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Author Topic: Overboosting or bad wastegate  (Read 523 times)

boomingbeetle

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  • Posts: 37
    • '92 XR2, '71 Porsche 914, '79 Trans Am, 13 Outback
Overboosting or bad wastegate
« on: February 28, 2018, 11:00:19 AM »

Hello all,
 I bought a very nice 92 XR2 this week from the original owners, with years of maintenance history.  The car has 135,000 miles and I'm very happy with it but I consistently reach the boost shutoff light/alarm at 10psi under hard acceleration around 3000rpm and the motor falls flat on its face for a few moments until it recovers.  I am about 90% sure my wastegate is malfunctioning so I'd like to know if there is a way to rebuild it or if I should just disconnect it and run a manual boost control and BOV.  I do not plan to go all-out modifying this car, really I only want a different intake, rocketchip, and mechanical boost control around 13-15psi.  I would be happy to hear any thoughts or suggestions from you before I begin working on it this weekend, but here is a little more background:

-Turbo is definitely working, I feel it kick in but do not hear any "mooing" or whoosh that I would suspect a bypass would sound like
-I will check shaft play on the turbo
-I will install a separate boost gauge to closely monitor my real pressure at the intake
-I will try to find any pressure or vacuum leaks and may just replace all the hoses I can
-I will try running a line directly from the intake tube to the wastegate actuator, or see if I can pressurize it enough to open
-The head was completely rebuilt at 116,000 by a professional shop along with new timing belt, plugs, wires, cap, and rotor

Pics will be posted this weekend along with any updates I have found.  Thanks in advance, -Boom
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greywolf27030

  • Old-Timer
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  • Posts: 738
    • 88 Festiva, 91 Capri, 91 XR2
Re: Overboosting or bad wastegate
« Reply #1 on: February 28, 2018, 11:54:20 AM »

Very interested in your progress as I'm still learning about turbos.  Good luck.

Jack Byrd
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boomingbeetle

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  • Posts: 37
    • '92 XR2, '71 Porsche 914, '79 Trans Am, 13 Outback
Re: Overboosting or bad wastegate
« Reply #2 on: March 01, 2018, 02:52:51 PM »

Well I just read through all the "did you know" sections that were pertinent to my issue... handy articles.  I will NOT be disconnecting the wastegate actuator if I can get it working, and assuming I don't have boost leaks anywhere.  If not, does anyone know of an aftermarket actuator that will bolt up direct to our turbos?  Bueller... Bueller?
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boomingbeetle

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  • Posts: 37
    • '92 XR2, '71 Porsche 914, '79 Trans Am, 13 Outback
Re: Overboosting or bad wastegate
« Reply #3 on: March 03, 2018, 04:57:18 PM »

Today I pulled out the air box, inlet piping, and the factory hose and valve in line to the wastegate. There is some oil in the piping from turbo to intercooler, but thatís a job for another day. Riser from the turbo compressor inlet was cracked and crumbling, so I replaced it with plumbing fittings. The turbo itself spins very nice and has no play in either axis. After running a new hose directly to the wastegate actuator, my overboost issue is gone! Now I am only running 5-6psi and wastegate seems to be working. Now there is another issue, after the car warmed up there is major turbo lag and hesitation. That only started happening after about 10min of running, it seemed to drive great before that... also the water temp gauge is reading at the high side of normal. I need to figure out how to post pictures from my phone...  I ordered a BOV and boost controller, should arrive by next week. Maybe that will help too.

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SHOwn

  • Sr. Member
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  • Posts: 287
    • 91 XR2
Re: Overboosting or bad wastegate
« Reply #4 on: March 05, 2018, 01:21:37 PM »

Welcome! If I had more time I'd say more, but I want to tell you that the reason for the overboosting was the porous actuator vacuum/boost line. Since the turbo had to push more PSI than normal (due to the leaky line) the actuator was opening the waste gate later, allowing you to enjoy more than stock setups generate. Your gauge is likely inaccurate (as most stock ones are). You were probably hitting around 11 psi and the waste gate kicked in.

Adding the manual boost controller and an aftermarket boost gauge will be helpful to set it up like you want. An intake system improvement should be matched by an exhaust improvement as well. The Rocketchip isn't really needed unless you start running higher boost than 11psi.

I'd recommend figuring out where that oil in intake is coming from first. That can cause all kinds of trouble, clogged rings, messed up turbine wheel, etc. If you want to test and see if the oil is coming from the valve cover, you can buy a cheap valve cover breather, cap off the "s" hose from the driver's side valve cover outlet and try a breather there. If the oil in intake stops, you found the culprit. However, if there has been leaking for a while, the intercooler may be loaded with oil and it can be hard to know what the source of the leak is until that is cleaned out. Usually, that circumstance comes after a blown turbocharger shaft seal though, so if yours is good, the intercooler is likely pretty clean.

There is much more to say, but I have to get going. Maybe later in the week I can chime in again. I have two cars to work on at the moment, and I need one for commuting.
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R. Powell
'91 XR2, LM 16" Chrome Drifters, White Gauge Faces, Kuhmo 40's, Big Brake UG, 2.5" Mandrel Bent CATback, BMW318 Heated Seats, `94 console, '99 Dodge Neon Spoiler, '94 XR2 Sideskirts Bumpers and taillights, Fresh Basecoat-Clearcoat Cardinal Red (Jul2014), vj11/vj14 hybrid, manual boost CTL.

boomingbeetle

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  • Posts: 37
    • '92 XR2, '71 Porsche 914, '79 Trans Am, 13 Outback
Re: Overboosting or bad wastegate
« Reply #5 on: March 05, 2018, 02:02:04 PM »

Thanks SHOwn,  I'll take any advice I can get.

I put a vent filter on the driver's side valve cover outlet, I'm reasonable sure that is where the oil in the intake came from since it was in front of the turbo.  I ran a hose direct from the wastegate to the smaller port on the intake pipe just above the exhaust manifold, and capped the 5/8" port on the driver's side just in front of the throttle.  I do have an aftermarket boost gauge to install, but I had been running a boost/vacuum test gauge to verify that I'm getting 5-6psi and no longer overboosting.  Now I have the other issue - I'm calling it fuel starving - because it acts like a loss of fuel pressure causing a very erratic throttle response, not fun to drive at the moment.
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