Terrible boost creep issues- need some ideas.

[86Shelby]

The car is a 91 Spirit R/T. Stock head, cams & intake. Adjustable cam gears; cams are not degreed. Spearco FMIC. T04E 50 trim/.63 STG 3 wheel; 3" exhaust. 3bar cal & +40s.

Before, the boost controller would easily hold the boost to 10 psi, WOT any gear any time up to 6500 rpm. No spiking. Idle vacuum was 13-15 in/hg.

I installed some piping to move the air filter off the turbo inlet and relocate it under the battery. I also advanced the intake cam 6-8 degrees since the engine lacked bottom-end grunt. Idle vacuum improved to 17-19 in/hg. Engine was much more responsive all around with much more bottom end grunt and plenty of top end charge. NO other changes made.

Now the boost creeps horribly at WOT; starts out at 10 psi by 3500, then ramps up to 18-20 by 5000 rpm. I let off since I haven't had the scantool hooked up to check for detonation.

I removed some preload from the actuator rod. No change.

I took the boost controller out of the equation and ran a hose from the nipple on the compressor directly to the wastegate actuator. Zero change to the boost creep.

I removed more preload from the actuator. The rod is pulled out approx 1/16" to go onto the swingvalve. Boost is 6 psi now at 3500, still ramps up to 18 by 5500 rpm where I let off.

Checked the actuator to make sure it wasn't broken, still moves freely(within reason that spring is good and stiff). Also checked the diaphragm and it holds vacuum for 5 minutes, no leaks. The swingvalve itself moves nice and free through it's range of motion.

Somehow I misplaced the allen wrench used to adjust the cam gear, so retarding it back to where it was is the next thing on my list unless someone has any ideas. I still don't understand why/how it could affect the boost like that... Thanks!

[turbovanman²]

It really seems like you have a can or preload issue.

[gvare001]

Back the cam timing a bit then go from there.

[Dave]

It worked fine before, you changed something now it doesn't work. Work backwards and retard the cam to see if that helps.

[risen]

My guess would be that you're making more power by flowing more air since you've adjusted the cam timing. Going backwards would leave you with... less power, not something that I would want. Plenty of other makes have this sort of problem all the time, some DSM turbos spring to mind.

You could always pull the turbo, and look to see if you can hog out the wastegate hole in the turbine housing to see if it can be made bigger. Or, you can externally gate it if the internal gate can't be made to flow any more (probably cost prohibitive). I guess there could be some flow obstruction in the WG passage, but it would have caused you problems earlier I would think.

[86Shelby]

Note: all tests done with a line directly from the turbo outlet to the wastegate cannister. I'm using high pressure F.I. fuel line, there are no tears, holes, etc. in the line.

Ok, so I readjusted the cam timing. No dice. I tried several different positions, retarding the cam slowed the spool up but it still creeped horribly. I tried the cam timing in several positions, still had creep.

I've checked the wastegate to make sure it holds pressure. It does. Appplying air to it with a blow gun it operated just fine. It doesn't leak down at all.

I checked to make sure the wastegate wasn't binding when it got hot. Nope, still moves freely when it's nice and hot.

I guess I'm down to swapping on the old air filter. I'll be extremely suprised to see that it was caused by the filter.

Sure would be nice to be able to go WOT with the car and not worry about it seeing the high side of 25 psi on pump gas.

Any ideas? I'm open to anything.

[overlordsshadow]

Interesting to see what happens with a different filter.

[86Shelby]

Changing the air filter back to the old one changed nothing. Sucks since I scratched up the nice pipe I had made for the new one.

I was able to get ahold of a couple different wastegate cannisters. I tried the one with the weakest spring, which was about as strong as a stock TII small cannsiter. I kept the preload fairly loose and still had creep like before. Went really loose so the rod simply slipped right on the wastegate, still creep. This is with the vacuum line running straight from the turbo outlet to the cannister.

In a fit of frustration I took the rod off the wastegate so it was free to do what it wanted. It still creeped just like before. You read that right, with the wastegate arm disconnected and fully open I am still hitting 18 psi before 6k rpm. I repeated the test several times, it did it every time. I'm lost on what is going on; what could be causing it; and why it happened all of a sudden. Before it would keep a steady 10 psi all the way to redline at WOT.

[MiniMopar]

Some sort of blockage of the wastegate hole is all I can come up with unless you had more exhaust system backpressure before and it suddenly went away.

[tryingbe]

Time to take the turbo off and inspect it.

[MiniMopar]

Does the arm have full range of motion when disconnected? I think mine move almost a full 90 degrees.

[Ondonti]

make sure that flapper is actually able to open....


And how lean is your motor running when it starts creeping?

When I advanced the cam gears 4 degrees my car started creeping badly and I had to reference to the compressor housing and douse the engine with more fuel (it was too lean). Simply adding fuel did most of the work.

So I think you need to check your tune.

[Pat]

Here's what I'd do...disconnect the arm from the WG completely and go for a drive. See if boost starts to creep up. If it does, the WG hole in your turbine housing needs to be opened up some. If not, it's probably an actuator issue.

Pat

[86Shelby]

Here's what I'd do...disconnect the arm from the WG completely and go for a drive. See if boost starts to creep up. If it does, the WG hole in your turbine housing needs to be opened up some. If not, it's probably an actuator issue.

Pat

Already did that. It still crept just as bad as before. I doubt I'll be opening up the hole since this started happening all of a sudden and before it would control 10 psi at WOT all the way to 6500 rpm. I'm going to be checking the tune with a wideband and also make sure something freaky didn't happen to the WG puck; like breaking off the arm & fusing to the turbine housing... -don't look at me wierd, stranger things have happened.

[dds78910]

My R/T had most of the mods done to it when I got it. 20% injectors, FWD Cal, Manual boost contoller set to 14, 3" turbo back exhaust and rebuilt head. And my car doest the same thing, I can be driving 35 mph, punch it and the boost will spike to 19 then go back down to 14 or 15. I was thinking it was my clutch starting to slip.

[Ondonti]

My R/T had most of the mods done to it when I got it. 20% injectors, FWD Cal, Manual boost contoller set to 14, 3" turbo back exhaust and rebuilt head. And my car doest the same thing, I can be driving 35 mph, punch it and the boost will spike to 19 then go back down to 14 or 15. I was thinking it was my clutch starting to slip.

That is not boost creep. That is a spike. Creep is way scarier because it gets worse in the higher rpms where you need more fuel and will blow your motor wide open

[86Shelby]

I took the swingvalve off last night to see if there's anything fishy going on there. Everything seems to operate just fine and doesn't appear broken. One thing I noticed that seems odd to me is the coloring of the turbine wheel and the wastegate puck & arm inside the swingvalve. Those pieces are a light tan, while the inside of the turbing housing and swingvalve body were the normal black with some very small light tan spots.

This is the first time I've seen such a contrast in colors here. Every other turbo I've seen the turbine wheel and wastegate buck are a nice black that matches the inside of the housings.

Fuel pressure is set at 58 psi static. I have not had a chance to put the wideband on yet.

[iTurbo]

Ray, the turbine wheel and housing on the TII turbo I put on my R/T was all tan. The inside of the 3" TU swingvalve was carbon black though. Before it was on my R/T, it was on my Shelby Lancer running 19 psi with stock cal and +20s. I'd say it's normal, maybe a little lean perhaps?

It's the one on the right:

http://www.turbosedan.com/misc/DSC03787.JPG

[risen]

I took the swingvalve off last night to see if there's anything fishy going on there. Everything seems to operate just fine and doesn't appear broken. One thing I noticed that seems odd to me is the coloring of the turbine wheel and the wastegate puck & arm inside the swingvalve. Those pieces are a light tan, while the inside of the turbing housing and swingvalve body were the normal black with some very small light tan spots.

This is the first time I've seen such a contrast in colors here. Every other turbo I've seen the turbine wheel and wastegate buck are a nice black that matches the inside of the housings.

Fuel pressure is set at 58 psi static. I have not had a chance to put the wideband on yet.

Assuming you still have the swingvalve off, maybe try a blowing a little (like 5-10psi) compressed air into the wg passage to make sure it isn't blocked up? I would exercise caution though, as you could spin the turbine up.

[86Shelby]

I put my finger through it. Zero restriction.