The majority of your map will be fine, it just needs tweaking at idle and fast idle where it is too rich.
The Lambda closed loop wont cycle it that rich, it only makes small adjustments to the map. Regardless of the Lambda input I would lean off the fuelling while the test is being done and with closed loop off until the CO drops. Once this is very close to perfect, than turn on closed loop with only a very small adjustment.
The majority of your map will be fine, it just needs tweaking at idle and fast idle where it is too rich.
The Lambda closed loop wont cycle it that rich, it only makes small adjustments to the map. Regardless of the Lambda input I would lean off the fuelling while the test is being done and with closed loop off until the CO drops. Once this is very close to perfect, than turn on closed loop with only a very small adjustment.
Dave
Cheers Dave,
I’m starting to wonder whether the lambda sensor is working at all because the Live Data screen of the Emerald shows it running very lean. if this is the case, wouldn’t the Emerald keep trying to push it richer and richer ?
Unfortunately I’m not really familiar enough with the adjustments you recommend to know how to use your suggestion. Can I literally sit there with my laptop and play with the fuelling at idle and Fast idle revs until the values come down far enough ?
I followed Dave’s advice and got through an MoT retest by adjusting the Emerald map with the laptop while connected to the exhaust analyser. When the values started to look OK (by leaning out the fuelling at idle and fast idle), the MoT guy hit the button to start the test. They have to be within limits for 30 seconds I think. My values were well out before adjusting the fuelling. The CAT and Lambda sensor were both known good items.
Don’t forget to save the map when you get through (and your “power” map before you start!).
The Emerald does not self map, it will not try to keep pushing the fuelling richer, the fuelling is determined by the firgure in the map… end of story. The only adjustments the ECU makes are small ones to try to cycle the fuelling from one side of Stoi to the other to keep the cat up to temperature, and that only happens in closed loop mode.
You can adjust the fuelling just as you describe, just have a read of the manual to see how.
Can someone explain something to me. Why does an engine need to run so rich at idle that it fails MOT’s - even with a cat. I think I can understand the need for enrichment if under high power / transient acceleration, but it strikes me that an engine at idle should easily be capable of running at an ideal fuel air ratio. Is it valve overlap timings? When these “Emralded” VHPD’s are running a so called “MOT map”, why can’t they be used with this mapping? Do they become undriveable?
An engine doesn’t need to run that rich at idle, slightly rich gives a better idle then stoichiometric. The chances are that the idle fuelling was never set as lean as it should have been, or something has changed since the mapping was done. Setting the idle to stoi will not hurt the perfomance in any way, nor will setting the fast idle correctly for an MOT pass.
I only have the one map and it was adjusted as explained above to pass the MoT, then left in there ready for the next test.
so are you saying that the pre-MOT map was just off a bit and the variables adjusted can be left like that for the rest of the year with no effect on power, torque, etc.
…I followed Dave’s and Steve B’s advice I should have said! (Thanks Steve!)
My understanding was that you only change the map around the 1200rpm natural idle and around 2500rpm fast idle. Everywhere else gets left alone as defined for optimum power.
I thought the leaned areas affected my driveability around town a little, so I loaded the original map back in after the test, saving the MoT map for next time.
I only have the one map and it was adjusted as explained above to pass the MoT, then left in there ready for the next test.
so are you saying that the pre-MOT map was just off a bit and the variables adjusted can be left like that for the rest of the year with no effect on power, torque, etc.
In all the excitement of making 245bhp, we forgot to map the MoT areas of the map!!
As for the effect on power/torque for the whole map, think about where you put your foot on the throttle for the two test rpm areas…
One is tickover and tickover is never mapped for peak power And you hardly have to press the throttle to get to 2500-3000rpm when the car is stationary. When the car is actaully being driven at that rpm, the engine will be under far more load pulling the car along, therefore its highly unlikely that the area of the map that you lean out for the MoT test is ever used for driving.