14CUX closed or open loop?

[blitzracing]

Can anyone confirm if the 14cux is in closed loop mode on the catalyst map throughout the entire rev range, or as Ive been told ( by an expert??) only up to 2500 rpm ? I have been closely testing the 3.9 TVR catalyst map with a lambda probe and dash display, and it looks very much like its in closed loop mode all the way. Either that or the TVR map is fantastically acurate in open loop....

Thanks

Mark

[GreenV8S]

As far as I remember (from what Mark Adams said, many years ago) it drops out of closed loop at higher revs. I thought it was 2700 rpm that it dropped out at but I could be wrong. The peculiarity is that this is independent of throttle.

[The AJP Griff]

I was told that closed loop goes as far as 3 or 3.1k on the Griff 500 if thats any help.Dont be too surprised by how good the original TVR map is,in my experience it's a lot better than some might have you beleive!

[GreenV8S]

The map should be OK, but under power it ought to be running a lot richer than lambda 1.0 (which the original post seems to imply).

[trackcar]

mine goes out of closed loop at about 3400/3500rpm.

[blitzracing]

That makes sense, I was doing most of my testing under load at 3000-3500 rpm when it was constantly correcting itself around lambda. Ill have to do a motorway run to see the results at a higher rpm under constant throttle.

Thanks

Mark

[neal1980]

i fitted an lc1 to my chim at the weekend and have also been monitoring afr. Under hard accelaration mine can go down to low 11's. Also seems to always smell very rich. Hopefully megasquirt fitted next weekend!

Thanks

[blitzracing]

I see around 12:1 under acceration, but its towards the limits my narrow band sensor will do, so maybe not so accurate and it drops to around 14:1 under constant throttle. The gauge never sits still, but simply averages around a mid point. Ive not seen it show rich and stay there when I expected it to be open loop, it still toggles around 14:1 hence the query. The whole issue is Ive messed around with multiple fuel maps (JE modified, Adams, TVR, Range Rover, catalyst and non catalyst plus fuel pressure) and a lot of the time its very hard to tell the difference when you drive the car (unless its miles out), so the gauge is a just a good guide. I hate to think how long it takes to get an emerald or megasquirt spot on, I dont think id ever stop tweeking it !

[Mark Adams]

The standard 14CUX program goes open loop at 3100RPM. Some of my modified versions go open at either 3000 or 3500RPM (due to the extended rev range). It also goes open loop at approximately 3/4 load at any speed.

Mixture control is very accurate on lambda control so long as the basic map is reasonably close. It's only meant to trim the mixture, not do all the work. The trimming range is + or - 22% which is huge, however you will start to feel the action if trimming is over 14%.

[blitzracing]

So that begs an interesting point..Your chip's are frequently sold with with a fuel pressure regulator for final tweeking. How can you knock out lambda control to get the fixed part of the map and fuel pressure as close as possible before the lambda control takes over? Changing the resistor alters the map, and I assume the ECU will go into fault or limp home mode if the lambdas are simply disconnected (??). Is there any point (within the ECU) you can monitor the amount of correction being appled with Lambda ? I tried monitoring the lambda outputs whilst tweeking the CO offset at tick over on the AFM from 0 -3.5 volts, but it stayed within lambda control all the way. I expected to see the probe output start to average rich or lean as I exceeded the the recommended settings, but I saw little change. That would imply a base mixture correction is made and stuck to untill the probe runs too rich or lean again. At that point a new base setting would be established??