New Turbo Install: Lags & Won't Boost (Part 2)

[Fearra]

Hello Supramania,

About I year ago I posted this thread in an attempt to get advice solving a problem I'd been having with an aftermarket T4 PT6262 turbo I had just installed. A year later I find myself still in the same situation. I've come back after trying several more tests/fixes in a last-ditch effort to come up with some ideas on what could be wrong. I'm afraid I'm at my wit's end now, and this may be the end of my Mk3 Supra romance if I can't figure it out.


Recap:
(Changes and additions since my last post are in italics)

Problem & Symptoms:
Manifold pressure builds to only 0-10 kPa (0-1.45 psi) at ~2500 RPM and holds until 4k+ RPM where it will rise again to only ~30-40 kPa (4.35 - 5.8) psi. No noticeable engine stumbling or roughness. The car burns a bit of oil when starting after sitting for a while, but clears up after the initial puff. It does seem to use a lot of coolant and the exhaust is a bit steamy, but nothing excessive, oil changes looked good, coolant flushes looked clean, and compression checks have turned out OK (so I'm hoping there's no BHG). I have been dealing with a stubborn CPS connector (replaced the female end, but still occasionally have trouble on start up in hot weather).


The Car & mods:
1988 Supra Turbo (7M-GTE)

R154 Transmission (auto to manual W58 done by previous owner, W58 to R154 done by myself)
DriftMotion Remote Oil Filter Relocation Kit

Apexi Power intake
V8 Lexus AFM
DriftMotion intercooler kit (includes 2.5" aluminum piping fabricated by DriftMotion, HKS knockoff BoV, 3" aluminum core intercooler)

550cc RC injectors
DriftMotion Aeromotive Fuel Pressure Regulator Kit (including steel braided fuel lines prepared by DriftMotion)
Walbro 255 LPH High Pressure fuel pump

DriftMotion Turbo kit (PT6262 turbo; .84 AR) (includes welded T4 tube manifold, HKS knockoff wastegate, turbo, turbo coolant bypass hose, oil feed line, oil drain line & flange, & 3" downpipe)
Magnaflow high-flow cat
HKS Super Dragger cat-back exhaust
EGR Delete (done by previous owner, appears to have correctly blocked off the intake & exhaust with flanges and removed the cooler plate from the back of the block)
PCV Removed (valve cover now venting directly to atmosphere, accordion hose and intake blocked off)

Aftermarket Defi Boost Gauge, EGT gauge, AEM UEGO (probe not yet re-installed in downpipe)



Troubleshooting Already Performed
Boost Leak Testing: I've pressurized the entire intake system (from turbo inlet through to the engine, with the BoV still hooked up) to ~ 25 psi and have negligible pressure loss (after blocking off the PCV pipe)
Pre-turbo Exhaust Leak Testing: Since my last post I've purchased a brand new exhaust manifold (one that wasn't molested by my questionable welding skills/cheap MIG welder) and pressure tested the system with the wastegate and turbo installed and torqued down. I did this by blocking off the manifold<->block flange with .75" plexiglass (re-used the old gasket), and duct taping my boost leak tester to the exhaust outlet of the turbine housing. No leaks (except for a bit from the duct tape and a tiny amount getting past the wastegate).
Wastegate Function Testing: In addition to the exhaust leak testing, I applied pressurized air to the referance tube to the wastegate. It cracked open at 10 psi, and fully open at ~15 psi, which is to be expected for a 14 psi rated spring.
Exhaust Blockage Testing: Checked the backpressure in the exhaust by hooking up a pressure gauge were the wideband O2 sensor fits into the downpipe. While idleing/free-revving there was no backpressure. I've also run the car down the street with the entire exhaust removed after the downpipe with no improvement in boost.
Missing Cylinder Testing: I've dripped water on each manifold runner to check and make sure they were hot after only a couple minutes of idle. All runners were hot (and presumably all cylinders functional).
Compression Testing: Previous compression tests showed good for all cylinders.
Engine Codes: none


As I mentioned I'm at my wit's end and desperate for potential solutions. Is it possible there could be some magical timing issue where the car runs fine but boost is retarded? Or some other issue with the engine itself that would inhibit the turbo from spooling, but otherwise appear to run quite well? I'm fairly certain it's not some sort of air/exhaust flow problem at this point. After a year of trying to solve this I'm about ready to give up on my Supra (even after all the work I've put into it). The only thing stopping me is that there has to be some sort of logical reason why it's doing this.

Please help!!
Thanks,
Jon

 

[hvyman]

Is the wastegate installed correctly?
It's a knock off wastegate so it could be bad.

Have you checked for codes?

Have you performed a block test and compression test to rule out bhg?

Have you checked the ignition timing?

Have you checked the cam and crank timing?

No really sure why you removed pcv. It's a good thing.

Are you using anything to tune?

 

[Fearra]

Is the wastegate installed correctly?
It's a knock off wastegate so it could be bad.

Yeah, the wastegate isn't leaking and it opens at the correct reference pressure.

Have you checked for codes?

Yes. No error codes.

Have you performed a block test and compression test to rule out bhg?

Compression tests have been good. I haven't done an official block test, but could a BHG really affect the boost so dramatically while not really displaying any other detrimental effects?

Have you checked the ignition timing?

I haven't checked it, but could the ignition timing affect boost this dramatically with the engine itself seemingly running just fine? I suppose I should check it.

Have you checked the cam and crank timing?

Again, I haven't checked the cam and crank timing, but I haven't touched the timing belt since before I installed the new turbo. Previously I was making more boost with the torn up CT26 than I can with my new PT6262. Again, though, to be thorough I suppose I should check it.

No really sure why you removed pcv. It's a good thing.

The crankcase can still vent, I just removed the eco-friendly routing back into the intake (via the accordion hose and throttle body). I noticed the PCV pipe created what was essentially a boost leak (direct connection between throttle body and the accordion hose), and I wanted to be 100% sure I had boost leaks ruled out. I blocked it off to confirm I have a near perfect seal between the turbo and the combustion chambers.

Are you using anything to tune?

No tuning done yet. Still running on the stock ECU and stock cams.

 

[hvyman]

The hose doesn't go to the throttle body for Eco. It's goes to the throttle so it can pull a vacuum on the engine. That is basic pcv functions. It was the even before the gas crisis on v8 with large displacement and big carbs.
And since the pcv uses manifold vacuum and is after the throttle body it is not a boost leak. It's also a very tiny hole.

Ignition timing has a direct effect on lag.

A compression test doesn't show everything.

I think you need to inspect more before going anywhere.

 

[Fearra]

The hose doesn't go to the throttle body for Eco. It's goes to the throttle so it can pull a vacuum on the engine. That is basic pcv functions. It was the even before the gas crisis on v8 with large displacement and big carbs.
And since the pcv uses manifold vacuum and is after the throttle body it is not a boost leak. It's also a very tiny hole.

Ignition timing has a direct effect on lag.

A compression test doesn't show everything.

I think you need to inspect more before going anywhere.

I suppose I should mention I don't intend to run the car permanently without the PCV pipe, I just removed it because when I pressurized the intake system it was functioning as a boost leak to the point where it was a clearly audible hissing. Since I wanted to be sure there wasn't any other possible leaks I blocked it off so ensure the system would hold static pressure, and to allow me to listen for any other leaks that there may be. Also to demonstrate to myself that doing some pulls without the open air path between the compression side of the turbo to the open-to-atmosphere side wouldn't make a noticeable difference.

Thanks for the tip on the timing, I'll check it this weekend. I haven't intentionally changed it since the turbo install (I was able to get stock boost on my damaged CT26 prior to the new turbo), but it's possible the CPS was bumped or jostled during the install. (Here's to hoping that's the problem).

 

[Fearra]

So in the past few weeks I've checked the timing and did a block check.

I also rechecked the engine codes and found a code 24. I've fixed it now with no appreciable difference in performance.

The block check came up negative for exhaust gases in the coolant. After about 3 minutes (the test recommended only 2) the solution was a bit green tinted, but definitely not end-of-the-world yellow.

The timing is confirmed at 10 degrees in diagnostic mode, however it's not very stable. The pulley mark stays on the number 10 mark, but bounces around a bit (I'd estimate +/- 2 degrees). Is this within reason?

Any other suggestions on what the problem could be?

 

[hvyman]

Depending on what block tester and fluid you used if its like a bright green its usually bhg.

you fixed the 24 by replacing the afm?

perform a compression test and leak down test.

 

[Quin]

Can you swap with a known good CPS? Are you absolutely 100% sure you installed it correctly? I had one a few years ago that was off a tooth but adjusted all the way to one side. Car idled and drove fine but would make zero/almost zero boost.

 

[Fearra]

Depending on what block tester and fluid you used if its like a bright green its usually bhg.

you fixed the 24 by replacing the afm?

perform a compression test and leak down test.

This block tester fluid was supposed to turn bright yellow.

The code 24 fixed itself. I disconnected the AFM, cleaned out the connector and proceeded to check the circuits for shorts or opens with a multimeter. I found no problems, hooked it back up and rechecked the codes. It was fixed. I'm betting it was just a dirty connector and cleaning it fixed the problem.

Can you swap with a known good CPS? Are you absolutely 100% sure you installed it correctly? I had one a few years ago that was off a tooth but adjusted all the way to one side. Car idled and drove fine but would make zero/almost zero boost.

Unfortunately I don't know any other supra owners here and there doesn't seem to be an abundance of supra parts. The thought of replacing the CPS had crossed my mind and I was looking around for used ones on eBay. I haven't ever removed/installed the CPS in my car since I got it, but I have been having troubles (i think) with the CPS signal. I replaced both ends of the connecter and that helped, but still occasionally have a prolonged cold start from time to time.

---

So I did a leakdown test. Here are the results:
Cylinder #1: 20-25%
Cylinder #2: 20-25%
Cylinder #3: 25-30%
Cylinder #4: 20-25%
Cylinder #5: 15-20%
Cylinder #6: ~20%
Everything came up green. Unfortunately I did notice something when testing cylinder 6.
When cylinder #6 was pressurized I heard the distinct sound of coolant flowing. I was listening to the block to try and hear exactly where it was coming from, cracked open the radiator cap and was sprayed with pressurized coolant.

Someone please tell me this isn't what I think it is...

 

[supraguy@aol]

Ok, Here's a dumb question. Have you actually reached insid the turbo and spun the impellor? Does it spin freely for at least a couple seconds before coming to a stop?

 

[Fearra]

Ok, Here's a dumb question. Have you actually reached insid the turbo and spun the impellor? Does it spin freely for at least a couple seconds before coming to a stop?

Yeah, I've generally given the turbo a quick check every time I've taken the intake off. It seems to spin fine. No ball bearing, but giving it a firm twist will spin it for several revolutions.

I think I'm gonna try resetting the CPS tomorrow and see if that does anything.

 

[Fearra]

Well, I pulled the cap off my CPS and checked it's alignment. I set cylinder 1 to TDC (verified by pulling out the spark plug and resting a socket extension against the piston, and ensuring the cam gear marks were at the top). The CPS seems to be correctly aligned according to this 'how to'. It's not adjusted all the way to the left or right at all.

I'm guessing from the lack of responses that people are running out of ideas (just like me)?

 

[hvyman]

You checked cps alignment but did you set it with a timing light?

 

[3p141592654]

The timing should not have 2 deg jitter in diagnostic mode. It should be rock solid at 10 deg with the throttle closed. Is the A/F behaving as expected? Does it go in and out of closed loop during acceleration from cruise? A 0.84 A/R is pretty big, you should expect low boost and laggy behavior I would think.

 

[hvyman]

Shouldnt be too bad. .84 on my 1j is 3800. on a 3l should be 3500 as long as the rest of the engine electronics and mods are good. which im not sure.

 

[Fearra]

Correct me if I'm wrong, but in diagnostic mode the ECU should be triggering the igniters based purely off the CPS signal plus an offset, correct? I'm beginning to suspect my CPS circuit may have some bad connections or something. I may try measuring the resistance in the wires between the CPS and ECU next to see if there's maybe a break in the wire or something causing the unstable idle.

When I took the CPS apart it looked very clean inside (not rusty at all like the one in this guide). I'm hoping the CPS itself is fine.

I still have to re-install my wideband O2 sensor into my downpipe. I'll try and get that done as well and get some current A/F ratio numbers.

 

[hvyman]

Diag mode changes the timing to fixed instead of using a table and constantly changing to variables.

It's so you can set the base timing correctly so it's adjustments under normal operation are accurate.

Without setting makes the all of the Ecu calculations off.