Question for Piper cam owners

[redzed]

My race zs has piper 270 cams in and very light flywheel. It's always stalled when idling and runs rich low down. Top end is fine and not lean as its running a remapped ecu. Question is what's other people's running like? Thinking It will have to get a piggyback ecu to make it run better low down and so it idles better but not sure on which way to go as the Siemens unit is a pain. Help appreciated

[JOHNDQ]

What ecu you running? I'm on emerald K6 with 285's, throttle bodies and 3.5kg flywheel idle etc is fine

[redzed]

What ecu you running? I'm on emerald K6 with 285's, throttle bodies and 3.5kg flywheel idle etc is fine

Yours is a 4 pot though right? Standard ecu, but mapped for the cams

[Skillen]

Standard ECU and flywheel
Never had a problem with stalling and idle is smooth.

Occasionally doesn't fire but a bit of throttle sorts it and then it idles fine.

[JOHNDQ]

Yeah sorry jumped gun bit there. If its running lean sure you doing have a air leak ect

[redzed]

Yeah sorry jumped gun bit there. If its running lean sure you doing have a air leak ect

It's not running lean, it's good over 4k

[talkingcars]

Was the ECU remapped to take account of the cams and flywheel?
If so it should be able to cope with the tickover etc.

[Mark S]

open the tb butterfly a little on the grub screw to raise the revs, 1050rpm works a treat

[redzed]

What's the best piggyback ecu to use?

[MG ZS STE]

Mine has started to do this since changing the thermostat. It never did it before and the only thing i removed during the thermostat change was the TB which makes me believe it is related to this. potentially a vacuum leak? ive cleaned (and yes properly cleaned) the IACV. Next i will probably remove the TB and make sure both mating faces are completely clean.

If that does nothiing i'll be investigating the possibility of the piggy back ECU may have packed in?

It passed fast idle test for the mot emissions but failed natural idle test. The examiner told me that the fast idle one was the important one so was happy to pass it.

Thing is, i would have thought that this would have been handled by the piggyback ECU. I think it was put on originally to overcome lean issues at top end but would they also not have looked into where the car was fueling rich?

I dont know, good luck anyway and if i do get to the bottom of it will let you know.

[Mark S]

there are a few adaption channels on the kv6 that can be accessed with the right equipment and reset, tps, iacv and a couple of others from memory, may be worth a shot first.

[redzed]

there are a few adaption channels on the kv6 that can be accessed with the right equipment and reset, tps, iacv and a couple of others from memory, may be worth a shot first.

Problem is I need to find some one in Australia who can help which is pretty none existent

[Mark S]

I use a vdo scanner that accesses this stuff as well as key programming, I assume the snap on and Bosch scanners do also? just standard garage equipment.

have you tried opening the tb butterfly a tad on the screw? that's usually all that's needed, the iacv is just out of range for the air needed with cams

[JOHNDQ]

You'll be lucky on Bosch the KTS was a nightmare on the MG/Rover cars would never get coms with any systems apart from maybe for few seconds then throw you out again. If you can find any one with auto diagnose that's what we use on them always works really well

[redzed]

Thanks guys will give this a go

[MG ZS STE]

Just to update on my issue. I decided to go over everything I had removed/disturbed in fitting the thermostat. Removed the TB, there was a lot of oil which had set like tar after the butterfly. I had cleaned some off when I removed it the first time but neglected the hard to reach parts like between the pivot points of the butterfly. So got to these areas with a cotton bud soaked in white spirits, made short work of it. All the edges of the butterfly that make contact with the inner wall of the TB. Both mating surfaces of the TB and inlet manifold, then reassembled tightening the torx head screws in a diagonal order (opposite corners) whilst holding the TB firmly in place the whole process with my free hand. I also checked the operation of the IACV and gave it one last clean with cotton buds and white spirits for good measure before reconnecting everything and firing up. Initially it was a still a little lumpy. That's no improvement at all I thought. Then gave it a blip on the throttle and the revs didn't drop below 700/800 rpm as they were doing before. That is an improvement I thought. It was also idling smooth again. But this was cold and the issue was always hot idle, so gave it a run this morning and it's definitely not doing the stalling and cutting out anymore when approaching a give way situation. The revs are actually holding around 2000prpm for maybe a quarter second when you come off the gas then dropping normally to idle (@770rpm). The throttle cable is set correctly with just the right amount of slack to allow the butterfly to close properly when the throttle is disengaged. But all in all I'm much happier with the way it is now running.

[MG ZS STE]

Also, try unplugging your IACV when it's idling then Rev the engine. When the revs drop the engine should stall. Plug the IACV back in and start the engine again. This improved my idling.