I guess the story changes every now and then.
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Originally Posted by Brettus
(Post 4030295)
/\ Go try it for yourself before you jump on MMs' bandwagon .
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Originally Posted by TeamRX8
(Post 4030366)
I'm not jumping on MMs bandwagon. I personally have no interest in exploring the subject. I suspect that neither are you. I'm sure there is more to it than has been discussed. As in any tuning scenario, the devil is in the details.
For one thing : an afr of 14.0 is an afr of 14.0 no matter what you did to the tune to achieve it |
Originally Posted by Brettus
(Post 4030379)
It just amuses me when you jump in assuming MM is correct when you have no idea yourself .
For one thing : an afr of 14.0 is an afr of 14.0 no matter what you did to the tune to achieve it I didn't assume anything. I was just clarifying what he was referring to. Apparently I know more about than you based on the rest of your reply. |
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One thing that has concerned me in the past WRT these maps is the seemingly excessive degree of precision that Mazda used to calibrate them. This is obscured when represented as Lambda values, but here are the tables represented in decimal.
https://www.rx8club.com/attachment.p...1&d=1310619988 I don't know how to interpret it, but those are lots of different kinds of "1.0 lambda." I've wondered if they are for per rotor fuel balancing... I have lots of theories, but need more tools to figure it out. |
Originally Posted by TeamRX8
(Post 4030393)
. Apparently I know more about than you based on the rest of your reply.
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"That would be telling."
http://www.youtube.com/watch?v=zalndXdxriI |
BTW - that is a piston motor (MZR) forum. You do realize I tune those, also? |
Originally Posted by Brettus
(Post 3983178)
Edit : just found this reference . Perhaps MM is onto something but wants to dissuade anyone else from trying :dunno: |
I know you tune Mazdaspeeds, they don't have "A/B CL multiplier tables." Not now, anyway, perhaps they did then, I can't find any reference.
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Originally Posted by Flashwing
(Post 4030508)
Sure, if you think MM is trying to dissuade people from driving 55mph on the highway.
Originally Posted by Flashwing
Now some real world data!
I have a couple instances of running lean during cruise. Between Gallup and Flagstaff I saw 190 miles for a little over 7 1/2 gallons of gas! Here is data showing my motor is capable of crusing with AFR's as high as 16.3:1 ... Either way being able to flash back to stock worked out fine. It was cool to see the limits of the motor in terms of lean operation and fuel mileage. Getting nearly 25 mpg out of a rotary motor is pretty impressive in my opinion. |
Yeah that worked out great.
To bad I couldn't actually climb any hills at one point. |
I think there might be a way to increase fueling with load. That might solve that problem.
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Honestly though, I'd love to believe that there is a secret to getting miraculous FE, but most of the reasonably well implemented tests I've found on leaning out an engine not designed for lean burn have shown 0-3% improvement. As usual, there isn't much rotary-specific info, and while there seem to be some believers on RX7 club, nobody is specific about their gains, nor how they tested...
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Holy crap. Are you guys even reading ANYTHING I put up here, other than to just bash me on it?
I've already TOLD you how to increase fuel economy? |
Originally Posted by Brettus
(Post 4030458)
do tell what you know - can't wait to hear it ....
I wish you the best on your travels and hope that you finally reach your destination ... |
I tried running .95-.92, at first I got good results, but averaged over a few weeks, same as before. However, apparently I did it wrong - using "closed loop" tables. I don't know what maps to modify. The only way I've found to get the ve table to affect CL AFRs is to over or undershoot the target by 25%. Then I'm only getting feedback control in one direction.
The only fuel map I haven't touched is the injector latency. |
Originally Posted by TeamRX8
(Post 4030978)
I know better than to fall for your stink bait challenge. ...
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I know this is thread necropsy, but I have found why the Rx8 won't lean burn. The rear o2 sensor acts as a failsafe and if it detects a mixture lean of stoich during cruise it will drive the mixture back to stoich. I've tested this twice both by feeding the front o2 sensor a offset signal to actually drive the mixture lean, and by feeding the rear o2 sensor an offset signal to show the mixture as being lean. Both times the ECU drove the commanded mixture down until the rear o2 sensor was no longer reading lean.
Here is a data set I collected. I turned on the offset during the middle of the drive and quickly revved the engine to signal the change. I then drove until it had dropped commanded AFR to about 14.4:1 and removed the offset. Avg commanded AFR before offset: 14.65 After offset: 14.45 Avg rear o2 voltage before offset: .61 volts Avg rear o2 voltage after offset: .53 volts I have also tried offsetting in the other direction. It did add to my cruise AFR slightly, but then it had no further effect effect. I imagine that is just the difference between what it expects to see after a CAT and what it actually sees after an empty pipe. Please note that this only applies when out of idle. The ECU recognizes the idle is supposed to be lean burn and completely ignores the rear o2 sensor. Edit: Forgot to mention the most important part. With about .2 volts added you can go as lean as you want. The ecu just doesn't want to be hitting the lean limit of the rear o2 sensor repeatedly. The only problem I'm having is a CEL for o2 sensor volts high. I'll either have to reduce my offset or put a zener diode in to limit voltage. |
thanks a lot for the update ... i've been lurking on this thread for a bit, waiting until my car is back to try this
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The front O2 sensor doesn't use voltage as its reference.
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The front o2 sensor is current based. But since V/R=I you can adjust voltage and trick the ecu. It's not a pretty nor entirely predictable solution, but it does get the job done.
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Just started looking at this, but...
There is a switch that sets the rear O2 active for fuel control. When the switch is "on" it can build a rear O2 fuel trim, and it switches to the fuel targets in the closed loop a/f targets B table. The subroutine that sets the switch checks for a bunch of conditions... I don't understand all of them, but some of the ones I do get: Looks for coolant temp over 70C. Looks for difference between measured and commanded equivalence ratio must be over ~0.099. It pulls a value from this load/rpm lookup table, and looks for a value equal to or greater than 128. https://www.rx8club.com/attachment.p...1&d=1331352704 It is like the closed loop exit determination, so some are hard limits, some increment a counter against a delay threshold. Not sure which is which right now. Anyhow, it seems to generally looking for cruising conditions and big errors in the wideband reading. Also worth noting, these are the condition under which it will change the rear o2 fuel trim, if a trim is already set it is always applied to the closed loop target. |
Originally Posted by MazdaManiac
(Post 4008126)
The rear is ONLY for CAT efficiency measurement.
Absolutely no engine management function is based on it. This is a fact, not conjecture.
Originally Posted by oltmann
(Post 4209124)
Just started looking at this, but...
There is a switch that sets the rear O2 active for fuel control. When the switch is "on" it can build a rear O2 fuel trim, and it switches to the fuel targets in the closed loop a/f targets B table. |
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