Yes it was done in third and it is hardly noticable in that gear, 4th is worse and fifth feels worse still.

I just blocked up the dv vac hose and took for a spin.Holy cow the hesitation has completly disapeared and no engine light came on.The car did feel slightly down on power though is this normal?

You need to check your hoses first, i think you have a leak in your dv system that is why your over boosting..

Try removing the vac line from benath the inlet manifold, the one that goes to the valves at front of engine. Get an electric air compressor or tyre inflator, with one of those pointed tips you use for the airbed. Pump air into the very short pipe you removed from the inlet mainfold, check for hissing, it needs to hold at least 17 psi before hissing.

hmm.. fair play, that's a bit different :confused:

with the DV vac pipe disconnected, it's quite feasible that the boost pressure on the bottom of the valve is enough to overcome the spring preload and start lifting it and effecting a boost leak. Normally there is equal (boost) pressure applied to the top of the valve as the bottom, PLUS the spring pressure holding it shut.

The fact that disconnecting the DV and taking away the peculiarities of n249 behaviour, improves boost stability noticeably, is an indication to me that the DV/n249 isn't the primary boost control, but more of an interference at the wrong time.

We are probably all agreeing I think that the n249 behaviour is responsible for the boost instabilities, which become more acute as boost levels rise with remaps etc.

I agree the n249 has a part to play. It cannot be bypassed since the ecu will throttle the boost using the n75, hence sudden drops in boost. By bypassed i mean directly connect dv to intake. Since ecu knows its still there, and doesnt throw a error, it will continue this urging behaviour

Its only when ecu sees the DVs not there ("mechanical failure of dv" error) that things begin to change. Ecu changers characteristics mayebe? to try and compensate for lack of dv? eg will open wastegate longer when foot taken off gas?

I don't know, but i think we're onto a winner

im going to try this tomorrow if i get home from Newcastle soon enough.

You need to check your hoses first, i think you have a leak in your dv system that is why your over boosting..

Try removing the vac line from benath the inlet manifold, the one that goes to the valves at front of engine. Get an electric air compressor or tyre inflator, with one of those pointed tips you use for the airbed. Pump air into the very short pipe you removed from the inlet mainfold, check for hissing, it needs to hold at least 17 psi before hissing.

Iam trying to find the vac line.There is 3 lines at the side of the inlet, 2 fibre and the middle is rubber.Is it the short middle one or a different one altoghther?

I tried the rubber one and the gauge shot round to 3 bar :eek: i did not hear any hissing let me know if its the correct line,thanks

P.s the car does not overboost at all with the dv vac line disconnected do you still think i have a leak?

Iam trying to find the vac line.There is 3 lines at the side of the inlet, 2 fibre and the middle is rubber.Is it the short middle one or a different one altoghther?

I tried the rubber one and the gauge shot round to 3 bar :eek: i did not hear any hissing let me know if its the correct line,thanks

P.s the car does not overboost at all with the dv vac line disconnected do you still think i have a leak?

Its NOT the pipes leading away to the valves at the side of the intake, there are 3 of those.

You need to look under the intake plenum

It is a very short rubber pipe, it connects to a brass nipple on the underside of intake plenum. There should be two connections. One is the short rubber pipe, the other is a fiber pipe.

If you follow the fiber pipe which connects to the fuel regulator to the intake plenum, where it meets the intake plenum there will also be a rubber pipe. it is this pipe you need to check/inflate. there should only be these 2 pipes connecting to the intake plenum.

Make sure you connect your dv backup first, or all the air will come out of the DV vac line. and it will help prove that when its connected there is no leaks.

jay

Its NOT the pipes leading away to the valves at the side of the intake, there are 3 of those.

You need to look under the intake plenum

It is a very short rubber pipe, it connects to a brass nipple on the underside of intake plenum. There should be two connections. One is the short rubber pipe, the other is a fiber pipe.

If you follow the fiber pipe which connects to the fuel regulator to the intake plenum, where it meets the intake plenum there will also be a rubber pipe. it is this pipe you need to check/inflate. there should only be these 2 pipes connecting to the intake plenum.

Make sure you connect your dv backup first, or all the air will come out of the DV vac line. and it will help prove that when its connected there is no leaks.

jay

Thanks Jay,just to clarify you mean the ones in the diagram 14 and 19 and its the rubber one?

This is the one i tried and there were no leaks

FPI.pdf

^^exactly right. pipe 14.did you have the dv installed at the time of testing? as you would normaly? inflate to 14psi. check for hissing around dv especially.

if your absolutely sure there are no leaks, its came to find a larger vac can to play with.

Well i went to the salvage yard today and bought a second vac can,which iam going to mount on the bulk head.

I also picked up a T connector a joiner and some more hose,so i will be running two vac cannisters.

All this came from a salvage seat leon with the same engine as mine and cost £5 in total.I will be hopefully fitting before the new year.

Fingers crossed it maybe the answer to me prob if not its only cost me a fiver.

hey Mart,

let us know how you get on - If I get chance over the festive period, then i'll be trying mine too

hey Mart,

let us know how you get on - If I get chance over the festive period, then i'll be trying mine too

Well i hooked up my extra box in line with the other today ,it never worked :( for me

The car still surged, i find this really annoying as when i disconnected and plugged the top dv line as in previous post the car was really smooth.

Back to the drawing board then i suppose.

Has anyone tried one of these you can get them for the 1.8t AUDI S4 / RS4 TURBO BOOST LEAK / INTAKE PRESSURE TESTER on eBay, also, Audi, Car Parts, Cars, Parts Vehicles (end time 26-Dec-07 22:45:58 GMT)

and would it work ok without blanking off the dv/n75 etc etc

Thought i might give it ago one day.

bugger :(

did you use a larger cannister or double up?

I doubled up mike.

Its a real shame as i said, when the dv top pipe is blocked off its as good as gold.

How long did it take to try Mart?

er about an hour, although i was bolting box back and cutting pipes etc for a neat look.I have taken it off again now though

I might have to nip to the breakers next weekend and give it a go then.