VNT turbo problem - solved... More or less (1 Viewer)

[nieboo]

After talking to Dougal about an overboost problem I was having on my rig, he suggested to post some pics, since the VNT's are rare in the States. So here goes. First the Rig:

The turbo itself is not easy to photograph, since they is a lot of stuff in the way when mounted. In the pics from above (PS), on the right is the PCV on the compressor side. In the middle is the vacuum actuator box for the vane adjustment. The box is supplied with vacuum from the VSV to right and above the actuator.

TBC...

 

[nieboo]

From below visibility is better, but not much more interesting... . The vacuum actuator is still quite visible though

FYI below two pages from the manual, depicting the turbo and components

If I can ever justify to the princess the aquistion of a Gturbo, I will put some more detailed pics on Mud, if interested.

 

[nieboo]

Now to the problem I was having:

Mostly occurring with a cold engine OR when closing trottle during cruise and then applying power again (worse if the AT has to shift down to a lower gear). Sometimes when requesting power, the engine goes into overboost - around 1,3 bar wheras it should control the boost at 0,8 - but with a total lack of power and a noise like there is a hole in the pressure hose afte the turbine. Feels like towing a 5000lbs trailer. If I keep my foot down, engine goes into limp mode and cuts out the turbo completely. If I release the throttle to allow boost below 1 bar, it regulates the boost back to normal after a while. Downshifts of the AT are paired with a more or less pronounced whistling sound from around the turbo, depending on the amount of throttle.

I replaced all relevant VSVs and sensors, but no change. It was better for a while after replacing the intake air temp sensor, strangely enough. Vane actuator is not sticking when applying vacuum to the actuator box. There is no wastegate, that can make a problem. I just got some vacuum hose and will replace all relevant rubber hoses this weekend. After talking to Dougal, I took of the downpipe, and filled up the turbine with oven cleaner, and worked the vane actuator every 10 min for about 2 hours. Went for a hard drive and it seems to take throttle better, shift cleaner and regulate the boost better... If it starts again, I will consider taking the turbo off and having it cleaned and/or upgraded.

I am happy to take any suggestions that might improve the situation though.

Cheers,
Niels

 

[gerg]

Good advice from Dougal. To keep the vanes free be sure to work the crap out of that turbo evey other day.its by babying that thing that allows little vane movement and carbon to form barriers which later restricts its full range of motion. Fully moving the vanes sweeps the carbon away sort of like a snow plow.

 

[nieboo]

Yeah, I guess that makes sense. I will do the hill going home full power the next days and then every so often. See what happens.

 

[gerg]

So boost at low rpms generally is vanes closed. Boost at high rpm is vanes open. Most vnt folks don't fully open them and baby the engine so to speak and get over boost problems as the vanes eventually can't open fully and get stuck in the semi closed position. Sort of like never ever bending over for a few years then doing yoga. Or another way of looking at it is to never do any maintenance for several years then get the dealership to give it the big tune up. That's a great way to get bent over.

 

[Dougal]

Yeah, I guess that makes sense. I will do the hill going home full power the next days and then every so often. See what happens.

That's how I do all hills. For the health of my engine of course!

 

[nieboo]

Cool, bending over is always a bad idea...

 

[Tapage]

how was the turbine inside look ( when took off the down pipe ) ..? much sooth ..?

 

[mgilvan]

Very unfamiliar with the turbo on the 100 , few suggestion, turbos go bad after 150k and they need to be rebuild again. If thats too much money I suggest to look at the spring on the waste gate and see if that’s working properly or not.
Good luck sir

 

[nieboo]

@Tapage:
I had to take off the downpipe and leave the bend after the turbo on, since I could not get it off. In the outside of the bend, it seemed like there was quite a bit of soot, but around the flange it was only 1-2 mm. Did not seem like a whole lot. Cleaning it with MrMuscle made a difference though, which tells me that it is majorly the dirt in the turbo. I am now officially saving for a Gturbo or similar upgrade turbo