Is E-85 worth it N/A?
 

Recently 104 octaine E85 became available less than a mile from my house, and wandering if it would be worth setting up flex fuel. All I'd need is the flex fuel sensor and a set of RX-8 420s... I could swing it for $300. My engine is around 10.5:1 with some moderate cams.. I'm thinking if I can make another 5%-10% more power it would be worth it. Is that reasonable, or am I wasting my time without a bunch more compression?

Less than 1 mile from your house? If you're ok with running the car on E85, do it. I switched mine recently. I have to drive A LOT further than 1 mile to get E85, but... I needed E85 for my setup. I'm going to buy a few more gas cans to make refueling not such a pain.

I think you'll see 5% gain minimum, possibly more. I wouldn't be surprised if you saw a 6-8% gain with your setup.

Yep. A real shocker too. Its a Mom&Pop place. A few months ago they got new tanks. My jaw nearly hit the floor when the pump said 104 octaine on it.

It's not consistently available at other stations around here though, so while I could just fill'er up and retune with larger injectors, I'd still need to go with flex fuel.

I've never seen an octane rating posted on an e85 pump. That's interesting.
It's usually worth it for the power increase and safety peace of mind.

This one definitely had an octaine rating, yellow hoses too. Under $2 if paying cash!

https://www.miataturbo.net/attachmen...ine=1440899006

TX pump is like that too, has octane on the pump.

<p>Make sure you have enough inputs for the flex fuel sensor.</p>

Flex support on the MS2 is supposedly crap, I'd run all or nothing or maybe use a table switch.

Or run with the sensor, let me know how it goes.

<p>There's no blending. Just a % fuel multiplier, and timing subtraction/addition.</p>

Anyone have firsthand experience with Flexfuel on MS2? If isn't that great, I wont bother. Not really interested in an on/off flip a switch solution.

Pretty neat. But it's really misleading. You actually have lower quality e85 than we do here. Be careful with that. The lower quality pumps here also say "minimum 70", which means it can be from 70-85, and it fluctuates quite a bit. The higher quality pumps say "minimum 85" and the difference on any given day between the two is quite significant. Sometimes a full 1-1.5 AFR worth. Anything between 95 octane and 115.

Just a heads up.

We have one gas station chain locally that sells E85 that tests in the E85 and E90 range. However, a bunch of local gas stations sell E85 and usually they test as E70 or lower. As well, the state of MN just passed a law for the stickers. Ours now say that the E85 has to be E50 or better. I don't know how they get away with the crap. So we just tell everyone to only use the brand that we have found to be the most consistent.

The ones I saw in TX said E85, E70 minimum. Sucks that if varies, but that problem should go away with a flex fuel sensor and tuning it. But I have not installed any flex fuel hardware yet, someone here was attempting it and I was waiting on him to figure it out so I could copy!

You've got me reading up on this again.

MS2 can only do a simple global scaling based on a flex sensor. You literally have 4 inputs, timing to add and fuel % at low alcohol, and the same at high ethanol blends. If you have decent injectors (rx8's aren't those) I bet it would be possible to use the simple scaling to get something pretty damn close. If you find you need 30% more at 5500, but only 20% more at idle you are seriously screwed.

I believe you'd probably want to leave timing on the table for safety, what with MS2 not doing knock, unless maybe you only buy one station's crap. That's where all the goodness comes from. I think you'd be leaving a lot on the table, probably not worth the expense.

<p></p><p>@yank&nbsp;has it wired up, im going to try and play with it this week. but everything looks good so far.</p>

What's wrong with RX8s?

On a 10.5 compression motor I think it'd be worth playing with, and you could do that with some $100 RX8 injectors. Virtualdyno.net can tell you exactly what kind of power you gain with a couple datalogs and if you're not happy with the gains it's easy to go back.

I've never bothered with the flex sensor. I use MSDroid on my phone a lot, when I started using E85 (about a year ago) I always kept a 93 octane map so I could switch over. Lately I haven't even bothered, I just run E85 all the time and haven't had a problem yet. If I do ever get caught without it it's easy enough to pull timing and fuel so I can make it home on 93.

They are older tech, they won't be as linear which would be helpful if you are multiplying the fuel table.

I wonder, is it possible to run flex sensor comps on a switched table? Then you could have a 93/91 table, and a dedicated E85 table you could apply flex calculations to.

I'd use MSdroid to disable the flex sensor when I went on a long trip away from E85, maybe just load a 93/91 table through the phone.

<p>*cough* buy an ms3 *cough*</p>

True story