2.5 PI Mk2 - 123 dizzy - which setting?

[iani]

My recently acquired 2.5 PI Mk2 saloon has a 123 dizzy fitted, the basic one with 16 selectable maps. The car is otherwise in standard spec', I don't think the current map (No 6) is quite right for the car, does anyone else have experience of this dizzy in a 125bhp car? what setting have you found works best?

[iani]

Checked the setting this morning, it was actually set on 3, this was giving a max advance of 17 degrees, I changed the setting to E, max advance of 26 degrees, the car is picking up from low RPM much more readily and no signs of pinking. Full power trial completed, now into the garage for more work on my GT6.

[Nick Jones]

Is that 26 degrees total @4000rpm including static?

If so, it’ll probably stand a bit more - 30 to 32 total @4000 typically.  How much idle advance do you have with that 26 deg?

Nick

[iani]

32 minutes ago, Nick Jones said:

Is that 26 degrees total @4000rpm including static?

If so, it’ll probably stand a bit more - 30 to 32 total @4000 typically.  How much idle advance do you have with that 26 deg?

Nick

14 idle, 26  is the max available, these units are a compromise as the maps can't be adjusted, the tune models are far better, I might change it out, just wanted to see if I could get more out of this one for now.

[glang]

Surely thats on top of static timing so curve E with 14º static gives a max of 40º reached at 4500rpm with 28º at 2000rpm. This is the 123 chart for 'most English cars' :

[Clive]

But I think you can still rotate the dizzy to change the idle or static timing? 

As Nick says, you want 30-32 degress max advnace, and the cars seem to like 12-14 degrees at idle, so teh old 17 degree setting was probably in the right ballpark. As Glang says, you are at 40 degrees of advance plus vacuum. On your current setting that could give a total  of 54 degrees, which is a lot! 

Did you check the idle setting with a strobe? I would be disconnecting the vac and seeing what the max advance is using a strobe.

The other possibility is a problem with the crank damper slipping and the timing marks having moved. 

[iani]

1 hour ago, Clive said:

But I think you can still rotate the dizzy to change the idle or static timing? 

As Nick says, you want 30-32 degress max advnace, and the cars seem to like 12-14 degrees at idle, so teh old 17 degree setting was probably in the right ballpark. As Glang says, you are at 40 degrees of advance plus vacuum. On your current setting that could give a total  of 54 degrees, which is a lot! 

Did you check the idle setting with a strobe? I would be disconnecting the vac and seeing what the max advance is using a strobe.

The other possibility is a problem with the crank damper slipping and the timing marks having moved. 

Timing with vac plugged is 14, that is set by the 123, this is a 125BHP Mk2, idle set at TDC as standard and normally no vac advance I believe.

[glang]

The way I read the 123 instructions is to install the unit with the engine at its correct static timing position and then the 123 will add advance according to revs. The discrepancy we have seems to be whether that static timing should be TDC or 12 - 14º? Going by the improvement you have found I would say the static timing should be the latter and then curve 3 will function much better...

[iani]

1 hour ago, glang said:

The way I read the 123 instructions is to install the unit with the engine at its correct static timing position and then the 123 will add advance according to revs. The discrepancy we have seems to be whether that static timing should be TDC or 12 - 14º? Going by the improvement you have found I would say the static timing should be the latter and then curve 3 will function much better...

I'll try various settings and see how it goes, I much prefer the Tune+ version in my GT6, I expect I will swap this one out when funds allow

[iani]

I have now fitted a Tune+ unit and after a few tweaks the car is now running beautifully, pulling strongly throughout the range without any stumbles, the map is:

500 0.0

1000 – 10

1600 – 14.6

1900 – 15

2000 – 17

2300 – 19

2900 – 21.2

4000 – 26

[Nick Jones]

Do those numbers actually translate directly to crankshaft degrees or do you have some timing lead to add? Seems quite conservative at the top end - should be able to take at least 30?

Would also suggest t-ing off the MU vac signal line and making use of the third dimension. No road car should be without it….

[iani]

40 minutes ago, Nick Jones said:

Do those numbers actually translate directly to crankshaft degrees or do you have some timing lead to add? Seems quite conservative at the top end - should be able to take at least 30?

Would also suggest t-ing off the MU vac signal line and making use of the third dimension. No road car should be without it….

I have the vac advance mod Nick, no idea what figures to use for it. Static timing is at TDC, nothing to be added. I will raise upper figure and see if it improves further. My CR TR6 owning passenger was very impressed with how my car performs 

[Nick Jones]

Is your PI the earlier “132” or later “125”. Latter is an identical engine to the CR TR6.

I can post the 3D ignition map (when I’m back at my computer) from my now departed 132Mk2, though as that was converted to single throttle body the vacuum figures won’t be directly comparable.

[iani]

10 minutes ago, Nick Jones said:

Is your PI the earlier “132” or later “125”. Latter is an identical engine to the CR TR6.

I can post the 3D ignition map (when I’m back at my computer) from my now departed 132Mk2, though as that was converted to single throttle body the vacuum figures won’t be directly comparable.

It's the 125 version Nick, I raised the 4k figure to 30 degrees today and 27 @ 2600, didn't notice much difference to be honest, it seems to be running very well now.

[glang]

Out of interest did you install the unit with the static advance already in place as the instructions say?

[iani]

Just now, glang said:

Out of interest did you install the unit with the static advance already in place as the instructions say?

static advance for 125bhp car is 0 degrees, installed at TDC.

 

[glang]

Right I see, theres seems to be some confusion about what the static timing should be for each model but anyway its minimal so not going to make much difference...