Why does my car make no boost with the wastegate safety-wired closed?
 

Just curious. :inout:

Came around a corner sideways in 1st last Thursday with my old T25, hit 2nd, and had no boost. I was planning to change the turbo anyway, so I did the swap to a GT2554R, but kept the old wastegate actuator. No boost. Then I switched to a new actuator, no boost. Then I wired the fucking wastegate closed, no boost. What gives? The only thing I can think of is that my EGR has somehow failed (I have a BEGI manifold with the EGR hooked up) and all the exhaust gases are rushing through there. I'm stumped, though; I figured wiring the fucker would give me at least a few PSI on roll-on.

You couldnt possibly have all exhaust gasses exiting through the EGR, maybe you have a boost leak in your charge pipes somewhere?

Wiring it closed should allow you to boost till you blow. I don't know much about how the EGR would work in this case but it's either going to be the EGR or the WG flap fell off.

The WG flap is still on my T25. It's not a boost leak because my car sounds like a fucking Mack truck spooling up. I can't hear the exhaust over my turbo noise normally, and right now there is NO turbo noise. All the basic ideas get shot to hell by the fact that I've changed the turbo and wastegate actuator.

How do I change the god damn EGR? I don't even know how it works. >.<

Kinda greek to me as well. Isn't there an EGR valve on the intake manifold that open's and closes relative to vacuum. The valves stick sometimes and I think you can clean them with brake cleaner or something to unstick them. (doing research)

My egr is replaced with a block offplate on the back of the intake.
http://forum.miata.net/vb/showthread...ight=stuck+EGR

Could it be that your new turbo isnt spooling at all?

As for EGR, I think it only activates at idle and cruise.

I've had this problem on two different turbos. Both spin freely with minimal shaft play. I could see the T25 spinning at idle with the intake tube off.

check charge pipes
then recheck

Will I really hear no turbo noise at all if I blew a charge pipe off?

actually this just happened to me like 2 days ago and the turbo would not audibly spool when the pipe blew off. I suppose with the lack of actual boost increasing the exhaust pressure, it just cant quite get spinning quick enough.

yeah you should hear some noise, but it will sound completely different than what you're used to hearing. you'll hear the 'spinning' but none of the 'wooshing', hard to explain

id also say check your pipework, if you have a cooler check that you havent got a hole in it also...... but in saying that you would normally hear a pipe come off or a cooler pop, it sounds like something poping & its loud, this happened to me once on my rx7 & trust me you know about it, in fact the pipe that came off did so with so much force that it dented the strut tower that it hit....

it does not necessarially mean any loud sound though, pipe can work off slowly.

I would still consider the EGR as a possible culprit stuck open, it's either that or a pipe blew off.

Mark

Cracked manifold? Blown manifold gasket?

+1 on manifold seating surface or manifold leak preturbo. Even with my charge pipe damn near off i got 3-5 psi most of the time :gay: Pull the manifold and inspect it thuroughly cracks are a bitch. and gaskets suck when they fail as well.

cracked mani/open pcv/blown hg, etc the car would still make SOME boost. even with everything functional and a tied open WG, it should still make a little positive pressure.

best explaination for no boost at all is a problem in the charge pipes.

I had the manifold off extracting a stud when I changed turbos. I did not see any blatant cracks; I would think a problem so serious that it wouldn't spool the turbo would come up as a really fucking loud exhaust leak. The car sounds normal, mabye a tiny bit louder. Certainly not exhaust-leak loud.

look at everything between the TB and turbo.

I just drove the car and pushed it pretty hard. I can get to around 3psi at 5000rpm. There are no charge pipes broken; I pulled on them all pretty hard and none came loose in my hand. The wastegate is still wired closed. It makes boost VERY slowly, which leads me to believe that the pressures in the EM and the IM are constantly trying to equalize.

How hard is it to block off the EGR? Can I block it off and have no issues if it has really failed?

Does a 1.6 have an EGR? I have a salvage 1.6 that used to have a turbo, and I cannot see an EGR tube on it. If I can find the EGR on that motor, I can use its blockoff plate, possibly?

Are you sure you don't have it wired open?

Totally sure.

I've removed the EGR. Is there a simple way to tell whether it's failed? The valve seems to be closed at rest.

What would happen if the turbo wasn't spooling properly? Would you notice a difference in the cars performance due to increased back pressure or lack of ease that the exhaust can escape?

This is the the turbo you got from ebay recently right?

Yeah, but the problem started with my old T25 which ran great for 2500 miles.

OH, I apologize I didn't understand that.

Maybe its not a charge pipe, maybe one of your vacuum lines came off somewhere.

is the boost gauge reading correctly? sometimes the simple things get ya....

The car is gutless, and the boost gauge is actually teed off of the MAP sensor hose for the Megasquirt.

damn i cant wait to find out wtf is causing this because if its not the charge pipes and its not the turbo, then I dunno what it could be?

Makes better sense though. Check couplers for cracks, then check IC. Would be easiest to shoot compressed air into the charge system post turbo and listen for leaks. Check compession and leak down as warranted. Remove BOV.

Ben has a point. If your BOV is recirculating, it may be wide open.

+1 on compressing the whole track with air.

huge crack in the IC?

Like ben and olderguy said, make a boost leak tester with a PVC elbow, cap, and tire valve stem. Remove the filter and clamp that to the turbo intake. Pump 12 psi through the system. You'll hear a psssst where the leak is.

Frank

I had a probleim with my compressor sealing not to long ago i where i would make 4-5 psi and it would all peeter down to nothing as i got towards redline. Some JB weld fixed my problem right up on reassembly

I just put 25+psi through the system, from TB to intercooler endtank, and it blew the fitting out of the TB first. (Nearly took my fucking finger off.) I'm going to figure out a way to test the hotside piping, but I'm also going to have the motor compression checked. I've been through everything but the motor itself.

Connect the cap to the turbo inlet and test the entire system at once.

FYI for others: you can make a pressure tester from junk at Home Depot for under $15.

If you have a turbo, being able to check your charge pipes for boost leaks with a compressor is essential. It should be part of basic trouble shooting for a turbo car with boost problems yet seems to be a huge mystery in the turbo Miata world. If you can't make boost you test for leaks first and THEN come to the forums. Period.

http://www.mirage-performance.com/Ec...aks/index.html

If your motor runs than it is not the cause of zero boost.

yep even with a blown #2 i made good boost

I found a pinhole leak in one of my hotside tubes. Nothing that would even come close to venting the amount of air required to cause this problem, though.

If the system is sealed from turbo to head and you have no boost = bad wg, bad wg actuator, or bad turbo. If all is sealed then the turbo isn't spinning fast enough to make boost. You can still hear it but something could be causing it not to spin fast enough. Oil cooled only? Maybe it's coked up. Damaged bearing? Could have a bad bearing but feel tight. Process of elimination. If you verified everything from point a to point b and still have a problem then you didn't properly verify something or you have a ghost.

Maybe you floated your valves and bent all the intakes. What did the compression test show?

The problem arose with my 2500-mile journal-bearing T25 and its actuator, then on the new-to-me GT25R w/ the T25 actuator, then with the GT25R and an ATP actuator, then with the GT25R and no actuator at all (wastegate wired closed). It was a sudden failure, so I don't think I bent the valves. The most RPM this motor has ever seen since I've had it has been 7400rpm or so (missed 3rd gear and the motor spun up pretty good, normal limiter is 7100-7200)

Tennis ball stuffed in the exhaust pipe will test the entire system. I don't listen for a hiss - I get a mustard bottle full of water and 10 drops of soap. It will foam when you find the leak. Just soak the hell out of everything and you will find it if it is a leak.

He as a point check for leaks that way.

It really sounds as if your wastegate valve.

If anyone is located near you run a second boost gauge off the turbo and to the wastegate, or straight into the gauge. See what boost the turbo is running off.

I am wondering if maybe you just have a bad turbo? The odds are against it but doesn't mean the the T-25 died and the GT25 was DOA.

How would a tennis ball in the exhaust pipe do anything different compared to what I've already done (ABS caps in the turbo inlet to the final elbow at the TB)? The IC pipes aren't broken. This is not a pinhole leak. If it were a pinhole leak or a tiny leak that were exasperated by pressure, the 30psi I fed the IC pipes today would have revealed it.

Can a turbo spin freely, have minimal shaft play, and still be bad?

Again, the wastegate is wired closed.

I thought you were looking to check the exhaust side for external leaks?

"I'm going to figure out a way to test the hotside piping"

Why would I care about an exhaust leak? That won't cause the turbo to suddenly stop making boost, would it?

Hotside = piping between the turbo compressor and the intercooler
coldside = piping between the intercooler and the throttle body

I'm going to give PR Motorsports a call on Monday. I'll let you all know what the cause of this was.

My bad - I thought by hotside you were meaning the turbo manifold (losing pressure before it hit the compressor). I've never heard that terminology before concerning turbos (only SC's where hotside refers to the exhaust side of the engine).

No problem. I'm pretty fucking irritated at this problem, so I'm a little on edge. If it was something obvious like a busted wastegate or a failed turbo, I'd be fine with it, but going through every single possible cause of this and still not knowing why is really frustrating.

I've been building this car for a year, and it's only been running for 6 weeks, and I leave for college in 3 weeks and the car fails? Fuck that. I want to drive the thing, not chase some bullshit ghost problem.

Not that it helps with your problem, but how did you wire the wastegate closed? Picture?

UGH, I meant turbine not compressor. Screw it, I'm going to bed...

Normally No if the turbo spins free and has minimal shaft play then normally the turbo is fine, but i think your problem goes pass normal. Maybe one of the interal seals on the turbo is shot and causing it not to build pressure but the bearings maybe fine.... again not a normal thing but I have heard of one turbo back in the DSM world that someone had that one of the seals was bad but the bearing was fine.

IF you know anyone around you with a working t-25, pull it from their car swap it to your and see if corrects the problem. Otherwise I am completely out of ideas man.

Good luck and please tells us what the cause is.

I'll shoot a picture when I load it up. Just some safety wire wrapped around the wastegate arm and the actuator bracket.

So, Andrew, what was the issue here?

Yeah! You have had almost eight years to figure it out:giggle:

Thread made by Andrew about something turbo. Must be ancient.

Andrew wiring GT2554r wastegate shut.

I like his style.

The divider that BEGi used to weld into their downpipes was holding the WG flap open, IIRC.

:rofl:

https://www.miataturbo.net/attachmen...ine=1397770602

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