( you could do this yourself with a die grinder and a burring wheel) is remove a small amount of material around the inside circumference of the wastegate opening in the turbo manifold. On one side the wastegate flapper door contacts the manifold, on the other side is just an opening about 1" and 1/2 diameter. Just remove a small amount of material around this whole and round over the edges where turbo manifold contacts the exhaust manifold(this is the piece that is attached to the engine and the turbo manifold attaches to the exhaust manifold). A small amount of material may be 1/2mm or 1mm depending on how much bigger the flapper door is than the wastegate opening. It's similar to port/gasket matching, except you don't remove more material than you need to. Just a small amount will help, too much will hurt! If you aren't having boost creep problems, then you won't really need to do this mod. Some cars just have a propensity to creep. You can also forgo this work and just install a Pop off valve, which you can put into the intercooler piping and will bleed off any excess boost you don't want. You can set it to open at a certain pressure. It's different than a blow off valve though, although you may have known that already.
Art

G 's 3rd gen

Thanks Art...I will play with the wastegate a bit to see if I can get a grip on my creeping problems.G....