Stupid Turbo Problem

[vwmike]

Ok, this is on my '88 Jetta TD. I've always thought the turbo spooled extremely slow on this thing. Well, I tried to cheat the wastegate and couldn't really see any boost increase. In frustration I finally just left the line to the wastegate plugged for all intents and purposes and I could still only get boost to spike up to 14 only to fall right back down again. So, something tells me the wastegate is bad and somehow not seating properly or being forced open by the exhaust pressure. Has anyone experienced this? Does anyone have another good wastegate they could sell me or know anything about where I could get parts to fix this stupid thing?

Oh yeah, I should mention that my pop valve has been removed so it's not that limiting boost pressure.

[vwmike]

I could kill a swarm of mosquitos when I'm getting on the freeway....still not enough boost. I have GTD nozzles and the LDA pin is turned around. I had to back the fuel screw out slightly but it was maybe like 1/8 - 1/4 turn.

[vwmike]

I'm beginning to think it is just heat related. I could have sworn this thing had more fuel than it should but maybe I'm just not pushing it far enough. That's mostly out of fear of melting a piston or two. I pulled the turbo off and checked the wastegate. I tested it with shop air at varying pressures. 10 psi gets it to open completely. 5 psi will make it creep about halfway.The wheels look fine. No damage to the fins. Now I'm off to the hardware store for a pipe tap so I can install the pyrometer probe and get my answer once and for all.

[vwmike]

Well, the exhaust is stock but to my knowledge there is no restrictions in it (besides it's small diameter). I was planning on doing a full 2.5" system, but I need to finish my Rabbit before I can get the Jetta in the garage and close enough to the welder to do that. I just finished tapping a hole in the manifold for the probe, so I should have my answer pretty quickly. I'm off to put it all back together right now  

[vwmike]

Well, I found one of the longest, steepest freeway grades I could find and after about 10-20 seconds in 5th with my foot to the floor in the steepest part of the grade I got it up to 1050 F, after which I ran out of hill and was catching up with traffic at about 75 mph (not many people can go fast up that hill - My NA Diesel Rabbit pickup could only muster 55 mph with a 70 mph head start and a tail wind). That sounds like entirely too little heat. So, I suppose I should dump some more fuel in....but how to do so without making it smoke continuously is the issue.  :?:

[fspGTD]

First off - is this a 1.6lTD engine code "MF" or an eco-diesel?

5 psi will make it creep about halfway.

A wastegate characteristic of the 5-cyl TD is available from the 4 and 5 cylinder TD SAE paper:

The wastegate characteristic of a 1.6lTD "MF" engine code is probably somewhat different, but I can't see it being a whole lot different.

If your wastegate is indeed creeping opening halfway at only 5 psi (.34 bar), it seems it is just opening with far too little boost pressure.  It should be remain completely closed until much higher pressure than that.

Have you or others tried making "adjustments" to this wastegate?

[vwmike]

It doesn't really seem like it's adjustable. There are no external fasteners so cutting it apart seems like the only option and since I only have the one I'm not going to take that risk.

[VWRacer]

Mike, have you tried a manual boost controller in the boost line to the wastegate? Like Jake said, that WG shouldn't even begin to open until nearly 10 psi. Sounds to me that for whatever reason, your turbo simply isn't supplying enough air for the engine. Stan

[vwmike]

I actually just put one in a few minutes ago....but I don't think it will change anything as it should have had a lot more boost pressure before when the wastegate was disconnected. There is also the possibility that the solenoid I had in there before may have leaked but that seemed unlikely. Oh well....we shall see in a couple of hours.

[vwmike]

Well, it's possible that the solenoid I was using just sucked and the boost was able to push it open. With the ball and spring valve in there I saw about 15 psi, but with how bad traffic is I haven't really been able to get the car going from a standstill and keep my foot to the floor to find out what max boost is. Boost will not climb that high without rowing through a few gears. This is one of the few situations were it seems like the car could really benefit from an automatic transmission.

Next I suppose I should think more about pump mods. Perhaps I'll start a new thread for that one.