gcthree

In the ever continuing saga of the 3rd gen that makes absolutely no boost, I have removed the cross over section of the efini y-pipe, and fired the car-up to see if there was any boost from the primary turbo. I felt no pressure whatsoever. Must be a bad turbo, right?

So, I removed the intake elbow on the primary turbo, and once again fired it up expecting to see a non-spinning turbine, and....it was indeed spinning, and as I increased revs, the turbine spun faster, but still no boost to be felt at the top of the y-pipe. The valve in the y-pipe was closed as it should be. Hop can this be?

The turbos are Wael's old TEC modified turbos, with absolutely mimimal play on the shafts. Likely have about 20k miles on them.

So, the question is: I am dreaming here? Should I feel some boost pressures at the y-pipe? Are the turbos bad, or should I be looking elsewhere? Again, they are making zero boost on the gauge. Go figure.....

Thanks for the help, guys.

maxcooper

It is only going to build up pressure if there is a closed volume. And turbos are not positive displacement pumps, so it will have to be spinning very fast to build boost. On a healthy car, you will only get a few psi built up when revving the car at full throttle with no load. I don't think feeling for boost is a reasonable test. And I wouldn't recommend feeling for boost with your hand under any conditions that really would produce it due to safety concerns.

Keep looking. Are there any openings in the intake tract between the turbos and the engine? Is the wastegate holding shut with the car at rest? If you remove the hoses from the wastegate actuator and CAREFULLY drive the car to induce boost (DON'T OVERBOOST!), do you get any boost? Does it sound like there is an exhaust leak anywhere, particularly before the turbos? Does the butterfly valve in the y-pipe stay closed below 4500 RPM? If you suspect any component, you can temporarily force them into a certain position (safety wire the butterfly or wastegate, etc.) or block them off (pull the BOV and plug the nipple on the y-pipe, etc.) and then do a CAREFUL test run to see if it changes anything.

Does the car make reasonable power without boost (it isn't going to be fast, but does it feel like it is running properly)? Maybe there is something else wrong, like a fuel system or igition problem. Have you verified that the plug wires are on the right plugs (middle coil goes to bottom/leading plugs, coils on the ends go to the top/trailing plugs)?

-Max

7racer

were you getting normal boost pattern before and changed something recently?

has your system ever worked?

What's your boost pattern currently?

gcthree

Thanks, Max, for the thoughtful repsponse.

No hands or fingers in there unless I want to get them grated...I wanted to ensure that the turbine was spinning freely..and it was.

No exhast leaks as determined by my ear. Does not seem to be any leaks in the intact tract at any point (new silicone couplers between efini y-pipe and PFS intercooler and between IC and stock elbow. New 0-ring at throttle body/elbow joint). The valve in the y-pipe is operating correctly (closed under 4500 rpm). I'll give the wastegate and BOV a try and see what happens.

Car runs absolutely perfectly and makes good power for a normal aspiration mode. Plug wires are correct and new. It runs great, except for the (literally) zero boost.

The wastegate thought is one I haven't considered; if it was opening, it would dump the exhaust and bypass the turbines and I'd get no boost. Correct?

Bob

-Max[/QUOTE]

maxcooper

Right. It could be that the actuator rod has come loose from the wastegate lever (it is held on with an e-clip) and it is just swinging open, letting all the fun go right around the turbos.

-Max

gcthree

It worked absolutely perfectly with a correct boost pattern. The streetported motor with all the necessary mods was down on power, and after a Steve Kan tune, he offered that it might be a restriction on the motor. I discovered that the throttle wasn't fully open at full throttle (pretty good restriction, huh?) and when I adjusted it and replaced the plug wires at the same time, the result was zero boost. Been chasing it ever since then.....

Sorry to report that the present boost pattern is: 0 - 0- 0

gcthree

Heading for the gargage and the floor jack as soon as I finish typing this, but it's difficult typing with crossed fingers....

Thanks, Max!

GustavOllufsen

im not positive about this. but i dont think that even a fully open wastegate on these turbos willr esult in zero boost. unless you're in neutral of course. but ont he road under load you should still get somewhat of spool since i doubt that that little 1 inch hole can fully vent all of the exhaust gas

areXseven

iTrader: (1)

Also, check the Y-Pipe to Turbo gasket nuts. If they're not tight, ..Ju aint gotty no boosty.

re_rotary7

ive seen one Y-pipe nut back off only halfway allowing it to raise up enough to keep the boost down to 2psi so arexseven brings up a good spot to look. you might also look at the vaccum diagram and make sure you have all the check valves in the right direction. I have ran into a no boost problem because of that and after replacing them with universal ones they went bad after a week, had to get dealer ones to get them to last. the others seemed to be failing due to heat.

gcthree

Well, Max Cooper, I'm in debt to you. The clip on the wastegate actuator had fallen off (you cannot see it because it's behind a heat shield), and sure enough the actuator arm was not attached and the wastegate was wide open= no boost.

Replaced the arm (not much room to work with there...) and rather than put a clip back on that would later fall off, I put a small drop of weld on the wastegate arm so that it will not come off (if I need to, I'll grind-off the weld and remove the actuator arm).

Test drive results? Perfect boost pattern, and I've finally gotten a chance to get a small sample of the TEC-modified turbo performance (Wael's old turbos), and they do spool fast. I'll report further when I give them a proper test.

Thanks to all who offered their advice and input!

KeloidJonesJr.

iTrader: (8)

Lines?

shipdriver

iTrader: (1)

*If you are getting 0 psig, then technically you are getting boost, just not very much. If there were no boost, your gauge would read a high vacuum. Since your not getting 8psig out fo your primary, your secondary will never come up.

*Your primary turbo will spin (even if the sequential system is not working properly) because there are no valves keeping exhaust gases from it, unlike the secondary. The only way your primary turbo will not spin is if it is seized.

*If your Charge Control Valve (the butterfly valve in the secondary side of the Y-pipe) is closing when you start the car as you say then it has to be a boost leak, like from the wastegate or piping or pressure hoses. BTW, how do you know that the Charge Control Valve is shutting? It shuts when the rod is pulled in toward the actuator. [If it is actually open, then a vacuum leak may be possible because a loss of vacuum will keep the Charge Control Valve open and will open the Charge Relief Valve (both vacuum operated) dumping boost out of the charge relief.]

Anyways, it seems like a control issue to me (vacuum sys, pressure sys, solenoids). Just my guess, which is worth about $0.02.

Rob

EDIT- Too late. Duh.