Ok - i've been trying to get the car mapped for some time now but have been running into problems.

First of all the car was boosting in peaks and troughs. Thoguht this was a dodgy n75 valve so replaced it. I originally replaced it with a n75j but then the car wouldnt hold boost at all so bought a std n75 and put that on.

went back to the tuners today and the car still has teh original problem. after some fault finding we found the following -

there's a pipe that goes from the n75 to teh wastegate if we clamped this the boost would stay constant and power band progressive as expected. none of this yoyoing effect. Tuners reckon there's a problem with the wastegate as we had already eliminated RECIRC/N75 and boost leaks.

Becuase of the location of the wastegate he said that this would be a costly replacement and suggested a release valve. By putting this in line between teh n75 and wastegate we could essentially fool th wastegate into thinking the pressure was right by opening and closing the valve accordingly. once we stop the boost increase/decrease we could start the map.

Does this sound feasbile/stupid/good/bad?

The guy has dealt with a number of VAG cars as well as skylines/scoobies/mitsis so is well versed in turbo cars. Just want an opionion on the problem and if you think this is a stupid idea.

Thanks in advance.

Bal

ps why cant i post in teh classified?

its sounds very much u have a boost leak some where me thinks,have they read ur car for fault codes?faulty dv can make boost fluctuate,usaully comes up with n249 mechanical fault on vag com when dv is faulty,also pipes frm n249 valve to dv could be persished and leaking,just some things to look for.

ps why cant i post in teh classified?

You can't post in the Classifieds as this is an extra feature exclusively available to freedom members. You are more than welcome to sign up, following which you'll be able to post in the for sale sections

http://www.briskoda.net/freedom/index.php?page=joinFreedom

no we arent getting any fault codes. that's the weird bit.

also i found this - http://www.briskoda.net/forums/fabia/bleed-valves/34810/?highlight=wastegate

basically the guy is talking about fitting a bleed valve. having read the thread in teh link im a bit worried about doing this now so i might tell him to allow it ???

doesnt solve my problem though :(

also pipes frm n249 valve to dv could be persished and leaking,just some things to look for.

where is teh n249 valve? i have a forge DV to fit but havent done it yet becuase i recieved the wrong spring (green and not yellow).

quesiton about boost leak - if by clamping shut the pipe from the n75 to the wastegate solves the problem how could this be a boost leak? i though this air was going to the wastegate to open it to release pressure from the turbo?? sorry am i being a numpty??

ok the more and more im thinking about this the more and more things are becoming clear.

the n75 regulates the air to the wastegate and basically when the a certain pressure hits the wastegate actuator it opens.

currently on my car it opens sometimes at 14psi and sometimes at 18psi but it's basically fluctuating between the two. by clamping the pipe between the n75 and the wastegate actuator it wont read the increase in boost pressure therefore allowing the car to maintain boost and not opening up.

so ... the mapper is saying put in a bleed valve - this way the wastegate will only see a certain pressure allowing him to get on with the map.

questioin - is this really a fault with the wastegate actuator?

again it cant be the n75 becuase iv replaced it a couple of times. it couldnt be a boost leak as we are effectively needing to put in a leak to fix the problem. so it can only be the actuator itself.

yes/no?

we clamped off all the other vacuum pipes to rule them out and the only one that fixed the issue or stopped it was teh pipe to the WA!?!?

man im sitting in front of the tv eating just thinking this throguh in my head.

right time to stop thinking abotu this lol ...

you say your car makes 14 psi and sometimes 18psi of boost,if it does its already been remapped,standard octys only run about 10psi.i had similar fault with my leon cupra,but never got round to sorting it,taxi wrote my car off first.if ur car is running that boost and its on standard dv,its sure to be faulty,running more boost on standard dv,s,they last no time at all.

Thwe wastegate is operated electronically by the ECU via the N75 based on a signal from the MAP/Boost sensor in the intercooler.

we put on a generic map to see how it would go and that's why it's running 18psi.

could it be the map/boost sensor which is playing up? how could i try one out? how much do they cost just for reference??? is this the n294 valve or whatever it's called?

i want to avoid this "bleed valve" idea if possible as it's sounding more and more like a bodge.

just wondering have u tried a new dv?the n249 valves job basically controls the dv,in theory it can open the dv under throttle if the ecu sees its making too much much boost,there are people who have done away with there n249 valves but thats another story.

i havent tried the DV. i bought a forge one but it came with a green spring which is only good up to 15psi. i'll get hold of a yellow spring before the weekend and try it.

Bal

well the forge is going on tonight as i now hav ethe spring. i'll keep you all updated. iv been doing more research on this and the other suggestion is that the throttle body might be closing early but i aint convinced.

it's on. took it for a rag down the motoroway ... a bit better i think but not entirely sure. still surged a bit.

Have you tried unplugging the MAF?

we tried the maf and nothing.

we tried the forge recirc valve and nothing.

so in the end we stuck in a bleed valve. set the car up and now i dont have any lumpiness.

I shall scan the graphs and stick them up fo ryou guys to see.

car has been mapped to 210 bhp and 225lb tourque. not amazing figures but enoguh given the yoyoing boost affect it had.