Convince Me to go e85

You can; Rob had a thread about shit going weird after 2.5 load and it turned out to be open loop trimming that Cobb had to add a table to adjust. VT already had it.

 

Yeah but you can't see the actual trim reading itself at WOT. Those tables are questionable. @nindoja and I have played with them and they haven't been behaving the way we've expected them to.

 

My understanding of how it works is there's just a hidden variable type table that records the disparity from target each pass. It's not a breakpoint based one for LTFT but more like a STFT that only goes into effect after you get out of open loop; thus, the first time you WOT on a map it will be MAF accurate; after that it starts trimming.

Is that what you mean?

 

Interesting @Enki. What leads you to think the last part about trimming after the first WOT pull?

What I saw was that above 2.5 load, my AFRs went crazy (obviously my MAF cal was wrong up top). I took the CL max load limit table and set it to my CL->OL transition values. AFRs were horrible, suggesting that the ECU was actually correcting in OL/WOT conditions as we suspected). I took a few logs, tweaked the calibration across the board to be fairly close (+- 0.3 AFR), and then moved the CL max load limit table up to 3.0. I would have thought this would result in super steady AFRs, but instead I saw 10.xx AFRs all over the place.

I thought it might be an issue with ATR and finally switched to VT. Re-did my map (most of it, anyways) and saw the same behavior.

 

I've heard stuff like this, but honestly have never seen it supported in my logs. When I self-tuned a lot (and tuned others), I was at first concerned about going WOT until the ECU had done some learning. What I found was that it made zero difference in terms of logged AFR. Now obviously I'd have minor variations pull-to-pull, but nothing ever so significant that I suspect some hidden ECU logic at play. I began telling people I worked with, "No need to wait to grab more WOT logs. You can flash and go log right away, but if we need to do MAF cal work, then we'd have to wait a while." YMMV
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AFRs going wonky after >2.50 load is a known issue. Some people go lean. Others go rich. I was one of the lucky ones who went rich (it's safer). The solution my tuner used was scaling my MAF down. Calculated load is a function of boost and grams/second, so scaling down your MAF table enough will bring your load down to <2.50. Voila, no more crazy AFRs.

 

Completely understood, which is why the CL max load limit table was released by Cobb (and found in VT too). The theory was that the ECU will do CL-style corrections when in OL up to a certain load value. We've certainly seen this to be true in that cars hitting 2.5 load and seeing lean or rich conditions would be "fixed" when upping that load limit to 3.0 or other unobtainable value.

What's odd is that lowering that load value, correcting the MAF curve without any CL compensation (across the whole OL/WOT region), and then resetting the load value (or setting it unreasonably high) seems to result in really weird AFRs, even when under 2.5 load.

 

That's odd. I've never heard of that fix. And I personally wouldn't want my ECU operating in C/L mode in WOT conditions. Another fix was to have the commanded AFR in all of the various fuel tables match. That one was hit or miss. Scaling the MAF and thereby bringing down calculated load seemed best. Heck, if that's what Justin used, having literally tuned over 1,000 Mazdaspeeds, it's good enough for me

 

I'm speaking from experience. I've seen the trimming thing in my own logs; first pull on a fresh flash/ecu clear is always off, next one and those after is always closer.

Not sure what happened with your closed loop setting going to shit; I'd like to take a look though.

 

I'll post up some logs in a new thread tonight. Will tag the interested parties from here and the VT guys as well.

 

I just made the switch to an E85/93 pump mix tune a couple weeks ago. My car is tuned by Will at PD Tuning so I have both a pump tune and a mix tune. Here is what ive seen so far:
Pros:
Moar go fasts!
Only mod required is HPFP internal upgrade
I'm pushing somewhere close to 300 whp/330tq (datalogs and Virtual Dyno)
Fuel mixture saves from the black death

Cons:
3-4 MPG drop in city driving
4-6 MPG drop on the highway
Less miles per tank

Side notes: Switching from corn to pump gas: I run the tank til the gas light comes on, fill up and reflash back to the 93 tune.

To switch back, fill up between 1/4 and 1/2 tank, put in 4 gal of E85, and top off the rest with 93.
**I drive about 15-20 miles STAYING OUT OF WOT before the mixed gas reaches the motor and so the ECU can re-learn LTFT's

 

You guys are chumps. Just use a fuel cell and port injection for your E85 like me. Best of both worlds.

 

Or, run E28 in the tank and 100% methanol in your separate tank, like me

 

I'm a believer. It's just effortless knock free power with E85. I love doing 4th gear highway passes with it.

One of my concerns was keeping a correct mix when filling up. Last night was my second fill-up and it wasn't as hard as I thought it would be. I did use a calculator to help me figure out how much E to put in since I had to fill up a little early.

I lost around 2 mpg but it is still a little too early to tell. I went from averaging around 22 mpg to 19.9 mpg after my first tank of pump gas/ethanol mix.

 

Lol @ all you guys losing MPG swapping to corn. Any of you have a lean burn tune? I was getting 27-28 MPG on 50/50 mix @ 75 MPH.

 

I've heard you mention this several times, Enki. At the same time, I've asked Justin about it, and the short of it is he is against it. I very much respect both you and him, but my concern is that my tuner, who's literally calibrated over 1,000 Mazdaspeeeds, is against it. I'd really like a more comprehensive explanation of his reticence. There are few people in the entire world who have more practical tuning experience that Justin, so his views resonate deeply with me, and I'm inclined to believe that he has a very good reason for not advocating it. Perhaps we can get @Atvfreek in here to offer a more comprehensive explanation?

 

For cruising, there are several people on here that do this with no issue. @Vansquish is one for sure that has been doing this for years.

I think where the problem lies is that Freek doesn't want to take any un-needed risk for his business; it's not common practice. I get it.

@Enki do you have any EGT differences w/ burning leaner on the 50/50 mix vs burning @ stoich on 93? If there is little to no difference, there is no problem.

 

I've been running a lean burn, minimized timing and zeroed VVT MPG modifications on the same tune as my power maker rape mode tunes since before I made this video back in April of 13:



EDIT:
On the new build I'm shooting for 30 MPG on full corn.
Also I should add that there's slightly less gains to be had on pump gas than on at least a corn mix, with the biggest gains (as far as MPG goes) to be had on full e85. Towards the end I was getting about 180 miles to the tank, and that's with at least one WOT pull per trip. On 91 I usually only got 20-30 miles more, same driving conditions but less sticky tires (lower rolling resistance).

 

@phate; you need to get on this for DD...unless you're just that hood rich not to care.

 

Not to detract from your vid, but what does calculations at the pump say your actual avg MPGs are? I ask because we all know the information center MPG rating reads notoriously high, and I don't personally put a lot of stock in the AP's reading either. The most accurate measure is miles driven/gallons to refill. I'm assuming it's good; I'm just curious if you observe a difference between the AP and the actual calculations; I know I certainly have.

 

From a thread at the other place:
50/50 E48 (post says E42 but that was before I knew it was full E85 from the pump), zeroed VVT, 40 degrees max timing and 16:1 AFR target at 3k RPM, tapering either direction (15.567 AFR @ 2500 & 3500).

10.611 gallons and 284.5 miles, 30% city driving, ~93.5 miles to the quarter tank on the highway; ~26.8 MPG. Not too shabby, no?

Another guy used my timing/AFR changes without VVT change and gained a little over 4 MPG for the tank, but still wasn't making what I was making.

Oh and this was posted on 1-25-2013.

I should probably note that this was also using relatively conservative driving compared to my normal driving habits.