Turbo slow to spool

After destroying an SRT-4 on the highway a few days back, and blowing an IC pipe off at the end of the pull, AND putting hte pipe back on the next day, i've noticed that the turbo doesn't hit full boost until 5200rpm now. Usually hit full at about 3800.

Important info: 10:1, Haltech, 1050cc, 57 trim T04E, Tial 38mm.

Things i have done/checked:
Turbine wheel and housing OK
Compressor OK
IC pipe leak test OK
Cylinder leakdown OK
Tial Valve and seat OK
Boost controller operation OK
Exhaust leaks OK
Timing is OK

I pulled the exhaust, and slid a flashlight up from the muffler, and i could see through the cat as usual. It's not a light brown like the used cat i have on the shelf, it's pretty black.

I'm going to go gut the cat, unless someone has any better ideas.

Anyone?

Well, it's not the cat. I disconnected the exhaust at the downpipe and scared the crap out of some cows up north but it didn't spool any different

Maybe one of the vacuum lines is partially clogged with a bit of dirt? It won't show a leak but it would obstruct the air flow.

Similar to when your vacuum cleaner is partially clogged you don't get full vacuum until the motor 'revs' at a higher RPM.

Maybe pull them off one by one and blow through them. It's free.

Just an idea.

Cheers Tony

I have been haunted by this problem since I have owned this Talon.

At fist with the 14b way back, it took way long to spool. Found out I had a bunch of vaccume leaks, and a massive crack in the waste gate opening.

Fixed the leaks and baught a big 16g (almost new) I ran that all last summer and still felt my boost wasnt comming on strong enough. I didnt think much of it and thought it was caused by a big crack in the exhaust manifold.

This year I got a near mint 2G mani, green turbo and all new piping and the thing still wont boost fast. I dont know if I am just used to my 90 (totally stock) and how it max boosts at the touch of the throttle.

When crusing in third gear at approx 3000 rpm, if I mash the throttle, I wont hit full boost till almost 5000. If I am in second gear crusing slowly at around 3000 rpm, when I mash the throttle, it picks up nicely but I still dont see 20 psi till around 42-4500. I thought greens were supposed to spool hella fast like a 14b/16g etc...

Now, you mention timing Nick. When setting my base timing, my idle at 750 rpms was so lumpy, I couldnt get a proper alignment on the timing cover to the pully. It bounced all around because of the lumpy idle. I set it as close as I could to 8* BTDC

I have no intake leaks, timing seems close enough, turbo is near new, no cat to worrie about etc... I am stumped as well.

The only time I can get boost on demand is when I am on the highway already doing high speeds and the engine is reving 3000 + rpm's.

Hope you find something out and let me know how you fixed it.

Tony, the vacuum lines on my car are all 1/4" ID. They're for the BOV, MAP sensor, and hte boost controller. BOV works fine, MAP reads fine, and there's tons of flow in he boost controller lines.

Rob, with a stock bottom end, a green will spool that slow. You just don't get boost at 3k on a larger turbo like that.

Even with an exhaust housing very similar to a 16g?

Hugh My bad

BTW, I dont know how much of a difference it makes but my bottom end was rebuilt with 95 pistons.

Rob, I have a 3" long crack on my ex. manifold. Is that my problem for a slow car w/ no boost control and only a BIT better w/ boost @ 15psi? Or my wastegate flapper is probobly cracked like your 14b was.

Yeah, exhaust leaks are just like boost leaks. Especially at the waste gate opening.

Nick, you are MUCH more knowlegable and experienced than me in DSM tuning, BUT... I am certain this green should be spooling very similar to a 16G.

anyways let us know what you find out about your problem.

Rob, it's a TD05-7cm exhaust housing, but it's a TD06H turbine, and a T04E 50 trim compressor. It's a BIG turbine! MUCH bigger than a 1G turbine.

Ken Barkhouse had one in his Eclipse with a 9:1 motor, and it didn't hit full boost till 4k or so. It was useless at 3k on the highway, he needed to downshift.

I pressure tested the exhaust, found a few minor leaks in the manifold, but nothing that would cause this. The Tial outlet gasket is pooched, and leaking quite a bit, but since it's downstream of hte turbo/gate, it's not going to hurt spoolup.

hey Nick what was the compression test reading (psi?)

also how much ign timing is there between 3500 and 5k ?

I don't have a compression tester, i just apply 100psi to each cylinder at TDC and check for leaks, and the amount of air coming out the PCV. No valve leaks, no gasket leaks, and just a tiny bit of air from the PCV, same as a few months ago.

12-15degrees. At 3k and 3k5 it drops sharply at atmospheric pressure to aid in spoolup. By the time it got to 4k it was always fully spooled, so i didn't put the same sharp cutoff in the maps at 4k and above. I was about to take the laptop to the car and try it out.

Could relieving all that pressure and airflow at full boost suddendly cause a large stress shock to the turbo cartridge? At the moment your hose lets go the turbine for a split second is still getting hot gases but the compressor is pumping with little to no restriction so the wheels spin up quite a bit higher rpm that normal? Its a long shot but...?

Turbo is perfectly fine. WHeels are good, bearings are tight.

Mr Petrie helped me do a compression test, 220psi across the board.

Now here's the weird part: It's fine now! WTF happened??

Maybe a vacuum line was partially clogged with dirt

Seriously, make a note of eveything you did while it is still fresh in your mind just in case the problem returns. The notes will give you a good base point for diagnosis.

I'm glad you've got the 'magic touch' and it's working.

Cheers Tony

I have my list at the top of this thread

4-5 psi at 3k, 15psi at 4k, and 22psi at about 4k2. WOW it's fast