123 ignition for Datsun L6 on my L28

Huw

Club Member
As an aside, it’s not just the radio that gets whacked by RF interference. The old EFI ECU in the s130 was and is quite susceptible to RF interference, this also includes the distributor module. Which is why I continue to run BPRES plugs. Question is tho, is the 123 susceptible to RF interference? I doubt it but it’s worth an experiment maybe?
 

AliK

Vehicle Dating Officer
Staff member
Club Member
As an aside, it’s not just the radio that gets whacked by RF interference. The old EFI ECU in the s130 was and is quite susceptible to RF interference, this also includes the distributor module. Which is why I continue to run BPRES plugs. Question is tho, is the 123 susceptible to RF interference? I doubt it but it’s worth an experiment maybe?
The moral of the story is, don’t drive too close to someone not running the RFI reducing one’s or your 280zx may end up misfiring :p
 
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Faster Behr

Club Member
One small suggestion - change one thing at a time. I did the EFi conversion and the 123 distributor all at once and was playing whackamole with issues. The primary problem was that I could not get it to start. The only thing that cured it? Changing to non-resistor NGK plugs.
 

AliK

Vehicle Dating Officer
Staff member
Club Member
One small suggestion - change one thing at a time. I did the EFi conversion and the 123 distributor all at once and was playing whackamole with issues. The primary problem was that I could not get it to start. The only thing that cured it? Changing to non-resistor NGK plugs.
That is super fascinating - I’m going to HAVE to experiment now with a set of non-resistive ones.

In case useful to anyone, this is a good chart ….

CE023FF5-69FC-4847-A904-ACFE883ED7C2.jpeg
 

240L31

Club Member
So I installed the distributor today. For some reason it idles poorly, it needs much more advance than it used to have with the ZX distributor. I was surprised that the shiny link of the chain was above number 2, not 1, could this be my issue? Lobe 1+2 were pointing upwards, the damper mark lined up at zero. So I assumed I'm at TDC.

With my timing light I could see quite some timing fluctuation at idle, is this due to the sloppy fit of the distributor drive?

BTW where can I find the online tune button in the app? Mine doesn't show any, I have to shut down the engine in order to write changes.
 
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AliK

Vehicle Dating Officer
Staff member
Club Member
Interesting, do you think the ZX dizzy had lots more vac advance at idle? I know mine did.
But that sloppy fit is an absolute pet hate of mine on this bit of kit.


Yes you do have to shut down the engine to save changes - it’s probably to do with the EEPROM not being able to be written to while the microprocessor is running.

Now then, on my app it’s quite prominent.

90C537A1-371E-4903-AFD0-0A00F89EB3A2.jpeg
 

240L31

Club Member
A few notes from my 123 installation:

- spark timing jumps a bit with cold engine (spark balancing, it's a feature, not a bug)
- my distributor is pretty close to the header, I'll add some heat shielding
- even the Bosch distributor cap doesn't sit really firm on the distributor body (the 280zx one was connected rock solid)
- I spent way too much time getting the engine to TDC as accurate as possible during setup. This is not required at all since you'll calibrate the dizzy by twisting later on anyways.
- my stock tach works (8/71 current loop, modified wiring to fit the 280zx distributor)
- idle is much smoother now
- test drive to follow in March.
 
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240L31

Club Member
I actually like the 123/Tune+. I made over 300hp on an engine dyno with a stroker L28 (modified cam, pistons & head). Works for me so far...

@alienpoker Would you mind sharing your centrifugal+vacuum advance curves for the stroker engine? Just as a comparison to my current settings. I'll head to the dyno in spring, I'd like to have a few curves to compare against each other.

I just looked up the stock advance curves 1972 L24 vs. 1979 L28, quite interesting:

1972
Initial advance 17 @ 650 rpm
Centrifugal advance 18 @ 2400 rpm
Total advance 35 @ 2400 rpm

Vacuum advance 0 @ 13 kPa
Vacuum advance 9 @ 27 kPa
Vacuum advance 12 @ 33 kPa
Vacuum advance 15 @ 44 kPa

1979
Initial advance 10 @ 800 rpm
Centrifugal advance 17 @ 2500 rpm
Total advance 27 @ 2500 rpm

Vacuum advance 0 @ 20 kPa
Vacuum advance 18 @ 40 kPa

Note how early full advance kicks in - way earlier than the often mentioned 3000-3500rpm .
 
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240L31

Club Member
This will be my starting point. I think it would great if others would share their settings together with engine specs as well.

3.1L, SU carbs, Delta cam, 210hp/315Nm at the dyno last time.
IMG_20230124_214004.jpg
 

atomman

Club Member
I can post mine up later for you Tim, unless I have already sent it over to you ?

Can I ask why you have a flat spot on the curve ? , I see a lot of American Z owners of 123's with a little bump or flat spot in there curve, they say as an anti stall but I have never needed to do this ,

What have you hooked up the MAP signal to ?

I spent ages sorting out a feed on mine and even a little tank with foam to take out the pulses and just took it off in the end as it wasn't worth it
 

240L31

Club Member
I can post mine up later for you Tim, unless I have already sent it over to you ?

Can I ask why you have a flat spot on the curve ? , I see a lot of American Z owners of 123's with a little bump or flat spot in there curve, they say as an anti stall but I have never needed to do this ,

What have you hooked up the MAP signal to ?

I spent ages sorting out a feed on mine and even a little tank with foam to take out the pulses and just took it off in the end as it wasn't worth it

It is just that I found my car idles best at 20deg BTDC. Idle speed varies from 800-1000 rpm depending on engine temperature (cold start vs. hot) and I just wanted it to be always 20deg. This might get changed as soon as I have more time for tuning.

MAP is hooked to the ported vacuum of the SUs. In my opinion vacuum advance is quite important for drivability, I wouldn't ditch it. The map curve is based on the stock '72 curve but with 3deg shaved off.
 

atomman

Club Member
Here's mine , only a degree every 1000rpm after 'all in' @3000rpm which is pretty safe ,

L28 bored out 1mm over , N42 head ported and polished, Camshaft is basically the same as sports option Rally specification (270-280 duration IIRC). Weber 40 DOCE's 34 or 36 chokes, would have to check though, I wanted it make nice torque not so have kept the choke on the small side, (cam makes power from 4k to 6500ish) pretty light flywheel etc etc

but think i may have tweaked it a bit since then , will have to check

my car idles about 850 rpm at 14:5-1 on the lambda (nearly stoichiometric but not quite)

Have you tried looking at your mixture ? maybe why you need 20 degree at idle ?
 

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240L31

Club Member
I think it's just the cam, mixture is similar to yours pretty much spot on Lambda 1.
I don't think there's any advantage by adding more timing at higher RPMs, did you test this on a dyno? In theory, less timing at higher RPM is required as volumetric efficiency increases.
 
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