Target AFR's at idle?
02-23-11, 05:30 PM
#1
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Target AFR's at idle?
I was trying to find some information on this but I couldn't get anything. I was wondering if there's an ideal target AFR for the car to run at? Or if it's basically find the one that idles the smoothest?
As a reference I have mine set in the low 13's
As a reference I have mine set in the low 13's
02-23-11, 05:41 PM
#2
There are threads on this in the PFC section.
However, as lean as you can while maintaining a smooth idle is the general goal. Air pump will need to be off for a valid measurement. If you have larger injectors, you may be limited in how lean you can go.
However, as lean as you can while maintaining a smooth idle is the general goal. Air pump will need to be off for a valid measurement. If you have larger injectors, you may be limited in how lean you can go.
02-23-11, 11:57 PM
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02-24-11, 10:10 AM
#8
this can't be achieved at a low idle speed on a pre-Renesis engine. That's why there is an air pump. The air pump dilutes the mixture at the exhaust ports or in some cases injects air directly into the catalytic converter. The Air Control Valve directs the air to the exhaust ports or the cat depending on the running condition.
02-24-11, 12:14 PM
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02-25-11, 12:36 PM
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*i havent actually done this, i'd like to, but i'm lazy and its supposed to snow
06-08-15, 09:20 PM
#14
Hey im kicking this thread back up to the top because it throws me off. I just installed a wideband in my car.
mod list-
HKS downpipe
4in midpipe( wideband mounted in here)
Apexi gt spec mated to 4in downpipe
Apexi power fc on base map????
stock turbos
stock intake
stock engine
So after install i started the car, the sensor went through the cycles and at idle and it read over 17. On my AEM wideband i think it only reads to 17 or 18? It shows ---- for out of range. Now my understanding is that perfect AFR is stoich which is 14.7. I bought the car with the apexi and was told it is on base map but i have never checked it. I did a pull 2nd gear at 2500rpm to the top of 3rd gear and the AFR was 10.8- 11.1. Now also cruising at 2k rpm it is leaned out to ---- but cruising at 3k rpm it is between 14-15.5.
Is this normal operation? i havent had any issues with the car. Beginning of the season i ran a 13.1@103mph with the stock midpipe and have been beating on the car every time i drive it for over a year now. are the AFR readings due to the air pump?
mod list-
HKS downpipe
4in midpipe( wideband mounted in here)
Apexi gt spec mated to 4in downpipe
Apexi power fc on base map????
stock turbos
stock intake
stock engine
So after install i started the car, the sensor went through the cycles and at idle and it read over 17. On my AEM wideband i think it only reads to 17 or 18? It shows ---- for out of range. Now my understanding is that perfect AFR is stoich which is 14.7. I bought the car with the apexi and was told it is on base map but i have never checked it. I did a pull 2nd gear at 2500rpm to the top of 3rd gear and the AFR was 10.8- 11.1. Now also cruising at 2k rpm it is leaned out to ---- but cruising at 3k rpm it is between 14-15.5.
Is this normal operation? i havent had any issues with the car. Beginning of the season i ran a 13.1@103mph with the stock midpipe and have been beating on the car every time i drive it for over a year now. are the AFR readings due to the air pump?
06-09-15, 09:38 AM
#15
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like any car the FD has different AFR's for different parts of the map, as the amount of load changes the AFR you want.
at idle, the air pump is ON, and the air pump air goes into the exhaust ports BEFORE the 02 sensors, so the AFR will be lean.
at low throttle between ~1500rpm and 3199rpm, the car is in closed loop, and will be running around 14.7.1 AFR.
at high throttle, you need a lot of fuel to keep it from detonating, and AFR will be in the high 10's low 11's
at idle, the air pump is ON, and the air pump air goes into the exhaust ports BEFORE the 02 sensors, so the AFR will be lean.
at low throttle between ~1500rpm and 3199rpm, the car is in closed loop, and will be running around 14.7.1 AFR.
at high throttle, you need a lot of fuel to keep it from detonating, and AFR will be in the high 10's low 11's
06-09-15, 11:58 AM
#16
I didn't realize the stock fd setup was purposely designed to put that much air into the exhaust. I thought they were only putting in enough air to get to 14.7 but 16.0 and up????? Damn! Doesn't too lean of a reading effect the emissions or is this what's needed for the old pp exhaust to past emissions? My 20b will idle at 13.7 without the air pump before stalling out. When I 1st engaded my air pump, A/F shot up to 16.5. Because of this, I started restricting the output flow to get it down to 14.7. Now I'm wondering if I should just let the full amount enter the exhaust.
06-09-15, 12:50 PM
#17
The air pump should make it leaner than stoich when measured with a wideband. You don't need a restrictor. The lean mixture promotes oxidation reactions in the exhaust. The air actually gets sucked into the intake ports during overlap and stabilizes combustion.
There's a whole science behind the air pump. It actually makes the engine burn much better and it's preferable to keep it in if you can put up with the complexity. Similar air pump approaches were used on piston engines at one point, such as 70s Porsches, although they didn't use cats but rather thermal reactors like the old school rotaries. Even now some new piston engines still use air pumps, but just for a few seconds after start.
There's a whole science behind the air pump. It actually makes the engine burn much better and it's preferable to keep it in if you can put up with the complexity. Similar air pump approaches were used on piston engines at one point, such as 70s Porsches, although they didn't use cats but rather thermal reactors like the old school rotaries. Even now some new piston engines still use air pumps, but just for a few seconds after start.
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06-09-15, 01:41 PM
#19
like any car the FD has different AFR's for different parts of the map, as the amount of load changes the AFR you want.
at idle, the air pump is ON, and the air pump air goes into the exhaust ports BEFORE the 02 sensors, so the AFR will be lean.
at low throttle between ~1500rpm and 3199rpm, the car is in closed loop, and will be running around 14.7.1 AFR.
at high throttle, you need a lot of fuel to keep it from detonating, and AFR will be in the high 10's low 11's
at idle, the air pump is ON, and the air pump air goes into the exhaust ports BEFORE the 02 sensors, so the AFR will be lean.
at low throttle between ~1500rpm and 3199rpm, the car is in closed loop, and will be running around 14.7.1 AFR.
at high throttle, you need a lot of fuel to keep it from detonating, and AFR will be in the high 10's low 11's
Also doesnt the air pump send air into the midpipe via the metal tube??
06-09-15, 03:17 PM
#20
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the air pump only uses that metal tube to the cat during transitions, most of the time the air pump air is going to the exhaust ports, or the air pump is off
06-09-15, 03:31 PM
#21
Hmm that's good to know. My airpump actually feeds those side rectangular ports on the side of the engine. From there, I know the air goes down to the exhaust ports. Given this info, I'll remove the restriction when I get back from my road trip this weekend.
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