Trouble with setting Co - Cosworth

[Mungus]

Evening all, Took my Cossie for a pre MOT, most keen to see what the emissions are like!! . . . . 8% Co at idle!! Didnt suprise me as the plugs have been black and the gaps were at 0.5mm - ive since set them to 0.65 So having read lots about Co's and fuel pressures, I went about dropping the Co down to a sensible rate. The setting screw by turning it anti clockwise dropped it down, but just to 3.5% - it would not drop any lower (ideally looking for 2.5%). Its going to be setup next month, but I worried myself into thinking there maybe a problem with my ECU and I dont want to travel to a tuner only to find that out there and then!! Game over. I did take the top off the ecu and checked/confirmed that the adjuster had contact with the gubbins inside. Any ideas guys?? Chip is NMS for T34 and greys. Huw

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[andycos]

Had the same problem as you with my stage 1 sapphire,and tried the same things as you.
My problem turned out to be the map sensor on its way out,once changed it was back to normal again
In my case the car was running perfect still,but i had only just got it back out of storage so hadnt done many miles.

[Mungus]

Thanks for your reply - getting the fuel pressure checked tomorrow as I have a possible theory.....

Out of interest, is there a min/max number of times that Co screw will turn before reaching a stopper?

I have logged all changes to return if necessary but the Co screw seemed to just turn and turn. It went 4 full revolutions until it reached 3.5% Co, but didnt go below that. Doesnt seem right to be so have returned as it was.

Is there an electrical test you can do on the map sensor - I would like to rule that out.

Huw

[JamesH]

I hope you marked the CO screw first?

Ring NMS

[Mungus]

Originally Posted by JamesH

I hope you marked the CO screw first?

Ring NMS

Owww yes!
Yeah will ring in the morning as im due up there next month - as I said, just didnt want to go all that way and have a knackered ecu

[andycos]

Have a look at this old thread about setting the co mixture

http://passionford.com/forum/ford-si...g-idle-co.html

[Karl]

Hi Huw,

I map all my greys cars to idle around 4 - 5% CO. If your car is just running an off the shelf chip or one from another car, then it will only achieve that CO level if the engine is pulling at least -0.65bar at idle. If it is pulling less vacuum then it will be richer at idle than that.

I do not run greys car leaner than that at idle, because the spray pattern of a grey is very poor and due to the variation in idle fueling caused by heat soak and hot restart, a greys YB mapped leaner than 4 - 5% CO will at times idle poorly.

[Mungus]

Originally Posted by Karl

Hi Huw,

I map all my greys cars to idle around 4 - 5% CO. If your car is just running an off the shelf chip or one from another car, then it will only achieve that CO level if the engine is pulling at least -0.65bar at idle. If it is pulling less vacuum then it will be richer at idle than that.

I do not run greys car leaner than that at idle, because the spray pattern of a grey is very poor and due to the variation in idle fueling caused by heat soak and hot restart, a greys YB mapped leaner than 4 - 5% CO will at times idle poorly.

Morning Karl,

Thanks very much for that - I think I will leave it till I see you on 17th May
Its one of your chips


BTW - how would I fare MOT time with idle co @ 4%?

[martysmartie]

Be careful as well playing around with the "Global mod" as it's called, aka co screw as it subtracts a percentage from the fuel table so you can end up with it running lean up the top end etc, it's worth getting your AFR checked etc to be on the safe side IMO.

Martin