AFR's at idle

[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]

Originally Posted by 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.

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]

Originally Posted by TitaniumTT

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]

Originally Posted by Rotary Evolution

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]

Originally Posted by Rotary Evolution

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.

Originally Posted by Rotary Evolution

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.

Originally Posted by RETed

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 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.