Bore Wash - at what AFR is it likely to become a danger....?

Hi - I'm currently in the process of attempting to get my idle stable / around the right AFRs - right now I'm struggling to get above 11.5 to 12.5 AFR at 950 rpm - I do have DH22 WRC cams and largish 1000cc (XSpurt) injectors - but I'm finding to get above those AFRs requires me to cut a huge amount of fuel from the base fuel table (lets say base a fuel cell value of 35 gives me 12 ish AFR and 10ish gives me 13.5 AFR) that I'm not wholly comfortable.

I'm sure I can work this issue to a more acceptable AFR level but in the mean time can anyone comment on the AFR level at which I should become concerned about bore-wash?

While bore washing may be a consideration, I'd expect the more immediate concern of a very rich idle will end up being constantly fouled spark plugs. Even with an aggressive cam I'd be targeting somewhere around 13.0-13.5:1. My own experience is that if you're consistently richer than about 12.5:1 you're likely to face problems.

The XSpurt 1000 should give you no trouble achieving a nice stable idle with a reasonable AFR. What ECU are you tuning?

Hi and thanks for getting back to me.

It's an Autronic SM4 (that's actually due to be swapped out shortly but ideally I still need to get to to the root cause as I'd like to re-commission this ECU into a another project) - and to be honest its displaying some rather odd behavior. Select injectors are the ID1000 @ 300 Kpa and I'm set to 300 Kpa fuel pressure (with vaccum line disconnected) - These injectors are new and replace the previous 740 cc Tomei units.

i) I went back this morning and spent a little time looking re-working cold startup enfrichement and base fuel settings - after bringing the engine up to operating temp (80 deg C) get the idle relatively stable and at around 14.5 AFR - I wasn't initially concerned that yesterdays over richness was now 'solved' as I added an additional column into Warm Up enrichment at 60 deg C and set that as 1x (along with 80 deg C) the thinking being that previously the table went from 30 deg to 80 deg so potentially it was still adding enrichment when the fans cut in and the temp dropped back below 80 deg.

ii) Drove the car around 10 metres and the 10 metres back again - noted AFRs had now dropped 2 points to around 12.5.

iii) Switched engine off for 5 minutes - started up again - still at 12.5

iv) Went out for a quick drive to check the rest of the map at at least light loads was good - it was fine.

v) Returned to base - noted idle AFRs had dropped another point and we were now back to around the 11.5 mark.

At idle logged injector pulse widths are at around 0.85 -0.9 ms for 14.5 AFR @ 84 degC then later 0.78 - 0.82 @ 86 degC - so not a huge difference...

I should add - there is one more thing that's disturbing - I'm seeing fueling occur even in overrun conditions with a 0 ms mean injector opening time - the attached log demonstrates this and the change from a rich idle with no adjustment in base fuel as described above.

Almost as if fuel is entering the engine by some other means or the ECU is adding fuel but not recording it.