RX8Club.com - Turbo Oil Pressure Regulator

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Turbo Oil Pressure Regulator

Rather than add to the restrictor thread I thought I would start a new thread since I am looking for a different solution.

Okay so my turbo is smoking after only 20,000 miles of being rebuilt (well Turdblown said they rebuilt it about 10,000 miles ago when the billet wheel was added but I have my doubts that is was). I have talked to a few re-builders about this issue and I recently had a blown Greddy sent to BNR and he stated that it surely could have failed due to too much oil pressure but that the exact cause was hard to say but he thinks the close nature of everything and heat is the real culprit. Bryan recommends a 0.85 restrictor and no more than 10psi of oil pressure per 1000RPM. But as many of you know, if we called many builders, we would probably get opinions all over the map. I also bought another Greddy that i will have looked at by majestic here in Texas. That turbo also only had 10k on it according to the guy I bought it from. Also, Shelldude and some others I have talked to that have owned Greddys for some time have reported for the most part, yearly turbo rebuilds but with varying mileage on them.

Personally, my uneducated opinion is that the death of the Greddys both standard, BNR, and customs like mine are due to the fact that our engines have too much oil pressure in the higher RPMS. A Journal bearing turbo should not see more than about 65psi (give or take between manufacturers) at full load. I have increased oil pressure in my Pineapple engine so I see about 88psi at cold fast idle and maybe 15-20psi when the oil is fully warm. So, when cold the turbo is seeing way too much oil pressure at idle and when hot, I can see 120psi or so at redline. So at full boost I am seeing about double the oil pressure that is recommended by Greddy, Garret, etc.

A stock S1 engine maxes out a 80psi, and on the S2 engines they bumped it up to 115psi. Okay, so most recommend oil restrictors and so I have a 0.65 restrictor in my -4AN line and I got that from ATP. These are not recommended by any turbo manufacturers except as a last resort and even then they are frowned upon. The problem for me with oil restrictors is determining the right size because you don't knwo what the pressure drop will be across the RPM range and the whole pressure versus flow science. Is the restrictor the right size and when restricted, is the turbo getting enough flow?

Well, this issue has been discussed the in the RX-7 world for a long time but i could not find one single decent solution.

The only solution I can find is this and it appears to just be an adjustable ball valve of some sort and not a true regulator.:

Turbo Oil Regulator | Freelance Motorsports LLC

Now this is where it gets too technical for me and I need help. In the hydraulic world, they use an item called a pressure compensated flow control valve. But the ones I can find are not really made for low flow, low pressure setups like what we would need. And they tend to have max operating oil temps of 175F, which we would exceed.

So do any of you have any ideas on actually regulating the turbo feed oil pressure?

I found these as well.

Pressure Compensated Constant Flow Control Valves On Oil-Rite Corporation

EDIT: My working setup. Pressure at the turbo at redline is 60psi with a flow rate of 1.0GPM

https://farm4.staticflickr.com/3870/...4f4637a1_c.jpg
https://farm6.staticflickr.com/5568/...22bccdc4_c.jpg

Oh, and I should add that from the people who have the BNR, it doesn't appear that they last twice as long between rebuilds. Traditional belief is that a water cooled turbo should last twice as long.

I'm not sure i love the idea of a ball valve of any sort. What if it gets clogged or stuck or restricts the flow amount?

I have thought about alternatives such as the oil-less turbos and a separate oiling system for the turbo. The thing about oil-less turbos that i have seen is that they still need frequent rebuilding and that is with none rotary formats where the exhaust temps are much lower.

My first Greddy lasted 50,000 miles and it got a hammering . It was on a S1 engine with stock oil pressure and with a restrictor (approx. 0.040" ) .

I would favor sizing your restrictor to get the optimum flow recommended rather than trying something fancy. Take off the drain line and run the engine for 30 seconds or so to get a figure ....

Quote:

Originally Posted by MadDog (Post 1432327)

Although it hasn't really been discussed much lately, for a while there, the GReddy turbos were failing at what seemed like a pretty high rate. I think a lot of owners were getting them re-built after 10k miles or less! That's not a lot of miles!

My own turbo lasted longer than 30k miles between the previous owner and me. I think that's probably the longevity record so far. But, sure enough. One day that sucker started smoking like a chimney. It was pretty embarassing to drive around town. I even had to apologize for smoking-out a guy next to me at a red light once. He had his window down and before he knew it, the cab of his truck was filled with smoke! :hahano: I could see people all around me checking their cars to see if they were on fire!! :mdrmed:

So, I sent it off to get rebuilt. The really crappy part is that it still smoked after being rebuilt!! I tried cleaning out the intake tract, thinking that there was some residual oil still making its way into the combustion process. But it was dry as a bone in there.

I finally clued-in as to what was happening. The smoke wasn't an indication of a bad rebuild. It was an indication that the turbo was getting WAY too much oil!

HERE'S THE PROBLEM:
That's my postulate. The GReddy turbos are failing at a high rate because they are getting WAY too much oil. The seals and bearings can't take the high pressure for very long. So, they fail permaturely. The symptom is that after sitting at idle for about 30 seconds or so, the turbo begins to smoke. If the seals are still good, it will only smoke out the tail pipes. If the seals are really gone, then you'll get some oil leaking out of the housing and onto the exhaust manifold, and somke comes from underneath the hood, too.

HERE'S THE SOLUTION:
(sorry, I lost my camera so there are no pics)
I used a nitrous nozzle as an oil line restrictor. They come pre-drilled to very small diameters that you need to do this. Plus, they'll fit just perfectly into the oil line tee, letting the hose tighten down on top of it. You just need to dremmel the conical end down to a flat. Use a brass nitrous nozzle. Its soft enough so that it acts like a crush washer when you tighten down the hose. I doubt the stainless nitrous nozzles would work as well.

HERE'S THE RESULTS:
I tried two different nozzle diameters. The first one was an 0.065" diameter. Since the GReddy hose is about 1/8 at the neck-down, I figured that the 0.065" nozzle would cut the flow by a factor of 4. The problem was that this still wasn't enough to stop the smoking. So, I went to a 0.047" nozzle. That seems awfully small, but I did a flow test. At idle, the 0.047" nozzle flows about 0.4 quarts per minute. That's just shy of the 0.5 quarts/minute that Corky Bell recommends. I didn't do a flow rate test on the 0.065" nozzle, but just ratioing the areas seems to suggest that the flow rate for the 0.065" nozzle is close to a full quart a minute and the GReddy hose alone flows close to a gallon a minute!!

I wish I had done a flow test on the 0.065" nozzle. But a quart a minute agrees pretty well with what I observed in the only test I did do on it: disconnect the hose and watch it drain on the floor while the car idled. I was amazed at how much oil came out of the turbo drain with the 0.065" nozzle!

So, that's my advice. Get a ~0.050" brass nitrous nozzle. Dremel the conical end down flat. Insert it in the oil line tee and tighten the hose down on top of it.

You'll save your seals. Plus, its a lot easier to do this than to pull that turbo off!!

I am familar with that valve. it is a needle valve. It will be a lot easier to adjust but a lt more likely to clog if ou get a little trash in it.

I've been thinking about this for a while also. My oil pressure is about 125PSI. I am thinking about using a restrictor from my oil source then the hose to the turbo. Then putting a regulator tee'd off of that hose.

The restrictor will keep my oil system pressure and flow up. Then the regulator should keep my turbo oil pressure down.

Yeah Brett yours lasted 50k but your the only one I know of. I'd really like a regulator on a -4 feed.

Posted From RX8Club.com Android App

Quote:

Originally Posted by 9krpmrx8 (Post 4562370)

Yeah Brett yours lasted 50k but your the only one I know of. I'd really like a regulator on a -4 feed.

Posted From RX8Club.com Android App

You missed my point - measure the flow ! Size the restrictor to get the right flow - jobs' done !

And how would go about determining what amount of flow is adequate by watching it flow out of the drain line at idle?

Quote:

Originally Posted by 9krpmrx8 (Post 4562391)

And how would go about determining what amount of flow is adequate by watching it flow out of the drain line at idle?

Measure it and compare with the recommended (0.5 qts/min) .

I guess I should just call Corky and get his opinion since he is local. I don't see anything in the book about 0.5 qts a min but I may be missing it. Corky and I actually had a little highway run together last month (he in a Miata and myself in a Merc SLS) so I have been wanting to call anyway.

Perhaps I can chime in here a little bit...

Quote:

Originally Posted by hoss -05 (Post 4562348)

The valve sold by "Freelance Motorsports" is less likely to get clogged than a hole on a restriction fitting. Also, if it does get clogged your oil filter has turned into exploding debris so you have bigger problems to worry about. Furthermore, it has a design like a ball valve assembly but its on some serious steroids.

I attached pictures of a customer that tried to use a conventional ball valve and skip out on our whole assembly. Long story short, it broke into pieces and fused its debris into the oil inlet. We rescued his car off the side of the road by installing our system on the spot after picking the pieces out. THANKFULLY, this was all on the first shakedown run and no damage happened to the turbo.

We developed the assembly years ago when customers and our personal cars were going through Garrett turbos (don't get me started). We never once had an smoking issue or a leaky cartridge assembly since. It's also a standard install item on any single turbo kit we build/install. The rotary engine "suffers" from high oil pressure due to our thicker than standard oil weight. Watch your oil pressure on cold start and you'll see it go over 100psi... Guess what your turbo's seals are seeing...!

When you run a different weight oil, your entire engine will have variable pressure readings all over. With this assembly you can always see what oil pressure your turbo has and make adjustments on the fly

Quote:

Originally Posted by Brettus (Post 4562397)

Measure it and compare with the recommended (0.5 qts/min) .

I broke out the book :) 0.5 gal/min. big difference.

http://www.flickr.com/photos/9krpmrx8/12079715824/
http://www.flickr.com/photos/9krpmrx8/12079953616/

do kiwis even do the imperial system for fluids? I bet they drink beer by the liter. Bryan told me foreign contaminants killed my last turbo…. my compressor wheel is still on display at the shop. The only contaminants in my system were the shavings from the shaft as the bearing ate thru it.

He recommended an inline filter which made no sense to me … ultimately I just bolted it back up with the same restrictor everyone else uses. This regulator idea is interesting. I'm considering pulling my BNR in the Spring and going back to a pristine GReddy setup. He's been very kind to the pocket book on my prior rebuilds… perhaps I'll have him re-build the current one back to stock. I learned last year to always have one in reserve.

So root cause for my first rebuild was (imho) cold weather and pressure. My second was (again imho) a far too heavy compressor wheel. My third and current was doing fine until we had some -F temperatures here this winter… that's when I got to thinking about pressure and seals. One very cold morning here she puked about a cup of oil. I've had that faint lingering tale tell sign of burning oil since.

http://www.flickr.com/photos/9krpmrx8/12079897913/

i added some fluff to my message between posts there, 9k.. not sure if you saw my additional commentary.

Yeah man, the excessive pressure thing just makes sense. And pulling a restrictor size out of our asses makes no sense. And an adjustable valve (or if it is a flow control valve) without knowing it's flow rate, temp rating, etc. makes no sense to me either. I'm not just going to trust that Freelance figured it out for every turbo on the market. Most of the stuff I found on the market that is similar to what they are using is not designed for temps exceeding about 180F. I think I know which valve they are using actually, just waiting to clarify. The turbo needs enough oil and not at excessive pressures. That is what I want to figure out.

well I'm subscribed and anxiously awaiting your findings :)

Quote:

Originally Posted by 9krpmrx8 (Post 4563469)

I broke out the book :) 0.5 gal/min. big difference.

I was quoting Mad Dog but he did say 0.5 qt/min at idle which is pretty close to the 0.1 gal/min shown .......
Anyway ... some good info coming out of this .

Quote:

Originally Posted by ShellDude (Post 4563473)

do kiwis even do the imperial system for fluids? .

No we don't , but we can still understand your antiquated system ;)

I talked with Bell engineering this morning and they have a solution for it, he wants me to come by so he can show me. It is not a one size fist all solution so I don't expect it to be cheap but I will take one for the team. I just don't want to do it until the turbo is fresh. So I need to get this S2 trans installed, the new clutch in, and get the turbo out for rebuild.

Quote:

Originally Posted by 9krpmrx8 (Post 4563703)

You won't be the only one~! Maybe Mr. Bell will give us a deal for two of them. maximum boost here we come.

Why not use a flow regulator? One thing is that we dont want to over engineer, but we don't want to be in the stone age either, do we?

There are different ways of doing this, but the way it works is just to keep a steady pressure over the orifice. This means constant opening and constant pressure over this opening. This means that you will get a constant flow. Very easy, very clever. I guess we'd want a normally open type. If any interest, I can do some more investigation to find for the relatively low pressure we are operating at.

We thought of that but I can't find anything that fits the bill in terms of a true regulator. I did find flow control devices that go as low as 3 gallons per minute but I called the manufacture of a few and they devices are meant for hydraulic systems and have a minimum working pressure of 500psi and a max of 5000PSI.

These guys claim minimum pressure to be 25 psi:
FLOW REGULATOR 1300L SERIES - LOW PRESSURE DROP INLINE FEMALE NPTF PORTS | Vonberg Valve, inc.

By the curves, it looks like a normally open valve as well.

Hmmm, nice find. I wonder how I didn't come across that one, :lol: I just got one on Ebay for $12.00 shipped. Time to test it.