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Old 08-14-2020, 06:43 PM   #1
90volvo
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Default megasquirt flex fuel

I have my megasquirt lined out running smooth etc. I try and keep e85 in it all the time. If I have to put gas in it I ad some good oct. boost. My question is it worth hooking up flex fuel sensor and activating it on megasquirt. Most of the searching Ive done most say that it doesnt change the tune much between premium and e85. But some of them are old post. Thanks for any input and advice.
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Old 08-14-2020, 07:59 PM   #2
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It needs something like 25 - 30% more fuel volume. And it needs more ignition advance.

On the plus side, you can run more boost, assuming pinging/detonation was holding down your peak boost on pump premium.

On the cautionary side - it's so detonation proof that you can blow **** up without ever hearing that ping ping before the boom.

I saw a fair amount of variation in ethanol levels - more from station to station than from the same station, but still - flex fuel sensor and flex fuel on the MS is the way to go - not a fixed 'gas' and 'E85' tune swapping (which I did with my older MS1 box).
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Old 08-14-2020, 10:01 PM   #3
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yeh, I carry a tester with me and test it before I fill up on it. Few weeks ago I stopped at MFA which always test out at E70. Woah behold it tested out at E15, I called them up and they think the guy filling tanks up messed up. Went down the road and got Caseys E85 it tested out at E80. But at the very bottom of the bottle I using was about 1/4 that seperated from the E85 and the gas. It was heavy cause it went to the bottom? No telling what it is. So what kind of warning signs start showing you are pushing the limits to timing and fuel? Would a stand alone Exhaust temp guage help? Thanks
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Old 08-14-2020, 11:12 PM   #4
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I should probably step back and ask why you're interested in running E85 in the first place.

I was running it for the detonation resistance (it acts like 105 - 110 octane, more or less) - so on my motor - 9.5 - 9.7 compression ratio - I'd get into a little sprinkling of deotonatoin on pump premium at around 15 psi, running it on E85 I could run up to 22 - 24 psi with no pinging, obviously made a lot more power at those boost levels, so that was the motivation behind running the E85. I'm not a great tuner, not even a bit, I thin I tended to add too much ignition advance, couldn't hear detonatin, thought it was good, and ended up being harder on head gaskets and such than I should have been for those HP levels. But still - made a lot more power on E85 with the higher boost, and I'd built the motor with a bit higher CR with E85 in mind in the first place.
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Old 08-15-2020, 09:10 AM   #5
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I should probably step back and ask why you're interested in running E85 in the first place.

I was running it for the detonation resistance (it acts like 105 - 110 octane, more or less) - so on my motor - 9.5 - 9.7 compression ratio - I'd get into a little sprinkling of deotonatoin on pump premium at around 15 psi, running it on E85 I could run up to 22 - 24 psi with no pinging, obviously made a lot more power at those boost levels, so that was the motivation behind running the E85. I'm not a great tuner, not even a bit, I thin I tended to add too much ignition advance, couldn't hear detonatin, thought it was good, and ended up being harder on head gaskets and such than I should have been for those HP levels. But still - made a lot more power on E85 with the higher boost, and I'd built the motor with a bit higher CR with E85 in mind in the first place.
pretty much the same reasons. I cant get good gasoline here; 91 octane is the highest I can get. Even with it I would get detonation with 16lbs. With E85 I can run up to 20lbs and car runs like a beast with it. Ive been keeping my timing on the conservative side. Thanks for info.
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Old 08-15-2020, 10:06 AM   #6
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Dude just install the flex sensor and let it set the ratio for you. Without it’s like turning a knob to adjust pwm to the injectors in the fly. Trust us. Install the sensor.

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Old 08-15-2020, 12:50 PM   #7
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I did fudge my pump gas fuel tables up by about 25%, but then I did a lot of autotune with E85 in the tank to let it get it right.

The wideband O2 sensor readings are interpreted to AFR values, it's really a lambda value - so you do NOT need to worry about the different AFR values E85 actually needs - you'd still tune to 14.5(ish) stociohetric, or richer/leaner depending on the engine RPM/MAP/throttle.

Do you have enough fuel pump/injector to handle 25% more flow rate at higher boost? Fuel pumps put out less flow the higher pressure they're pumping out. So as your new E85 system hits high RPMs and high boost, it needs a LOT of fuel, and the pump can be struggling to put out base pressure plus 20 - 25 psi on top of that (pressure referenced to MAP).
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Old 08-15-2020, 01:14 PM   #8
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Yes fuel pump is an AEM. Thanks for the info, I’m gonna order the sensor and let auto tune do it’s job.
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Old 08-15-2020, 01:38 PM   #9
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I never read up on it enough to figure out if autotune would work well in flex fuel mode, but I don't think it would, and I never tried. You have two fuel tables - which would it adjust? Maybe both, but only one could be wrong, so an interpolted correction to both could be off target.

I always just tanked up on one fuel - made sure it was a 'good' tank via the flex sensor readings, then turned off flex fuel processing and pointed it solely to the tables I wanted to tune (I forget how exactly, not too complicated in TunerStudio) and then autotuned. And when done, turned it off, engaged flex fuel functions again.

If you could autotune with the flex fuel stuff active, I'd be curious how that works.

ALso - the flex-fuel processing has a curve that affects how it interpolates between your E85 and pump gas tables - I think by default it's pretty flat, but you can tweak that some so the E85 kicks in sooner/stronger - a little ethanol goes a long way - E40 is a lot better than just midway between pump gas and E80/85.
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Old 08-15-2020, 04:56 PM   #10
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I ended up pumping out the pump gas and filling with e85... then retuning VE3 with e85. After that the flex seems to handle the mix without too much difference. I tried getting as empty as I could and filling up but the best I could ever manage was e63.
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Old 08-15-2020, 04:59 PM   #11
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I never got some 'reference' fuel to calibrate the flex sensor, so I just assumed the strongest batch I normally saw was actually 85%, and calibrated to that.
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Old 08-17-2020, 03:23 PM   #12
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Put the flex sensor in. It works perfect
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Old 08-21-2020, 02:39 AM   #13
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So, Ive searched to try and find flex fuel sensor. Most links are broken or no longer available. What sensor are you using. Also, noticed in some older posts that there was problem running auto tune with flex fuel sensor. Something about seeing spikes in the percentage that were not correct. Is that fixed now? Thanks for any info and appreciate it.
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Old 08-21-2020, 12:14 PM   #14
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Before you get a flex fuel sensor, you need to find out what I/Os you have available. Since you're using a plug-n-play microsquirt system from Kenny (I think...), you might want to contact him and see what he suggests.
I/Os are Inputs/Outputs
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Old 08-21-2020, 12:47 PM   #15
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Before you get a flex fuel sensor, you need to find out what I/Os you have available. Since you're using a plug-n-play microsquirt system from Kenny (I think...), you might want to contact him and see what he suggests.
I/Os are Inputs/Outputs
Culberro, again thanks for you wisdom. I did alot of searching last night and the way I understand it is, the megasquirt 2 is limited on what you can do with flex fuel tune etc. But, I will reach out to him. I might be better off to skip the flex fuel sensor and set my tune parameters to safe settings. Continue to check my fuel everytime. Anyways Im just brain storming. Thanks
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Old 08-21-2020, 01:18 PM   #16
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MS2 and MicroSquirt have basic Flex Fuel support but not blending. Basic support scales the fuel injected by the measured ethanol %, and adds timing advance also based on ethanol %. If you have a MicroSquirt, one of the wires is labeled FLEX and is usually a spare input (purple/white).

Here's a somewhat recent thread on E85 and MS - IIRC, MS2/MicroSquirt are limited, but better than manual % guessing and manual table switching. MS3 has full blending support.
Megasquirt flex fuel tuning E85 with ethanol sensor.
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Old 08-21-2020, 01:33 PM   #17
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I was using MS3 on my flex fuel. Prior to that it was MS1 with no flex fuel processing (that I know of) - and I was just doing 'dual fuel' table switching - using the Nitrous On functionality to swap fuiel and spark tables via a dash switch. Run the fuel low on one kind, tank up on the other, start it, let it run for a few seconds, flip the switch. WOrked fairly well, but the E85 tune was a constant work in progress that I later realized was due to varying amounts of E in the E85 I was getting.
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Old 08-21-2020, 03:14 PM   #18
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Quote:
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I was using MS3 on my flex fuel. Prior to that it was MS1 with no flex fuel processing (that I know of) - and I was just doing 'dual fuel' table switching - using the Nitrous On functionality to swap fuiel and spark tables via a dash switch. Run the fuel low on one kind, tank up on the other, start it, let it run for a few seconds, flip the switch. WOrked fairly well, but the E85 tune was a constant work in progress that I later realized was due to varying amounts of E in the E85 I was getting.
yelp, seems like Im chasing my tail. Local e85 was always 65-70 so, I would tune for that and get it all lined out. I had to travel and test a caseys store and it was E88, I thought man this is awesome. But car wouldnt idle and had a part idle miss. IT was way lean, so, I had to put a few gallons of 93 octane in in. It cleared right up. Yeh, I remember seeing a flex wire, I will procede. Still looking for correct part number for the flex sensor.
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Old 08-21-2020, 03:18 PM   #19
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Easy Option: https://ecumasterusa.com/products/wh...smart_campaign

Or Amazon and buy all the linked parts: https://www.amazon.com/ICT-Billet-GM...a-897701707083
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Old 08-21-2020, 03:28 PM   #20
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That's (more or less) what I'm using. GM fuel sensor and a pigtail. Plumb it into the return line - it doesn't need to see pressure (and might not like it?).

When I put the bigger fuel system on mine, I'll need more flow on the return, so I'll plumb a 'Y' with the sensor on one leg, joining back together to return to the tank. Under the assumption that the sensor will still get enough flow to work.
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Old 08-21-2020, 04:43 PM   #21
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Thanks a million guys.
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