Datsun Roadster Forum-311s.org

This thread probably won't see much action considering that adoption is still growing. However I think it might be handy, especially once more Roadsters have theses.

I've been have fun experimenting with a few different configurations. In conjunction with U20 B-cam, Solexs and ~10:1 compression
This one was with 16d of static advance.

This is my current curve. 0 static, 100% programed advance.
It's working very well, great power, response and no pinging (at sea level, 75ish air temps, 91oct).

The only downside I see with an advanced ignition system is you still have to factor in the two chains and gear slop. I spent a bunch of time perfecting the mechanical curve on mine with a Pertronix but it never performed at the level of the crank fired ignition setup I an currently using.

spyder wrote:The only downside I see with an advanced ignition system is you still have to factor in the two chains and gear slop. I spent a bunch of time perfecting the mechanical curve on mine with a Pertronix but it never performed at the level of the crank fired ignition setup I an currently using.

As I had posted, this was my only concern as well... some timing scatter simply due to the fact that there can be some slop in gears and chains. Probably not a big deal at all on the vast majority of engines, a bit more important when your running on the edge with high compression etc. The 123 appears far easier to install and program in general than a crank fired systemy. Without a machinist, most would not be able to do the crank fired system by themselves, where as the 123 is a shade tree mechanic install. It's also very cool that you don't need to pack around a lap top... sure wish I could play with the timing on my megajolt so easily.

Roadster weather is apon us here in Santa Cruz CA. As such I spent the day testing and tuning a new summer curve.

Car is loving it!

fun run time!
We can put your new ignition map to the test

I think you have too much advance......32-36 degrees is what my gut tells me. Maybe Alvin can ask what the dyno run setting they used.

Another method would be a CPI from SDS EFI.
Price for basic 4 cylinder automotive, single coil unit kit is $700US
Picture with the optional Knock sensor.

Phil, I hear you on the max timing issue. But just the other day I was reading through the Bob Sharp manual and noted they were running up to something near 50 degrees total! They said a Datsun U20 likes lots of advance. I don't think I dare run anything like that, especially on pump gas (92 here). I do wish the megajolt had provision for a knock sensor (or maybe they do?). I'll have to post my current curve when the car is up and running again.

I think Brian has a max of around 47. The stock dizzy hits max (36) by like 3500rpm and I'm right about the same. The difference is I can add a little more high up.

The 123ignition uses F1 style spark balancing to individually optimize spark timing at higher rpms. The only naysayers I have run into, in a variety of forums, come from folks running crankfire systems.
Michael

re max timing, I don't know U-20's, but the Z L6 usually runs 33-35 degrees max mechanical advance - plus 12-18 vacuum advance - which does add up to 50+ (when you are off throttle, coasting down a hill, etc).

mlwebb wrote: ↑Tue Apr 03, 2018 9:38 pm The 123ignition uses F1 style spark balancing to individually optimize spark timing at higher rpms. The only naysayers I have run into, in a variety of forums, come from folks running crankfire systems.
Michael

Please elaborate on what F1 style spark balancing and how F1 applies to our cars.
Michael

AidanDawn2000 wrote: ↑Tue Apr 03, 2018 9:14 pm I think Brian has a max of around 47. The stock dizzy hits max (36) by like 3500rpm and I'm right about the same. The difference is I can add a little more high up.

This is a knock sensor tuned ignition of a U20. On 98 Octane, B Cam. Tuned for Minimum timing for best torque up to 7000 rpm. In other words, advance til knock, then work back to least amount of advance that gives max torque. Table is compressed on X-axis. Normal RPM cell progression is 125 rpm/cell.

U20 likes advance in mid range rpm and mid throttle. It's important to pull the advance back with wide open throttle however.

This engine does not ping with this timing setup on 92 octane.
Michael

The knock sensor feedback is a neat tool as it let's you know what's too much so you can work back from there, just as you described. In the past we have not had much discussion on ignition timing work because there has been no way to adjust it at specific rpms... no more with the 123 or crank fired systems like mine. So noted, every engine is different, as is the gas we have available and where. What works well for my modified engine on Washington state pump gas and air density, temps etc may not be optimal for others, but it does give us some general parameters to work from. I do not have any vac advance built into my curve but it is a feature that is set up... right now it's all mechanical like the solex dizzy was.

I appreciate the experiments being done with those with 123 or crank fired systems. We should continue to share maps and engine configurations. When my car is up and running and I'm satisfied with the cam timing and cam, I'll start playing with the timing some again. Before then, I should be able to post my current curve when the engine is running again. Thanks!

A knock sensor really is imperative when programming an electronic ignition. It can detect pre-ignition well before its bad enough for the driver to hear the ping. Max brake torque tuning allows you to find the minimum spark advance for max torque, therefore allowing the greatest leeway in the case of lower quality fuel and other changes that might predispose an engine to pre-ignition. Unfortunately my EFI computer does not have a knock-sensor loop and the timing was done on the dyno on 98 RON petrol. I have however put 91 RON in with no problems, the benefit of having room to move. Please see this link to clarify the compatibility of Australian/Euro fuel octane rating with USA octane as the scales are different, so our numbers don't compare. My understanding is our 95 RON fuel is equivalent to your 91. https://www.etuners.gr/fuel/

The engine I inherited when I bought the car has a heavily shaved head (113.5mm) and therefore has h20 dished pistons. Compression won't be the greatest which may be why it likes a bit of 'extra' advance. Ignition is crank sensed with full 3D control by the ECU. It has a B-cam and complete EFI of course. Approx 145 FWHP (Real world vs the old school 150hp which dyno's at about 135hp according to Lou). So it is not a special engine. That said a Lou Mondello stroker will be sitting in it's place within 12 months

I agree Greg, we should share our curves etc as there is not a lot of data lying around about these kinds of specifics for the U20. They tend to like a little more advance than the factory curve especially in the mid range, light to mid throttle, but I would not go there unless I could pull advance out on WOT, so if the ignition system cannot adjust according to RPM AND throttle position, I'd be more conservative. It appears the factory solex mechanical curve included a compromise between optimal advance and pinging under load which seems to occur on these motors especially at lower rpm. The max advance on that curve is 36deg or 16deg above base idle timing of 20deg (solex setup).

EFI offers numerous advantages over carbs, however the Solex are a very good carburettor. So for fuel metering, it seems a well tuned Solex would be rather comparative. The largest benefit of EFI is probably that no chokes are required. That said I would go for 40mm throttle bodies, not the 45's that came with my engine as they are a little too big, especially given the 50mm solexes run a choke around 41mm. Anyway, getting to the point of my blabbering, the full ignition control seemed to give the most benefit around midrange torque and throttle response in this area. Before I had the ignition tuned as above, a makesift curve that reflected the factory curve was programmed. The benefits were noted after it was retuned and they may also be influenced by the lack of points ignition, like the full transistor Hitachi's that were a factory option. Electronic ignition offers better, longer spark dwell and a much higher amperage spark.

It will be interesting, in time, to see what the stroker likes.

Michael

Gregs672000 wrote: ↑Tue Apr 03, 2018 6:57 pm Phil, I hear you on the max timing issue. But just the other day I was reading through the Bob Sharp manual and noted they were running up to something near 50 degrees total! They said a Datsun U20 likes lots of advance. I don't think I dare run anything like that, especially on pump gas (92 here). I do wish the megajolt had provision for a knock sensor (or maybe they do?). I'll have to post my current curve when the car is up and running again.

It'd be interesting to know what fuel they used as that may have necessitated more advance, much like the 85 tends to need more advance as I believe it has a slower flame front.