Way too much turbo lag...exhaust issues?
 

I think I've had this problem for a while. It's only lately that I've begun to pay close attention to it. Car is an 89 951, bone stock, with almost 180K miles.

It's almost impossible to get any boost in 1st gear. In 2nd gear I get full boost around 4500rpm. In 3rd gear it's much better, full boost is around 3500. But that still seems late.

I have noticed the car seems to have 2 distinct modes...good days and bad days. I have never checked carefully on good days when I get full boost, but it seems to come on much sooner. The above figures are from a bad day. About 4/5 are bad days. On bad days, I seem to have a flat spot at around 1 bar before eventually going into positive boost....then it quickly shoots to the top.

I have recently replaced all boost hoses and almost all vacuum lines (except for the one from the AOS to the block underneath the turbo, and a few of the small hard lines). I do get full boost every time so I think the turbo is ok.

I am convinced I have an exhaust leak - would that make sense? My sense of smell is not the best but I think I can sometimes smell exhaust, especially with the hood open and the engine idling. On good days, when I get on full boost, I sometimes get a sooty smell.

I jacked up the car and had a look at the cross over/wastegate area with the engine idling to see if I could feel a leak...nothing. I think my headers look strange though. There is a small soot mark around #2, as if it's leaking form the gasket, but it looks very small. At idle I can't feel anything there with my hand.

But actually the headers look very uneven - here are some pics - it looks as if there is an outer pipe that is not pushed all the way up to the flange on some of them...

Here are 4 & 3 - 3 looks to me like there is a bigger visible section of the inner pipe:

http://i1189.photobucket.com/albums/...manifold_1.jpg

2 & 1, same thing - 2 has the gap, 1 doesn't:

http://i1189.photobucket.com/albums/...manifold_3.jpg

Anyone know if that unevenness is normal or not?

You can also see the soot tiny mark I mentioned on #2, it's on the block right next to the gasket (it's very small but it's not there on the others).

Does any of this shed any light on my problem? I was thinking of using seafoam next to try and flush out my leaks.

I am planning to delete the cat also, and I noticed something odd on it today, like someone has been at it already. The downpipe seems to come into the cat at a funny angle, and there are some pretty rough welds there. Does this look normal?

http://i1189.photobucket.com/albums/...c_si/cat_1.jpg

Close up:

http://i1189.photobucket.com/albums/...c_si/cat_2.jpg

Thanks!

You will hear an exhaust leak.

What would it sound like? I hear all kinds of noises from this car from time to time.

There is a kind of fluttering sound that I hear sometimes. I don't notice it much when driving but as I slow to a stop I hear it winding down...it seems to lag behind the engine rpm a little so I get to hear it clearly for a few seconds after I stop.

Your exhaust is the normal factory exhaust - thats the standard construction appearance.

Intermittent boost problem could be a sticking WG valve, or possibly the CV.

If it's intermittent, I wouldn't suspect an exhaust leak. I had a similar problem that was a collapsed cat pipe, but that was all the time.

Thanks..helps to know that about the exhaust set up.

I did try clamping off the wastegate hose and it didn't really make any difference. I thought the exhaust had a different sound but the severe lag was definitely still there.

Yeah I need to pay more attention to see how intermittent it really is. The last time it drove really well was on a fairly cold day so maybe the turbo was just working better because of that. I will pay more attention to the actual numbers.

I recorded a video of a strange fluttering noise it makes at cold idle. The sound is made a bit sharper by the phone camera. Weird thing is if I pop the hood I can't hear this from the engine - it's only audible from inside the cabin. When warm, the noise is barely noticeable, but I can tell it's very faintly there:

I cannot hear much in your video but if the sound is kind of a faint knocking sound it is generally the water pump and is not an issue. Once warmed up the noise will cease.

Yeah it definitely does fade a lot as it warms up, but does not go away completely. In particular, I hear it as I roll up to a stop even with a warm engine. The noise seems to wind down slightly after the engine rpm.

In the video it's the loudest sound...sounds a bit like a helicopter in the distance.

Hard to tell what I'm hearing from the video.

If you clamped the WG feed line and it still doesnt make boost, you've got a WG leak. Valve is stuck or the valve seat is shot, etc.

If your car is bone stock, then your symptoms point to the cycling valve. An aged CV typically can cause that pause of boost rise at 1 bar absolute (or slightly above) and inconsistent boost, different gears, etc.
An aged wastegate and cat don't help either.
Full boost at 3,500 RPM for a bone stock '89, in higher gears, with aged components, I would say is about right.
Time for a freshening up/parts replacement.

haha I am kicking myself right now because I had the CV off the car a little while ago, AND I had a new one on standby, in case I broke the original one. But it didn't break or feel as brittle as I had feared, so I went ahead and reused it.

Still, wouldn't clamping off the line to the wastegate rule the CV out?

hmm...intermittent sure changes things. However I had slow boost after the turbo install. At that time a lot of other changes were made. I got the vacuum lines/system hooked up to a smoke machine and flushed out some leaks. I also installed one of Laust's vacuum manifolds to really clean up the vacuum routing.

I'll have to admit this because it may help you. We also had a vacuum line routed incorrectly, that one problem was most of the lag.

All of the leaks smoked out were repaired other than I could what i guess you woould call the throttle body.

Hmm ok I will look carefully at vacuum lines. The thing is, I replaced most of them, and all the boost hoses mainly because of this issue and a rough idle issue I was having. I am still having both issues. But, I was convinced at the start that my main vacuum leak was from the AOS, and I didn't replace those seals (I have them on hand but I didn't have time to pull the turbo). There is also one vacuum line coming off the AOS that I did't replace. Still I didn't think that could be the cause of such a severe boost problem.

As far as routing, the stuff under the intake is pretty simple so I don't think I went wrong there. Racerxrick, what exactly did you have routed incorrectly?

[QUOTE=divil;10493252]Hmm ok I will look carefully at vacuum lines. The thing is, I replaced most of them, and all the boost hoses mainly because of this issue and a rough idle issue I was having. I am still having both issues. But, I was convinced at the start that my main vacuum leak was from the AOS, and I didn't replace those seals (I have them on hand but I didn't have time to pull the turbo). There is also one vacuum line coming off the AOS that I did't replace. Still I didn't think that could be the cause of such a severe boost problem.

As far as routing, the stuff under the intake is pretty simple so I don't think I went wrong there. Racerxrick, what exactly did you have routed incorrectly?[/QUOTE]

Sorry but I don't recvall exactly..

[quote=racerxrick;10493336]No worries. My car did not have the venturi from the factory so the set up is simple. IIRC the manifold has 2 connections for the CV, one to the banjo bolt and 2 to connect the AOS to the J-boot.

But the small hard lines around the fuel damper area have always been a mess. My car has a 4-way connector, which I have never seen in any vacuum diagram online. I will have to take a closer look.