AFR's at idle

[vex]

I'm curious on what everyone runs at idle? I've got it set to 12.3:1 and I think that might be a little rich...

[SPICcnmFD]

Whatever idles the best if what you want.

[classicauto]

Yes its really a matter of what the engine likes. Mine is most stable around 12.7

Should be able to go a little closer to 13, or even low 13's though.

[RETed]

This is why I don't like widebands...

If you read the FSM, it tells you to adjust everything possible until idle is highest.
The FSM does not mention anything about AFR's or widebands - you don't need it accord to what Mazda recommends.

A lot of things can affect wideband AFR's, and it's not going to be identical for all engines.
Most have reported that anywhere between 12.9 to 12.5 is about normal.
The engine just doesn't like idling any leaner than that - probably due to the fact that atomization is very poor at that low RPM's.

Bottom line...adjust AFR's until idle is highest; don't adjust idle trying to hit some target number.


-Ted

[vex]

This is why I don't like widebands...

If you read the FSM, it tells you to adjust everything possible until idle is highest.
The FSM does not mention anything about AFR's or widebands - you don't need it accord to what Mazda recommends.

A lot of things can affect wideband AFR's, and it's not going to be identical for all engines.
Most have reported that anywhere between 12.9 to 12.5 is about normal.
The engine just doesn't like idling any leaner than that - probably due to the fact that atomization is very poor at that low RPM's.

Bottom line...adjust AFR's until idle is highest; don't adjust idle trying to hit some target number.


-Ted
I was/am curious on what peoples idle AFR's are not to adjust my idle, but to figure out if I should consider the smoke I am seeing intermittently at idle could be caused by the AFR's I'm seeing.

[classicauto]

Shouldn't be smoking at 12.

10, yes perhaps. But not idling at 12 or even high 11. What colour is the smoke? fuely smell?

[vex]

http://rotarycarclub.com/rotary_forum/showthread.php?t=7982

[gkarmadi]

mine is 13.2-13.4

[FC3S Murray]

Mine at idle is 11.5-11.3

That is due to the larger 750cc primaries and the stupid Power FC curse. For some reason you can't raise the AFR when you run larger primaries.

I idle at a solid 1015 rpm

Also a large street port

[FerociousP]

Mine idles between 10.6-11 and was about to make a post about it. It idles a little rough but drives fine, but to Reted, it doesn't seem to "like" where its idling. I've been using the idle adjust screw on the top of the TB, but its almost all the way in (can't raise idle an higher) and it still adles around 700rpm. I don't have a BAC, could adding on help any? What could manipulate mixture (so to speak) on an s5?

90 vert
stock t2
550s, 720 sec with Rtek 1.7
no emissions
throttle body mod
FMIC
*TPS is adjusted, though I haven't checked voltage range at ECU

[NoDOHC]

I have found that it is more about your manifold vacuum than anything (Idle AFR).

It has been a little while since I did this, so I have tried to indicate the accuracy of the numbers listed.

Ignition Timing (BTDC) Manifold Pressure at Idle (kPA relative) Idle AFR
20 -75 to -80 12.2-12.7 *These are very close
15 -70 to -75 12.5-13.0 *These are also very close
10 -65 to -70 12.8-13.2 *More of an estimate on the AFR, vacuum is right
5 -60 to -65 13.0-13.5 *Pretty accurate (ran for a while at this)
0 -55 to -60 13.4-13.8 *Ran for a few minutes only
-5 -50 to -55 13.7-14.4 *Ran for weeks
-10 -45 to -50 14.4-15.0 *Was running at 14.8, closed loop until my fuel system gave up the ghost from the E85.

This was all with a 15 degree split.

edit: I have found that rotaries like a richer mix than piston engines at high vacuums (low absolute manifold pressures). I don't know why, but my guess is that the compression ratio is low and that the large surface area of the rotor face tends to draw the fuel out of solution.

The rotary actually likes a very similar mix to a piston engine at WOT, which largely discounts the surface area reasoning.

I found that cruising at 65 mph (-65 to -60 kPA) Manifold pressure, 2700 rpm) I needed to run absolutely no leaner than 14.8:1 in order to keep from misfiring. However at higher speeds (I won't state them here) when the engine is running at significantly higher load (say -35 to -30 kPA) I could run 18:1 all day without a misfire.

This actually resulted in my peak fuel economy being well in excess of the speed limit anywhere except for maybe Montana.

The engine speed had nothing to do with it, I could run at 18:1 at -20 kPA at 1,000 RPM without a misfire, but try to run at 18:1 at -50 kPA, forget it.

I am sure that this is not new news to a lot of you, I am just trying to make the parallel.

Piston engines do this too, but will run without a misfire at 14.8 up to about -70 kPA (although most of them have significant higher compression ratios than my rotary).

I am really looking forward to the high compression rotors, maybe I can run leaner at cruise... (wouldn't 40mpg be awesome?)

To ReTed's point, I have 460 cc/min injectors in mine, so I am likely getting better atomization at idle.

Actually, the longer durations may lead to better atomization and metering precision too.

Less vacuum gives longer time... I think you are on to a good theory, ReTed!

[Whizbang]

for WOT my engine seems to run best at about high 12s to the 13.3 mark. around the mid 11s and lower it sounds like its missing. My idle is around 12.2 to 12.7

[TitaniumTT]

This is why I don't like widebands...

If you read the FSM, it tells you to adjust everything possible until idle is highest.
The FSM does not mention anything about AFR's or widebands - you don't need it accord to what Mazda recommends.

A lot of things can affect wideband AFR's, and it's not going to be identical for all engines.
Most have reported that anywhere between 12.9 to 12.5 is about normal.
The engine just doesn't like idling any leaner than that - probably due to the fact that atomization is very poor at that low RPM's.

Bottom line...adjust AFR's until idle is highest; don't adjust idle trying to hit some target number.


-Ted

Speaking on that atomization point, since I've changed to my new injectors (WAY better atomization across the board) I can idle my engine MUCH leaner. My spark also has something to do with it as well I'm sure.

Shouldn't be smoking at 12.

10, yes perhaps. But not idling at 12 or even high 11. What colour is the smoke? fuely smell?

Depends how much premix you're running. When I first started my car up this year I went with some Idemitsu pre-mix @ 1/2 oz/Gal (what they rec) and the OMP working as well. So basically I over oiled the engine for about 1/2 hour idle after sitting stationary for about 5 months. After I added some gas without premix, the smoke went away, AFR's didn't change much at all.

I have found that it is more about your manifold vacuum than anything (Idle AFR).

It has been a little while since I did this, so I have tried to indicate the accuracy of the numbers listed.

Ignition Timing (BTDC) Manifold Pressure at Idle (kPA relative) Idle AFR
20 -75 to -80 12.2-12.7 *These are very close
15 -70 to -75 12.5-13.0 *These are also very close
10 -65 to -70 12.8-13.2 *More of an estimate on the AFR, vacuum is right
5 -60 to -65 13.0-13.5 *Pretty accurate (ran for a while at this)
0 -55 to -60 13.4-13.8 *Ran for a few minutes only
-5 -50 to -55 13.7-14.4 *Ran for weeks
-10 -45 to -50 14.4-15.0 *Was running at 14.8, closed loop until my fuel system gave up the ghost from the E85.

This was all with a 15 degree split.

porting plays a HUGE role in that as well ;)

[NoDOHC]

Ignition Timing (BTDC) Manifold Pressure at Idle (kPA relative) Idle AFR
20 -75 to -80 12.2-12.7 *These are very close
15 -70 to -75 12.5-13.0 *These are also very close
10 -65 to -70 12.8-13.2 *More of an estimate on the AFR, vacuum is right
5 -60 to -65 13.0-13.5 *Pretty accurate (ran for a while at this)
0 -55 to -60 13.4-13.8 *Ran for a few minutes only
-5 -50 to -55 13.7-14.4 *Ran for weeks
-10 -45 to -50 14.4-15.0 *Was running at 14.8, closed loop until my fuel system gave up the ghost from the E85.


Please allow me to correct some misinformation here. These numbers were taken using my old AEM wideband.

A new, calibrated Haltech wideband is now indicating that my AFRs were not stoic as I originally thought.

The table above should actually read more like this:
Ignition Timing (BTDC) Manifold Pressure at Idle (kPA relative) Idle AFR
20 -70 to -75 12.4-12.6
15 -66 to -70 12.6-12.9
10 -62 to -66 12.9-13.1
5 -58 to -62 13.1-13.2
0 -53 to -58 13.2-13.3
-5 -49 to -53 13.4-13.6
-10 -45 to -49 13.8-14.0

I tried retarding the timing more, but the AFR had to actually go richer again as I went in that direction.

This is all taken at 700 RPM (my new idle). I was idling at about 1,000 rpm before, but I got tired of waiting for the trans to stop to use reverse.

Advancing the timing past 20 degrees didn't really increase the manifold vacuum any, nor did I see any changes in the AFR (went from 20 to 40 degrees with no noticeable change.
The engine will idle at stoic, but it misfired every 2 seconds or so (very annoying).

I apologize for the misinformation, it was correct to the best of my knowledge.


porting plays a HUGE role in that as well

Correct you are!

I should list my porting - stock port timing (open/close), slightly cleaned up.

[Rotary Evolution]

there is no target AFR for idle.

plain and simply adjust the idle until the idle starts to surge and then richen it up a tad. tap the throttle a few times to make sure the engine doesn't want to stall out when it sets down to idle, if it does richen it up a tad more.

that's all.. you don't even need a wideband to tune a car out of boost.

going based off of AFRs doesn't mean your wideband is even accurate, it may give you an idea if it is not however. most rotary engines will struggle to idle when going much leaner than 13.8:1 on my wideband.

[88turboii]

ive been idling in closed loop (14.7 afr) for the past 6 months or so. timing is about +3 degrees, about 900rpm. it will hunt, but never had it stall on me

now the question is, what gets better fuel economy, idling at 13's AFR with smooth idle or 14.7 AFR with hunting idle?

[RETed]

Leaning out the idle isn't going to get you that much gain in your gas mileage...
Unless you sit in your car all day just idling, you might pick up 1 or 2mpg tops.


-Ted

[TitaniumTT]

100% agreed, you spend such little time idling it's not going to make a difference. Messing around with the L's and timing picked up a few MPG on my trip. Nest step is to lean out everything up to atmosphere and hopefully pick up a few more MPG's... but I need someone in my car driving with me on a long trip really dial this is.

For what it's worth, when I set my idle, I unplug the BAC valve and get it within a 100-150 RPM of where I want it by mechanically setting the throttle and the adjusting the L's and timing. Then plug in the BAC and shoot for the target RPM's Using the BAC valve to get that last few RPM's and limiting in it's duty cycle ability.

[NoDOHC]

I know that a six port will idle at stoic. I was able to do so using the factory narrow band sensor when I had to pass emissions (at 5 degrees ATDC Leading and 20 degrees ATDC trailing). If the timing is set retarded enough to idle closed-loop, you are using much more fuel than you would at 15 degrees advance and 13.2:1. I was listing the information to correct previous erroneous information that I posted, not to endorse idling with 10 degree ATDC timing.

TTT, shoot for 16.2:1 AFR (1.1L) and about 50-60 degrees BTDC for fuel economy (at -45 kPA, 2,700 rpm). You will have to run rich of that if you pull more than about 45 kPA vacuum driving down the road.

[RICE RACING]

12.4:1 @ 850rpm idle

[tweiss3]

This is an interesting bit of information. I wonder what mine is

[88turboii]

for me, the difference between 13.0 and 14.7 AFR at idle is about 6.5 cc/min, so with gas at $3/gal that comes to about 1/2 cents saved per min idling :)

and it costs me 3 cents/min at idle lol

[TitaniumTT]

I know that a six port will idle at stoic. I was able to do so using the factory narrow band sensor when I had to pass emissions (at 5 degrees ATDC Leading and 20 degrees ATDC trailing). If the timing is set retarded enough to idle closed-loop, you are using much more fuel than you would at 15 degrees advance and 13.2:1. I was listing the information to correct previous erroneous information that I posted, not to endorse idling with 10 degree ATDC timing.

TTT, shoot for 16.2:1 AFR (1.1L) and about 50-60 degrees BTDC for fuel economy (at -45 kPA, 2,700 rpm). You will have to run rich of that if you pull more than about 45 kPA vacuum driving down the road.

Few problems with that... I cruise @ ~80-85mph and that's ~4000 rpm. So my mileage isnt going to be the best regardless.

I'm running 1.05-1.1L and 45-50* timing and the EGT's came WAY down.

So when you say -45kpa.... do you mean 55kpa or 45kpa?

Problem is you give it hte slightest bit of throttle and all of a sudden you're at atmosphere running .85ishL. It's the

[FRED]

The RX does not go into closed loop in the driveway. Period.

The only way it'll go into closed loop is if you remvoe the TPS connector and put it in gear and rev over approx 1700 rpm. See book.

Stk timing is 5L and 20T at idle last time I looked. Its that below approx 1100 rpm. Then it advances all by it's lonesome.

Series four idle good at approcx 13 afr give or take a touch. That's reading the AFR with NO airpump/acv dumping air into the exhaust ports which are prior to the 02 sensor. If your reading afrs with a active airpump/acv then your not reading the REAL engine afr.

[Rotary Evolution]

Few problems with that... I cruise @ ~80-85mph and that's ~4000 rpm. So my mileage isnt going to be the best regardless.

I'm running 1.05-1.1L and 45-50* timing and the EGT's came WAY down.

So when you say -45kpa.... do you mean 55kpa or 45kpa?

Problem is you give it hte slightest bit of throttle and all of a sudden you're at atmosphere running .85ishL. It's the

take his suggestion with a grain of salt, every car reacts differently to different AFRs and 16AFR cruising on most 2nd gens simply wont happen because the car will want to fall on its face to even keep up with itself, perhaps he runs a smog pump which skews his figures up or runs an AEM with a crappy bosch wideband sensor which also seems to have figures a bit off..

at any rate, lean the AFRs out as much as you can first while cruising that can maintain speed while having a steady foot on level ground. then advance timing up to about 45 degrees of advance with a 8 degree split. you don't need wideband figures at all, the engine will tell you where it wants to be because it will begin to lose power if you push the AFRs too far on the lean side, on the rich side the engine will not hate you so much before it starts losing power. when leaning out AFRs there is a radical ramp you will reach when the engine doesn't like what you're feeding it.

[RETed]

take his suggestion with a grain of salt, every car reacts differently to different AFRs and 16AFR cruising on most 2nd gens simply wont happen because the car will want to fall on its face to even keep up with itself, perhaps he runs a smog pump which skews his figures up or runs an AEM with a crappy bosch wideband sensor which also seems to have figures a bit off..

First, if we're going to assume the AFR #'s are off, then why even bother mentioned #'s at all?

Second, I've run a 13BT past 16.0, and it did not "want to fall on its face".
This was at 4kRPM+ and EGT's were creeping past 1,000C or over 2,000F.
The engine will push ultra lean mixtures like that but EGT's are just too hot to be comfortable.
There was no hint of lean surge - see below - and the car kept running with no hiccups.
Granted, we were cruising at a spritely speed of over 100mph on the expressway...


you don't need wideband figures at all, the engine will tell you where it wants to be because it will begin to lose power if you push the AFRs too far on the lean side, on the rich side the engine will not hate you so much before it starts losing power. when leaning out AFRs there is a radical ramp you will reach when the engine doesn't like what you're feeding it.
Those in the industry call this "lean surge".
I guess you can call it "lose power", but it's more like a hesitation.
It's more likely an ignition misfire, cause you don't have a coherent burn inside the engine.


-Ted

[TitaniumTT]

take his suggestion with a grain of salt, every car reacts differently to different AFRs and 16AFR cruising on most 2nd gens simply wont happen because the car will want to fall on its face to even keep up with itself, perhaps he runs a smog pump which skews his figures up or runs an AEM with a crappy bosch wideband sensor which also seems to have figures a bit off..

Few other things matter as well I've noticed. Exhaust, intake, and plugs will all slightly effect how the engine reacts. I've not noticed a huge ramp up between .85L to 1.05L... in fact, aside from the engine sensors, you really couldn't tell engine was running any differently.

at any rate, lean the AFRs out as much as you can first while cruising that can maintain speed while having a steady foot on level ground. then advance timing up to about 45 degrees of advance with a 8 degree split. you don't need wideband figures at all, the engine will tell you where it wants to be because it will begin to lose power if you push the AFRs too far on the lean side, on the rich side the engine will not hate you so much before it starts losing power. when leaning out AFRs there is a radical ramp you will reach when the engine doesn't like what you're feeding it.

First, if we're going to assume the AFR #'s are off, then why even bother mentioned #'s at all?

Second, I've run a 13BT past 16.0, and it did not "want to fall on its face".
This was at 4kRPM+ and EGT's were creeping past 1,000C or over 2,000F.
The engine will push ultra lean mixtures like that but EGT's are just too hot to be comfortable.
There was no hint of lean surge - see below - and the car kept running with no hiccups.
Granted, we were cruising at a spritely speed of over 100mph on the expressway...



Those in the industry call this "lean surge".
I guess you can call it "lose power", but it's more like a hesitation.
It's more likely an ignition misfire, cause you don't have a coherent burn inside the engine.


-Ted

Psh, if only I could be at 4k rolling down the highway :rofl: I was at 4k around 80-85....

Anywho, like Ted said, I really wouldn't tune a car like that (ignoring sensors) for the reasons that Ted mentioned. Granted my EGT's were up there (1700 at cruise) to begin with but I woudn't blindly tune by just cruising down the highway waiting for lean surge to happen without monitoring EGT's.

For what it's worth, advancing the timing will allow you to run leaner, and it'll bring the EGT's down as well.

Like just about anything related to tuning an engine, there is a sweet spot withen the cruise to keep the EGT's down, and I feel that it's rather difficult to find it running blind

[Rotary Evolution]

i don't know why people worry so much about the car out of boost...

the emphasis i was trying to make is you should focus on what the engine is telling you, not ignoring the sensors but the wideband figures are just a basis and not always to be used as a fine tuning instrument. even tuning in boost i don't always treat the wideband as if the figures i am seeing are factual, there are many reasons that a sensor can be giving you false readings.

but 1700 EGT while cruising? now that isn't normal.

y'all can do what you want, you can call it blind tuning or whatever. back in the day before widebands and standalones that is how people had to do it. the tools just help make sure adjustments are working properly, the best way to ensure that the car is accepting the changes accordingly is still by feel to how the engine reacts to those changes.

just like a dyno is a tool, they aren't always the best tool for making adjustments with. some dynos don't load to real world loading, causing your adjustments to be off as soon as you take it off the dyno and drive it on the road.