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-   -   Low boost issue, need to know what to do next (http://forums.pelicanparts.com/porsche-944-turbo-turbo-s/794454-low-boost-issue-need-know-what-do-next.html)

kdjones2000 10-30-2019 07:38 AM

If you pinch off the hose going directly to the WG, you should be able to get boost up to whatever will grenade your engine, even with a stock WG setup.

Sounds like either your WG has failed, or your crossover pipe has collapsed.

How does the engine run when on boost? If it's choking, then it's likely the crossover. If not, then I would look at the WG.

Mike Goebel 10-30-2019 10:21 AM

Quote:

Originally Posted by kdjones2000 (Post 10640886)
If you pinch off the hose going directly to the WG, you should be able to get boost up to whatever will grenade your engine, even with a stock WG setup.

Good to know as I get about 1.8 BAR fully pinched off.

Quote:

Originally Posted by kdjones2000 (Post 10640886)
Sounds like either your WG has failed, or your crossover pipe has collapsed.

How does the engine run when on boost? If it's choking, then it's likely the crossover. If not, then I would look at the WG.

Checked WG and its good 5psi to open 11psi fully open. The only thing I haven't checked is the Crossover and the CAT pipe!!! :mad: I had the Downpipe off 400 miles ago and it looks perfect! Engine does not choke on hard acceleration.

Thanks
Mike G.

Mike Goebel 11-01-2019 08:27 AM

Used an endoscope for iPhone and here is what the Crossover pipe looks like going in from the Waste Gate "T". Looks good but its kinda difficult to get a good view farther down the pipe.

https://mikegoebel.smugmug.com/944-Pix/i-B8drTdg/A

P.S. I've got an aftermarket CAT. Are these typically straight thru? If so I'm going to try the scope going from the rear of the car.

Why doesn't it show my pic. I attached it with IMG from smugmug???

Thanks
Mike G.

Mike Goebel 11-01-2019 12:07 PM

Quote:

Originally Posted by Mike Goebel (Post 10643217)
P.S. I've got an aftermarket CAT. Are these typically straight thru? If so I'm going to try the scope going from the rear of the car.

FYI CATs don't go thru!! :D

Thanks
Mike G.

chip18 11-02-2019 01:18 PM

LOL ... but seriously a scope is not gonna work?? If you constantly run rich at part throttle and idle, you'll cook it!

But a lot of crap would have had to been blown out for you to see daylight thru one??? I doubt that ever happens but if the honeycomb structure has broken down it will tend to rattle over bumps and stuff??

Anyway ... here's a good clip and most likely more that you wanted to know.?? :)
https://www.youtube.com/watch?v=v9ju2rZ8YmM

Mike Goebel 11-02-2019 02:08 PM

I'm going to try something else now. I'm going to put a vacuum on the WG hose to insure the WG is not opening at all or much less. I still believe that the WG is the culprit even tho it tested ok with 5 psi to open and 10 psi full open condition.


Thanks
Mike G.

Mike Goebel 11-03-2019 10:19 AM

Lazy mans update!

I unplugged the power to the CV and 1 BAR absolute was achieved. So I still thinks its the wastegate! Just not ready to dump $450 into a trail test!

Thanks
Mike G.

chip18 11-03-2019 01:46 PM

Quote:

Originally Posted by Mike Goebel (Post 10643217)
Used an endoscope for iPhone and here is what the Crossover pipe looks like going in from the Waste Gate "T". Looks good but its kinda difficult to get a good view farther down the pipe.

https://mikegoebel.smugmug.com/944-Pix/i-B8drTdg/A

P.S. I've got an aftermarket CAT. Are these typically straight thru? If so I'm going to try the scope going from the rear of the car.

Why doesn't it show my pic. I attached it with IMG from smugmug???

Thanks
Mike G.

I think on here you have to use the "Click Here to Upload Photos" button where it says attach a photo?? I've done it and it seems to work fine. :)

Mike Goebel 11-03-2019 02:06 PM

Quote:

Originally Posted by chip18 (Post 10645381)
I think on here you have to use the "Click Here to Upload Photos" button where it says attach a photo?? I've done it and it seems to work fine. :)



http://forums.pelicanparts.com/uploa...1572822338.jpg

DOH!!!!!!!!!!!!!

Crossover pipe looking from WG "T" off towards Turbo!!

Thanks

Mike G.

Mike Goebel 11-03-2019 03:15 PM

Just ran a test pulling 15in of vacuum on the WG hose to help keep the WG valve closed. Makes a huge difference. Can reach 2 BAR absolute easy!!! Tried to keep it to 1.8 in 1 ,2, 3 gears. Makes me think the WG is the culprit!! BOO!!!

Thanks
Mike G.

dme 11-15-2019 09:44 AM

You can always add shims to help tighten the springs. A manual boost controller shouldn't even let the WG see boost till you near your desired level.

Mike Goebel 11-15-2019 12:14 PM

Quote:

Originally Posted by dme (Post 10658521)
A manual boost controller shouldn't even let the WG see boost till you near your desired level.

I was thinking about this and I came to the conclusion that I wouldn't be able to reach my desired boost level even with a MBC. Reason is that I've already pinched off the WG hose and still could barely reach the 1.8-2 BAR. So its either a WG spring that sagged or the CAT pipe. I'm going to try to get my **** together this weekend and check the CAT pipe.


Thanks
Mike G.

Mike Goebel 11-21-2019 06:44 PM

Added 1/8 inch shim to WG and now getting about 1.6 BAR. Need to test on fwy tomorrow morning in higher gears. BTW there is a noticeable difference in acceleration. Wouldn't have thought so.

Thanks
Mike G.

soxnail 11-30-2019 08:07 AM

Had similar issue, was a clogged catalyst.
Sox

Mike Goebel 12-02-2019 08:09 AM

Quote:

Originally Posted by soxnail (Post 10674084)
Had similar issue, was a clogged catalyst.
Sox

The Cat has less than a 1000 miles on it :mad:

Thanks
Mike G.

Mike Goebel 12-08-2019 08:42 AM

Added another shim for a total of 1/4 inch!!! Still didn't reach 1.8 BAR!!!

BOO!!

Thanks
Mike G.

dme 12-08-2019 10:17 AM

I picked up an OEM waste gate off of eBay that had 5 shims on it!

DannoXYZ 12-09-2019 10:03 AM

Mike's wastegate is fine, one of the best stock ones I've ever seen. Tests fine. It's not issue. With this strong of wastegate, pinching off line should generate 20-25psi boost no problem!

https://drive.google.com/uc?export=d...QLkfRLqY-ivvf4

Problem is there's excessive exhaust backpressure forcing wastegate open or turbo to not spin.

- Either crossover is collapsed. Most likely issue as I've replaced over 5 of these over the years.
- exhaust clogged, not likely. Modern cats are ceramic and do not melt with heat to cause restriction.
- or turbo is worn-out with dragging bearings or wobbling has caused extra clearance at edge of blades. This could be possibility.

Grab turbo's axle and wiggle it up & down. How much radial-play do you feel?

Mike Goebel 12-09-2019 03:55 PM

Quote:

Originally Posted by DannoXYZ (Post 10683283)
- Either crossover is collapsed. Most likely issue as I've replaced over 5 of these over the years.

Looked as far as I could with a bore scope on my cell phone and it looked ok, but I guess I need to take it off and really check it out. Unless there's another way to do a lazy A$$ check!

Quote:

Originally Posted by DannoXYZ (Post 10683283)
Grab turbo's axle and wiggle it up & down. How much radial-play do you feel?

Turbo rebuilt by evergreen less than a 1000 miles ago!

This is starting to wear me down a bit!!

Thanks
Mike G.

91cab 12-11-2019 12:18 PM

Just because the turbo was rebuilt recently does not mean it is in good condition. I have had new parts that are bad right out of the box. The best rebuilders do make mistakes. Or maybe something went through the exhaust and damaged the turbo. Remove the j boot and look at the blades, also try and wiggle the shaft - both right - left and in - out. While the j boot is off check it for any cracks.
I would do a pressurized leak test to check for vacuum leaks. If you have a big leak you will never get full boost. With wastegate out of the picture you should run unlimited boost. Since you are not it comes down to turbo working properly or air leak or restriction.[img]http://forums.pelicanparts.com/uploads2
6/20191211_1612351576098852.jpg[/img]
Here you can see a split in the bottom of the hose coming from the aos into the j boot. Not visable, but will cause slow spool and low boost. Visual inspection is not good enough.


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