Trevor Harp

So, im in the process of boosting my 91, 1.6 miata. I've read some things, here and there, about E85. At first, I thought it HAD to be tuned on a dyno, it seemed like that was the only option. But i've been trying to do more research, because it is very cheap (I live in Iowa), and it just seems like it will be a "more safe, less stressful" fuel. From what I can understand, the only modifications I will need to run E85 will be Megasquirt, Injectors, and some extra fuel filters. I have all of these things (MS2 running DSM 450s), and I was just wondering what exactly I would have to do, tuning wise, to run this fuel. All I have gathered so far is that I will need WAY more fuel on startup, and adjustment to the req_fuel to run stoich for E85 (9.8 a/f right?).

That was a lot to read, so, 1. Do I have a proper understanding of what is needed mechanically to run E85? and 2. What exactly needs to be done to the tune to run E85? and 3. Does it NEED to be tuned on a dyno?

Thanks in advance

deezums

iTrader: (3)

Read more. It has different stoich values but your meter probably reads lambda which does not change. That doesn't change the fact that you should probably change your targets to match e85. If this confuses you, you need to read more till it makes sense.

No dyno, no filters, nothing more than injectors and pump large enough and a way to tune fuel and spark. I drove to the station and swapped over and haven't looked back, never been on dyno, mostly autotuned. I do all the timings, it hasn't gone boom yet and I think the rods are still straight. All the timings is not the right way to do it. Dyno is required, or lots of illegal VD pulls. It will still be fun without it, and likely won't asplode.

Reqfuel is a global scaler in the fueling equation. If you change from 14.7 to 9.8 it will increase this value to scale to the richer mix. Real life never works that way, you need to tune, it's not a linear scaling. IOW, reqfuel or more VE, same fuggin thing.

Oh yeah, read mas.

Trevor Harp

Thanks for clearing that up. I am running a LC-2 wideband so i can readily switch from lambda to A/F Ratio. I keep it on afr since it is easier for me to understand when it comes to tuning. I figured you could just change the req_fuel and then retune the fuel table. Can you keep the stock timing and change it after tuning the fuel table? Also, is there any good articles about converting to E85, or should I just pull information bit-by-bit where I can? Thanks again

deezums

iTrader: (3)

Yes, you can keep the stock timing table and it will run fine. If you want more power, or more efficiency you need to read more and tune to e85 requirements.

You can't change a timing table and expect the fuel table to be any good afterwards.

Read more. Don't care where. Google goes everywhere. miata e85 tuning, megasquirt e85 tuning, miata e85 timing, e85 fuel ratios....

18psi

iTrader: (76)

the singlemost largest problem with e85 is how much utter nonsense the armchair experts spew about it online and in person having not a slight clue about it but pretending to know cause "they got a friend who knows a friend who's got a friend that ran it". then you end up with people like you who are so confused about it and have the stupidest paranoia's about it that make no sense whatsoever.

it's really really simple. most people overthink it for some dumb reason

Like Deezums said, do your homework and read trusted sources and not morAns

90civichhb

iTrader: (5)

You're gonna max out those 450s pretty quick on E85. I run 460s in my 1.6 on 93 pump gas and see 85% duty cycle up top on 13psi.

I don't have anymore information but, after I get my ignition sorted (which you should think about as well, LS coils, Fab9 COP, DIY, ect..) then I will be going E85.

1993z32

Here's my 2 cents: When you swap to E85, you need to re-tune your fuel map the same exact way you had to tune it when you first installed Megasquirt. Just start off by adding 30% to your VE table (or do it through req_fuel) and tune from there. The whole table will need tweaks but it should run well enough to start street tuning. What has been stated about lambda is true, and my MTXL is still set up to read in "gasoline numbers" so my brain understands it, lol (9.8 actual = "14.7" on my gauge). As far as ignition, I ran my dyno-tuned 91 octane map and the car ran just fine. When I got to the dyno, that's when I started messing with timing. Do you need to run more aggressive timing to be on E85? No. But if you're going to go through the hassle of an 18mpg Miata, you should chase all the benefits, at some point. Now if you have a 2560R and you just want a cool 220whp then I'd say there is zero point in the inconvenience of E85 (some cities less than others). If you really want to max out your setup, are going to be tracking a lot, etc; it may be worth it to you. As far as the equipment required, big injectors, a higher flowing pump, and change your fuel filter.

18psi

iTrader: (76)

rule number 1: please STOP repeating the stupid gas vs e85 conversion crapola.

just stop.

don't even mention it. you use the wideband just like you used it with gas, and it will show you exactly the values it's seeing and you keep tuning just like you did with gas. nothing needs to be "switched over" or converted. so many people keep talking about the "conversion" and it's always so confusing and never helped anyone. just confused a ton of folks

as for the "inconvenience": it burns cooler (and helps car run cooler), it makes more power (even at same ign and boost), and it's SAFER on your engine. I think the pro's are pretty stout

pdexta

iTrader: (17)

I just wanted to reinforce what other guys are saying here, this is an incredibly simple process that's way over-complicated by idiots that have no idea what they're talking about. As long as you have a megasquirt and can supply a lot more fuel then you're ready to go.

When I've swapped cars over I add (if I'm remembering correctly) ~5 degrees of timing to the boost portion of the map, 35% fuel (30% hasn't been enough in my experience), I drive as low on fuel as I'm comfortable, fill with E85, swap the tune and drive away. When I swapped my current car I took a 4th gear datalog going to the gas station and one leaving the gas station.



200rpm quicker spool, +33hp, +30tq and that's completely untuned on E85 beyond a guess at what I needed.

I'd love to see what kind of timing map other E85 guys are running if anyone is willing to share. It'd be nice to get an idea what I'm running vs other cars. It's such a help to the community as a whole if we share that kind of information. I can post a map when I'm at home later.

18psi

iTrader: (76)

we ran 20* in the midrange tapering up to 30* at redline on ryans built 1.6 on corn on 21psi
made 360whp with a chinacharger and a basic log manifold

Joe Perez

iTrader: (8)

To amplify and clarify the above:

All wideband O2 sensors function naively in lambda, where 1λ represents stoichiometric combustion of whatever fuel (or blend of fuels) is being burned.

For pure, unblended gasoline, the stoichiometric ratio is approximately 14.6:1, which is 1λ. For pure Ethanol, it's around 9:1, which is also 1λ. For blends of gasoline and ethanol, the stoich AFR varies between 14.6:1 and 9:1 depending on the mixture, but it will still always be 1λ.


Now, over the years, we've all been conditioned to think in terms of AFR rather than lambda. So, for the sake of convenience, most wideband display gauges have the capability to convert from lambda to AFR, by applying a fixed multiplier to the displayed value. And, out of habit, most displays use the standard conversion ratio for gasoline, which is that 1λ = 14.7:1.

But the thing to remember is that this is just a display. The numbers being shown don't tell you what the actual AFR is, they tell you what the AFR would be if you were running pure gasoline. But again, we actually don't care about AFR, we really care about lambda.


THUS:

If you have a display gauge and software which are configured to convert lambda to AFR at a ratio of 1λ = 14.6 AFR, then go ahead and tune with the assumption that 14.6:1 is the correct stoichiometric ratio for your engine. Because what you're really doing is tuning with the assumption that 1λ is the correct stoichiometric ratio for your engine, which it always is, no matter what fuel you're burning.

If we'd grown up speaking lambda rather than AFR, none of this confusion would exist. But like everything else Americans weigh or measure, we came up with a complicated and nonsensical way of describing things.


To restate: If you haven't specifically set up your wideband system to accomodate a lambda/AFR converstion ratio other than the one it came out of the box with, then don't sweat it. Just tune with the assumption that 14.6:1 is your target stoichiometric mixture, and don't introduce confusion by wondering about what the actual stoichiometric ratio of whatever fuel you're burning is. It's always 1λ, and when your gauge says 14.6, what it's really telling you is 1λ.





TL;DR:

This is all too important to skip. Don't be lazy, read it.

18psi

iTrader: (76)

Stealth97

iTrader: (5)

So it's just a matter of add 30-35 % more fuel and start tooning.

18psi

iTrader: (76)

if you're not swapping injectors, you can just scale req_fuel and go from there. if you don't touch the timing table
the only part of ve that will change will be from timing changes iirc

patsmx5

iTrader: (16)

Interesting. 30* at what RPM at 21 psi?

Leafy

iTrader: (1)

Stop, you stop. Dont ******* touch your fuel tables when converting to E85, at least to start. Change the required fuel to reflect the different stoich value, and then tweak if you need to, most of your work is going to be done getting cold start to work right, and it will work right if you dont suck.

And listen to Joe.

18psi

iTrader: (76)

7500

pdexta

iTrader: (17)

I completely understand being conservative with spark tables, but I simply cannot understand converting a car to E85 from 91/93 octane and not advancing your timing. You're moving to a fuel that burns cooler with 10-15 octane higher, clearly there are some safe assumptions you can make regarding timing adjustments. Timing is where the power is, use it.

Here's the map I'm running. Based on what 18psi is saying it should be pretty conservative but a hell of a lot better than some 91 octane basemap your MS came preloaded with.

'96 block
'99 pistons & head
eagle rods



Virtual Dyno:

18psi

iTrader: (76)

your map is actually too conservative as well

but yeah, car is already flying

pdexta

iTrader: (17)

I assumed it was, I've just seen so few Miata E85 timing maps that there isn't a lot to go on. Thanks for the feedback though. I sure do like the idea of finding another 25hp, just need more time to mess with it.