I have just finished rebuilding my motor. I bored it .20 over, wiesco pistons, scat rods, ported head, nitrated valves, and a bunch of other goodies. I went to get on it tonight, and the turbo lag was something awful. I had pressure tested for boost leaks and had none prior to this. It was really weird. It lagged to 4500 rpms, then just piled the boost on. I tried a few more times but sill massive lag. I know this turbo is suppose to spool much faster 4500 rpms So with no boost leaks how is this possible? Then engine timing is right on. And sometimes at idle I can hear a hissing/scratching noise comming from the turbo. Is there such a thing as reverse compressor surge, because thats what it seems like its doing? BTW I have the 38mm internal gate.

Did you adjust the actuator arm?

Also, double check your cam timing. And you could be running really rich down low...

Pre turbine inlet exhaust leak? Check the exhaust manifold gasket and turbine inlet gasket! Are the turbo bolts staying tight? Are ALL the exhaust manifold nuts tight?

I've seen a lot of reviews for this turbo spooling 4000+ so it's not too far off.

I also have the t04b vtrim, and I was having about the same problem. Turned out to be an exhaust leak at the manifold outlet. The surface was no longer flat it had hardened raised surfaces from many years of use on the stock gasket. With a different manifold I now spool at about 3500 RPMs.

I'll go ahead and hate on it.........but you get what you pay for. Alot of people are or were complaining of slow spool times with that turbo. However with that setup you definitley got something cooking. Boostleak test again/exhaust leak prior to the turbo. You'd be amazed by how much those loose studs can slow you down

I frankly never bought into the 50trim trend............straight old school 20g, couldn't be happier!! Couldn't hardly tell the difference in lag stepping up from a b16g, but the power......DAMN

Usually the slow spool with these is the actuator arm being misadjusted. I have an external wastegate and mine starts spooling around 3000.

turbo90gsx said:

I have just finished rebuilding my motor. I bored it .20 over, wiesco pistons, scat rods, ported head, nitrated valves, and a bunch of other goodies. I went to get on it tonight, and the turbo lag was something awful. I had pressure tested for boost leaks and had none prior to this. It was really weird. It lagged to 4500 rpms, then just piled the boost on. I tried a few more times but sill massive lag. I know this turbo is suppose to spool much faster 4500 rpms So with no boost leaks how is this possible? Then engine timing is right on. And sometimes at idle I can hear a hissing/scratching noise comming from the turbo. Is there such a thing as reverse compressor surge, because thats what it seems like its doing? BTW I have the 38mm internal gate.

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As everyone has said check the wg actuator for proper adjustment, boost leaks, exhaust leaks etc. but at idle you hear hissing/scratching noises? That doesn't sound to good to me. I'd check to make sure the compressor wheel isn't coming in contact with the comp cover (ie to much side to side shaft play).

Thanks all for all the responses. I decided to try another boost leak test today right at the throttle body. I heard a leak that I didn't hear before that was comming from around the brake master cylinder. I cooked up some soapy water in a spray bottle, and sure enough there was a HUGE leak comming from in between the mater cylinder and the brake booster. I took off the master cylinder and tested again. It seems that the seals in the brake boost have completely failed. I tried using some silicon sealent around the master cylinder but then it just started blowing through the rear seal into the interior. Are there kits out there that I can rebuild the booster, or do I have to buy a whole new one? Has anyone else had a boost leak there? I've been searching around and haven't found anyone that has bad this problem yet

...Edit...
Wait a second...

"After some searching, I found I forgot to put the check valve back in the line I replaced from the intake to the brake booster, so that should fix that loud ass moaning noise that was coming from the booster, "

I think I forgot that too...

turbo90gsx said:

Wait a second...
"After some searching, I found I forgot to put the check valve back in the line I replaced from the intake to the brake booster, so that should fix that loud ass moaning noise that was coming from the booster, "
I think I forgot that too...

Click to expand...

I did the exact same thing

How's the v-trim boost now? I just ordered one up with internal gate and was wondering how the spool time is at low boost.

Mine used to spool around 15psi @ 3800rpm untill it blew up on the track @ 20psi. I am not sure if it's due to the high pressure(20psi?) or it's been damaged from the previous owner, but all i can say is I will definilty not go back and rebuild this one.

I loved the vtrim very quick spooling turbo but i had to get rid of it because it was surging with the built motor. Went 50trim and never looked back

Mine's a dog lag wise. But when it comes on, it hits like a brick wall. It's odd tho. I hooked up my compressor to the wastegate actuator and tee'd my VDO boost gauge into the line from my compressor gun to the wastegate actuator.

Using my compressor pressure knob and my boost gauge to confirm, the internal gate starts opening at 2psi. It makes a horrid sound at 12psi ONLY and doesn't fully open until 20psi. I think with an external gate, this turbo would be better for spool.

Not to mention, I basically can't run less then 20psi of boost pressure. The actuator doesn't fully open until 20psi so when I have it set for 12psi, it'll creep to 20. If I have it set for 16, it always creeps to 20.

This IS with a gasket matched ported 2G O2 housing.

Just an input. Have you guys considered the possibility of the 38mm flapper being blown open by exhaust gas? Test run with the flapper wired shut and see if situation improves.

oldman said:

Just an input. Have you guys considered the possibility of the 38mm flapper being blown open by exhaust gas? Test run with the flapper wired shut and see if situation improves.

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I left the wastegate actuator hose off once for a test run. The turbo spooled like a crazy turbo from hell. I'm confident there's an issue with the wastegate actuator.

Well after I fixed the brake booster vacume line leak, I've been able to make 16psi around 3700rpms. There is a slight surge from 16psi to 20psi, but only sometimes. I have yet to see the true top end potential of this turbo because 1)I still only have 450's 2)I'm still keeping the motor below 4500rpms. It seems like it has alot in it though. The car pulls pretty hard in its 700 rpm power band.

16psi is too high for that turbo on stock 450's especially without a logger, I strongly suggest that you keep the boost down as low as you can until your fuel system is ready. You bought the turbo too early.

oldman said:

16psi is too high for that turbo on stock 450's especially without a logger, I strongly suggest that you keep the boost down as low as you can until your fuel system is ready. You bought the turbo too early.

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Defently turn that boost down without a logger. At 15 psi with my evoIII I was seeing 107% duty cycle on the stock injectors, and I would imagine you will be making atleast as much if not more lb/min. Before I had the upgraded fuel system installed 15 psi was still fine in my case as I had dsmlink to monitor knock, but every car is different & your running blind.

assa 98gsx said:

Mine used to spool around 15psi @ 3800rpm untill it blew up on the track @ 20psi. I am not sure if it's due to the high pressure(20psi?) or it's been damaged from the previous owner, but all i can say is I will definilty not go back and rebuild this one.

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Sorry to hear of it. I confirmed it today...20psi at 4400rpms (4th gear). stock 7 bolt, tubular manifold, external wastegate. But i still take out TD05 20g cars...