I have seen somewhere (but obviously hidden in a safe place!) the CO readings that should be seen throughout the rev range on a RV8
I have a 3.9 with adjustable (flapper) ECU which has just gone through MOT at 0.8% Co at idle, which kind of alarmed me because I thought it should be around 2% and hence rather lean.
I can find suggested Air/Fuel Ratios at various rev. ranges (as used for setting up Megasquirt), but does anyone have similar for CO levels for us mere mortals on semi-stock efi systems?
Thanks.
Setting CO levels - what should they be?
Moderator: phpBB2 - Administrators
If yours is one of the flapper ECUs with a big dial and a small brass screw (most likely built by Mark Adams), they were built to run a different mix to standard.
The standard ECU would give about 2% CO through the rev range, which was a compromise - but remember this wasn't an extremely refined injection system!
Mark's ECUs ran dual mode, so they would richen up (way beyond 2% - Mark told me 5% or more) under heavy throttle, but lean back to a fraction of a percent under gentle throttle for best economy.
(If it is one of those, the big dial adjusts mixture under power, and the brass screw does so for part throttle)
The standard ECU would give about 2% CO through the rev range, which was a compromise - but remember this wasn't an extremely refined injection system!
Mark's ECUs ran dual mode, so they would richen up (way beyond 2% - Mark told me 5% or more) under heavy throttle, but lean back to a fraction of a percent under gentle throttle for best economy.
(If it is one of those, the big dial adjusts mixture under power, and the brass screw does so for part throttle)
No substitute for cubic inches
Thanks 5000SE. I believe it is one of those, but unable to confirm. It has the 2 adjusters as you suggest (see my other thread trying to identify it). I have tried emailing Mark Adams, but without success.
Really just need some figures that are safe to run so I don't cook the thing. Especially the long duration motorway type run figure which I understand to be the killer for lean V8's.
For example would sub 1% be OK up to around 1,000 RPM
2% at 2,500 to 3,500
3% at 3,500 to 4,500
4% at 4,500 +
or should the curve be more exponential?
Really just need some figures that are safe to run so I don't cook the thing. Especially the long duration motorway type run figure which I understand to be the killer for lean V8's.
For example would sub 1% be OK up to around 1,000 RPM
2% at 2,500 to 3,500
3% at 3,500 to 4,500
4% at 4,500 +
or should the curve be more exponential?
As I recall, Mark's systems ran under 1% at all rev ranges when in 'cruise mode' (ie, not under power).
There was an LED on my control unit which lit up when the foot went down hard, and this identified when the ECU switched to power mode.
Under light throttle, the whole useable rev range would be set up (using the small brass adjuster screw) to be something like .5-1%, then the power mode (when the extra light comes on) would richen up to over 5%. Mark said the Rover would produce maximum power with anything between 5% and 8%. Seems a bit rich to me, but he knows the engine better than most people.
It doesn't come in varied at different ranges as you suggest - the whole lot runs lean under light throttle, then all revs richen up under high demand. My car drove well - there was no noticeable transition between the two modes, and a 313bhp 4.6 litre engine gave me 25mpg on a steady run.
The fiddly bit of setting up is to match the spring on your airflowmeter to make sure that's giving full range but not opening up fully before you have full flow. Takes a bit of trial and error setting the spring tension, but you need this done before you tweak the screw and dial.
There was an LED on my control unit which lit up when the foot went down hard, and this identified when the ECU switched to power mode.
Under light throttle, the whole useable rev range would be set up (using the small brass adjuster screw) to be something like .5-1%, then the power mode (when the extra light comes on) would richen up to over 5%. Mark said the Rover would produce maximum power with anything between 5% and 8%. Seems a bit rich to me, but he knows the engine better than most people.
It doesn't come in varied at different ranges as you suggest - the whole lot runs lean under light throttle, then all revs richen up under high demand. My car drove well - there was no noticeable transition between the two modes, and a 313bhp 4.6 litre engine gave me 25mpg on a steady run.
The fiddly bit of setting up is to match the spring on your airflowmeter to make sure that's giving full range but not opening up fully before you have full flow. Takes a bit of trial and error setting the spring tension, but you need this done before you tweak the screw and dial.
No substitute for cubic inches
