Basic questions about NOS, Propane and ECU mapping

muddyboots

Still hanging around
Oct 16, 2002
5,739
1
I've been following the various threads over recent months about using NOS, propane etc on TDIs.

What I don't fully understand is how this fits in with ECU mapping.

Am I right in thinking the ECU is mapped to assume NOS and/or propane is always in use ?

If so - what happens if you run out or turn of either of them - presumably the mapping is then far from ideal, resulting in mucho overfuelling, smoke etc ?
 

devonutopia

fabia-lous
Mar 30, 2004
1,200
1
Exmouth / Exeter
Well, to be as short as I can. When I get mine mapped, it will be mapped to assume the lpg is on all the time. The lpg is a fuel source like the diesel so will need to be tweaked along with everything else to get the best combination (lpg cuts in low down and gradually increases in rate as boost goes up)

NOS on the other hand will not be factored in in the same manner. This is because it will only cut in at around 22 or 24 PSI like an on/off switch. Therefore I'm going to ask that a little extra fuelling is left over on the map, so that when the NOS is used it will have something extra to burn and give the kick it needs. I won't be using the NOS all the time (not at £6+ per lb to buy) so the map has to be a little bit "overfuelly" but not too much as mine does now.

Hope this helps. Ideally you want a switchable map for "diesel" then "diesel + lpg" then "all three" but this isn't an option with my tuner plus I just want one good map, and I will never run without lpg, and if I run out it will merely run a little lean - a good reminder for me to tank up. :)
 

muddyboots

Still hanging around
Oct 16, 2002
5,739
1
OK, so I'm not missing something clever then, mapping makes assumptions that LPG/NOS is always available; if not then you will get less than optimal performance.

Ta
 

devonutopia

fabia-lous
Mar 30, 2004
1,200
1
Exmouth / Exeter
You could say that, if the (estimated 40) bhp loss without NOS is the outcome. :) The car will simply have to be setup to run on lpg and diesel for the main part, and simply adding the nitrous makes it even better.