How to convert the E46 M3 to be 100% flex fuel compliant?

[ATB88]

Should work fine with whatever your tune is, that's why it's a piggyback system. You should only need to retune if changing injector size.

Wow, rad. And if I'm only running pump blend E85, I shouldn't need to change injector size?

[heinzboehmer]

I happen to live a mile from a Sheetz station w E85 and my car is strictly pleasure/fun now so this makes sense for me.

One thing to keep in mind is that ethanol is hygroscopic. If your car sits for extended periods of time (few weeks or so) then keeping E85 in the tank is not the best idea. It will absorb moisture from the air and potentially cause components in you fuel system to rust. Shouldn't be an issue if the car is used frequently though.

[heinzboehmer]

Wow, rad. And if I'm only running pump blend E85, I shouldn't need to change injector size?

That depends on a ton of factors. What the percentage of ethanol actually is, elevation (for air/fuel ratio), tune, power you're making, etc.

I remember there being a spreadsheet on the old M3Forum that allowed you to calculate injector duty cycle based on injector size, power, ethanol percentage, and a couple other things. Unfortunately can't seem to find it now. However, I do remember doing the calculation for my car and deciding that to be safe, I probably shouldn't go above ~E50 at sea level with my setup. I plan on getting bigger injectors whenever I get a custom tune done.

[Jimbo's M]

Wow, rad. And if I'm only running pump blend E85, I shouldn't need to change injector size?

If you mean all corn and no gas, that I personally would not do just for the simple fact that stock DME will adapt up to ~98, maybe 99 octane. So after that,I don't think you'll see anything (at least for me), and plus you will work the injectors harder for nothing. At least that's the way I look at it.

[ATB88]

If you mean all corn and no gas, that I personally would not do just for the simple fact that stock DME will adapt up to ~98, maybe 99 octane. So after that,I don't think you'll see anything (at least for me), and plus you will work the injectors harder for nothing. At least that's the way I look at it.

No, I meant the E60-E70 type stuff I would expect to come out of a run of the mill pump labelled E85, maybe sometimes mixed with normal gas if I decide to fill up on that sometimes if it's more convenient. From what I understand there's nowhere I could get "all corn no gas" from a pump anyway.

[Jimbo's M]

No, I meant the E60-E70 type stuff I would expect to come out of a run of the mill pump labelled E85, maybe sometimes mixed with normal gas if I decide to fill up on that sometimes if it's more convenient. From what I understand there's nowhere I could get "all corn no gas" from a pump anyway.

What I mean by "all corn, no gas" is running straight E85. The E85 here is just about E82 according to my AFD. That's why I chose about a 13-3 ratio. I also live in Tucson at 2500' with common density altitude of over 6000' (I had that info available at work everyday). I imagine that'll play a difference as well.

[ATB88]

What I mean by "all corn, no gas" is running straight E85. The E85 here is just about E82 according to my AFD. That's why I chose about a 13-3 ratio. I also live in Tucson at 2500' with common density altitude of over 6000' (I had that info available at work everyday). I imagine that'll play a difference as well.

Ah, okay, got it. In any case, I guess what I mean is running a blend of my local pump E85 and normal gas that won't completely max out the injectors. I understand that this'll wear them out faster, but that's not so much a concern for me.

[mrgizmo04]

I ran AFD kit before getting a tune from Paul, and then after getting the tune. Tuner doesn't have to work around it at all, as mentioned, it's a piggyback setup, so it works independently. I dont know at what point you need to start upgrading injectors and fuel pump. On fully stock cars (if those still exist), running full E85 should be ok. Once you start doing headers, CSL box, cams, etc, I don't know when you have to start either scaling down E85 by mixing it with 91, or getting injectors/pump and a retune.

I run Eventuri intake and full Supersprint, but as a safety margin I don't go over E50.

A lot of guys who got APE kits really liked them because compared to AFD app, APE app gives a lot of calculations. I don't know how true the duty cycles are that they capture in the app, they are most likely estimated based on electronic signal that the injector is open, but what is the actual flow rate? And I dont know if it captures and adjusts based on mods, so theoretically the more mods you have the lower the ethanol it should suggest you run in the tank on stock injectors?

[Arith2]

I read the at WOT at around E70 to E80 maxes out fuel injectors back on M3forum. It has all the info on the injectors sadly. Can anyone post the stock duty cycle at WOT with 93? Preferrably one of you guys that can read the ethanol content so we can get an accurate number. Everything is at least up to 10% and ethanol free only goes up to 89 from what I've seen. From this we can figure out the sweet spot for needing larger injectors or not. It won't be perfect but we can get a ballpark number. Who knows, E70 could have the injectors working at 100% and anything above that is pointless. I'm super interested in this and it's reassuring to see a few of you loving your conversion.

[mrgizmo04]

Here are a few screenshots I saved from old forum to add to the discussion:

[Jimbo's M]

The power from this kit is made by taking advantage of our 11.5 to 1 compression ratio and our DME's ability to adapt close to 100 octane. I see no reason to run higher than necessary ethanol on a basically stock car.

[M3Guy]

As mentioned just a piggy back. I'm running a epic motorsports race tune in conjuction with my ApeX 85 kit.

[Arith2]

I referenced the government energy website to use as a baseline for the math which I linked. Basically 120,359 btu/gal is what E10 has. I used pure gasoline(124,340btu/gal) and E100(84,530 btu/gal) to find this number. That's not really relevant until compared to actual E85 where percentage matters. Here's the percentage of the ethanol needed to accomplish the same amount of btu's. Just a note, fuel injectors shouldn't be going over 80% duty cycle. From what I read on wikimotors, 247cc was supposed be the rating but Buildjournal was getting 260cc when testing them at 3 bar.

I have written fuel, btu/gal, how much more is needed, increased cc's based on the 272 number, and percentage of 340cc max. 340cc is an accurate number after doing the math. Based off of 260cc it would technically be a 337cc max but there's a 2% tolerance so it can slide.

Fuel - BTU/GAL - % More Needed - Req Flow - Inj Duty Cycle:
E50 - 104,435 - 15.2% - 313.3cc - 92.1%
E55 - 102,445 - 17.5% - 319.6cc - 94%
E60 - 100,454 - 19.8% - 325.9cc - 95.9%
E65 - 98,464 - 22.2% - 332.4cc - 97.8%
E70 - 96,473 - 24.8% - 339.5cc - 99.9%
E75 - 94,483 - 27.4% - 346.5cc - 102%
E80 - 92,492 - 30.1% - 353.9cc - 104%
E85 - 90,502 - 33% - 361.8cc - 106%
E90 - 88,511 - 36% - 369.9cc -109%
E95 - 86,520 - 39% - 378.1cc - 111%
E100 - 84,530 - 42.4% - 387.3cc - 114%

In conclusion, stock fuel system is maxed out on where it should be at 80% already. Ideally you want to upgrade no matter what. I doubt an injector 15 years old is functioning at 90%. Remember commanded duty cycle and actual flow are two different thing. I've found in multiple places the 85-90% is the max an injector will actually flow without problems. The computer can only measure what it sees. It doesn't read flow, just what it thinks is flowing because it's pulse width modulating. Theoretically, without accounting for worn injectors, the absolute max you can run is E50 without losing efficiency. This injectors work and your ECU will adjust for AFR to run well but that doesn't mean it's working as it should. Cars are smart enough to not cause knocks.

I would assume advertised injector flow is tested at 3 bar which is 43.5psi while ours function at 5 bar or 72.5 psi. Upgrading to a 330cc injector gives you usefulness to 340cc. Switching to a 440cc rated injector will give you usefulness up to 454cc effectively. This is based on keeping the duty cycle at 80% or below. For an E85 goal, the perfect injectors to complete the needs required are 440cc minimums to do the conversion properly. 330cc is only good to E70.

Hopefully this was helpful in some way. Feel free to verify my math. I used the chart above and these websites. I have a feeling someone isn't going to like the whole injectors don't work well past 90% ordeal. Well, they don't and I'm sorry this isn't a perfect world. My chart is subject to be a few percent off due to fuel temperatures, actual fuel pressure, sea level, and gas additives.

Chart for flow:
https://www.deatschwerks.com/fuel-ca...ure-calculator

Fuel reference:

https://afdc.energy.gov/fuels/properties

Flow reference(go to step 5):
https://thebuildjournal.com/diy/e46-...-injector-diy/

Fuel Injector Efficiency:
https://www.hpacademy.com/forum/gene...r-duty-cycle-1

https://books.google.com/books?id=OTOYHRSX_XcC&pg=PA147&lpg=PA147&dq=why+keep+injector+duty+cycle+under+80%25&source=bl&ots=eKZ-jN5j1h&sig=ACfU3U08qqyUP1d31kYG_PiEfeJKZiGZOA&hl=en&sa=X&ved=2ahUKEwivs4i8gZLpAhVBmuAKHR56Dn8Q6AEwDnoECAgQAQ#v=onepage&q=why%20keep%20injector%20duty%20cycle%20under%2080%25&f=false

https://books.google.com/books?id=cx...080%25&f=false

https://help.summitracing.com/app/an...s-do-i-need%3F

[Obioban]

Piggybacks are a recipe for long term issues.

On the old forum there was a thread about integrating a GM flex fuel sensor with MSSMapper, to switch between tunes automatically on the stock ecu, depending on what ethanol level was used. I never followed it that closely, as I have zero desire to run ethanol, but that seems like the correct way to do it imo.

[Arith2]

Piggybacks are a recipe for long term issues.

On the old forum there was a thread about integrating a GM flex fuel sensor with MSSMapper, to switch between tunes automatically on the stock ecu, depending on what ethanol level was used. I never followed it that closely, as I have zero desire to run ethanol, but that seems like the correct way to do it imo.

Isn't this what the Jcobbs and JB4 tunes do for the turboed engines now? I remember that post. It was so much cheaper than the flex fuel kits. Do you have a write up on MSSMapper?