Let the tinkering get serious!!....

[Transporter]

I put self vulcanizing tape around all C clip connections in my T5 I could get.

[Greg Roles]

Thats a damn good idea Miro, I'll do something similar!

Found something interesting. The top clip was popping off when pulled, whereas the bottom was rock solid. Tried the other coupler I had, and it was the same. Swapped clips and still the top was the weak one. Put the stock hose end back in, and it failed at the top before the bottom when levering the C clip slightly, the bottom just didn't want to come apart, whereas the top did with the slightest lever.

So I filed out the top and bottom slits with the side of a small and perfect fit 2nd cut flat file, but mainly the top.

Now it's so solid that I can move the entire radiator assembly with the coupling. Seems that the top clip, in the TDI at least is the suspect one, and if anyone has coupling problems, well my bet is it's the top.

My aftermarket alloy couplers have a bit more play than the stock ones in the teeth to clip so it's more obvious, but it was an interesting thing to find.

HOPEFULLY that's it for the cold side!

[gldgti]

If your only spiking to 24 ish psi, I dont understand why they're blowing off, unless the clamps arent done up tight enough. Mine is now doing 24-25 psi sustained boost, and i just have ordinary old tridon hoseclamps.

Its great when you're not worried about them popping off, because you can give it the beans without 2nd guessing yourself all the time.

I think once they get way up in the high boost region, diesel tuners tipically run as few unions as possible. I've seen pictures of flanged joints

[Greg Roles]

Yeah, I'd say I was just way too easy on the clamps, I have tightenened them all down till it actually gets hard to turn the nut, and it's been ship shape so far. I'm still driving around like a wuss though, and it SO friggen hard to actually stick to about 10psi or so, the thing really wants to spike at the 2000rpm mark. I've got a full on week work wise and can't afford a pop off till the weekend, so I'm babying it. The turbo seems far more willing to boost up now, even though I can't see that my hot side pipework is that much different from stock....

I did however just give it a bit of stick tonight, and it's showing spikes beyond 25 psi at the manifold, which means towards 30 psi on the hot side!!

I have yet to man up and do a full flat out effort, but I felt a "fuel cut" style feeling up that high, as it would seem my pipework is allowing the turbo to overboost and the car is freaking out and pulling fuel? I'm going to continue babying till I can investigate properly.

Geez, it's getting serious......but that IS the thread title!!

[Transporter]

Yeah, I'd say I was just way too easy on the clamps, I have tightened them all down till it actually gets hard to turn the nut, and it's been ship shape so far.

Greg, re-tighten them again after one week, they very often need to be tightened second time. I always choose clamps with rolled edges and not perforated (solid band).

[gldgti]

Yeah, I'd say I was just way too easy on the clamps, I have tightenened them all down till it actually gets hard to turn the nut, and it's been ship shape so far. I'm still driving around like a wuss though, and it SO friggen hard to actually stick to about 10psi or so, the thing really wants to spike at the 2000rpm mark. I've got a full on week work wise and can't afford a pop off till the weekend, so I'm babying it. The turbo seems far more willing to boost up now, even though I can't see that my hot side pipework is that much different from stock....

I did however just give it a bit of stick tonight, and it's showing spikes beyond 25 psi at the manifold, which means towards 30 psi on the hot side!!

I have yet to man up and do a full flat out effort, but I felt a "fuel cut" style feeling up that high, as it would seem my pipework is allowing the turbo to overboost and the car is freaking out and pulling fuel? I'm going to continue babying till I can investigate properly.

Geez, it's getting serious......but that IS the thread title!!

Glad your finally getting serious Greg, hehe.

You havnt dyno'd your car yet have you? If/when you do, I'd be really interested in seeing the a/f ratio curve. In fact, you might learn something from it too if your thinking the ecu is responding to some kind of overboost signal.

Depending on where your manifold pressure sensor is, you might be able to trick it by making a tiny leak just before it...

[Greg Roles]

It's very weird to drive now. The pipework is holding up to the pressure, but despite the hot side being quite similar to the stock stuff in diameter, the turbo is FAR more willing to spike at 2000rpm, and at part throttle openings I'm routinely seeing 20psi whereas with the stock pipe I saw 10-15 usually. It seems to me that the turbo comes on song at the same 1750rpm point, overshoots and tries like mad to sort itself out. There's a definate hesitation at 25psi, like it's pulling fuel, and then it carries on a few psi more. The really odd thing is there are no Vag Com error codes popping up!

I'm thinking the stock VNT operation can't handle the free flowing system I've built, and this is only going to compound on adding the custom cold side. I'll carry on, but am thinking of putting the stock pipework back in for now, and will have my custom pipework ready for the time I get the car tuned, and someone can jigger the VNT control a bit. It definately feels like it wants to flow, and the turbo is amazingly different in it's boosting.

I'm starting to think I'm at the point of having to get some custom tuning done to handle the mods from here on out, so it may be a case of fabbing them up and then shelving them for that time. Oh well, I guess it's a good place to be, think of all that fuel I can add to that extra boost!

[Buller_Scott]

well like the boys on tdiclub like to say- the only way to deal with overboost is to get a bigger turbo...

do you reckon you'll go that route? my understanding was that any exhaust mods (de-cat, DP etc) on a VNT would assist overboost, but i didnt know it could also happen by opening up the turbo-ic pipe diameters as well. interesting.

would adding fuel to an overboosting turbo make your turbo/car/you explode? it'd be interesting to see the result of applying more fuel to an on-the-very-edge turbo, if you had a backup ready to put in, should the tune be too much for the turbo...

awesome reading!

[Greg Roles]

Well I've been trying to nut this out, it's obvious there's a nasty boost spike occuring due to my plumbing changes. I can't see that I've changed the volume that much, but the one thing that was quite different was the coupling to the turbo outlet. The stock one has a transition pipe that appears to be as much acoustic control as anything, whereas my version is a long way from where I'd like it to be flow wise, with a bigger difference right of the turbo.





So I thought I'd swap back to stock at this coupling, as I figured it was possibly the main reason for the overboost. All that has happened is the turbo noise dropped a bit, but it's still overboosting just the same. Really has me confused!

[gldgti]

spiking to 25psi shouldn't be a problem.