Losing boost at 6400rpm. Help!

Slow_Sc3

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Apr 2, 2005
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IJ.;1175793 said:
J Told me he bypassed the Boost Controller plumbing the WG directly to a boost source and did the exact same thing.

Can't say I'm surprised that shimming the valve springs didn't help as 70 pounds seat pressure was adequate.

try out an 18psi wastegate spring and see what happens since it looks like the 13psi wastegate spring is working just fine.
 

suprahero

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Aug 26, 2005
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bigaaron;1175790 said:
That's a lot more money then just a simple inspection of the turbo, if it was causing a problem like this it would be obvious. Either the shaft wouldn't turn or the compressor or exhaust wheel would be damaged. I wish I could see it in person, we could probably figure it out in 10 minutes.
Yeah, it cost more, but I was wanting another turbo anyways and Vonda will be getting her a new one now.

IJ.;1175793 said:
J Told me he bypassed the Boost Controller plumbing the WG directly to a boost source and did the exact same thing.

Can't say I'm surprised that shimming the valve springs didn't help as 70 pounds seat pressure was adequate.
I have disconnected the avc-r and ran it on wastegate only and it does the same thing. I hooked the side port to the turbo and left the top port open on the wastegate.

Slow_Sc3;1175911 said:
try out an 18psi wastegate spring and see what happens since it looks like the 13psi wastegate spring is working just fine.

I still don't see how this will help Matt, but if I had an 18psi spring, I'd try it.

I'm going to buy a leak down tester and see what that tells me. I'm also going to recheck the compression on all cylinders and I"ll post up the results tomorrow. Hopefully I can get a leak down tester locally and see if that helps with anything.

List of things replaced so far:
wastegate
bov
turbo
intercooling pipes
couplings
tbolt clamps
vacuum lines
stinger standalone (I used George's and it did the same thing)
intake gasket
rebuilt the head........again
tried a different spring in wastegate (11#)
disconected exhaust and did a pull
checked intercooler for leaks
Did boost leak test numerous times
 

suprahero

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Would it help to do a leak down test on my car? I'm really open to any suggestions.

I know you want me to try a higher rated spring Matt, but I don't have one and I used the thirteen pound spring flawlessly on my last build. If I had one on hand, I would try it though. Thanks, Jay

Does anyone think it could be my cams being off a little causing this? It seems a little farfetched that they could have that much of an effect on it, but who knows?
 

tissimo

Stock is boring :(
Apr 5, 2005
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If it does it on wastegate spring pressure (creeps to 17 then falls the 13) I would say its probably the manifold. Just tune the boost controller to get rid of it. Try a manual boost controller on the bottom/side port and leave the top port open. See what that does.
 

suprahero

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I'll try that Justin. I also have another manifold, but it's a T3 manifold and my new turbo is a T4.

Do you know what could make the manifold do what it's doing? This is the manifold that I had on it in Texas and it worked perfectly.
 

turbodriz

mk3 onwer
Feb 25, 2006
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try replacing the exhaust manifold gasket. As far as the cams being a little off. I would try to get them exactly where they need to be at least at that point u can eliminate that as a possiably issue.
 

tissimo

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Apr 5, 2005
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suprahero;1177508 said:
This is the manifold that I had on it in Texas and it worked perfectly.

oh yea, forgot about that.

Did you change your AVC-R Settings between now and texas?

Try a manual though.

Also did the car before on wastegate act the same way? The boost controller cant control the boost accuratly if the wastegate pressure is steady.
 

suprahero

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buckshotglass;1177533 said:
Did you get the crack bags out of the intercooler yet?
I didn't find any crack bags in there Dave. Are you sure that's where you left them?
turbodriz;1177536 said:
try replacing the exhaust manifold gasket. As far as the cams being a little off. I would try to get them exactly where they need to be at least at that point u can eliminate that as a possiably issue.
I'm going to try it with a manual boost controller and see how it acts first and then I'll start adjusting the cams. I don't think the cams can be off bad enough to make it do what it's doing though. Thanks for your help.
tissimo;1177592 said:
oh yea, forgot about that.

Did you change your AVC-R Settings between now and texas?

Try a manual though.

Also did the car before on wastegate act the same way? The boost controller cant control the boost accuratly if the wastegate pressure is steady.

Justin, I haven't changed any settings that I"m aware of. If I can get it to operate fine with a manual boost controller then I will find an AVC-R specialist and have them go over my settings. Thanks again for your continued help.
 

suprahero

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dd, yeah they are within specs and I just had the head rebuilt and checked last week. Everything is correct in the head. Thanks for the suggestion though.
 

suprahero

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I did another compression test today and came up with these numbers.

Last time I did this the numbers were as follows:
1: 146
2: 141
3: 147
4: 141
5: 140
6: 139

I bought a new compression tester and this is how the looked today.

1: 150
2: 145
3: 150
4: 150
5: 155
6: 150

Of course none of this has helped my problem. I'm going to try a smaller wastegate spring to see if I can get it to make a smooth pull @ around 9 or 10 psi. I'm also going to install a manual boost controller and make a few datalogged runs with it and see if it has any effect on it. Just thought I'd update the thread in case some of you are still brain storming this for me. I'm not giving up yet, but I did see a good looking Mustang GT for sale today locally.............:aigo:
 

jmcboost

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Mar 31, 2005
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bigaaron;1175790 said:
That's a lot more money then just a simple inspection of the turbo, if it was causing a problem like this it would be obvious. Either the shaft wouldn't turn or the compressor or exhaust wheel would be damaged. I wish I could see it in person, we could probably figure it out in 10 minutes.

You should buy Aaron a plane ticket and he can come out and fix it.:naughty:

Sorry, that's the only thing I got.... I wish I could help.
 

da89soup

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Dec 2, 2005
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jmcboost;1181274 said:
You should buy Aaron a plane ticket and he can come out and fix it.:naughty:


Im sorry but the flying Aaron to Alabama to help you out card can only be played once in life. I am sorry to say Jay has already played this card and is out of luck on this one. :sarcasm::biglaugh:

You know dave might be on to something here with the plugged intercooler. Have you checked it mabey you hit a possum or sumptin???? I mean you never know it is Alabama!!!:biglaugh:

4999_2500_painted-road-kill.jpg
 

hottscennessey

DONT BE A BITCH!
Jun 3, 2005
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Jay, I'm starting to think it's your tune. Looking back at your datalogs you posted

RPM............pressure.......Ign timing...........TPS........Injector ms.............Engine Temp
6462.............16.969.........17.8................100...........22.34......................154.4
6524.............16.607.........18.0................99.8..........21.78......................159.8
6591.............14.286.........18.2................100...........17.942.....................181.4
6681.............12.256.........19.0................100...........16.988.....................172.4
6764.............11.095.........19.2................100...........16.306.....................167.0
6837.............10.443.........19.4................100...........15.068.....................183.2
6897.............10.805.........19.4................99.8..........15.364.....................176.0
7026.............11.893.........19.2................37.4..........17.208.....................165.2

That ignition timing is really conservative... for instance, where boost starts to drop off, I run 10* more ignition timing than you.. and that's before my methanol even kicks in. For reference I have about 9:1 compression ratio and run 93 pump.
 

suprahero

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Thanks Scott. I calculated my compression @ 8.67:1 when I built the motor. I think that's what Cade and I came up with. I wanted my timing on the conservative side because I don't have any knock detection at all. I also run on 93octane. Do you think I should add a few degrees of timing and make a pull and see if it affects it?
I did a pull yesterday with my wife's manual boost controller and it seemed to hold boost until it got up in the 6400rpm range again. Then it fell off drastically. I have nothing but time here today, so I'll see if a few degrees of timing changes anything at all. Thanks.

Ryan, I went out and looked just to make sure, and I didn't have a possum or any other rodents in the intercooler. I'll have to take it off and check it later to make sure one hasn't built a nest inside the intercooler though..........:aigo:

Dave, I have checked the intercooler itself when I redid all of the piping and it was fine with no obstructions. Thanks.

jmc........I doubt I could get Aaron to fall for that trick twice............:biglaugh:

Scott.....All good things must come to an end sooner or later......:sarcasm: