Let the tinkering get serious!!....

[Greg Roles]

Thing is Ayden, I was basically seeing this:



Whereas in the stock green boost line, you could feel it spike to the normal 22 and then settle down to 17psi or so and pull through to 4000rpm, in the red overboost state it was rapidly hitting 25psi, stuttering terribly then topping out around 30psi all before 2000rpm. There was just no power to be had in this range either, it was obvious the fueling was out. I didn't want to get into it much, as this was most likely surge territory, and I didn't want to pop the turbo. You had to creep around till you passed the boost spike, and even after say 2500rpm, there just wasn't the usual strong torque or psi, something was obviously way wrong. It was horrible to drive!!

[Greg Roles]

Well yesterday arvo was very educational.

After driving back from the coast and pulling up off the highway, the car was behaving badly, lots of turbo flutter and hiss, so I stopped and had a lookie see ( impressing my girl no end... ). I was happy to work out that the boost pressure hose going through to my Snow controller had popped off, and this was causing all the noise, and amazingly to me, making the poor turbo wig out even more as it tried to come on boost. I closed this off entirely, all excited this was the problem, even though I had no concept of how such a small hole could cause all the problems, but I hopped in all excited to go for a normal drive!

It was back to the "normal" overboost, but still terrible!! Arrgh!

I got home and decided the volume had to be it. My plumbing must be greater volume / flow, and the turbo was blowing into less backpressure than stock and overboosting. So I got all scientific. Don't worry about the pipes looking a little different, I just wacked them together to get a volume, but you can see how they are pretty similar really. Turns out amazingly so !

I taped up one end, filled them with water and weighed the water they held ( 1mL = 1g ). This blew me away:

[Greg Roles]

Stock pipe:

2416g
2413g
2412g
av: 2414

Custom pipe:

2565g
2560g
2567g
av: 2564

I'd almost replicated the stock volume, with only 150mL difference !

So how the hell could it STILL be so different to drive ???

I spent the rest of the arvo pulling all my custom pipes out, and put it back to stock. Finished about 6pm, and went for a drive.

It was still overboosting, the same as before, still acting crazy. Arrrrgh!!!!!!!!!!!!!!!

I pulled up at home, totally bamboozled. The only other change i had made before it started wigging out was to put in a better MAF mount, I purchased from Steve at Modshack. I had been using the stock mount, but Steve has a nice solid one, and I thought perhaps the MAF was sitting differently and this may be the cause.

Nope. It was the exact same height and position as stock, which I would expect from Steve at Modshack.

[Greg Roles]

It was whilst inspecting the MAF that I noticed that little hose just prior to it was blocked. I had epoxied a small connection into the pipework to allow it to connect as per stock, and a bit of that epoxy had blocked this connector. Now I've always wondered as to what exactly this hose was for, as there's just no mention of it in Erwin, or anywhere I've read thus far, so I figured it was something minor.






I cleared it out by hand with a small drill, it was that thin, and thought what the heck, lets take it for a drive......

FIXED !!!

Back to normal, peaking at 22psi, and beautiful diesel torque all the way through to 4k. I was SO happy !

So it turns out that that little hose blockage caused ALL my overboost problems, and I can most likely put all my custom pipework back in. That hose must measure the vacuum the turbo is pulling and be a very important part of the VNT feedback.

Beware blocking the little non descript hose people!!

[team_v]

Glad you found the solution Greg.
Seems odd that they wouldn't descirbe that part if it is important enough to mearue turbo vacuum.

[Greg Roles]

Glad you found the solution Greg.
Seems odd that they wouldn't descirbe that part if it is important enough to mearue turbo vacuum.

You're telling mate! It's been several days of driving around like a grandad, holding up traffic, with my heart in my mouth waiting for the turbo to explode, doing my utmost to avoid beyond 20psi which happens in an instant beyond 1/4 throttle. I've had a super busy week and HAD to make it to cases each day, so to say it's been a tad stressful is a small understatement!

Add to that the sheer embarassment of baby cars pulling out and around me from the lights as I creep up to 60k....well I'm gonna let rip at the lights today!!

[gldgti]

heheheee.

I'm very glad to see you've fixed it. I hadnt checked the thread until just now after my last post, but after seeing that graph you made I would have offered that no way did your intercooler pipework make that much difference.

Ahh well, at least now you know all your pipework backwards

the only other thing is that -

My plumbing must be greater volume / flow, and the turbo was blowing into less backpressure than stock and overboosting.

- doesnt make sense, because if there was more pressure after the compressor, the turbo would be "overboosting". That is to say, if your custom pipework is "better" than stock, the difference in pressure between the outlet of the compressor and the inlet manifold will be less. Also, the boost pressure reading (wherever its taken) will have an inverse relationship to the vane control mechanism with respect to controlling compressor speed, so if, lets say, the vane control took a sensor reading from just after to compressor, the turbo should work less hard to make the same boost if you have more efficient pipe work.

Finally, realising your position over the last week, I hope my previous post didnt exaserbate (spelling??) you too much, sorry if it did. It can be stressful worrying about your car's reliability when you really need it, i know

[Greg Roles]

Well it's been a while between posts, and there's not a whole lot new to tell on the tinkering scene, but the reasons WHY will become obvious soon...don't fret, just a side project has been consuming my time, but this one will help the whole community...stay tuned : )

I did want to mention a strange type of regeneration that has been happening whilst my first DPF pressure sensor is on the fritz. Seems these are giving up a fair bit especially on the MK6's. When I scan it with Vag Com, it tells me "mileage" is on, which is obviously a mileage DPF regen cycle rather than the usual sensor regulated one. The mileage function is the default the ECU goes back to if any sensors fail according to my service bulletins. If I clear the code, the car immediately does an odd regen, in that the EGT's increase as per the usual regen, but there is no idle increase. The car becomes quite obviously noisier thanks to my mufflerectomy, and it's the noise that alerts me that it is happening, actually sounds quite wicked for a diesel, I like that part! What's not so good is the rough drive, it's very different to drive at this point, the accelerator becomes quite unresponsive, and the car feels quite jerky, the fuel map / inlet flap or something is really making the car run poorly, it hesitates, stutters, feels very on / off. Also it has been doing these regens about every 2000k, so looking forward to sorting that pressure sensor asap!



On a brighter note I put my 42 Draft Designs shift bushings in last week, and the difference is quite apparent. Makes the box FAR more solid, and when in gear the stick is rock solid. Changing is far slicker, and the 2-3 zig zag is lightening quick in comparison now. What IS a bit tricky is setting it up just right, and I'm still trying to get the change into first perfect, it is getting hung up a little at the moment ( going ever so slightly into the reverse gate ), but it's just a matter of tweaking the cable length at the gearbox end, which is very simple to do. Amazing what a bit of a tweak there does actually, still working it out exactly which way does what but will post my findings. You could certainly tweak your gearbox in it's stock form, and let's face it the diesel 1st gear definately needs that!

Just to head down a new path I videoed the process, as the instructions from 42DD whilst very comprehensive were a little confusing to me. This set with the drill bit isn't just some bushing ends, but upgrades the main pivot as well, and is a fairly involved process, but one I'm sure glad I did. Should get me a little more off the 0-100 with the slicker shifts, and that's what it's all about baby!

Hoping to get the video up on you tube in the next few days, been a steep learning curve on the editing.

[Russ59]

I did want to mention a strange type of regeneration that has been happening whilst my first DPF pressure sensor is on the fritz. What's not so good is the rough drive, it's very different to drive at this point, the accelerator becomes quite unresponsive, and the car feels quite jerky, the fuel map / inlet flap or something is really making the car run poorly, it hesitates, stutters, feels very on / off. Also it has been doing these regens about every 2000k, so looking forward to sorting that pressure sensor asap!

Hey Greg, that sounds very similar to the first experience I had with regenning back in 2008 not long after I took delivery of my GT, I made mention of it in a post back then and it continued to give me trouble right up until I remapped it with the ChippedUK tune back in June '09, the car hasn't missed a beat since and the regens are barely noticeable any more. I've been following your tinkering thread for a while and will be interested to see how it all pans out when the DPF delete is done.

I videoed the process, as the instructions from 42DD whilst very comprehensive were a little confusing to me. This set with the drill bit isn't just some bushing ends and that's what it's all about baby! Hoping to get the video up on you tube in the next few days, been a steep learning curve on the editing.

I wouldn't have thought you'd have trouble handling a set of 42DD and a bit of bush, you better be careful posting that sort of stuff up on You Tube though.

Cheers mate

[Greg Roles]

Wouldn't suprise me Russ, for the engine cel light has turned back off, so apart from Vag com and the odd driving feel you would have no idea there is a problem / anything going on. Perhaps you need to have your car Vag-commed to check for any sensor errors?

Had a good day of driving with the new 42DD shift bushings, and WOW, it's a different gearbox, so much so that I can feel myself "dropping the clutch" in the now lightening fast 2-3 change. My foot isn't used to keeping up with that fast a change even in just normal driving, and I felt the clutch "drop" in 3rd as my foot caught up with the now much quicker change. Definately would make for a swifter bolt to 100k, and there's no nasty vibrations or anything unless you lean on the gearstick whilst in gear - then you KNOW it's linked directly to the gearbox. Best $60 odd I've ever spent, can't see how anyone wouldn't like this mod.

Funnily enough Russ I'm old enough to actually appreciate a bit of bush, but that'll only confuse the youngin's, so back to out regularily scheduled program.....