Unless you have a non-return valve in the engine breather hose ,your engine,oil pan and oil separator will be pressurised when you boost.

 

Can you quote what the reference pressure should be at idle, around 750 rpm? 'Cause my pressure gauge says it's around 8-10 psi at that point. Even if it is in spec don't you think that's really low?
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WENDIE 99

 

I think that would be fine. I've always heard generally you want 10psi for every 1k rpms.

 

Yes,it is in the 2004Service Highlights(part no 9999-95-102F-04)and on p01-00-3.

Also please ignore the above post on engine breather checkvalve,I am doing mine different to the Greddy set up and I forgot.

 

Sorry,I really should read what you wrote!I have not found a reference oil pressure for idle speed.From my TII days,10 psig at idle and hot was typical.

 

Are you sure about that? My sources indicate RX-7s were at 30psi at idle and anything below that was cause for concern.

To expand upon what Moostafa wrote, Rick noticed the RX-8's oil pressure regulator is (in his opinion) unusually small. It may be my 10psi @ idle is lower than spec due to diverting some of the oil pressure to the turbo. This is speculation on his part but sounds reasonable.

He installed a Racing Beat oil pressure regulator (pn 11810, $90) originally intended for a '71-'92 RX-7 in Sapphonica's car during his rebuild. It should add roughly 15 psi across the board. I note MazdaManiac's concern about too much oil pressure but think what Rick said about low psi @ idle makes sense and might be a contributing factor to the turbo bearings wearing out so soon. I have one on order and plan to install it shortly.
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Expert Insurance

 

actually quite a few 350z's are having problems with the turbos they actually released a tsb sorta thing about it i know someone whos turbos ate themselves after less than 6 mo

 

Again the standard way to evaluate oil pressure is at 3000 rpm,and the spec for the 2nd gen is 64-78 psi at 3000rpm.I had 6 RX-7s over a14year period and 5 had idle oil pressures in the 10-15 psi.

 

Is it a particular turbo kit that the 350z's are having problem with?

 

I called Greddy to see if I could get the turbo covered under warrenty. They will rebuild it if the seals are bad, but will not do anything with it if the bearings are shot. They claim there's no way the bearings could have been defective, so it must have been a faulty install or abuse. Really, I think its a matter of, its cheap for them to replace the seals, its just new gaskets, but it would be expensive for them to fix blown bearings/damaged housing. So they're going to concede on the easy one. I think thats really screwed up considering the warranty statement they have posted on their website. It specifically states they do warranty their parts and do not rebuild parts, they replace them to ensure reliability. I don't understand how they can post a statement like that and then totally not honor it.

 

The RX-8 turbo kit has a disclaimer at the end that indicated that this kit is completely NOT under warranty.

Checking oil pressure before the turbo won't tell you anything if you have a restrictor. I looked at mine last night - it is 1/16". I had taken it apart because I needed to look the setup over.
Right before I put it in the garage, I lost boost. Turns out it was a piece of metal that broke loose from the internal deflector inside the manifold and lodged into the turbine! I had driven it like that for 5 or 6 miles when the boost stopped.
Absolutely no damage. Garrett makes one tough turbo...

 

I've been calling around to a few places looking for some options and one of the places I called is Turbo Trader, a dealer for Bullseyeperformance, the company that performs the Greddy turbo upgrade. They have rebuilt a few blown Greddy turbos and told me the cause of the failures was due to compressor surge destroying the bearings. They said the 18g just isn't a properly sized turbo for our engine. It isn't happening to everyone because it just depends on your driving habits whether you hit that surge line or not. They replace the 18g wheel with a Garret 50trim and claim it is much better sized to our flow requirements. I have no idea if this is true of course, just one shops opinion. Surge damage could also be from running around without a BOV.

 

I have plumbed my Greddy system with a recycle line in a similar fashion to the Mazda TII system(in fact I am using the TII air by-pass valve).Hope fully I will avoid any surge issue.

 

yea i remember dan at bullseye telling me that the gredy turbo was all wrong and would surge.

I really really dislike greddy!

 

Well, I installed my Greddy turbo and manifold yesterday and drove it a bit today.

It is trying to produce boost all the time, even under light throttle. I can see why it is sitting at its surge limit all the time.
However, there is also something wrong with the way Greddy has you set it up.
The boost signal for the wastegate is coming off of the intake manifold. That is the wrong place.
There should be a return signal at the outlet of the turbo itself that feeds the wastegate. That way, it isn't trying to build full boost all the time.

That said, I can't wait until I get all moved in and get my welding rig here in AZ from MD so I can fix my manifold and go back to my turbo.

 

Wrong Thread.

 

bullseyepower is making me a restrictor for the oil feed line, its all making sense now, i just noticed some oil in the intake pipe, which makes sense that there is blow by in the turbo from too much pressure, probably is the reason the greddy ones don't hold up coupled with the surge.

 

The oil in the intake pipe could be blow by from the crankcase ventillation and not from high oil pressure pushing oil passed the seals though. Do you have an oil catch can?

MM, do you think tapping a fitting at the outlet of the turbo for the wastegate signal could help the Greddy turbo stay out of surge?

Do you think the turbo could be corrected by just replacing the compressor side as Bullseye does? Or do you think it would need some work done to the turbine side as well?

 

It really makes no difference were you tap the reference line for the wastegate. The only difference that you would see is if you are just useing the spring in the wastegate to control boost you will see two different boost levels. The one off the intake would most likely be a higher boost pressure than the one that is referenced off the compressor cover because when you reference off the compressor cover it does not compansate for the pressure drop across the intercooler (if you have one).

IMHO Greddy just dropped the ball on the turbo match for the Renesis motor.

 

I would think it could make a difference because the boost level should be proportional to throttle position. If you tap the signal after the TB then there is no relation to throttle opening, it just means the turbo is less efficient at part throttle because it has to squeeze all that air through a smaller opening, but will always make full boost. If you tap the signal prior to the TB then the boost level in the manifold would be better controllerd by throttle position.

 

You can not make any boost unless you have the throttle open. If you do not open the throttle you will not make enough exhaust energy to spin the turbo.

 

I can make full boost at <1/2 throttle. Close to full boost at <1/3 throttle.

Considering my throttle plate is going to be acting as a huge restriction at <1/3 throttle, I would think the turbo is spinning the begeses out of its bearings trying to make full boost in the intake manifold. I bet the pressure at the turbo outlet is much higher than the 6psi I read in the manifold, and with very little actual flow -> Can you say Surge.

 

I know that there is more pressure that compressor then in the manifold.

You are correct when it comes to not enough flow. When the motor cannot injest enough air it gets backed up in the compressor cover and causes surge. There are some turbos that have a wider range of air that they can flow.

Look at the compressor map of the 50 trim compressor wheel:



At 6psi or a pressure differential of 1.4 it can flow any where from 8 lbs/min up to 28lbs/min. Which makes it very forgiving on the amount of air flow that it can move.

 

I think I've missed your point. Are you saying that the Greddy turbo should be fine based on the 50trim wheel being so flexible? If so, I don't think thats a very good comparison. Not all compressors are that flexible, and the 18g is completely different from a 50trim. It would be nice if we had a compressor map for our turbo though.

 

Sorry for not being too clear. I am saying the 18G (which I can not find a compressor map for) must not be as forgiving. That is why it is getting into surge so easily.