james81

I've gone GT35R with a 0.63 AR hotside for autox, 55mm ching-chong made spring type wastegate, greddy profecB II (working perfectly), large street port motor and all supporting mods.

Set at 6psi and gains on 20%, holds perfect 6psi from low down until about 5500rpm, then it starts climbing quickly, by the time its at about 6500rpm boost is over 12psi.

I've set the boost cut on the microtech at there so it just limits the motor at 12psi. These symptoms seem just like boost creep problems with a small w/g, but its a 55mm!? The profecB is working 100%, not 100% sure about the gains I've setup tho, that wouldnt really affect this anyway? And can't think of anything other than maybe the w/g spring is too soft?

Please, any advice or ideas would be greatly appreciated.

Thanks!

arghx

iTrader: (3)

completely disconnect/disable your boost controller. does it hold spring pressure or does it creep? You are asking a lot out of a single wastegate... you want to hold 6psi with a tiny hotside.

Turblown

iTrader: (12)

Which exhaust manifold are you using? How is the waste-gate vented?

You need to move up in the turbine housing and stick with 12+psi. You're setup is very mismatched. Why aren't you just running 12psi; do you not have the rest of the proper modifications for the turbo?

mono4lamar

iTrader: (32)

Check your manifold. It could be how the wastegate runner tubing is routed into the manifold. Other than that it could be the wastegate itself or improper vacuum reference to the wastegate

Trots*88TII-AE*

iTrader: (11)

+1. If you wanted to stick to 6 psi, you should've stuck with stock equipment. 12 psi is very minimal, and you should have a setup that will take that. Also, any housing smaller than a .84 T3 I would consider too small for a rotary. Crazy high backpressure is not your friend.

Also, by boost cut I hope you are cutting ignition back and dumping fuel, otherwise you will blow your motor.

buldozr

iTrader: (1)

way too small of a hotside would cause crazy boost creep issues as well, that is a fairly large w/g though..... we are talking about .64 on a t4 flange right, not the gimpy t3 flange? The stock twins would be a better matched setup for autoX in my opinion but still doesnt make sense why that large of a wastegate shouldnt be able to bypass enough to stop from creeping.... if its a 6lb spring, just go direct wastegate and retry like mentioned before above, if it still creeps, you might consider going to a ~.84 hotside.

Trots*88TII-AE*

iTrader: (11)

turbine A/R should not effect boost creep, the wastegate and manifold (if properly routed) should be able to control it efficiently before the exhaust gas reaches the turbine housing. I just read your last post when you switched from a manual BC to the EBC to try and solve this issue. It is clearly boost creep, and your options to fix it are to buy a different WG (maybe this cheapy isn't working properly, diaphragm issues or w/e) or we still haven't seen the manifold to determine how the WG runners are setup.

My advice on the turbine housing has nothing to do with the boost creep, I just think it's too small to be healthy on a ported rotary.

james81

Thanks so much guys, the w/g runner(single runner) comes from just under the flange where the two headers meet , out at a 90deg angle. im not sure abt the psi conversion but iv heard its close to 1/10th of a bar reading, so im running 0.6 bar boost. that was just testing it, didn wanna run too high incase it crept too fast an detonated.

SO maybe im running too low boost and ill pull the w/g and check it out internally.
In the profecB troubleshooting section, it describes my problem as too much exhaust back pressure or too little gain on the EBC? Maybe that 0.63 is too small for the street ported motor?

Turblown

iTrader: (12)

That wastegate placement will not work for your turbo and engine combination at that low of a PSI.

Even the biggest turbine housing available for that turbo will not cure the problem, however you should still have a much bigger one. You've only got two options; new exhaust manifold or run 12+psi...

james81

what do you mean the wastegate will not work for my motor and turbo setup?

Turblown

iTrader: (12)

Your motor and turbo combination flow too much at high rpms for the waste-gate placement. Its not the wastegate, its how the exhaust manifold is designed. You need an exhaust manifold where the waste-gate runners pickup at the outside radius of the main bends.

james81

Oh I see, thanks for the help guys. I've been setting the gain and upping the boost on the profecB and its creep much slower now, but its still creeping. I fear the electronics won't be enough to stop the creep and the manifold might have to go under the torch...

Kanho

iTrader: (3)

I have been having boost creep problems also but It seems that I have found the problem this morning at 4 am :-) (what wouldn't we do for our beauties!!) I'm only telling my story to maybe benefit this thread.

My set up 20B with a single turbonetics GT-K 850 and a 0.96 turbine with a tail 44mm wastegate with Profec B-spec II boost controler and microtech ltx12 ECU.

Problem the boost just goes up as long as a keep my foot on the gas. But my ECU is set tu cut at 12 psi so that I don't blow a thing. I have a 8 psi spring and these test happen while my boost controller is OFF.

First thing you have to make sure that your set up is well hooked up so that everything works. My set up: there are to openings on the tial wastegate. One at the top in the center and one in the middel on the side before the diaphragm. The middel is connected to the intake (on the pipe leaving the turbo and just before the intercooler) and the top of the wastegate is connected to the black box of the boost controller on the OUT nipple. The IN nipple it connected right at the exit of the turbo (boost side).

For my experience boost creep occurs when the pressure exerted from the top of the waistegate is higher than the pressure exerted from before the diaphragm. Basically, the waistgate never opens (your spring inside can't do anything) so no exhaust is being relieved out and the turbo keeps spooking up and generating as much boost as it can until it goes poofff!! Therefore, the key is that the wastegate opens and stays open depending on the amount of gas that you are supplying through your right foot.

I changed all vaccum/boost lines on the waistgate and disassembled the waistgate and checked if the diaphragm is riped. Everything was good and tight!

I disconnected the line that goes to the top of the waistegate ( I did it from the boost controller side since it is easier to reach). This means that the only thing that should be working to hold my boost steady is my 8 PSI spring inside the waistgate. I sure enough at 4:10 am this morning the car was holding 8 PSI at WOT!!!

This means my solenoid of my boost contoller is faulty. I thought it didn't matter because boost creep occured even with my boost controller at OFF but I was wrong! It still is part of the equation and must be considered!

By the way I'm looking to buy that black box with the two nipples IN and OUT of greddy profec b-spec II (I have the old controller with the 3 ***** no digital screen). If someone has a working one please let me know.

I hope this information is helpful!!

Andrew Kanho

dreed7235

iTrader: (3)

Full Race makes a really nice dual gated manifold.

ErnieT

iTrader: (2)

6 psi is just crazy. No wastegate in a single turbo will accurately go that low. There's no reason for it. Put a 10lb spring in and you'll be fine. It will hold 10lbs all day. If you have a larger single turbo and would like to run such low boost (although I don't see why) and dual wastegate setup will help more.

DriftDreamzSS

iTrader: (4)

Do you have a cat? My rx7store gt35r kit with an .82 hotside would not control boost at all on my streetported motor, creep to 16+ psi when trying to run off an 8lb spring in the tial 44mm. I think most of the problem was the junk manifold that came with the kit but the only thing that fixed it was using a cat instead of my midpipe. Ill be buying a new manifold since I never planned on running a cat, and atleast want the option of having a setup that can control boost without back pressure.

djseven

iTrader: (56)

I think he is running .6 bar which is roughly 9-9.5 lbs, which makes it make a little more sense. Going off that it leads you to believe he is hitting 1.2 bars which is approaching 18lbs so depending on his fuel/tune he could be in dangerous territory.

arghx

iTrader: (3)

It's easiest to control boost if your target pressure is slightly higher than your spring pressure, maybe 2 psi. That's assuming your manifold/wastegate combo flows enough to maintain steady boost pressure at that target level.

SmogSUX

iTrader: (12)

^To add when you say ching chong wastegate are you talking cheap OBX type ones? That could be a factor..but yeah 6 psi is ridiculous on a 35r

james81

Thanks for all the help! Here's a pic of my manifold so you can see the w/g runner.

junito1

My personal experience with a 1988 TII with BNR 3 and boost creep.
Boost controller OFF.

With full 3" turbo back exhaust and stock TDI with cone filter results like this.
1st gear. 6-7 psi
2nd "" 6-7 psi
3rd + gears 7-9 PSI <---


I tried upgrading the stock TDI to single 45 deg. 3" mandrel bent to cone filter.
With this MOD alone ANd boost controller still OFF.

1st gear. 14-15 PSI
2nd '' 14-15 psi
Never tried third. BUt it wasnt creep. The psi kept rising with the rpms. so 15 psi by 7000-7,500 rpms.


My suggesting. Make the turbo intake pipe less efficient.
If the turbo intake is 3" try reducing the intake pipe to 2.5".

This is the cheapest way i can think off.

seandizzie

iTrader: (1)

Did you try to run the vac line strait to the waste gate to take the boost controller out of the system??? It could be a tuning issue with the profec b. I would try this before changing the manifold or wg. But those could just as well be part of the problem.

I ran a 7 psi spring for the same reasons with the same boost controller same turbo (1.06 hotside though)and it took me a while to get it set just right. There is a balance that must go on between the set boost and gain and set gain(sart low and work up). When I figured it out I had 7, 10 and 13 psi nailed at a push of a botton.

Turblown

iTrader: (12)

Your manifold is the problem.

Its a good design for bigger power, but a bad design to try and run low boost.

You still need a bigger turbine housing, unless you really intend on no higher than 6 psi...

JBurer

The diameter of the header's pipe looks extremely large. What size is that?

Turblown

iTrader: (12)

Looks like 2.25" to me. Good for big power, and boost control, but bad for " spool " ...