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-   -   Adding fuel with req fuel for e85 change (https://www.miataturbo.net/megasquirt-18/adding-fuel-req-fuel-e85-change-100819/)

AliveMX5 08-04-2019 07:11 PM

Adding fuel with req fuel for e85 change
 
3 Attachment(s)
So I drained all the 91 and added 5 gallons of E85, I added 30% to my VE table but it maxes out my top row at 255, I will likely never go that high but still would rather balance the table a little bit.

It's been a while since I set this up but when I went with ID1000's I had reqfuel at 3.0. Can I get a little help on how to add 30% fuel to my table by changing the reqfuel value or another method that anyone is aware of?

Thanks

Current 91 map
Attachment 228021

Current map with 30% added
Attachment 228022

(ignore the 4.0ms i was messing with the number)
Attachment 228023

AliveMX5 08-04-2019 07:21 PM

I'm having a moment but is it as simple as: 3.0 + 30% = 3.9 ?

Just not sure if the reqfuel scales that way.

Thanks again.

Savington 08-04-2019 07:43 PM

The correct answer to the question you should be asking is "buy a flex fuel sensor". E85 content varies per pump/supplier and seasonally as well, so unless you are buying it by the drum from a race gas company, there is no way to guarantee consistency. The flex fuel sensor will unlock all of the additional fuel multipliers and VE3/Ign2 maps necessary to accurately tune the car on E85 and compensate for E70 or E60 blends as well.

If you insist on being too cheap to add a ~$100 sensor to your system to tune the car correctly, the FIRST thing you should have done was re-calculate ReqFuel using the new stoich value of E85 (9.8:1 IIRC). This will put you in the same city as the ballpark, but you'll now need to completely retune your VE table from scratch in order to compensate for the different fueling requirements of E85 at low vs. high load.

it sounds like you assume that you can just add 30% to your existing map and carry on. That is an extremely inaccurate assumption.

Savington 08-04-2019 07:47 PM

Also, if your current 91octane map has cells at 234%VE at 250kpa, you have something else wrong (either ECU settings or physical fuel system limitations, probably too little fuel pump given your injectors).

AliveMX5 08-04-2019 08:33 PM


Originally Posted by Savington (Post 1544433)
it sounds like you assume that you can just add 30% to your existing map and carry on. That is an extremely inaccurate assumption.

Thanks for all the feedback. To the above quoted I realize that the entire table will need to be retuned, I'm just trying to get into the ballpark to begin that process.

Savington 08-04-2019 09:27 PM

Then ReqFuel is the number you need to change. There's also a setting called "Incorporate AFR" that will be helpful to you.

For reference, the top row of the VE3 map from Acamas (the 300kpa row, and yes, it's tuned to 300kpa) varies between 110% and 122%VE. That is without Incorporate AFR. With that setting on, the values should be right around 100-105%.

If you use IncorporateAFR, leave the AFR setting at 14.7:1. The only place you need to enter the true E85 stoich is in the ReqFuel calculations.

AliveMX5 08-04-2019 10:51 PM

I've been using Incorporate AFR for my 91 octane tune for the past few years in CA. I recently moved to AZ and now have E85 available to me. With ambient temps regularly reaching 110-118F I would like the added stability that the fuel will add with the increased IAT. Not trying anything fancy here.

Thanks again.

Savington 08-04-2019 11:05 PM

If you are using IncorporateAFR, you have a big mechanical problem to sort out before you go to E85. Are you actually using the 220/250kpa rows in the map above?

AliveMX5 08-04-2019 11:47 PM

I am not I should have clarified that earlier, I have boost control set at around 205 and overboost protection around 219.

That top row is untouched so may be a default value in the tune provided with the MS (Brain).

Savington 08-05-2019 12:07 AM

OK, then you're not that far off. Adjust with ReqFuel first, then tweak the VE as needed.


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