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OK, so I am looking for to replace my TBB, no real reason except that I have read soooooo much about them going and so want to be proactive in protecting my Turbos.....

So....

What is everyone's preferance ? a Samco TBB replacement TBB or full Kit, or the APR Bipipe Kit.

It would be useful to get some feedback before going for one or the other.....

Cheers


Mike

If you really want to be sure, a solid replacement such as the APR bipipe or RS4 unit is the only solution. It's not cheap, and it takes some time to fit, but then you can really forget about it, unlike any other solution.

I'd agree with Dippy.

Personnaly I lived with the stock item and had replaced three within 18months. The last one was jsut beginning to develop a split after 12 months.

So, will the APR bi pipe work with a K04 upgrade if I wished to do that at a later date ?

Thanks for the responses guys to those that have voted !

Cheers

Mike

Do people think that it's worth replacing the stock TBB with a revised/3rd-party one even if the current one "seems" ok? Same question with the BPVs, go with 710N's as a precaution?

Cheers,
Alex.

Mike,

Certainly a 'standard' K04 upgrade will be OK with the bipipe, and probably the more extreme ones too. The ICs and DVs are joined to the bipipe with flexible hoses, so no problem there. So only if you replace the throttle body itself could there be an issue. I don't know if the RS4 throttle body is different, but of course if it is then you can always use the RS4's 'bipipe' instead: If your upgrade goes as far as replacing the throttle body then the cost of disgarding an APR bipipe would be comparatively insignificant!

Don't forget that the OEM TBB is clearly not up to the job of a stock S4. So it is going to be severely strained by a tuned S4 and personally I wouldn't risk it for a K04 tune. Don't forget that the average boost pressure for a tuned S4 is about the same as a stock RS4. Cosworth decided that the flexible TBB was not good enough for the stock RS4 - so that says something about a tuned S4 doesn't it.

N.B. when comparing a stock RS4 and tuned S4 in this respects, I believe only absolute boost pressure is of concern, not maximum airflow.

P.S. The only other S4 owner I know did the APR bipipe upgrade was Joshie, and he's and ex-S4 owner now.

ajsl wrote:Do people think that it's worth replacing the stock TBB with a revised/3rd-party one even if the current one "seems" ok? Same question with the BPVs, go with 710N's as a precaution?

Cheers,
Alex.

The latest Bosch BPV/DVs are certainly an improvement, however they are still based on a flexible diaphragm which is the part which fails. In terms of reliability, you can always keep a spare, however you don't always know when there's a leak, and any leak puts a strain on the turbos. In my opinion a solid piston DV should have longer term reliability and have a similar (fit and forget) factor as the APR bipipe.

The other thing to consider is the spring tension. The Bosch valves are designed for stock engines. In my experience a tuned engine needs a stronger spring to avoid hesitation between gearshifts. AFAIK you can only get stronger springs for aftermarket DVs.

Dippy, thanks for that. I'm still bone stock, so perhaps the 710Ns would be a reasonable compromise (especially as they're around £17!).

mmmm..... I am about 340bhp but only real low mileage, and only about 7000 since the chip/pipe/DV/susp/wheel upgrade.... TBB looks ok at the moment too.

But in the next month or so I think I will probably go for the APR bi-pipe.

Dippy/other guys, one thing that got me thinking about all this, is that from a slow speed second gear roll, putting the foot down the turbo's do not seem to always spool up.... but only in that gear.... initially thought it might be TBB boot related, but someone said not a chance and that it could be MAF ?

Anyone got any thoughts ?

MAF problems are usually either lack of power at top end or in the worst case instability throughout the rev range because the fuelling is totally incorrect. From your description it sounds like hesitation - do you mean that you put your foot down and nothing happens for a couple of seconds and then the boost comes in?

If so then the most likely culprit is a DV (or both) not closing quickly enough. I assume you have aftermarket DVs? If not then get some. If you have, check the springs. For your tune you need stronger springs.

I had hesitation which was almost completely cured by using stronger springs. Based on my discussions with more knowledgeble people, I am now confident that the DV control system is not perfect and so unfortunately hestitation can still occur. But it has only happened to me a few times in the last year.

Dippy, cheers for the info, she is going in to see the doctor on Tuesday, not an Audi dealer but a back street guy, but he normally works on Porche turbo's etc, when I went to book her in there was an lovely example of the RS2 there, so it seems like he does know what he is doing.....

I will tell him the symptoms and see what he finds, I was thinking of buying some parts first, but don't want to splash out on bi-pipe and other stuff until I find out if something else is goosed....

Dippy, it had new aftermarket DV's at AMD last year, before I bought the car, to be honest the boost (or apparent lack of it) happens so infrequently that I think it might be tough to get to the bottom of it, however homefully there will be something that garage can pick up on the disgnostics that can point them in the right direction.

Once I know what needs replacing, if anything then I can splash out on getting the BiPipe and some other nice stuff.....

BTW has anyone seen the intercooler kit on the achtuning.com website ? absolutely gorgeous.... shame to put the bumper back on ! and 32Whp - yes Wheel HP !



Cheers


Mike