Normal timing behaviour on a T25

[madoc]

Changed my alternator belt (pretty shagged) and oil.
Flushed with success, I'd thought I'd check the timing

Pulling the vaccum advance pipe off the dizzy, as instructed, stalls the engine. I increase the tickover until it doesn't.
I need to adjust the dizzy a bit until my strobe gets it on the single timing mark at around 850rpm. All well and good.

Putting the vacc advance pipe on immediately pushes the revs up. Is that normal ?
I can re-adjust the idle down, which I do.

My strobe reckons the I am topping out around 30 degrees at advance, with the vacc advance on and around 3500 revs (can just about see rev counter in cab - maybe I should connect my meter to the coil).

Is this normal ?
Should the vacc pipe have that much effect ?

[kevtherev]

what engine????

[madoc]

1.9DG

I got the numbers wrong. Might between 30 and 40 degrees at speed, with everything connected.
I reckon the vacc pipe (when idle) adds about 15/20 degrees (my strobe has a twiddly knob to do this) and the dizzy seems to advance by itself around the same.

[madoc]

Ok.
Well.I just read on another forum that I can time to 8 degrees BTDC with the vaccum on, so that's what I'll do and then check what the advance runs to when revving.

I know it's advancing
It's just the vacc advance has me confused and why I am timing without it and why it immediately advances the engine when re-connected.

[kevtherev]

My strobe reckons the I am topping out around 30 degrees at advance, with the vacc advance on and around 3500 revs (can just about see rev counter in cab - maybe I should connect my meter to the coil).

Is this normal ?
Should the vacc pipe have that much effect ?

at full throttle there is little or no vacuum.
What you see is mainly mechanical advance at 3500
vacuum advance is for economy in the main.

chart shows advance without vacuum

[madoc]

Ok.

1. Pull off vaccum pipe
   
2. Spin engine up to 4k revs
   
3. Check I get about 30 degrees advance.

Thanks.

[HarryMann]

Well, yes, but put another way, from that graph, check you get an 'additional' 18 or 20 degrees

I wouldn't go changing the static timing at all unless you are sure it is out...

Why do you think something is wrong, or just checking...

The vac adv. (could be vac ret. too, not sure on DGs) can quite easily 15 degrees

[Max Vacuum advance is quoted as 12~16 degrees for both DG and DJ (see below) ]

https://club8090.co.uk/wiki/Pe ... nce_curves

Yes revs going up is normal, as heavily retarded without vac advance connected, so 'smooth but chugging', 'faster and more ruffled' with lots of idle advance ?