Lean burn with negative split timing
05-27-2014, 01:47 PM
#226
It will open in the 3200-3800 (approx.) range depending on load . After 3800 it will open regardless of load.
FWIW on my FI engine I have taken to opening it at 4000 and did notice an improvement in gas mileage (as well as a better transition) by doing this .
I don't believe the mileage improvement be there if the same was done to an NA engine however , plus the NA engine would probably lose some torque by doing this.
FWIW on my FI engine I have taken to opening it at 4000 and did notice an improvement in gas mileage (as well as a better transition) by doing this .
I don't believe the mileage improvement be there if the same was done to an NA engine however , plus the NA engine would probably lose some torque by doing this.
Last edited by Brettus; 05-27-2014 at 01:52 PM.
05-27-2014, 04:39 PM
#228
I really felt a difference, probably because of going into higher loads much sooner with the turbo.
sounds like there is a hidden table ssv open rpm vs load?
could the coolant label acually be load?
sounds like there is a hidden table ssv open rpm vs load?
could the coolant label acually be load?
06-02-2014, 08:39 PM
#229
Ok, so here is what I've learned. I'm not 100% on any of the conclusions, but it goes along with what I've seen.
As you lean out the trailing plug gets more effective and the leading plug gets less effective. Kinda makes sense if you think of the differences in AFRs around the plugs.
I reached a point quite quickly where as I pulled fuel the engine acted like I was pushing more advance. The only way to get everything back was to pull timing (I pulled leading, but probably needed to pull both.) I had cruising EGT dropped 60F+ and very retarded leading timing.
Now to answer some questions I'm returning to stock and getting a fresh baseline. After that I'm going lean first then pushing trailing timing. No negative split going into it.
And to answer some previous concerns, transition to rich afrs is smooth as long as its spread across a decent change in load, and so long as low load is at the same lean AFR. You can go from lean to rich, but not rich to lean! No jerkyness or otherwise just a rapid increase in power top end. Should be able to smooth is out using throttle tables.
As you lean out the trailing plug gets more effective and the leading plug gets less effective. Kinda makes sense if you think of the differences in AFRs around the plugs.
I reached a point quite quickly where as I pulled fuel the engine acted like I was pushing more advance. The only way to get everything back was to pull timing (I pulled leading, but probably needed to pull both.) I had cruising EGT dropped 60F+ and very retarded leading timing.
Now to answer some questions I'm returning to stock and getting a fresh baseline. After that I'm going lean first then pushing trailing timing. No negative split going into it.
And to answer some previous concerns, transition to rich afrs is smooth as long as its spread across a decent change in load, and so long as low load is at the same lean AFR. You can go from lean to rich, but not rich to lean! No jerkyness or otherwise just a rapid increase in power top end. Should be able to smooth is out using throttle tables.
08-23-2021, 03:17 PM
#230
The neg split timing is definitely responsible for the smooth, lean idle in the RX8 (which people still complain about.) I reversed the timing at idle, it becomes very lopey and unsteady.
Reddozen, I bet your car wouldn't idle at all without it. Just don't set your idle above 1700rpm, that is when the timing starts to go "normal." Also, if you can't get the MAF calibrated enough so you can idle normally due to turbulence, you should try making it richer in the fuel VE table. Bigger values make it richer, so try setting it to 1.4 at the idle areas.
I tried to use both that table, and the closed loop table to force a 17.5:1 AFR. Open loop fueling max is 1 lambda.
Lean burn isn't a new concept, but piston engines need special modification to make it work. The Civic HX had VTEC-E, which closed one of the intake valves to swirl the lean mix. Supposedly rotaries have the ability inherently, but I'm stymied by the ecu. I've read that Mitsu and Subaru Renesas-based ECUs also have a lean limit.
Reddozen, I bet your car wouldn't idle at all without it. Just don't set your idle above 1700rpm, that is when the timing starts to go "normal." Also, if you can't get the MAF calibrated enough so you can idle normally due to turbulence, you should try making it richer in the fuel VE table. Bigger values make it richer, so try setting it to 1.4 at the idle areas.
I tried to use both that table, and the closed loop table to force a 17.5:1 AFR. Open loop fueling max is 1 lambda.
Lean burn isn't a new concept, but piston engines need special modification to make it work. The Civic HX had VTEC-E, which closed one of the intake valves to swirl the lean mix. Supposedly rotaries have the ability inherently, but I'm stymied by the ecu. I've read that Mitsu and Subaru Renesas-based ECUs also have a lean limit.
Idk if you'll get this or not but looking into reversing my timing. 04 rx8 13b n/a. Will it do what yours does? Unsteady and lopey? Probably not legit like a bridgeport but is it at all similar? Pros vrs cons? I want to but don't want to ruin anything
08-24-2021, 10:50 AM
#231
not sure you’re likely to hear from him, but you’re best chance at ruining something is to unnecessarily mess with things you don’t understand.
am I understanding correctly that you just want to pretend to have BP trying to play the brap-brap look at me and how cool I am game by ruining the way your engine runs at low rpms?
I recently bought an REW engine swap with real BP and let me just say I can’t get rid of the BP’s soon enough, but eventually will. What a loud, annoying, uncivilized pitb it is for any kind of normal street driving. Definitely a track/competition only mod imo.
.
am I understanding correctly that you just want to pretend to have BP trying to play the brap-brap look at me and how cool I am game by ruining the way your engine runs at low rpms?
I recently bought an REW engine swap with real BP and let me just say I can’t get rid of the BP’s soon enough, but eventually will. What a loud, annoying, uncivilized pitb it is for any kind of normal street driving. Definitely a track/competition only mod imo.
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