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  Topic Review (Newest First)
09-24-2020 05:27 PM
mcromo44 Another way to look at it is this:
Use the Map Compare feature of the PC software to compare the OEM map, a.k.a Zero Map, to a street and high performance oriented map of well known and proven excellence.
For stock cans see mw919-3stk.djm
For aftermarket cans see mw919mori4.djm
Even a quick glance reveals the following for both the above based comparisons:
1 Good map corrections involve both richening and leaning.
2 The amounts of richening and leaning across the entire matrix vary by significant values.
So, while in theoretical terms, one could develop a corrective factor to account for a fuel brew's different stoichio', my guess is that highly skillful dyno work would find something a wee bit better.
In real terms, I see a far larger issue being the prospect of E15 displacing E10 in some jurisdictions, noting also that engine OEMs are not exactly enthusiastic about anything beyond E10.
By the way, a good winter time storage protocol is to use E0 premium or super premium, even more so if the riding season fuel is E15.
Especially for areas with very long cold winters.

By the way, "mw" is LDH, nowadays of Dan Kyle Racing
09-24-2020 02:53 PM
Originally Posted by robtharalson View Post
The bottom line is while an existing map that was worked up before the common use of ethanol may be slightly too lean, subsequent maps would be done with E10 for the simple reason that "pure" gas may not be commonly available.

Correct. The dates listed on the map files I downloaded were what got me thinking about it in the first place. Some of the maps available for download from Dynojet and at least some of the maps I found on this site have been around for a while. Some were definitely made in the early 2000s. I wasn't really paying any attention to how much ethanol was in gasoline in 2002-2003. My interest in ethanol content was exclusively beverage-related at the time. According to https://www.historicvehicle.org/ethanol-timeline/ it seems like E10 didn't become the norm for a few more years in the states.

I guess the point I was trying to make (if I was trying to make a point at all) was that there's a fine line between a little too lean and just plain too lean. Given the circumstances, seems like the later is more of a possibility than I would have thought.
09-24-2020 11:46 AM
robtharalson Actually, vehicle manufacturers had to make adjustments in the late '90's to suit the E10 fuels, primarily to change the rubber lines and seals adversely affected by the ethanol, when it became obvious that it was not going away, and since then it has been prevalent across the nation. The 919 falls in that category, so maps for fueling are almost universally done with E10.

Of course with a dyno and a skilled operator it is possible to make a custom map for anything the will burn in an IC engine including E85, but without modifications to the engine such as a higher compression ratio and ignition advance curves it would not be optimal. Nonetheless, it would work.

The bottom line is while an existing map that was worked up before the common use of ethanol may be slightly too lean, subsequent maps would be done with E10 for the simple reason that "pure" gas may not be commonly available.

09-23-2020 12:47 PM
PCIII and E10

I had a passing thought today. In 2020 I have to go hunting for ethanol free gas, whereas in 2002 that wasn't the case. Ethanol in gasoline wasn't prevalent like it is today until after 2007 if I'm remembering correctly. Most of the PCIII maps available for download for the 919 look like they were made during the production run, so it's probably safe to assume they were made using pure gasoline. Stock fuel maps in general seem to run on the rich side, so the difference between E10 and pure gas on a stock 919 is probably not as much of a concern. On the other hand, if I'm using a PCIII with a custom map that's already running on the leaner side for gasoline, I think that same map would be running a little too lean for E10.

For example, if a PCIII map was created targeting an AFR of 12.9:1 at full throttle, on pure gasoline that's a lambda value of 12.9/14.7 = 0.878, which is on the leaner side of where maximum power is found for most naturally aspirated gasoline engines, but not overly so. With E10 having a richer stoichiometric AFR of around 14.07:1, wouldn't the same map be yielding a lambda value of around 12.9/14.07 = 0.917? I think the stock ECU compensates for this to an extent by increasing fueling as the engine temp rises, but as far as I know the PCIII doesn't monitor the temperature input so it's adding/subtracting fuel by the same percent regardless of engine temp. I know I can just pony up the extra $2/gallon at the local gas station for "recreational fuel" or $300 for a custom map if I'm that worried about it, which I may end up doing anyway.

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