RS2 Overboost issue - newbie

[wowow]

My turbo starts spinning at around 3k and I can hear a very distinct "wee" sound and when I push it to 4k gently, it starts to stutter and no more power coming out. Then when I let off my foot, I can hear a very loud "woosh-cha" sound. I tried a friend's RS2 and his wee and woosh-cha sound is very very subtle as I can hard hears them. If I "floor" the gas padel ( rather then push it gently ), sometimes power comes in full, but sometimes it just keeps stuttering and I can see lots of black smoke coming out the back.

I search the forum and someone suggested that the stuttering can be a result of boost leak post MAF and therefore resulting in more fuel than air, hence running rich and produces black smoke. I will try to look for air leak, but I like to get some advice and maybe there are other things I should look out for as well.

I have no boost gauge so I have no idea at what boost level it happens. I want to get one, and will gauge range covering -1.0 to 2.0 bar be good enough ? Is it ture that Max boost on RS2 is 1.8 bar ? Is there a specific connector type that I need to get in order to use it on RS2 ? I found a very nice example of fitting a gauge in the middle of the vent ( without seeing the rest of the grill )

Many thanks

[Lloyd]

Bit of a wild guess, but if you can hear a leak, I would check the throttle body hose for a split. Usually these are parallel with the jubilee clips.

[Carl Avant]

RS2 + woosh-cha sound =

[UrS4boy]

Don't you have a digital boost gauge in the trip computer in the dash?

"Woosh-cha" sounds like you have an aftermarket blow-off valve (BOV) instead of the stock OE by-pass valve (BPV). Here is some info regarding the BPV (it was developed for the AAN but applies equally to your RS2 ADU engine):

http://forums.quattroworld.com/s4s6/msgs/20994.phtml

That said, you might have a leak in a hose between the turbo and the intake manifold, including those into and out of the intercooler.

[State'd RS2 Coupe]

3-4k could just be the turbo spooling up, but as stated test for air leaks.

Also check your MAF connection. Unplug the connector and spray in some electrical contact cleaner and do a slight brushing on the senor blades. I searched forever until I figured this out. I have no airleaks on my RS2, but have to clean this senor connection every 6 months or so or the stutter and black smoke come back.

[Jamo]

Don't you have a digital boost gauge in the trip computer in the dash?

"Woosh-cha" sounds like you have an aftermarket blow-off valve (BOV) instead of the stock OE by-pass valve (BPV). Here is some info regarding the BPV (it was developed for the AAN but applies equally to your RS2 ADU engine):

http://forums.quattroworld.com/s4s6/msgs/20994.phtml

That said, you might have a leak in a hose between the turbo and the intake manifold, including those into and out of the intercooler.

S2's and RS2 dont have boost gauges

[UrS4boy]

S2's and RS2 dont have boost gauges

Seriously? I did NOT know that. I have driven one of the four RS2s in Canada and I am sure that I had seen a digital boost gauge in the trip computer, as shown in this photo frome the 000375 km RS2. Learn something new everyday.

[LunarWolf]

i think you're right about the digital boost. I seem to remember one too.
The Late S2 and RS2 have the same central cpu as the urS6, and we have a digital boost output.
I could be wrong, but i too remember seeing this digital display in an (R)S2!

[wowow]

Guys, thanks a lot. That should give me enough to work on and I will get back with my findings. Just a few more request :

1/.Anyone has a picture of how the stock blowoff valve looks like ? Mine is loud and can well be aftermarket. But does that have anything to do with the over boost ? I thought the blowoff valve is only used when one backs off the gas and release the pressure in the turbo ( sorry, I am a real turbo newbie )

2/. Is the large and distinct "wee" spooling sound a sign of "leak?". It is indeed much louder than my friends rs2.

3/. I don't think my version I rs2 has a digital boost gauge. Can someone pls suggest a model to me, one that requires least modification ( on connection ).

4/. Yes, I read many threads on the connector and I will surely give that a good clean up.

5/. Other than leaks, anything I need to pay attention to on the waste gate ?

[UrS4boy]

Suggest you re-read the link I provided (now with a new photo) regarding failure symptoms, etc.:

http://forums.quattroworld.com/s4s6/msgs/20994.phtml

[Ross]

I've never seen an RS2 or S2 with digi boost guage, my brother has a very late S2 Coupe and that doesn't have one. Not saying it doesn't and I'm not sure if the posts above are serious or not. You don't have a boost gauge so it's irrelevant anyway.

I'm not sure where you'll find the central vent holder - I have one the same on mine, looks great - but as for the gauge you'll want any mechanical one. For power to the light you'll need to plice it into another power feed - recommend the glove box light - and run a vacuum hose down the vent and out into the footwell by the ECU. Pop the vac line off the ECU, put a T-piece on and then you can connect both ECU and boost gauge to the same feed. That's the way most do it.

Get in touch with 'Rusty' on here, he was supplying a VDO gauge that matches the RS2 stock look:

http://www.s2forum.com/forum/showthread.php?t=41629&page=12&highlight=vdo+boost

It does sound like an air leak to me. The 'spooling sound' is louder (1) because the turbo will be spinning it's heart out trying to make target boost, which is 1.4bar on stock RS2 ECU and (2) because the sound is 'escaping' from the leak. The hard 'whoosh' sound is sudden release of pressure; it could be a non-standard valve as mentioned or just the leak holding pressure - i had that when a jubilee clip slipped on my RS2, it would hold to about 1bar then 'whoosh' and no pressure... Also a performance air filter will allow you to hear alot more induction noise.

Check all hoses and jubilee clips along the intake, i recently had a similar problem and it was just a jubilee clip, if one has broken visually it'll look fine - get in there and check they're all attached, tight, with no splits in hoses.

[Fat Audi 80]

I am betting there is a non standard diverter valve on there not working correctly...

[Jamo]

I know there is a mod you can do to get the output the ecu does have the pin output for the info I think s2central posted details I'll have to dig

[wowow]

Hi Fat Audi, can you tell me where the "diverter valve"is located, or part number so I can check on the part list. ( Like your "Sirus" avatar )

[newsh]

DV is down below the RH side headlight. Very common for it to rub on the chassis leg or towing eye and have a hole in it. I must say your car sounds like it has a leak in one of the hoses. Have a search for boost leak test.