Definitive answer on Upping the boost on 1.8t

[CupraGTi]

Hey guys,

I have done a lot of reading, as well as assuming, as well as listening to people perspectives on increasing the boost level on a modified though NOT chipped AGU 1.8t. It breathes much better than stock, and has a 3inch turbo back.

I understand that the n75 is basically an electronic boost controller. and from what I have experienced it is very touchy when it comes to being in the loop whilst trying to bleed off boost reference to the wastegate.

In all other turbo cars I have owned, putting a MBC in the mix has not affected things drastically. Of course I would never raise the boost above what I deem to be a safe level, but then again I am not a rocket scientist and I can not just guess what A/F ratio I am achieving.

Can someone please explain to me if my assumption is correct in that the VW's are much like other turbo cars in that the Air Flow Meter will measure how much air is being sucked in, and adjust the fuel map accordingly? If the n75 is taking care of boost levels only, then surely it must be the AFM and computer that dictate how much fuel is used to supplement the increased air.

I understand that I wont be getting full advantage of the increased boost, as timing changes wont be made by the computer... but I'm only increasing it a maximum of 4psi. It feels like it is taking it well, and I am not getting any pre det or knocking.

Advice please on what is happening regarding the extra boost I am achieving.

[h100vw]

Hey guys,

I have done a lot of reading, as well as assuming, as well as listening to people perspectives on increasing the boost level on a modified though NOT chipped AGU 1.8t. It breathes much better than stock, and has a 3inch turbo back.

I understand that the n75 is basically an electronic boost controller. and from what I have experienced it is very touchy when it comes to being in the loop whilst trying to bleed off boost reference to the wastegate.

In all other turbo cars I have owned, putting a MBC in the mix has not affected things drastically. Of course I would never raise the boost above what I deem to be a safe level, but then again I am not a rocket scientist and I can not just guess what A/F ratio I am achieving.

Can someone please explain to me if my assumption is correct in that the VW's are much like other turbo cars in that the Air Flow Meter will measure how much air is being sucked in, and adjust the fuel map accordingly? If the n75 is taking care of boost levels only, then surely it must be the AFM and computer that dictate how much fuel is used to supplement the increased air.

I understand that I wont be getting full advantage of the increased boost, as timing changes wont be made by the computer... but I'm only increasing it a maximum of 4psi. It feels like it is taking it well, and I am not getting any pre det or knocking.

Advice please on what is happening regarding the extra boost I am achieving.

I am sure it will have max airflow/N75/rev combinations in it's 'head' deviate from those and it will call time. Basically there's not much you can do to fool with it.

[CupraGTi]

but its running so well at 14 psi, 15 in fifth. It's running off its head at night. A/F ratio is fine a friend of mine hooked up his system, and it was all in the midrange to rich, the computer is adapting to the new boost controller and is remapping the fuel ratio itself to an extent. I should get it on a dyno. New spark plugs have made a big difference as well.

[1GTI4]

but its running so well at 14 psi, 15 in fifth. It's running off its head at night. A/F ratio is fine a friend of mine hooked up his system, and it was all in the midrange to rich, the computer is adapting to the new boost controller and is remapping the fuel ratio itself to an extent. I should get it on a dyno. New spark plugs have made a big difference as well.

Hey man,
I was running a MBC for roughly just over a year at 15psi. Also it's running an "APR Stage 1 Tune" (which I don't like very much) and a custom TB exhaust that backfired all over the place. Just recently took the MBC out (thanks to Gav) so now it's just back to the Stage 1 tune and no extra boost (peaks at about 12psi with the tune). I found immediately that it spools quicker, holds boost more efficiently, hasn't backfired yet at all (I'm not an expert but that indicates to me that the timing is running a lot smoother), and already I'm seeing improvements in economy. I'm in the midst of a Phase 2 Custom Code tune, which from memory should peak at about 18psi. I feel like 18psi through a proper tune without the MBC will be a lot more responsive, efficient and economic even if you up the boost with your MBC to the same level. Basically, from my rather short experience, for longevity of your engine, efficiency of your timing system and fuel map, and for all-round better performance, etc - I'd say look to a tune rather than a MBC. Maybe you could put the money you would spend on a dyno towards a Stage 2 Tune and not have to worry about the MBC altogether... food for thought.

On another note, what spark plugs did you change to?

Adam

[parso_rex]

Well the A3 has no map sensor, it uses a reverse lookup table that references the MAF sensor. The thing you can't change is the boost cut and it will be running very rich up top until you max out the injectors and then will progressively run more lean. There is no way of seeing this due to the lack of wideband sensor.You will probably find that the timing is infact low even though the boost is high.
S3 is a bit different but you'll hit a cut so some kind much more easily

What is pre det ?