How To Replace N75?

[cammmy]

Hi All

As those who've read my 1st gear power cut thread know, I've been experiencing an overboost condition in 1st. I don't believe it's the DVs as I don't see how that could be the cause (I would expect a boost leak or spike when throttle is shut if they were faulty) and have replaced all three MAP sensors. I'm suspecting either N75 valves starting to stick or perhaps a small leak from the signal lines. Does anyone have any tips/pics on getting access to them for inspection/replacement? I was thinking about trying to change the lines first but if it's a pain to get to, I may just do the valves and lines at the same time.

Ta
Cam

[Jim Haseltine]

From what I remember, with the engine in place even if you strip off a lot of hardware they'll still be be pretty difficult to get to and the far end of the lines will be near impossible. I might have some pics on another computer, I'll look for them tomorrow.

[cammmy]

Thanks Jim

Should be selling another car shortly, maybe now is the time the engine finally comes out of the RS. If that happens though, there's no way it's going back in with standard turbo's.

Edit - Just spoke to Unit 20 and they don't recommend putting bigger turbos on anymore. They think low to mid £3k to do oil pump and N75s without dropping the engine, incl new water pump core and replacement of every seal that's disturbed.

Apparently price has gone up because Audi are charging over £40 for o-rings that used to cost £8

[Jim Haseltine]

Turbos off car, N75s circled

Ton and a half of pipes and other gear removed from the RH side of the engine, lines circled. See what I mean about difficult?


If I had to replace the N75s I'd probably try it with the engine in place (at first) but that's because I'm stubbon and have already pulled the engine more times than I wanted to.

[zex]

Just spoke to Unit 20 and they don't recommend putting bigger turbos on anymore.

What's the reason?

[cammmy]

Thanks Jim, much appreciated.

Zex, they said the main reason is that the heat can cause the pistons to swell and destroy the bores but also as they age they're seeing more broken components in the drive train. Probably a blessing in disguise as it would add £3k to the labour bill, plus however many thousand for the turbos and then another £1k plus for tuning (and whatever supporting mods are required for fuelling).

[Jim Haseltine]

I've been under the car this morning draining oil from the intercooler hoses. I'm now pretty certain that the subframe would have to come off to be able to get to the N75s. Might just be able to do the job with the anti-roll bar removed but I doubt it.

[IanH755]

Zex, they said the main reason is that the heat can cause the pistons to swell and destroy the bores but also as they age they're seeing more broken components in the drive train.

I think that may be due to Grizz's experiences with my car TBH and I currently don't know of any others at 900+ that've blown an engine like I did (piston swell scoring the bore) but maybe he does.

[cammmy]

Yeah, it was a case of thinking if I'm having the oil leak done, I may as well put bigger turbos on but realistically, I'm probably looking at an additional £8k for another 200-ish hp.