remap ecu?

[PiterS2]

Hi.

I´m about to make a 3" exhaust system for my S2. Do i have to remap my ecu or how will the engine respond?

3" all the way

Thanks
Piter

[S2central.net]

Exhaust mods are essentially "free" on a MAF equipped car but what you might find is that the reduction in exhaust back pressure means it could make slightly lowerboost than before. The ecu might be able to adapt to this or you might have to add a little extra mechanical spring pressure to help with wastegate control.

Try it and see - would be good to capture boost levels observed before and after.

[prj]

Lower boost does not mean less power with more VE... less backpressure is always good.
In fact, ECU will still try to make the same target, even though it might not able to, because VE will increase.

Long story short - no, you don't need a remap unless your car is highly tuned and the exhaust was a large restriction before. Even then, you only "need" it to get more out of your car.

[Ross]

I'd never thought of a more free-flowing exhaust being a reduction in VE, makes sense though. Fair to say the same principle applies if one were to fit a Wagner EVO EM and head work as well?

[prj]

I'd never thought of a more free-flowing exhaust being a reduction in VE, makes sense though. Fair to say the same principle applies if one were to fit a Wagner EVO EM and head work as well?

It is not a reduction in VE, it is an increase in VE.
More VE - more flow at same boost level.

[PiterS2]

Thanks for fast response guys.

Is it possible to buy a 3" back box for Audi S2?

[prj]

Btw, decatted stock exhaust does not really pose a problem until 370-380hp...

[macspring]

Btw, decatted stock exhaust does not really pose a problem until 370-380hp...

Prj, presume you're referring to an RS2 oem exhaust, rather than an S2 oem exhaust ?

Thanks.

[Ross]

It is not a reduction in VE, it is an increase in VE.

Yep that's what I meant, slip of the 'tongue'.

It is not a reduction in VE, it is an increase in VE.
More VE - more flow at same boost level.

So I take that as a yes to my question.

This extra flow, does this present a hazard to over spinning a turbo in extreme examples? I've asked before but didn't see an answer, so sorry if this has already been explained before.

[prj]

Prj, presume you're referring to an RS2 oem exhaust, rather than an S2 oem exhaust ?

Thanks.

I am referring to my UrS6 OEM exhaust... which should be similar to an S2.

This extra flow, does this present a hazard to over spinning a turbo in extreme examples? I've asked before but didn't see an answer, so sorry if this has already been explained before.

In theory yes, in practice, no.

[porkkis]

It's not similar. urS cars have excellent flowing factory exhaust. This is not the case in S2's.

[prj]

Fair enough.
I actually spend most of my time looking at C4 bodied cars