Turbo slow to spool and not full boost

[KingKong8247]

Engine is a ka24e-t. Gt30 turbo, tial wastegate, ebay fmic, JWT ecu.

Here is the problem. Car was working fine, spooled very fast and hit full boost (10.5 wastegate spring, 14psi manual boost controller) in every gear. One morning, went for a drive and noticed the turbo was spooling very slowly and wouldn't hit over 8psi of boost. Got on the hwy and it overheated. Replaced the thermostat, rad cap and bled it very well and fixed that problem. The boost problem is still there.

I have removed the wastegate and cleaned it, replaced all the vacuum lines, and checked for boost leaks. I know there is small leak where the throttle plate shaft goes into the TPS and where the BOV connects to the piping.
I know these are not the problems because the other day the car was having this problem then it somehow fixed itself and ran perfect, with the leaks and all, but only ran well for 15 minutes or so. It idles pretty well and AFR's are fine. Lean at idle but when driving they are good.

I also disconnected the boost controller and hooked the wastegate vacuum directly to the compressor housing, even left it disconnected and still wouldn't go over 8lbs.

I have pressure tested the cooling system and there is no leaks.

I'm sure it is something so stupid but I just cannot figure it out. Any ideas?

[slider2828]

Are you sure that it was just the coolant system cause the over heat? Did you check compression and timing?

[e1_griego]

Sure there's no leaks at the head/manifold or the manifold/turbo?

Yay for another ka24e-t!! :P

Alex

[KingKong8247]

Yea forgot to mention I did check compression and it is good. I have not checked timing, I meant to today but forgot. Ill do that tomorrow.

And there is no leaks around the manifold that I can see. Anyway good way to test for leaks around the manifold besides looking and feeling for air?

[ExtremeD]

check to see if the turbo spins freely when its not started. my sr was doing something simular after my manifold got a big ass crack in the bottom of it. make sure evrything is cold then start it and run ur hand all along the mani to see if you feel air or something, where it bolts on to the head and the waste gate flange

[KA-T_240]

Do you have oil in your IC pipes or DP?

Check your timing just to be safe, even though I really do not think its your problem, as timing doesnt just change. (unless your ECU is screwed up).

For exhaust leaks, you should be able to hear them. My old mani cracked, and it whined really loud on decel and as it got worse, it could hear it at idle. Next step after that, you will get getting suit in your engine bay.

Have your tried a different boost gauge, or changing the location of where you boost gauge is hooked up?

If you take the WG line off, you should build as much boost as your foot allows.

Do you have a wideband to monitor A/F ratios?

[KingKong8247]

Do you have oil in your IC pipes or DP?
I have checked the pipe coming right out of the turbo and the pipe right before the throttle body, no oil at all. Have not checked in the downpipe.

Check your timing just to be safe, even though I really do not think its your problem, as timing doesnt just change. (unless your ECU is screwed up).
Timing is good.

For exhaust leaks, you should be able to hear them. My old mani cracked, and it whined really loud on decel and as it got worse, it could hear it at idle. Next step after that, you will get getting suit in your engine bay.
I cannot feel or hear any exhaust leaks.

Have your tried a different boost gauge, or changing the location of where you boost gauge is hooked up?
I have not but I do not think that matters because I feel the loss in power.

If you take the WG line off, you should build as much boost as your foot allows.
My thoughts exactly but doesn't work

Do you have a wideband to monitor A/F ratios?
Yes I have a plx-m300. It reads around 18 at idle which is lean but when cruising it is around 14 and WOT around 12

[KingKong8247]

Could it possibly be the spark plugs blowing out? Would this cause some type of stumble or roughness?

[DJ_Sunrise]

You live in jersey, nice. Want help? I'm located near Princeton.

-Bart

[KingKong8247]

You live in jersey, nice. Want help? I'm located near Princeton.

-Bart

Hey, thats really cool of you. Im not too far either, located near Bordentown.

PM me if you want to meet up

[gippy87]

Basically the same exact problem here so if you figure it out lmk

[KingKong8247]

I tried switching the vacuum source of the wastegate but still the same.

Any more ideas?

[slider2828]

PCV valve? Change that?

[gippy87]

turns out one of the studs backed out on the mani to turbo. Sort of figured that since my last sr20 did the same damn thing. Im going to tighten and do very small spot wleds to prevent this from happenin ever again :-)

[KingKong8247]

Hey Gippy glad to hear you figured yours out!

No pcv valve in my car.

[steve shadows]

Yea forgot to mention I did check compression and it is good. I have not checked timing, I meant to today but forgot. Ill do that tomorrow.

And there is no leaks around the manifold that I can see. Anyway good way to test for leaks around the manifold besides looking and feeling for air?

Doesnt matter. You compression could be fine under test, but under leak down or under higher boost your head could be lifting.

Are you sure your cooling system is pressurizing and your thermostat is working?

Is it an internal or external wastegate. I would get an external if your still running an internal

[KingKong8247]

I am using ARP head studs and had a well known shop in this area install the head to the block so I am hoping it is not lifting.

I know the thermostat is working because when bleeding the system I can tell when it opens and coolant needs to be added.

When I tested to see if the coolant system is pressurizing this is what I did. I rented one of them rad cap tester, got an adapter for my radiator, and pressurized it. It held around 13 psi no problem.
I did this when the engine was cold.

External wastegate.

[sr20boostn20]

check all the gaskets before the turbo. manifold to block, mani to turbo.

check and see if the wastegate is tight.

check the manifold for cracks.

all of these things can be attributed to added lage and less boost.

[KingKong8247]

Yea its gotta be a leak before the turbo somewhere.

Im probably going to take off the manifold and replace all the gaskets and check it for cracks.

[KingKong8247]

OK still having this problem. I took the mani off, check it over and over for cracks, none. Buddy gave me a wastegate, another Tial to use, same deal.

Replaced the gaskets, mani to head, turbo to mani, and the ones in the exhaust.

Anybody have any ideas or wanna come check it out and help me I'd appreciate it and can provide the beer.

**EDIT** Forgot to mention that the other day i was driving to a friends house and about an hour into it on the hwy, the car boosted like normal again, fast spool to 14psi. That lasted all of about 5 minutes.

[Z U L8R]

let's remove this as a possibility all together. i concur with steve atm.

do you have any brown or black specs/flakes/carbon on top or your radiator cap, any crap in your coolant? you know it's recommended to retorque arp head studs after a couple heat cycles right?

i feared i was lifting my head on my rb, 1500miles after the rebuild, i retorqued the arp's to 80 ft lb and 2 of them got a full turn and a half before reaching 80ft lb.

i also noticed a little carbon on my radiator cap, so just take a peek. let's rule this out tho.

gl man,

Dave

ps, can you pm me your specs, like is it a 30/71 or 30/76, when do you hit full boost, that is when it's boosting correctly, what kind of power is it making, what a/r etc etc, i'm trying to decide on the perfect turbo for my ka-t 510. i appreciate that.

[KingKong8247]

do you have any brown or black specs/flakes/carbon on top or your radiator cap, any crap in your coolant?

I have flushed my coolant system a few times since this has started and its always clean. Ill double check it tomorrow morning though.

you know it's recommended to retorque arp head studs after a couple heat cycles right?
I havn't re-torqued them since the engine was built. That could be a good reason for this to happen so I will check both of these hopefully tomorrow after work.

[mifesto]

boost test it!

[KingKong8247]

Done it.

I know there is small leak where the throttle plate shaft goes into the TPS. I have tried 3 different throttle bodies and all leak in this area. Im gonna try to use some type of sealant this weekend to fix this.

[KingKong8247]

Ok I checked the head studs and they are all torqued to 65 foot lbs.

I just noticed something though. When I went for the quick drive to see if tightening did anything after the car warmed up to 165ish I just started doing some hard pulls from 1st to 3rd gear, just beating on the car ya know. Anyway the temp shot up right to 200*. Usually the car is at 185* After I got out of boost it would go down but when I would pull hard again through the gears it would go back up to 200*. Seemed like with boost it would get hotter.

[Z U L8R]

torque em down to 80 ft lb's in sequence

Dave =]

[KingKong8247]

Yeah, I keep reading that but its all for DOHC's and I know the studs are different for the SOHC and DOHC. So I am going to call them tomorrow and see what they say.