Got a GM flex fuel sensor for my 96, have power and ground wires ran. I've read that the output wire from the sensor needs a resistor? If so, how do I go about doing so inside the ECU?
Thanks in advance!

 

can ms2 even do flex fuel?

 

Yes it can, but it's very rough around the edges.

 

Notes on flex fuel input for a DIYPNP are here:

https://www.diyautotune.com/diypnp/d...lex_Fuel_Input

 

i guess that makes sense since there's an input called "FLEX" :P

 

Forgive the thread necromancy, but I did not want to start a new thread and searching brought this post up.

Has anyone actually run a flex fuel sensor with a DIYPNP? I know a ton of people do it quite successfully with the MS3x, but I already have a DIYPNP running very well in my '99 VVT swap daily (Made 148whp in 98 degree dyno conditions). I don't want to spend any additional money on another Megasquirt, especially if the DIYPNP can handle E85 input and actually function.

 

I tried to check how MS2 handles flex fuel, but can't get any good info (a lot of blocked sites at work). I seem to remember it being set up so it adds a fixed amount of timing and % of fuel per content of alcohol. Either that or you have dual tables, but it will only allow you to straight line blend between them.

If you can just add fixed levels of timing and fuel, it may not be as precise as dual tables but I would still feel pretty confident doing it, and you should definitely gain power doing it. If you have dual tables and it blends between them, that's exactly how I'm running my MS3X. The fancy blend curve stuff looks nice and all, and I'm sure it'd make a little more power with mixed fuels if you took the time to dial it in perfectly, but straight line blending seems to be safe, easy, and has worked well for me when I've gotten lower ethanol E85.

 

Fixed levels will run pretty poorly on E85. MS3 starts with a fixed multiplier but to actually get the car to run smoothly you need a lot of VE3 table tweaks. The fuel requirement differences vary heavily based on coolant temps and load.

 

I would think Flex Fuel would be beneficial with a DIYPNP for small changes in ethanol content. Say you tune for E78 and you fill up with E82, a fixed multiplier is better than nothing. But I wouldn't tune for gasoline and use a fixed multiplier to run E85.

 

I know Hondata recently added flex sensor support via fixed multipliers and all the honda bois around here are jumping on that. For me personally, since I set up flexfuel I haven't filled with anything but E85. I just don't have any reason to swap fuels. At the very least you can dial in a tune for your primary fuel, and you at least know you've got decent secondary fuel map that will get you around.

If you're really going to be switching all the time it'd be easy enough to set up 2 tunes. Have a 93 tune that uses the fixed values to get close enough on E85. Then a E85 tune that uses fixed values to get close enough on 93. Before I had a flex sensor I just tuned for E85, and kept a 93 tune on MSDroid for the off chance I got stranded somewhere.

 

I switch all the time

I run separate maps. for those 1 tanks in-beteween when there is like 15-20% ethanol still in the tank or vice versa andI adjust the injector flow I then also give the EGO correctionb more authority.

It sounds like the E85 sensor is not worth the effeort on MS2 PnP ? I'm on the verge of a 1.8 conversion & was thinking of installing it.

My car seems to really like the 20% ethanol....on a 93 tune.