Hi prj. I've read all of your posts related to LPG tuning on NefMoto. I have a question to you related to a (future) LPG installation.

The car in question is a 2002 Fiat Stilo 1.6 16v 103ps (1596cc, 182b6000, last gen of Fiat SOHC engine block, with a DOHC 16v valvetrain). When new, these cars could hit 113hp at flywheel. I don't know how mine holds but, it can hit easily 205kmh (GPS tested, straight line) with 2 people and 100kg of stuff in the boot. So I suppose pretty close to that.

I bought it used at 300.600km from the countryside of Greece. Right now it sees tons of city stop-go traffic in Athens and with fuel prices heading to almost 2eur/Liter I would get an ROI in less than 8000km (LPG 0.86eur-0.92eur per liter). I also do long highway trips of 300+km every 3 months or so.

In Greece the auto LPG mixture is 80-20 (Butane+Propane) with slight variations towards 70-30 in some cases.

I know many people have used LPG in this engine and it has last over 360.000km of city driving with proper maintenance. The ECU is a Marelli IAW 5NF.T9 that uses a MAP sensor.

Now the question is: should I invest +200eur to get a kit with a EuropeGas ECU that can also dual inject petrol (up to 50%) in high load scenarios? Bear in mind that the better LPG kit also has Hana injectors which are very fast won't create issues with idle etc. I don't know if cheap LPG ECUs can handle the ignition advance separately but I think that something that is needed to achieve good fuel consumption using LPG AFAIK.

Or should I get just a basic quality LPG kit and tune it all the way to the redline (7100 rpm rev limit) using ONLY LPG? Should I always target the lean best torque AFR? And maximum lambda 0.92? Stoichiometric should be close to 15.5:1 for our LPG mixture.

I want to say that I plan to keep the car for at least 4 more years. In any case, these Fiat engine did not have issues with head gaskets as they mostly had oil consumption issues. Mine burns around 180ml/1000km (a quart per 3200 miles) with low quality 5w40 oil and I plan for a good 5w50 next change to see how it helps. In any case, the LPG conversion will pay itself, even if the engine eventually breaks down (which can also happen using petrol btw).

Thanks!

What is your WOT lambda and ignition advance?
If it is close to 0.77 lambda, then probably you never made just a few WOT runs during those 140K kilometers.

There is a simple thing that make the things goes wrong - if ME7 (or any petrol ECU), decide to keep EGTs low it inject more fuel, for a simple reason that this unburnt fuel will evaporate taking thermal energy from combustion chamber or/and exhaust manifold.
So more fuel = less EGT.

However lpg is already evaporated when injected, so instead of cooling down - it getting hotter.

ECU thinks it is hot - let's cool it down => put more fuel... ufff it is still hot => then put MOOOORE fuel... Aghhhh it is really hot here!

So I installed a EuropeGas LPG kit with fast 1.9 ohm Hana injectors. I did 13.000km with it before opening the engine (for an issue unrelated to LPG).

Due to a head gasket leak on cylinder no1 (which did exist before installing the LPG, as apparently I was losing coolant) I did a cylinder head job: skimmed head, milled exhaust valve head seats, 8 new exhaust valves (stronger stellite ones specifically designed for LPG use, IVAM or Freccia, don't remember which ones the builder chose in the end) and of course new valve stem seals and head gasket.

The kit was tuned to use 100% LPG (even though it supports gasoline enrichment or full switch) due to a lazy tuner. In fact, after 5000 RPM I had noticed reduced power compared to gasoline mode.
I now want to tune it but because this is not a typical Bosch ECU but a Marelli the support is limited (I've yet to find a Damos file for this IAW 5NF ECU for WinOLS).

If I manage to adjust the ignition advance, what should be the target vs gasoline to achieve better power (if possible more than gasoline) at high RPM without ruining the valves? I have to say that in the 1800-3000 RPM range, LPG was giving me far more torque, so I suspect that the ECU was adjusting the ignition advance on its own given the higher octane content of the fuel.

The factory ECU is rather dumb though: no EGT probe, no wideband lambda and only one mixture correction metric (and I've yet to understand if this is equivalent to STFT or LTFT).

Could the loss of power at high RPM be due to wrong ignition advance and slow burn time of LPG? Or just too rich of a mixture? Do you think it's pointless to try to achieve the same power at high RPM and I should just switch to gasoline above 5000 RPM? I have found a good LPG installer (and tuner) that will take care of it, but I need to learn more so I can help him to achieve my goals with this setup.