Turbo won't boost past 18psi....

[craracer05]

So went to TPG yesterday to get my car tuned now that have the motor broke in. Everything was going good beside a big puff of smoke after each pull. I have determined that the turbo seals are damaged because I was running too much oil pressure. I now have a turbo oil restrictor installed. The turbo is an old SBR G60 turbonetics hybrid turbo. We got to the point where the car was making 350whp and then we couldn't get the turbo to boost past 18psi. We checked the MBC spring (large one was installed ~ hallman), checked the wastegate tension (it was good), pulled the intake and checked the turbo shaft play (was acceptable), and finally we did we a pull with the vacuum line pulled off the wastegate. Full pull and car still wouldn't boost past 18psi. The only thing we can come up with is the turbo is tired (worn/damaged). I have a $150 rebuild kit I just got from summit, but I'm thinking I might just take it back and use the money towards a FP red while they are still on sale. Anyone know of anything else I should check for before I jump the gun?

 

[craracer05]

Ok, just went out and dropped the o2 housing to check the if the wastegate was sealing correctly and it was. So I figured before I rip the turbo off I would do another boost leak test to be safe. Sure enough the entire backplate of the compressor housing is leaking. Hoping this is why I can't make more than 18psi and I can just seal it up.

 

[talontd92tsi]

It is possible that the wastegate flapper is simply too big and the exhaust backpressure is forcing the valve open even when the vacuum line is disconnected. Only options would be a heavier springed actuator, or going external.

To test (and I cant believe I am actually going to say this), you COULD wire the gate shut and see if it boosts past 18psi. Just be ready to lift off the throttle

(and Im not responsible if you blow your stuff up )

 

[livedsm4g63]

The exhaust housing could be cracked. It also could be many other things. The only way to tell is to rip the turbo off. It takes 15 mins, if that. Don't complain about it being hard to rip off.

 

[JusMX141]

These turbos had an extremely large wastegate hole and flapper from the factory. Depending on backpressure, keeping the flapper closed would be a huge problem.

I stock very strong actuators which are a direct-fit for these turbos- and you were about 15 minutes from me when you were at TPG. Would've been interested to see what actuator yours has and if it could be improved.

 

[craracer05]

Well upon another boost leak test through the turbo not just the intercooler piping the compressor cover seal to the backplate was leaking the whole way around. I sealed it with copper based rtv retested and it's now sealed and I'm on the process of putting the turbo back in. Nothing was cracked and at 6 turns on the wastegate it has good preload on the flapper. Hopefully this fixes it.

 

[Seamus]

That would seem to do it. But I will say I have had a turbo where the compressor cover was so loose you cod clock it on the car and it still made almost 30psi, and this was a little 20g which can struggle to make big boost with everything correct. Also a gut has a post right now where his snap ring wasnt seated and his car boosted to its proper 28psim before
the compressor cover fell off
suddenly. So they may have to work
hard as hell to do it, but a lot of these
turbos seem calable of mKing a lot of pressure with these big leaks at the back of the cover.

 

[JusMX141]

I doubt the boost leak was so prominent at the cover that it would limit boost production. It's retarded how these turbos are clearly grooved for an o-ring on the seal plate/cover union but nobody ever uses one. I do.

 

[livedsm4g63]

RTV in place of an o-ring... Priceless haha.

And Justin, yes it would. Happened to me once. I hit 6psi at 5k, haha.

 

[craracer05]

The cover is not machined for an o-ring I checked that first because I was going to order one. Copper rtv is the only thing I could do without having the turbo machined.I'm not investing any money into this turbo as I was only going to run it this year.

 

[JusMX141]

What cover is on the turbo? Literally every Kinetic / Turbonetics / Garrett cover I've ever seen used on these G-series turbos had the o-ring groove.

 

[livedsm4g63]

That is very odd. I wish the OP would have taken a picture. It would be a very interesting sight to see.

 

[craracer05]

Well had it out last night and I was able to boost to 20psi. I picked up two pounds of boost by stealing the compressor cover and I have the wastegate one additional turn.now the wastegate has 7 full turns of preload. I'm not sure what rise could be the issue now because it was holding just over 22psi when I boost leak tested before hand. I'm going to go another turn on the wastegate, but is it recommended to go any higher than 8 full turns? I'm looking for about 22-24psi max boost.

 

[craracer05]

Here a photo of the backplate I didn't get one of the compressor but it was just flat to match the backplate. The other is a picture from when I did the boost leak test.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

 

[Seamus]

Ooooh is that one of those fancy comp turbos backplates? No offense, but that design is junk. I can't believe the cover doesn't have a little recess for the o ring with the factory backplate though.

And maybe its the picture or its pushed out of the way and not connected at the pan but you drain looks like it has a nasty angle on it.

 

[craracer05]

It's a Turbonetics backplate, I have no idea who would think it's a good idea to not put an o ring on there or any kind of seal for that matter. I'm going to try and tighten the wastegate some more this weekend and see what it does.

 

[Seamus]

What about that drain? Does it just look like that in the pic? Cause that could have caused oil to leak past the turbine seal.

 

[craracer05]

Drain is good no kinks, 45 degree fitting out of the turbo to a straight fitting going into the pan. Standard off the shelf drain kit.

 

[Seamus]

You should have those fittings reversed. A straight into the pan is not a good idea. With that stiff thick hose you end up with a long section horizontal and parallel with the ground and that is bad. You wouldn't want more than the 45 degree in any section of your drain. With the way you have it, you might have an extra 2 it 3 inches of hose just to make the bend from a 45 fitting to a straight at the oil pan without kinking.it may seem trivial since it is only parallel with the ground for a bit but that is a very poor drain that could cause smoking and seeping. We all know that the oil only has gravity to return it to the pan, but we often don't think about it having to fight crankcase pressure to get from the drain into the pan. When using braided or that thick high quality push lock like that blue hose you are using, a straight fitting at the pan does not work.

 

[craracer05]

Straight fitting will not fit on the turbo it goes straight into the motor mount and the hose is kinked severely to get over to the pan. Thanks for the advice though.

 

[wishihadatalon]

Did you get the boost issue fixed? I had an issue similar to this with a BEP t3 HX35 and it wouldn't make more than 20psi. Tried a new wg spring, made sure the wg was sealing at the seat, inspected turbo, did boost leak tests, checked for pre-turbo exhaust leaks. Nothing seemed to fix it. One day my buddy had it up on a hoist and noticed that the muffler shop that did his exhaust flared the ends of a 2.5" resonator to 3" to match his pipes. As soon as we swapped it out, the car instantly made 30+psi and wouldn't go lower. We had to swap the wg spring back and everything worked out.

 

[craracer05]

NO, I didn't get a chance to try it out yet after i tightened the wastegate some more. For some reason now my fans won't kick on. If I jumper the temp switch at the radiator they turn on, so I replaced the temp switch with a new one and they still don't work. So now I have to figure this issue out.

 

[livedsm4g63]

Use a jumper on the relay on all the time! haha

 

[craracer05]

That is how it is right now, but I don't want to leave it that way.

 

[wishihadatalon]

The 1g fan circuilt is incredibly simple. If your temp switch is fine, it is likely the relay.