Car will not make boost. Need some help

[Sprayer84]

Also, with my boost controller turned all the way up it will only get to almost 7 but still not until 4500 rpm or later. Next, I unhooked both lines going to the wastegate, and capped the compressor port, it will get to about 10psi. Then I ran the line from the compressor to the top of the wastegate and I stopped at 15.6 psi. Just for kicks I took the BOV off and checked the diaphragm & oring, both looked good. Switched to the softer spring just out of curiosity and no change, didn't really expect one, but it no longer gets a fluttering sound when shifting. This spring is obviously too soft however because it is opening the BOV at idle. Seems as if i need one between the two but thats a separate issue. Being only 4 actual components in the kit, Turbo/WG/BOV/Pipes, I can only assume at this point it is an issue with the turbo. Any thoughts? Also, is there a serial number on this thing I can use to verify its specs? I'm going to do another boost leak test when I can but I'm sure it will pass just like before.

 

[Makdaddy]

Next, I unhooked both lines going to the wastegate, and capped the compressor port, it will get to about 10psi.

Are you sure the lines to the gate are not collapsing?

Seems odd with everything disconnected it goes to 10psi
and thats on a 7psi Spring

Plus I would think if the turbo was an issue you wouldnt build that much pressure.

 

[Sprayer84]

Next, I unhooked both lines going to the wastegate, and capped the compressor port, it will get to about 10psi.

Are you sure the lines to the gate are not collapsing?

They are brand new silicone hoses and are pretty stiff.


Seems odd with everything disconnected it goes to 10psi
and thats on a 7psi Spring

The only thing opening it would be back pressure. My understanding is that with it unhooked completely it should boost to the moon.

Plus I would think if the turbo was an issue you wouldnt build that much pressure.

 

[michael.konor]

Okay, I know you said that you did the smoke test and only found the two leaks. However, when I've seen smoke tests done, the piping isn't pressurized.

Is it possible you have a leak that's remains sealed up to or slightly beyond 0 inHg/0 PSI, then begins to leak once you start building boost? If so, do you have the ability to seal off both ends and then pressurize the system?

 

[Sprayer84]

I came to the realization that a smoke test is totally invalid when dealing with boost leaks. The smoke test revealed no leaks however when I made a homemade boost leak tester, I found about six large leaks which I fixed. And the problem still remains.

 

[JeremyH]

Does the turbo impeller spin freely at idle?

I agree about smoking the coldside there could be leaks you wont see until there's some pressure there, pressure test is the way to go which you found out. What pressure did you test it to and did it hold the pressure? Don't forget there are the still the 2 connections you can't test on either end which you have to plug during the test.

I dont think its the turbo but to rule it out with out removing it you can do this. Just put a plug or short section of pipe and plug on the turbo output and then instead of capping the boost reference port on the compressor cover, hook your boost gauge up to it and go for a ride and see if its making boost like it should as soon as you start to hear it spool up.

 

[Sprayer84]

Is it possible that exhaust back pressure is opening the wastegate prematurely? That's makes more sense to me. Because with the wastegate forced closed it will build tons of boost.

 

[Sprayer84]

And the turbo is pretty loud, I'd def say its spooling.

 

[Sprayer84]

I took the filter off to check the turbine. This is on startup. Almost stops around 27 seconds in
http://youtu.be/w8Y3igxa19g

 

[JeremyH]

That's odd, it should stay spinning like it did after initial start up. Is the wastegate opening when it starts to slow down? Although it would be a little hard to check since you are recircing your wastegate vice dumping to atmosphere.


I will go take a vid of mine.

 

[JeremyH]

Uploading the vid now. On mine at idle it doesn't stop I even try to grab it and stop it and I can't. Also it spins for a good bit after shut off and spins easily by hand when its off. Check it when it off and see how it spins.

So two thoughts, the gate is pushing open at idle and exhaust is bypassing the turbo or there may be a bearing clearance issue in the turbo causing it to slow down. But if it is in the turbo it would have been like that from the get go and do it all the time.

 

[Sprayer84]

I applied pressure to the top port of the wastegate which should force it closed. Still was not spinning at idle. Spinning it with my hand I didn't feel it hanging up but I'm not sure what a good one feels like

 

[JeremyH]

I applied pressure to the top port of the wastegate which should force it closed. Still was not spinning at idle. Spinning it with my hand I didn't feel it hanging up but I'm not sure what a good one feels like

Correct if the valve seat is good and its not leaking or leaking internaly, putting pressure to the top port will help keep it closed.


Was everything fine prior to the overboost issue when you hooked up the hose wrong? I doubt its a turbo issue if it spins easily by hand and spins up like that on start up, it looks like mine on startup. Vid is almost ready.

The slowing down part def shouldn't happen though. I'm leaning towards the gate opening/leaking and its bypassing exhaust from the turbo so its slowing down.

You could take the downpipe out to watch the valve in the wastegate to see if its opening and feel for exhaust coming out while at idle that would seal the deal on wether its the gate or not and then I would consider having the turbo looked at.

 

[JeremyH]

Vid

 

[Sprayer84]

I've already replaced the wastegate and it didn't make a change.

 

[JeremyH]

I've already replaced the wastegate and it didn't make a change.

Then that's what I would do for sure. Pull the downpipe and physicaly watch the valve. (since you would have to pull it anyway to remove the turbo). If the valve is staying shut like its supposed to. I would give Comp a shout, and tell them the symptoms and how its slowing down like that at idle. If you need to send it in and can't get a hold of Zimmers just let me know if I can be any help with it.

 

[Sprayer84]

So, here is an interesting tidbit. Pretty sure I found the problem. Under full throttle acceleration there is over 15psi or exhaust back pressure. Which I'm sure is more than plenty to push the wastegate valve open.

 

[JeremyH]

So, here is an interesting tidbit. Pretty sure I found the problem. Under full throttle acceleration there is over 15psi or exhaust back pressure. Which I'm sure is more than plenty to push the wastegate valve open.

The boost pressure plus the spring pressure will/should overcome that back pressure though.

What kind of exhaust/mufflers do you have?

Taking off the downpipe will shed some light on this as well since then you will have no back pressure at all.

 

[Sprayer84]

The boost pressure plus the spring pressure will/should overcome that back pressure though.

What kind of exhaust/mufflers do you have?

Taking off the downpipe will shed some light on this as well since then you will have no back pressure at all.

Correct me if I'm wrong but the boost pressure will only help open the wastegate not keep it closed. The back pressure is pushing on the valve to open it, boost pressure is pushing on the lower part of the diaphragm to also help open it. That would explain why when hooking to boost source to the upper port on the wastegate it will boost to the moon. Thats when the boost would be helping keep it closed. Is my line of thought correct or is that not how it works? Also, I should make clear that I am talking pre-turbo back pressure. Measured at the front o2 port on the passenger side.

 

[JeremyH]

Correct I was referring to if your on the top port. The spring pressure plus boost pressure will easily over come the pressure in the exhaust and keep the valve shut.

You have exhaust pressure on both sides of the valve though. There is pressure pre turbo on the valve seat side and pressure in the exhaust chamber post turbo on the downpipe side. A 1:2 or even 1:3 ratio is normal and manageable like this though. ie 10psi at the manifold could mean 20psi-30psi in the exhaust.

Where did you measure the exhaust back pressure at and was this at idle?