Losing boost at 6400rpm. Help!

[suprahero]

After my rebuild and break in period, I went to the dyno to tune the car and see how much horsepower it was making. The results are kinda embarassing. It was either making 430 or 410rwhp, I can't remember which. The turbo spools to 17psi easily and holds it until 6400rpm and then it drops it to 12, and then 10, and then it tries to come back up to about 12psi. It does it right around 6400rpm everytime within a couple hundred rpm. It also dyno'd within three tenths of one horsepower on four consecutive pulls. It's hard to believe that a boost or vacuum leak could be that precise everytime.

Things I've changed trying to fix it:
new intercooler piping, couplings, and tbolt clamps.
new wastegate (Tial) w/ 13lb. spring
new vacuum lines everywhere
I installed a new Tial blow off valve while rebuilding the new motor. It's the new Q model.
I removed the intake and checked the gaskets on it, and they are fine.
With the rebuild I installed Aarons new blue intake gasket, but it seems to have sealed fine as well.
I did a compression test this morning after getting the car warm. Here are the results:
Cylinder 1: 146
Cylinder 2: 141
Cylinder 3: 147
Cylinder 4: 141
Cylinder 5: 141
Cylinder 6: 140

When I rebuilt the engine, I went with .040 cp pistons and eagle rods. I have new clevite bearings also. This problem is starting to get to me because I can't figure it out. I'm hoping some of you have some suggestions. I'll add more details as I remember them. Thanks.

 

[suprahero]

I have also replaced the valve that controls my AVC-R with a MAC valve. I thought it might be something with the boost controller since it's so precise, but that hasn't changed anything. It still does it at the same point everytime.

 

[10secdream]

Have you tried increasing the duty cycle on your AVCR in the higher RPMS? I know that in the higher rpms I had to significantly increase the duty cycle in order to maintain the boost I wanted.

For instance from 2500-4000 rpm my duty cycle is around 33% and then from 5000-7000 rpm my duty cycle varies from 40%-54%.

That is just for an example for you. I also found that learn gear is completely useless and I only adjust my boost manually.

 

[suprahero]

I never had to adjust it any differently than the way I have it now for the 1jz and the first 1.5jz that I built. There's definately something amiss though. Thanks for your help and I'll look into the avc-r instructions.

 

[Slow_Sc3]

take you boost controler off and hook the wastegate up to the back of the intake manifold see if it will hold a contant boost setting.

use the port on the side and leave the top open.

 

[Turbo Drifter]

/\/\ x2 that will rule out any boost controler problems.

Didi you rememeber ot install the Tial WG seat? I'm sure you did if you are building any boost but had to ask.

Jeremy

 

[suprahero]

take you boost controler off and hook the wastegate up to the back of the intake manifold see if it will hold a contant boost setting.

use the port on the side and leave the top open.

I just remember that I have tried that already. I bypassed the boost controller and it still fell off. My wastegate spring is suppose to be 13lb, but it boosted up to sixteen psi before it fell back off. Is this normal for it to boost over the wastegate spring that much?

/\/\ x2 that will rule out any boost controler problems.

Didi you rememeber ot install the Tial WG seat? I'm sure you did if you are building any boost but had to ask.

Jeremy

Yeah, I installed it Jeremy, but thanks for asking just in case. I've done dumber things before I'm sure, but I'm not going to go into that..........:aigo:

 

[tlo86]

are the compression #'s supposed to be that low with those pistons?

 

[tissimo]

have you checked the wastegate at all? thats really weird.

 

[10secdream]

are the compression #'s supposed to be that low with those pistons?

He did the compression test with the engine warm.

 

[tlo86]

what ecu are you running again? i dont remember the details of your build hehe

 

[suprahero]

I have the Stinger standalone and I also have the Crower cams and a ported and polished head.

Justin, the wastegate is brand new and the one that I had on there was probably good to begin with. I bought the new Tial because I though the other wastegate was the reason it's doing what it's doing.

I'll check back in in a few minutes. I"ve got to take my daughters to a volleyball game. I just got through installing my new LIPP traction bars. Thanks for the help guys.

 

[Turbo Drifter]

He did the compression test with the engine warm.

The comprestion numbers should be higher with the engine warm than when its done cold. My 2jz built engine with cams (HKS 264's) and head work compretion numbers are low 160's warm.

I just remember that I have tried that already. I bypassed the boost controller and it still fell off. My wastegate spring is suppose to be 13lb, but it boosted up to sixteen psi before it fell back off. Is this normal for it to boost over the wastegate spring that much?

My Tial 44 WG with a .9 bar spring runs .9 bar solid with no boost controler.

I think you may have somthing else going on in your system there, any chance you have a pluged or damaged cat or collapsed muffler?

Jeremy

 

[suprahero]

No cat's and a I have a brand new Magnaflow muffler on new 3" exhaust.

 

[Turbo Drifter]

No cat's and a I have a brand new Magnaflow muffler on new 3" exhaust.

Damn I'm impressed you have me stumped!

Any chance you are having injectors lifting and boost getting out by the injectore seats? (really hard to test) I have seen that happen once on a car but it was at 30+psi. Whats the tune like? is the A/F constaint dose timing change a lot in that area were the boost is falling off or creeping?

Cant wait to hear what the problems is when you find it.

Jeremy

 

[tlo86]

The compression numbers should be higher with the engine warm than when its done cold. My 2jz built engine with cams (HKS 264's) and head work compression numbers are low 160's warm.



My Tial 44 WG with a .9 bar spring runs .9 bar solid with no boost controler.

I think you may have somthing else going on in your system there, any chance you have a pluged or damaged cat or collapsed muffler?

Jeremy

thats why i was wondering why they were low heh, my compression was mid 140's to mid 150's on a used engine.

and the timing is not off? engine has no other sound odd at all when you are around 6400? turbo spins free and nice?

 

[tissimo]

thats why i was wondering why they were low heh, my compression was mid 140's to mid 150's on a used engine.

and the timing is not off? engine has no other sound odd at all when you are around 6400? turbo spins free and nice?

Its the Cams, they cause the air to leak out cause the valves are open longer, I wouldn't be worried about the compression.

So it was doing this before with the 1jz then too by the sounds of your reply about the wastegate? Or this just started happening after the 1.5jz?

If so, it sounds like an intake restriction (intercooler maybe?)

 

[suprahero]

Justin, the 1jz ran flawlessly all the way up to 24psi and 543rwhp. The 1.5jz ran flawlessly at 18psi and 517rwhp before the Texas meet.
All of this happend with the rebuild after Texas. I only changed the wastegate because I thought that was what was causing my problem and I also wanted a Tial wastegate. I took the intercooler off and soaked it in water while spraying air through it with one end capped off. No bubbles. I've literally tried everything I could think of and everything everyone else can think of. When the car cools down, I'm going to drive it again with just the wastegate and see how it does. I"m going to datalog the run and if anyone can tell me how to copy it from my laptop to Supramania I would be more than glad to upload it so you can see what I'm talking about.

 

[suprahero]

Come on guys, don't quit on me now. I've never seen anyone have a question that stumped all of you guys and I don't want to be the first. I didn't get to drive the car tonight, but I was told that I can do a screen grab and it will take a picture of my datalogs for me to post up on here. Does anyone else know anything about that? I have to find a way to download it onto my computer and I don't have internet on my laptop. I'll have to buy something that you use to have internet capabilities for my laptop at home I guess. I'll check in tomorrow after work and hopefully they'll be some more suggestions............:x:

 

[tlo86]

your hampster-powered turbo needs a break?