Acceptable Afr's During Cold Start And At Idle

[Mad Scientist 106]

Hello!

 

Can anyone help me fill in some blanks please?

 

I am currently tweaking my map to make the car safe to start and drive (under low load and revs). I need to get some miles on it prior to final mapping.

 

The AFR's at idle (once warmed up) and during warm up from cold start are what I am after.

 

I would like an indication of what is "acceptable" in terms of avoiding bore wash. I know its going to be rich when warming up, but what are others seeing?

 

At idle, what sort of AFR is acceptable? Forget about HC emmissions and MOT's for now, what sort of AFR is considered "safe".

 

Just to give you an idea of engine spec:

 

Gti 6

Satchell bodies (GSXR 1000)

Catcams 110 cams

 

I don't expect to get it to idle in the 14's, but is low 13's going to cause issue?

 

Thanks,

 

Pete

[Tom Fenton 1,525]

You may be suprised, assuming you have a wideband have a play and see what the engine seems happy at, it may well idle leaner than you think, don't be too hung up about numbers as such. So long as it doesn't start with 12 then you will be fine. But you may find it is fine with an AFR that starts with 15.

[Grahamrally 0]

I aim to hit a target of lambda = 1 always, or 14.7:1 afr. However different setups produce different types of idle at different lambda. Most comprehensive ecus or original ecus have a lambda target of 1 on idle and light cruise, so for me, the closer I get to this, the less work the closed loop feedback system has to do!

 

Graham

[sideways danny 0]

cold start idle AFR you want to be around 12.5-13:1 and gradually leaning out as you get warm. coming off fast idle at around 60deg C at which point you want to be at around 13.6:1, then normal warm idle at 14.7-15:1 at 90deg C

[Mad Scientist 106]

I can't get anywhere near that Danny.

 

Cold start idle is 10.5 to 11 ish, higher when driven straight away, which is what I try to do.

 

As it warms up it obviously leans out. Warm idle is approx 13.8:1.

 

It won't start without a ruck of fuel when cold, and it won't idle any leaner.

 

It needs final setup by Sandy, but as long as i'm not risking bore washing my ££££££££££££ engine, i'm happy to run it in now.

 

Not sure about the cold idle numbers though...............any thoughts?

 

Pete

[sideways danny 0]

I'd think you probably need to look at your static throttle and idle ignition timing. open the throttle a bit more at idle and it should start easier. This will normally require spark scatter to pull the ignition timing out a little to hold the revs down. Do you have a synchrometer?

 

oh, and i need to speak to you about parts

Edited November 12, 2010 by sideways danny

[Mad Scientist 106]

I don't have a syncrometer, but I borrowed a very simple one and balanced the throttles as best I can. I think the best thing I can do is get the car to Sandy. He provided the base map and has been very helpful so far.

Thanks for the advice Danny.

Judging by the post time you are having trouble sleeping! The pressures of your own business!

I'll pm my number. Give me a call some time.

Pete

[sideways danny 0]

sleep is for the weak

 

I'll give you a bell in the next few days