Problem with boost decrease

[Dragons88Supra]

Modifications:
HKS 3” down pipe, HKS super Dragger 3” exhaust, 3” test pipe (cat eliminator), Venom 550cc injectors, JE Forged pistons & rings, new stock cams, valve springs, oil pump, gaskets, new radiator, new hoses, new NGK plugs, NGK wires, KN air filter, 3 angle racing valve job on the head, HKS metal head gasket 2mm, ARP head bolts (75ft/lb), ARP rod bolts, shot peen & beam polished stock rods, new bearings, Aeromotive 13109 adjustable fuel pressure regulator, Greddy Turbo kit (TD06SH-20G), Ebach lowering springs, Tokico Illumina 3s, cusco front strut bar, cross drilled slotted front rotors, new rear axles (CVs), RPS puck clutch kit, Fidanza fly wheel, UR under drive pulleys, UR adjst. Cam gears, HKS super Seq. BOV, Cobalt A/F meter, EGT gauge, Fuel pressure gauge, HKS turbo timer, Lexus V8 MAF, Apexi ACV-R boost controller, Apexi SAFC2 fuel controller. Not installed HKS FCD.

CURRENT PROBLEM:
Now a few months ago I was driving the car with my wife on a nice day and the cars boost was spiking to 1.20bar with the boost controller set to 1.00bar and 1.15bar (which had been no problems in the past). When it did this it also would jerk, backfire, and loose power with a chck engine light. This only happened a few times each time I let off. I reset the boost controller to 0.90bar then tried again same results. Then the car set another month or so. Then driving it again it did the same actions as above but this time at .89bar of boost up. So I cut off the boost controller, then the problem went away along with some boost. The boost then would peak at 0.81-0.82bar with boost controller cut off. Still running pig rich. Suspect fuel cut maybe, but not sure why didn’t do this from beginning, if it is fuel cut out.

So now after hooking up the Apexi SAFC2 and getting a friend to help me tune it while driving we got rid of the pig rich condition while on the highway boosting up to a peak of 0.81bar. Then the day after that we tried to fine tune it and started again this time after a few runs we cut the boost controller back on. With some interesting results this time. Car would only boost up to about .7bar now with the boost controller on or off.

Now the car is not boosting over 0.53-0.59 (8psi) peak. We can not figure it out. Why I am loosing boost or can not boost up any more. Does anyone have an idea? How do I check the boost controller to make sure it is still working? I have no smoke or anything funny from the car. It runs strong up to the boost peak of 8psi or so. Like nothing is wrong with it, except for the fact the car was boosting to almost 19psi two months ago. You would not notice anything wrong at all? Please help.

[bgrieger]

bypass the hose on the stepper motor/solenoid and turn it off to remove the boost controller from the picture. If you know your wastegate peak pressure, see what happens. If there are still problems, you have a) a big boost leak, b) a bad wastegate spring), c) some other problem. Find which before continuing.

[Dragons88Supra]

Thanks....

I will try that after work tonight.

I may also start replacing rubber vac lines with silicone vac lines, soon just to help make sure there are no vac leaks in the system.

I keep hoping to find a cut line or unhooked vac line somewhere to solve my problems simply. But no luck.

Thanks again. Any other help would be great. I will post the results from bypassing the boost controller.

Thanks again.

[Dragons88Supra]

Well I took off the air filter and tried to clean it but not sure I did good enough. I checked the wastegate of the Greddy turbo. It takes all my strength to pull it open. So I performed some other test after bypassing the boost controller.

I unhooked the waste gate vac line. So the waste gate would stay closed. Then in 4th gear started pulling at 20mph. Same reults I could only reach a peak boost of .56bar (10.5psi). Still not sure what gives.

I can find on vac line leaks, I tightened the HKS BOV screw (spring), still nothing over .56bar. I plan to try running without the air filter tomorrow and see what happens, as a test to verify the air filter or intake is not the problem.

[bgrieger]

Filter is not going to do squat. It would have to be so completely coated it would implode to get to 10 psi...but try taking it off and see what happens (It's easy to get to!). How about an intercooler piping leak (like on the compressor outlet flange)? Exhaust manifold leak? turbocharger impeller problem (though you should get some funny sounds along with it). Here's an odd one, you have adjustible cam gears...any chance one has slipped on you/skipped a tooth and thrown the valve timing way off (big overlap would bog it down in a hurry). I would have said cat, but you don't run one. Have you retrieved the engine code yet to see if the computer can help pinpoint it?

[Dragons88Supra]

Sorry I didn't get time this weekend to work on the car. Only about 20mins Sat. afternoon between other jobs. I changed to a new stock type Fram air filter and drove the car to pick up some plumbing items at Lowes. No change still only .54bar boost max.

I plan to check the engine code tonight. I will also check the cam gears (remove the cover) and see if they have slipped or anything.

I don't think I have any exhaust leaks, but not 100% sure. I will try my best to check that out as well in the next day or so.

I'm still not sure what the heck is going on with this. Since the turbo pulls strong and the car runs good up to its max out of .54bar boost? with no funny sounds. So I don't suspect the turbo is bad. It also only has about 6k miles on it or less.

I will check the intercooler piping like you suggested also. I'm really lost on this one.

Just can't understand why it happened so suddenly. One day boosting fine the next boosting a less, then 3rd day boosting low but staying at the low level all following days????

Thanks for your help so far bgrieger. Your the only one who has offered any feedback.

[Tosh]

i would go with option b, it really sounds like the wastegate spring isn't holding up. the tdo6 has an internal wastegate like our ct's right? try shimming it to increase the pressure on the spring. takes 5 mins, couldn't hurt right.

playing the cam timing is beyond me right now so i can't give you any tips.

g'luck

[Dragons88Supra]

Good news I think.

Guys I think the problem was found last night. While taking the intake off and trying to figure out how to re route my HKS SSQBOV as to use the return to intake air.

Anyway. I was checking the turbo shaft (spinning the wheel) to make sure there was no problems with that. Then I was about to remove the cover for the cam gears and I decided to Check the hardness of the turbo outlet tube since I checked all the other intercooler piping. Then check the wastegate spring/ waste gate. And Whala! When I reached around to give it a squeeze my finger pushed into a crack right at the turbo outlet. Where I couldn't see from the bottom or the top of the car. So I removed it.

But no local auto stores seem to carry turbo parts for older cars at least. So I will order one from Jay marks toyota in texas with the supra club discount Monday. I hope to have it overnighted and get it on the car by Wed. so I can tune and take the car to the drag strip Friday night. I will post again if this fixes it or not.

Thanks for all your help and sugestions.

[bgrieger]

Yup. Hot area, rubber hose, 16 years of driving. All adds up to IC hose failure.

Bob

[Dragons88Supra]

Thanks guys.

The issue is solved and car is back up and going strong.

I got the new hose from Toyota last night and installed it, along with replacing some older vac lines with silicon lines at the same time.

Got everything put together and let it warm up and then started to make a test run.

With Boost controller off, hit 0.89bar boost on first try. Then 0.9bar (13.1psi) on second run.

Now I have to re-tune the SAFC2 today at lunch, to make the drag strip tonight to fine tune the fuel in.

Hope to make it to the Battle of the Imports at Rockingham Dragway in Rockingham, NC Sunday.

2hour drive but worth it.

Thanks again for everyone’s help.

[Tosh]

glad to hear.
what e/t and mph are you expecting?

[Dragons88Supra]

I'm hoping to reach my goal of 400 RWHP.

I also hope to get a 12.5-12.9 ET for 1/4

I would like to see 102-110mph in there also.

I haven't run it up to 20psi yet but I will once tuned in and at the strip.

I'm running about 12.5-14psi currently. Would guess in the high 12s or 13 flat time range, in current condition. (at about 100-103mph)

I plan to go to Dyno soon and schedule some tunning time. In the next week or two and tune it in. Right now I'm using a autometer A/F gauge and stock O2, to try and tune. So I can get close as I can before going to the dyno.

Thanks again, Take care all.

PS:

Anyone know anything about a intake that will work with a 7MGTE but unlike the stock unit it has the throttle body at the front of the motor like on a 2JZGTE motor?

[Tosh]

good stuff. I trapped 103 mph a couple weeks ago at the track on stock ic + piping, stock 440's and 12psi stock turbo. Too bad I'm a shitty driver!

high 12's or 13 flat with that trap speed would be awesome. what kind of 60' times are we looking at. 1/8th et +mph...

[Dragons88Supra]

Well the wife gave the okay. So I will know exactly after Friday what to tell you.

I will be going to the local 1/8 drag strip in Farmington, NC Friday night.

I should be able to get one or two runs in before bracket racing starts.

I will report the results Sat.

Two weeks ago I took my 1988 Toyota Celica GT 245,000 miles, paid $550.00 USD for it.

Ran 10.65 at 65mph best time. My reaction time sucked since it was my first time at a track. USed to street racing light turns green go for it. hahahaha...

Dial in at 10.9 but ended up with my best of 10.65 and lost.

Reaction times from .80-1.11 asleep at the light once and spinning in a Celica with the 3sfe motor 115hp

[J's91supraturbo]

Hey, since it seems you guys did a lot of thinking about ic piping on a mk111! I just bought a new ic (24X12X3) for my 91 mk111 and I was wondering what o.d. the stock piping is, and whether I need to get some couplers! (the new ic o.d.'s are 3") Thanks for any help!