Not sure how to describe it. Actual idle is fine but if I blip the throttle the revs drop momentarily before picking back up. As this happens the engine goes completely quiet, like it shut off. Then it picks up and feels a little rough until around 2k rpm.
Doesn't happen at all on petrol and seems fine on LPG once the engine is warmed up. I'm not 100% sure but I think it only does it in neutral or park. I've not noticed any issues pulling away.
Any ideas on what it could be?
Best have a word with Simon, he fitted it after all......
I saw this thread just a few minutes ago and immediately phoned RutlandRover Dave to explain what's happening, what settings are causing it and why I made those settings.
The KME ECU allows setting momentary switching back to petrol if reducer temp or gas temp fall below a certain level if engine load rises above a certain level. The feature is useful as a safeguard (to prevent issues) and is also useful for effectively allowing setting of a cool changeover temperature at light to moderate engine load but a warmer changeover temperature for higher engine loads. The two points almost imply the same thing for the majority of vehicles but there are some vehicles (very high powered but with little coolant flow, which doesn't apply to P38s) where the two points can mean different things. *Edit: The two points can mean different things on any vehicle if some problem occurs with the vehicle in future, e.g. a partly blocked heater matrix could effect reducer temp stability at high engine loads if the reducer is plumbed in series with the matrix.
I set a cooler than usual changeover temperature but set the system to momentarily switch back to petrol if higher engine load is applied while either the reducer is below 20c or gas temp is below -5c. What's happening when Dave blips the throttle so soon after changeover is engine load momentarily rising above 30% (and 30% is more than you might assume, you could probably cruise at 100mph at 30% engine load) while reducer temp is below 20c, so causing the system to switch back to petrol... only during the throttle blip and only while the reducer is cold. But Dave notes it doesn't do this when he pulls away etc in actual driving even when the system has just switched over to LPG... that's either because engine load doesn't rise above 30% during those conditions or because when he pulls away the reducer has already risen above 20c. Note that this isn't the same as what is usually considered petrol addition or inability to run on LPG flat out, the system does run on LPG under any driving condition once the reducer and gas temp (gas temp won't be a factor here) are warm enough.
If I hadn't applied the settings it might have been a good idea to set a warmer changeover temp, in which case Dave would save less money because he would be running on petrol for longer during the warm up stage..
The OMVL injectors are perhaps the best performing injectors with cold gas (I told LPG shop this a long time ago and they seem to have invented a fake review on their website from someone who says OMVL are the only injectors that work properly in Alaskan conditions lol), the reducer is unlikely to get cold enough to freeze up or spit out liquid gas (causing high pressure problems) even if he booted it when the reducer was still at the cool changeover temp I set - So if Dave wants I'd be happy to leave changeover temp as it is and disable the facility and it would be fine,, but it is probably a good idea to leave settings as they are because (as Dave said) it isn't causing a drive-ability problem and the settings help make the system pretty much bombproof... I could trip most LPG installs that change over at normal/low temps up by immediately booting it following changover to gas from a cold engine start but even I would struggle to find a way to make this install throw a wobbly other than the compromise of the hesitation reviving the engine when it's just changed to LPG from a cold start. Many installers/customers have moaned on LPGforum about getting the balance between changeover temp (money saving) and owners likelihood of booting it with cold reducer right (thus causing drive-ability and component issues) right, the KME settings can be used to allow a very cool changeover temp while preventing problems caused by too cold gas / cold reducer in case the driver boots it very soon after changeover with cool temperature setting for changeover.
Just saved a screenshot of the settings I mentioned, will upload to the net and post a link when I get time if anyone wants?
Simon
Sorry for a late response to this - I don't get much opportunity to get online now I'm back at work. Our lovely IT dept have installed an incredibly strict web filter in the 6 months I was off so I can't access the site there.
Thanks for such an in-depth explanation on what's going on! The phone call was much appreciated too.
Now that I understand what's going on with it I'm happy to leave it as it is :)
No probs Dave :-)