Barwick

I just got the main cat removed and replaced with a straight pipe, and the car STILL boosts up to 5 psi and then slowly goes down as the RPM goes up.

I still have the precat on there on the downpipe, is it possible that the precat is actually what's clogged? I thought that the precat just took a crap and clogged the main cat, but I could still see through the main cat ok.

Should I still be looking at the exhaust for my problem? Or do you think it's somewhere else?

HAILERS

I'm betting money on the precat. Buy a downpipe to replace it.

Barwick

craaaaap... now I gotta find one and have it installed by Friday..

Barwick

sonofawhore.. I just typed a whole response and it disappeared.

Anyhow, I got a FULL custom exhaust on it now, basically wide open, no cats, no nothing, only an OBX muffler that's basically straight through also. And it STILL will not boost beyond 5.5 psi.

I'm wondering what else to check, it's really beginning to **** me off here.. The only other thing I can think of is to replace the wiring for the pressure sensor, and assume that's the problem, that the ECU isn't seeing 5.5psi of boost, and consequently it isn't opening up the Duty Solenoid Valve?

Barwick

*bumpidy friggin' bump bump*

NZConvertible

Wouldn't it make more sense to check the sensor itself?

Barwick

I kidna did, but I don't have a vacuum pressure tester to see if it is at the -300mmHG to test with.

Barwick

ok I checked the error codes..
13
17
30
33

Reset the codes, and 13 and 17 went away, left with 30 and 33. No big deal, emissions stuff only.

Come on guys, what else should I be looking for.. I've checked all the intake piping, haven't seen any cracks (matter of fact, the tube coming out of the turbo is aluminum, so it's in pretty good shape still).. It's boosting up to normal, then goes down to 5 or 4 psi as I approach redline.

Barwick

Is it possible that the ignition being off would cause this?

Is it possible that the O2 sensor being wacked could cause this? Maybe the ECU thinks something's wrong?

TheAnalogKiddd

iTrader: (2)

Full exhaust and still only boosting to 5.5.. hrm..

does it "feel" faster? What's telling you that's it's only at 5.5 psi?

not likely, but look for restrictions and/or problems in the intake area.

other than that, do you know what kind of shape your turbo's in? Could be going bad.. let's hope not :/


Good luck.

Barwick

I'm wondering if the turbines were clipped and the wastegate was ported, all by the other guy who owned this J-Spec before me.

To tell you the truth, I really can't "feel" when it's faster.. I can't really tell the difference between it and my Civic, until I get back into my Civic. But yeah, it IS faster than my Civic, but I don't know if the exhaust made it faster.

And yeah I have an aftermarket boost gauge, and it's showing the 5.5 psi. Now it ALMOST looks like it's hitting 6 psi.

I'm really close to just unplugging the wastegate bleed line and leaving it wide open, then seeing if it boosts correctly. But I REALLY don't want to, in case I blow the engine.

Barwick

forgot to mentino.. I've already been over the intake system too.. only thing I haven't messed with is the filter. I'm close to just pulling the filter out and seeing if it boosts fine too. This thing is REALLY irritating..

Usually with a full exhaust, you get boost creep, even with the wastegate full open on a S5, correct? It seems like I'm getting anti-boost-creep or something..

Piranha

Matt, what I did to test my sensor was to detach the vacuum line going to the boost sensor, then holding an air compressor at a certain PSI setting to the hose and checking the voltage with a multimeter. Just use an extra gauge to check the compressor, then hit it on the sensor (with the ignition in) and you should see a certain voltage. To check it at the ECU, pull up all the crap around the ECU. Get some wire taps from radio shack, and some wiring, and tap the line off where it goes in. On my post with my semi-writup (its up here somewhere) I wrote what wire it is.

I'm wondering if it is your duty solenoid (?)... whatever the one is on the S5s that make the turbo boost more. 88s don't have one, so I don't know much about it. look it up in the factory manuals, you can download them at fc3s.org.

Barwick

I've checked the Duty Solenoid, and it's within specs on its resistance, AND it clicks when 12V is applied to it. I'm pretty sure it's ok. The only thing I can think it MIGHT be is that the Duty Solenoid isn't being told to open. But that doesn't explain why the boost is slowly creeping DOWN after a certian RPM.

Piranha

mine does that too... but on S4 with full exhaust it is known to (as far as I know). I just figure it as the engine is taking on more air. In your case... I dunno. Is the S5 wastegate is mechanical, right?

Barwick

you say your boost goes down after the RPM goes up also? And with full exhaust it's known to do that? Or it's known to boost creep with full exhaust?

And I think the wastegate actuation is the same on mine as it is on yours.

HAILERS

Whats the deal with the precat????? When are you going to dump it and get a downpipe? It sounds like its your problem to a tee. Its clogged. You should be hitting 8-10 psi.

HAILERS

Or, looking at the 89fsm online, I see its a duty cycle solenoid. Seems you could put a wire tap on pin 3R and monitor the voltage while boosting to see if there is a change or not. Even better find a digital meter that can monitor duty cycle and watch it while driving. It would give you a clue at least. Right now your parts swapping. Expensive.

Or if your on the cheap, tap into the line that goes to the wastegate actuator with a long, long piece of vac hose and run it to the drivers seat and monitor the output of that hose while driving. Chose your own method of monitoring the pressure.

Barwick

I got rid of the precat already, I got a full turbo back exhaust. I thought I cleared that up earlier.

Piranha

Hailers reads too fast. But he knows how to test stuff.

Barwick

Hailers: Any more ideas? I hear you're the man with the plan here..

HAILERS

Sorry, but I saw your first post on 07-25-02 at around five oclock and then somehow by 11 oclock you went and got a replacement for the precat????? It seemed too quick, especially at five in the evening to eleven in the evening.

AS you know, I have a 87 without a duty solenoid for the wastegate, so I have no practical experience. Soooooo...... I'd put the wire tap on the output to the duty solenoid at pin 3G and see what the voltage does under boost. Goes up or down or remains steady. It would be helpful if you knew if the duty solenoid was cycling or not. Get a idea of which way to go into looking at your problem.

Only 5.5 with a fully open exaust. Cheeeez. Sad. Another idea is to take the turbo inlet duct off and spin the turbine wheel to see if its got a lot of play in it.

Anybody that has a good idea, just pitch it in here. Bound to be a better way to check the duty solenoid (besides just applying 12v to it to make it click).

Barwick

yeah.. the "click" makes sure it itself works, but not that it's getting control. Any idea what pin on the ECU sends to the DSV? That'd be easier to splice into with a multimeter, won't have to run a wire or nothing..

And the sad thing is, I would think it would boost creep with a full exhaust, wouldn't you?

Barwick

oh yeah.. and I DID check the turbo when I got it, it really didn't seem to have excessive play, but there was SOME.. I don't think it touched the turbine housing though.. it was all good as far as I can tell. I REALLY hope the turbo isn't bad.. because I'm wanting this sucker to last me until the engine goes, and/or I can afford a rebuild over the winter, and get myself a 450+hp beast built

hypntyz7

Crack in manifold or bad block-to-manifold or manifold-to-tuirbo gaskets can cause this. This is part of the problem on my t2...its an 87 with a rebuilt engine making 100psi on both rotors, pretty tight turbo, no smoke, DP adn MP, TID adn cone intake, and wont go past freaking 6psi. I have cracked manifold and maybe bad gaskets as well. Remember, the turbo is "driven" by exhaust gases, so any loss of velocity before the turbo will cause lack of boost.

OTher than that, pull that wastegate line off and plug it for a run...be cautious, but youre not going to blow that thing making one run. IF it responds normaly, your problem is related to the boost control bullshit...if it responds the same, your problem is either airflow related, or turbo is bad.