v8 3.9 lpg ignition timing

bodger · Post by **bodger** » Sat Jul 09, 2011 11:31 am

Further to this .. maybe a silly question but i have always wondered ..

does it matter where number 1 is as far as where the rotor arm ends up

as you just move the leads around the cap to match it ???

?

DaveEFI · Post by **DaveEFI** » Sat Jul 09, 2011 11:35 am

bodger wrote:Further to this .. maybe a silly question but i have always wondered ..

does it matter where number 1 is as far as where the rotor arm ends up

as you just move the leads around the cap to match it ???

?

In theory it makes no difference. Although dizzys with an amp on the outside might want that in the best airflow.

It's a bit like the crankshaft being 360 degrees out of phase with the camshaft.

bodger · Post by **bodger** » Sat Jul 09, 2011 11:46 am

Thankyou Dave

...
i wasn't thinking of moving the dizzy as such

more when the gear is engaged at the wrong place and the rotor arm ends up pointing in the wrong direction when no1 is at TDC ..

ie: does one one always have to be at the same place on the cap ???

instead of pulling the dizzy and repositioning it just put no1 one lead where the rotor arm is ?

DaveEFI · Post by **DaveEFI** » Sat Jul 09, 2011 12:34 pm

It *might* have an implication as regards crossfiring as the leads will no longer be laid out as per the spec - if they ever were.

But nothing else I'm aware of.

bodger · Post by **bodger** » Sat Jul 09, 2011 1:04 pm

lol

the only reason i ask is i tried it on a mini that i had years ago and it didn't work ...i had a right old row with the bloke who owned it who was going on about dwell angles and the like ... to this day i'm sure it was somthing else that stopped it working ..

jan_rrc39v8 · Post by **jan_rrc39v8** » Wed Feb 01, 2012 3:16 pm

softdash3.9 wrote:If you clean up the pulley there should be timing marks.

I run my RR Classic 3.9 on 16 deg BTDC base timing for LPG with vac disconnected.

16 deg is beyond the std timing @ 12 deg, I use a paint marker to mark TDC and the timing marks

This 16degr setting is to be set at idle speed, right? 800-1000rpm?
got to dig out my strobelight. it's been a long time since i used it.

softdash3.9 · Post by **softdash3.9** » Wed Feb 01, 2012 9:42 pm

jan_rrc39v8 wrote:
softdash3.9 wrote:If you clean up the pulley there should be timing marks.

I run my RR Classic 3.9 on 16 deg BTDC base timing for LPG with vac disconnected.

16 deg is beyond the std timing @ 12 deg, I use a paint marker to mark TDC and the timing marks
This 16degr setting is to be set at idle speed, right? 800-1000rpm?
got to dig out my strobelight. it's been a long time since i used it.

Yes

jan_rrc39v8 · Post by **jan_rrc39v8** » Mon Feb 06, 2012 1:16 pm

I adjusted the timing from 12 to approx 16 degr. (no visible scale! but i just extrapolated)
Also took the chance to inspect the rotor and distributor cap, both were in good condition, the wires looked fine and newish as well so i left them as is. And while i was in the general area i installed a new thermostat.
The temp gauge now reads 1/3rd from cold, a bit higher then before. (< is that normal?)

I now have warm feet in the car, even at -17.4C as recorded over here last weekend!

On LPG the car seems to respond slightly snappier to throttle changes. (but-dyno!) The switch-over point from petrol to LPG is now a bit sooner/earlier. maybe because the engine is warming up faster?

Nice improvements! Well worth fidling in the cold.

jan_rrc39v8 · Post by **jan_rrc39v8** » Sun Feb 12, 2012 6:51 pm

i'm kind of confused right now. When i go flat out WOT in 3rd the engine seems to 'rumble' from 3500rpm on up. petrol(RON98) or LPG, it didn't make a difference, it just did not feel right.
The timing was set on the E (after | | | | | 0 | | | | |bEfore)
So i was wondering what one increment on the crankpulley scale actually realy represents... is it 2degr? 3 degr? 5 degr? There is no indication!
I started to take out timing to just after the 3rd mark before-TDC. If one mark = 5 degr that should give me 16 degr.

I also tested the vac advance with the engine running, stobe on the pulley and applying sucktion on the hose. timing did move so the advance mechanism works.

Then i went for a testdrive. result: much less imput needed to get the engine to rev. ??? Almost all WOT rumble is gone. ???
I can only conclude that timing was set way to advanced.

Can anyone confirm that 1 increment = 5 degr?

jan_rrc39v8 · Post by **jan_rrc39v8** » Sun Feb 26, 2012 6:50 pm

update: i couldn't get the engine to behave like it should so i took the dizzy out and disassembled it.
- it had been tampered with before.
- one of the springs that's supposed to eb attached to the bobweights was lose...
- the bobweight mechanism was not exactly clean so i cleaned it using WD4o and some presurised air. I reassembled everything after lubricating the mechanism with some ATF.
- reluctor gap was to big, so i adjusted it to spec
- i tested the advance mechanism again and... i have to conclude that it is leaking.

- reinstalled the dizzy and timed it to 6degr BTDC (@850rpm/no vac)
(i also cleaned the crankpulley, now i have a visual on the complete scale, 1 increment = 3 degr)

It runs smooth and starts OK, i think i made a little progress but i will have to source a new vac advance actuator to get to where i want the engine to be: optimal stock condition.

DaveEFI · Post by **DaveEFI** » Sun Feb 26, 2012 11:47 pm

If I remember my DLM dizzy correctly, one of the springs was loose at rest.
Presumably to give a 'knee' to the advance curve?

jan_rrc39v8 · Post by **jan_rrc39v8** » Mon Feb 27, 2012 8:50 am

Do you mean lose as in not having any tension?
or do you mean lose as in dangling with one end free...?

DaveEFI · Post by **DaveEFI** » Mon Feb 27, 2012 11:09 am

jan_rrc39v8 wrote:Do you mean lose as in not having any tension?
or do you mean lose as in dangling with one end free...?

Not dangling free, no. Wouldn't be much point in that.

jan_rrc39v8 · Post by **jan_rrc39v8** » Sun Mar 04, 2012 6:40 pm

new advance actuator installed, timing set at 13degr BTDC (@850/no vac)
i'm calling it good.