passat APU and flex fuel

[danny_p]

is it possible to add a flex fuel sensor to an APU ecu ?  or what options are there for switchable maps with this ecu proably the better solution as it'll allow igniton to be optomised.

basicly i'm planning to start running it on E99 or E85 and only straight petrol when off on a long trip

[RTechUK]

I have never looked into this..yet, but a lot of tuners in the states are playing with it on the 20VT

I dont know how a narrow band ecu would cope with it as the primary fuel is based on air mass?  IMO a ME7.5 1mb ecu could cope better as the mapping is based in lambda 1,  which mean is easy to dial in a richer burn for the E99-E85 via the thermal protection map and lower the EGT limit to kick in the maps early to be safe.

I will have a read up, ans see what the APU ecu can offer in means of mapping for the E** fuel.

As for map switching, you can have 2x PSOP44 stack on top of each other in the ecu, one stock the other for E** and a toggle switch on the dash which will allow you to swtich between maps a the click od a button.

[danny_p]

thanks for the repy

i've looked at some of the bodge it and scarper E** conversion kits   but all most of them are is a box that you connect inline with the ecu and injector and it simply adjust the pulse width to supply the right (ish) amount of fuel  but they ae about useless as ecu will flag codes as the lambda readings are all wrong,  fixed that easy enough  just used an innovate LC-1 and adjusted  the output  that keeps the ecu happy but turns a cheep bodgey conversion into a not so cheep bodgey conversion, rather spend a bit more and do it right preflably without a shed load of wireing.

the optimal solution would involve flex fuel sensors then its no fuss no bother what goes in the tank.  but i dought the APU ecu is going to support them so map switching is probaly going to be best for the passat.
 we got the old m3 running flex fuel with a megasquirt the way it dose it is a bit crude so end up swaping maps and just use the flex fuel function when theres a random mixture in the tank,  goes bloody well on E99 uses it tho

[RTechUK]

Using the LC1 wideband output feed to replicate the ECU o2 sensor readings and changing the output scale... good idea
But only to the max of the MULT LTFTs as they all run from a primary fuel map based on the conversion of relative fuel mass v relative air mass. IMO deviation from primary fuel by using fudged injector pulswidth or scaled o2 reading will still cause issues and could become unsafe..... the reason that many large cc na LPG conversions having melted pistons.

With the innovte systems it you can set the stoich values for AFR for what ever fuel your running. ( I just brought the new innovat all in-one wideband gauge for my golf, and binned the LC1. Hve a look on there site )

I just been watch How its made Auto on tv and they were talking about ethanol fuel, and the higher octane rating really took me in and got my brain ticking So you know what I am going to start playing with now on my car...    more timing more free power!!!

I need to read up in the lambda scalings for where the best burn is for torque and power and produce a new fuel map and do some logging.  They also mention the mixed it with petrol and ran it in a saab turbo which when the dialed more timing in the mapping made a lot more power that the petrol.

Using E85 in a gasoline engine has the drawback of achieving lower fuel economy, as more fuel is needed per unit air (stoichiometric ratio) to run the engine in comparison with gasoline

google and wiki here I come...