What are your actual afr's at that rpm with the ac off?

Have you tried to reduce your excessive timing yet?

Have you not noticed that your Ignition timing becomes erratic once the fault starts?

You are aware that at Idle the pfc locks the timing to 18 degrees?

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Hi Ross,

The AFRs dont really change between AC on and off - they sit steady at about 13 (when cold) to 14.7 (when warm).

Yep - I pulled it right back with no effect

Yep noticed the timing but it matches up with my ignition table when at that RPM eg the 19 degrees is the correct angle for 1066rpm @ 3079 load.

I wasnt aware of that

im starting to question if this could be a pre-existing electrical issue like maybe the main relay or one of the other relays has given up the ghost and when the aircons on it puts too much stress on the main relay and it cant hold the load - maybe something down those lines like a relay thats still working but only just and cant handle the full load it should?

its a doosey of a problem isnt it

Thanks
Rich

`Run an extra earth from the block (or alternator bracket) directly to the battery, there are known earthing issues in the GC chassis.

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will do mate - thanks again - let you know how i go

Your theory about high compression & more ignition advance is incorrect btw, I was meaning to mention it earlier.

As the compression ratio is increased, so is the speed of combustion. All other things being equal, a high-compression cylinder requires less advance to deliver optimal results - the opposite of your current thinking.

Why else do you think the timing is retarded as boost increases?
(Ignoring intake charge temperatures) Adding boost raises the dynamic pressure in the cylinders way above the static C/R & hence for the combustion process to remain stable we need to ignite the fuel mix later in the compression cycle (retarded).

Simply put, higher cylinder pressure requires LESS timing not more - certainly not 60 degrees BTDC!

The STI 99-00 ej207 is 9.0:1

Liberty TT (98-03) motors are as follows:
BH5A, EJ206 9.0, EJ208 8.5
BH5B, EJ206 9.0, EJ208 8.5
BH5C, EJ206 9.0, EJ208 9.0
BH5D, EJ206 9.0, EJ208 9.0

Ej206 is used with the Auto, Ej208 is the manual trans variant.

There's no way that translates into a timing difference of 20 degrees load for load between any of them off boost.

How much manifold vacuum do you see with the a/c on?

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Hey Rossco,
I was about to embark this conversion on the foz but when i checked out the coil on plugs im missing the 3 pin plugs. How did you source them or did they come with your COP's?
Tried to find a part number for them but no luck

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MY00 GT Forester with STi goodies

Hi Muggz!

Mine came with the sub harnesses are Proto-rob had used them in his Lib. You could try JWS for the ignition loom off any 01 -> wrx.

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Cheers Rossco! That looks like the easier option

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MY00 GT Forester with STi goodies

hi ross,

Your %100 right there - not sure what i was thinking when i wrote that, must have had a brain fart! think i was getting confused with "higher compression means same power with less boost". Im about %90 sure mine is the 9:1 (think i checked the engine stamp a few years back). Ive since dropped the advanced areas to 45-50 permanently but left the rest of my maps the same as they run smooth as with bugger-all knock.

If it stops raining for a few minutes this evening ill try the extra ground and let you know the results

thanks
Rich

Hi Mate,

Ok now im just confused... last night i put a temporary link (4 medium sized speaker wires is all i could get a hold of) between the battery and the bolt on the alternator - drove around for about 5 mins then about an hour later for another 45 or so mins - had the aircon and lights and demister on pretty much the entire time and it didnt buck once - i was convinced it was fixed but too many times ive jumped to conclusions so i just waited til this morning. This morning jumped in my car on the way to work, drove about 100m and decided to test it again and as soon as i wacked on the aircon, it started bucking again - just as usual! At the moment im not too convinced of anything but tomorrow ill go to Jaycar and get some gold terminals and some 2 guage wire and mount a second ground to the engine and see how we go - ill keep you posted.

Thanks
Rich