AFR during idle

[Silver Surfer]

Guys,

What should the AFR be during idle around 1100rpm?

SS

 

[Elite]

14.0:1 - 16.0:1

No richer than 14.0:1 though.

 

[DDozier]

Are you talking about a OEM ECU or a tuned car using a Standalone ECU?

OEM ECU in closed loop will target 14.7, you may see 14.2 - 15.0 but the goal is 14.7. If the car is in cold start you can see anything from 12.5 - 14.7 depending on how cold it is but this will be for a very short period of time, once the car warms a little and cold idle drops you should see closed loop numbers around 14.7.

On a standalone your AFR will be what ever the tuner wants them to be but if tuned correctly a turbo or CTSC needs nothing special to idle correctly and you should have the car tuned to mimic the OEM cold start and idle AFR's. The only thing the CTSC at least with the Whipple likes is a little more idle RPM to reduce gear lash in the blower and quiet them down.

Dave

 

[Silver Surfer]

Yes, my car is on the Low-boost set up with the Whipple SC....so has a piggy back Comptech with Stock ECU.

It idles after start-up of around at AFR of 12.8.

Will let it warm up to see what reading it gives.
I just replaced my damaged Whipple with another and just checking the fuel injectors etc before running it properly.

SS

 

[Mase]

immediately after startup, the o2 sensor probably isnt even heated up yet. hence you wont have any o2 correction for a bit. the fuel enrichment is higher during cold starts.

 

[Silver Surfer]

After warming up the AFR settles down to around 14.6-14.9.

That seems to be more in range of acceptability.

SS

 

[NSXCessive]

Mine is around 14.7 once warmed up & settled running SOS Intercooled S/C.

 

[goldNSX]

Normal behaviour. Richer at cold start, 14.7 when after a few miles warm-up. Every car runs around 13 after a cold start.

 

[EAC]

How about cruising afr?

 

[goldNSX]

How about cruising afr?

Should be the same behaviour unless you step on the throttle and let it boost.

 

[EAC]

Should be the same behaviour unless you step on the throttle and let it boost.

I'm talking with zero load, what is the best afr for optimum mpg?

 

[SuperSonic]

Normal, hot day my cruise is at 14.4-15.1, wot will drop to 11 ish. Same wot on cold day but cruise speed on a cold night it bounces a lot like 13.9-15.2

 

[kookoo4nsx]

With zero load, you would be going zero MPH thus MPG is incapable of being able to compute.


:biggrin::biggrin::biggrin::biggrin:

I'm talking with zero load, what is the best afr for optimum mpg?

 

[Elite]

I'm talking with zero load, what is the best afr for optimum mpg?

There isn't a magic number, as every car is different. But if tuning a standalone for cruising, you can go as lean as the car will accept without bucking or drivability issues. I know people in the "green/mpg" forums will go way past what people think is possible.

 

[Silver Surfer]

In order to run an AFR of around 14.5-15.3 at idle...my Fuel pressure is set around 70 PSI via the old blue/silver FPR.

Is this acceptable or should I be worrying about hose bursting concern?

Will be Rolling road the car next week.

SS

 

[Elite]

In order to run an AFR of around 14.5-15.3 at idle...my Fuel pressure is set around 70 PSI via the old blue/silver FPR.

Is this acceptable or should I be worrying about hose bursting concern?

Will be Rolling road the car next week.

SS

That doesn't sound right. Can you clarify what's its doing at lower psi's? And what are you tuning with? You are not just playing with fuel pressures are you?

 

[Silver Surfer]

I have turned down the pressure via the FPR as I notice the nut that fixes the screw for adjusting the pressure was loose ...I have turned the pressure down from 70+ PSI to 56 PSI and the AFR at idle remains at 14.7 and have tightened the locking nut! The car now idles warm at 800rpm.

Will further adjust on the rolling road this week.

SS

 

[Silver Surfer]

Rolling Road after cleaning the injectors and keeping the FPR setting at 56PSI:

At the crank: 394 bhp
Transmission loss: 53 bhp
At the wheel : 341 bhp

AFR at peak: 11.5

Much happy with this setting.
Amazed that just ultrasonic cleaning of injectors has improved the AFR at peak to more safer level.

SS

 

[Stephen@NCAutoUSA]

Cold start AFR I'm in the 10's...

At normal idle and operating temps I'm any from 12.3-12.9 or so.

 

[Elite]

Cold start AFR I'm in the 10's...

At normal idle and operating temps I'm any from 12.3-12.9 or so.

That's a bit rich. In warmer temps, it was in the upper 14's. I'm assuming it may be compensating for cooler IAT's due to the cold ambiant air.

 

[Stephen@NCAutoUSA]

Is there a way I can change it without getting or paying for "retuning"?

Well I know there's a way, but is there an easy way or is it worth doing?

 

[DDozier]

Is there a way I can change it without getting or paying for "retuning"?

You should never make a change to your fuel system without verifying the results are safe either by logging the results in real time with a wideband or by dyno. If you do not take these steps to protect your engine you will likely loose it.

Dave