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Old 07-22-2008, 04:02 PM   #1
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Default Doesn't need rehasing, BUT...

After hearing the success some folks (Ben) have had with gas mileage, I decided to revisit the AFR table issue I've back-burnered.

I had a totally FUBARED (complete with negetive numbers and 5 decimal places) my AFR table, my guess is it's an MS-II think... Anyway, so I tried to salvage it, and came up with this:



Now I'm wondering if these are reasonable. Could someone comment? I took a lot out of the no-boost end of things, since I'm cruising on the freeway (granted, this is a california, 80-100 mph cruise) at <14:1 and it seems dumb. On the other hand, I don't want to burn any pistons.

Anyone like/hate what they see?
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Old 07-22-2008, 04:59 PM   #2
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I run closer to 13.8 at 100kpa, and 12.8 when crossing in boost and 12.2 when at 10psi.
Why are your Y values in percent and not in Map?
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Old 07-22-2008, 05:07 PM   #3
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no no no YER DOIN IT WRONG. You're still only going to be at 16:1 in cruise.

You really want to be a tad bit rich at the very low loads for smoothness. Don't be afraid to lean the bitch out in cruise areas. I'm like 19:1 at 4k rpm and 90kpa. The difference between my map and yours is probably 5 mpg.

I'm still getting ~30mpg with the top down and the a/c on, in all sorts of mixed driving, rush hour, boost, and big double tire trails tattooed to the road behind me.
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Old 07-22-2008, 05:18 PM   #4
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really I wouldn't get leaner than 14:1 above 80 kpa. you dont need to. assuming you're stepping on the gas for a reason, it's better to have the power than not.

then I'd add a row below 20 kpa. or maybe change the 35 kpa row to 30 and the 25 row to 10 or 1 or something small. set the 1kpa row to 20:1 or some ridiculous overrun/engine brake AFR.

above 2500 rpm up to 80kpa, run as lean as you are comfortable with. probably start adding gas back in at 5000 rpm.

cruise, as you'll notice in logs, is primarily 25-80 kpa and 2000-4500 rpm. concentrate on that area and smooth into the rest of the map.

Ben: how on earth do you run 19:1?
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Old 07-22-2008, 05:27 PM   #5
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Quote:
Originally Posted by y8s View Post
really I wouldn't get leaner than 14:1 above 80 kpa. you dont need to. assuming you're stepping on the gas for a reason, it's better to have the power than not.
I disagree. High speed cruise is >80kpa. The instant I step in it, accel enrichment comes in and adds the extra fuel required for response and power.

Quote:
then I'd add a row below 20 kpa. or maybe change the 35 kpa row to 30 and the 25 row to 10 or 1 or something small. set the 1kpa row to 20:1 or some ridiculous overrun/engine brake AFR.
Not needed, there's an auto overrun based on MAP and TPS. Save the limited resolution.

Quote:
above 2500 rpm up to 80kpa, run as lean as you are comfortable with. probably start adding gas back in at 5000 rpm.
I start adding fuel back in around 4200 rpm or so. I have no business with a lean cruise over 85 mph.

Quote:
cruise, as you'll notice in logs, is primarily 25-80 kpa and 2000-4500 rpm. concentrate on that area and smooth into the rest of the map.

Ben: how on earth do you run 19:1?
I agree that smooth is key. There should be small value changes between a cell and any of the other cells around it. Anyone who has ridden in or driven my car is amazed at how smooth it is, especially in the transition area between vac and boost. Really, if you didn't watch the gauge and couldn't hear the turbo, you wouldn't know it was happening.

I'm at 19:1 because I got some occasional studders at 19.5:1. I just leaned it out until the car didn't want me to lean it any more.
Big gaps (.050"), COPs, and lots of timing.
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Old 07-22-2008, 06:56 PM   #6
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just looked at a commute datalog. barely ever get above 80kpa and that's only when I'm over 20% throttle. ie, passing.

and yes enrichments will eliminate tip in leaning, that's no big deal.
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Old 07-22-2008, 07:28 PM   #7
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High speed cruise for me is more like 45-55 kpa with elevation variations. I run 16:1 at cruise and allow overrun fuel cut to remove fuel when I let off the throttle. I like that better then setting the target table to really lean on the bottom row because of cell averaging. Averaging two cells from 20:1 to 14.7:1 makes for some weird driving characteristics so I leave my bottom row no leaner then 16:1, overrun does the fuel cut for me very well it seems.
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Old 07-23-2008, 10:51 AM   #8
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I'm around 16.3:1 average at cruise, getting 29mpg. My car gets a little funny at around 17.2:1. What timing is everyone running at highway cruise at this AFR? I'm around 3800-ish rpm (3.90 torsen) and 38-ish deg's advanced. EGT's around 1250F in 2 cylinders (I only have 1 EGT gage, probe is in rear 2 cylinder's manifold).
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Old 07-23-2008, 11:17 AM   #9
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did i miss something? what's the deal with the Y axis being percent instead of kpa? and how do you go 205% if it's TPS?
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Old 07-23-2008, 11:38 AM   #10
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I saw that and ignored it, thinking it's just how the axis is labeled in MSII
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Old 07-23-2008, 02:35 PM   #11
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this is more or less what i target:



i'm getting something like 25mpg city only, never over 50mph.
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Old 07-23-2008, 03:11 PM   #12
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Looking at my logs, it's in the ballpark of 4500 RPM (I'd say 4200-4700), and running around 55-90 kpa, mostly around 75-85.

A long time ago, I was running leaner, and when I went richer, I got better throttle response. I think I need to revisit the whole accel enrich thing.

Do you guys find EAE or the standard TPS/MAP-based one to work better?

The other thing I'm curious about is how is the top end? 32-36*, mostly around 34 is my advance. I've never felt comfortable with my EGT guage, what should I be looking for? I guess I don't know "when to stop", other than no more leaning when it bucks.

---------------------
Hey, Ben, post your AFR table, Y8s too. :-) I use overrun, but I do want to get this ballpark in other areas.

Last edited by AbeFM; 07-23-2008 at 03:24 PM.
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Old 07-23-2008, 04:17 PM   #13
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What I'm curious about is why stop running lean at higher RPMs? Are you afraid more total gas will heat the engine more? Out here in Cali, it's not unreasonable to cruise at 90, even 100 mph from time to time. 4500 is perfectly reasonable.

Clearly, not destroying the motor comes first, but I'm still wondering how you draw your lines in the sand.
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Old 07-23-2008, 04:29 PM   #14
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as long as im cruising i don't mind being lean. But i have yet to cruise over 4.2K or so. I believe my targets table on my map has 15.5:1 until 5K. beyond that i blend in fuel simply becuase im probably wot at that point, or have more load.
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Old 07-23-2008, 08:13 PM   #15
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you guys have NO idea how impatient I am about this!! :-) Speak to me!



Does that look better? I want to actually RUN something maybe tonight, depends....
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Old 07-23-2008, 08:16 PM   #16
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I took a cell phone video of me driving home at 70 mph and 19:1, but my freakin SD card reader isn't working. :(
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Old 07-23-2008, 08:20 PM   #17
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When I FIRST put in my MS, I was 18.5-19.5:1 all the time under ~50kpa, and it was fine. Then I richened up the whole map, and got better throttle response. I was comfortable down low with it.

I think I just need a passanger to bump things around in real time. But as targets go, they look alright? I'm more wondering when and how steeply to transition into a power-map up top (on both axis)
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Old 07-23-2008, 08:36 PM   #18
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Abe's been bugging me offline for a copy of my AFR targets, so here they are:



The car wants to idle in the mid to high 14's, and I threw that 13.5 cell down there at the bottom to give it a little extra oomph back when I was having some idle problems. That probably needs to be raised back up a bit...

I'm not running nearly as lean in cruise as some, principally out of fear. I only just started leaning it out and have been watching the EGT gauge faithfully. I think I've still got plenty of room to go.

Like others, I start enrichening at the higher RPMs simply on the grounds that if I'm 6,000 RPM to begin with, I'm probably more interested in power than economy. I also think I need to lean out the 100 kPa row just a few points, just haven't gotten around to it.
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Old 07-23-2008, 08:40 PM   #19
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That seems like an awfully lean AFR to be able to idle.

I tune to this AFR target table

Edit. My 101kpa row seems a lil high to what some of you are running. When I was running the stock ECU with my UEGO I could see the factory had the thing at 11afr at WOT over 4000rpm, even saw some 10s. I didn't want to deviate too much from that so I settled on 13. Truth is I don't think I am ever at/near 101kpa. I'm either cruising or boosting. I get at least 27mpg city and I drive the car hard. This is my daily driver miata with the 2554. the other car is at least 30mpg
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Doesn't need rehasing, BUT...-afrtarget.jpg  
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Old 07-23-2008, 09:01 PM   #20
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Ok, that's what I got. How's my table-by-committee going now?
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