A3 Hesitation, Boost?

[mnadeem1984]

Hi I have an audi A3, 1.8T 2000X reg (DBW) and i seem to be having a slight problem. The car has had a jetex exhaust cat bac system, K&N cone filter with heat shield and a Remap from http://www.E-Maps.co.uk.
For some reason, the car seems to have power and then the power goes and then it suddenly kicks back in. I have diagnosed the car using vagcom several times and all erros which occured were wiped first time and have never occured again. I have replaced the MAF, engine temp sensor and serviced the car, however no difference. When using vagcom, i get an MAF reading of 175g (so this works out to about 175/0.8 =218bhp).

I took the car to an audi specialist in midlands (UK) and they told me that it was a problem with my boost. The remap which had been done is causing too much boost or something and that i needed to lower the boost by 2-3psi. The alternative was to move the DV and have a different set up for this. He mentioned something aboput a solenoid or something and this was causing problems on the later cars. (i think the older cars do not have this setup or something). Anyway, do you think that this shortage of power in the mid-range is due to boost (i.e. lower boost on remap settings) or do you think it may be something else.

Any views etc would be highly appreciated.
Sorry for the long post

Cheers

 

[rojocho]

have you checked the n75 map sensor, which regulates boost. dont know, but think you have one as only early cars i think like my agu didn't. mate is having same problem on leon cupra r, only when revo'd, changed maf, but seat looking into boost solenoid/n75. map sensor should regulate boost, so faulty one might be your problem

 

[imported_bubstar]

[ QUOTE ]
have you checked the n75 map sensor, which regulates boost. dont know, but think you have one as only early cars i think like my agu didn't. mate is having same problem on leon cupra r, only when revo'd, changed maf, but seat looking into boost solenoid/n75. map sensor should regulate boost, so faulty one might be your problem

[/ QUOTE ]

Yes - The N75 is a good place to start /ubbthreads/images/graemlins/ok.gif

BUB

 

[jcb]

lose the K&N as they can play havoc with the MAF, something about the oil in the filter,.... can't be helping.
Doubt that is your problem if you say you changed it and still have the problem.
sorry can't help apart from that

 

[mnadeem1984]

I have run a diagnostic on it and nothing has come up. can the n75 still be faulty?

Whats the best n75 to go for then? and where from. like i sed it has been remapped, and exhaust, so its pushing around 200bhp. (using maf and vag com i got a valuve of 218bhp).

 

[mnadeem1984]

Bump /ubbthreads/images/graemlins/confused.gif

 

[AL_B]

Boost problem or hesitation, whatever you want to call it, has been experienced by a number of folk on here. And there are not many who have got to the bottom of it, me being one.

Basically, you are going a long the right route of, temp sensor, MAF and testing with VAG com.

I certainly do not believe what the independant is saying about "moving the dv". No need at all. Although you could try replacing the dv for an uprated 710N OEM one, or perhaps a piston type one from Forge or other tuner. I'd stick with a recirculating valve.

The N75, with signals from the ECU, controls the wastegate.

Depending on your engine code, you may also have what is referred to as an N249. This is the "air recirculation valve or the turbo charger". Basically it is another electronically controlled soleniod with vaccum pipes attached. As far as I can tell, this solenoid allows the ECU to control the "mechanical air recirculation valve", what we refer to as the "dv".

You can get both the N75 and probably the N249 from www.vagparts.com or the audi dealer. Be careful with vagparts and the n249, as when I enquired, they shipped me the normal DV, and the guy would not take my word for it that the two were different.

I'll try and dig out the part number for the N249.

So it may be worth trying a new n75 first, then an N249.

Let us know how you get on.

AL

 

[mnadeem1984]

I was told that since i have had the car remapped, its a good idea to replace the stock dv with the forge one. Wheres the best place to get one from and how much am i look at? Same as the N75 valve, shall i go for a stock?

 

[AL_B]

You could probably pick a Forge one up by browsing the For Sale sections of various Audi/Seat/VW forums. Or get one direct from Forge (www.forgemotorsport.co.uk). The AmD Viper valve is also recommended by a number of people on here (www.amdtechnik.com). You are looking at around £80-100 for a Forge/AmD Viper.

Whilst you are trying to get to the bottom of the cars problem, why not get an OEM 710N for about £17. It will last quite a while.

There are other DV's to, do a search of the forums on here to get peoples opinions.

N75, stick with the standard OEM version for your car. For now at least. Until you have your problems sorted. There are different versions of these N75 solenoids. Some allow a little more boost before activating the wastegate (I think thats the theory)...but this can in-turn cause your ECU to go into limp mode because the car has over-boosted.

Hope this helps.

AL