Ignition Timing Mechanical Advance

[jonbill]

So speaking of vacuum advance and load sensing adjustments to the timing...

Aren't some of you guys are running aftermarket ignition controllers or full engine management systems? Are you using TPS or MAP instead of vacuum?

[mention=32052]AK260[/mention] , [mention=32065]jonbill[/mention] , [mention=19298]Zed Head[/mention]

Yes, mine is a Speeduino EMS controlling fuel and ignition. Both spark and fuel maps are using the TPS for load because I have ITBs and I read that the MAP signal is unreliable at low engine speed on one cylinder runner. I might try it one day.

 

Idle is controlled by spark timing. I set 1100rpm as the target speed and set it to advance ignition if the speed falls below and retard ignition if the speed exceeds.

so when cold it has maybe 18 deg advanced at idle and when warmed up I think it drops to 10 or 12.

 

[AK260]

The 123 ignition I use, has a MAP sensor connected to the same place on the intake manifold as the vac advance used by the stock Datsun distributors.

I’m currently running zero vac advance as my needlework is ongoing and while she holds a perfect 11.5-12 on the AFR all the way to the redline, she is running very rich on the cruise at around 12.8-14 (below 4K rpm) and 15 on the overrun. But once I get the next set of needles in and adjusted, I’m hoping for a leaner cruise of around 15; and 17-18 on the overrun, at which point I will be looking at about 7 degrees of vac advance max.

Does that help at all?

[Captain Obvious]

Thanks for the input guys.

Zed, I've used my OBDII scanner on a number of newer vehicles and the timing numbers are way up there. Like fifty degrees BTDC. That's one of the reasons I started this whole discussion. I was wondering why a 2006  Hyundai can run that much advance, but our Datsuns top out at under thirty.

jonbill, I heard the same thing about trying to use the vacuum signal from just one runner. I saw some pics of a "balance tube" sort of contraption to combat that. I don't remember if I saw that at Speeduino, or at Megasquirt (or jolt). In any event, I understand. Neat trick with the idle speed. I didn't know that was a thing.

AK260, Yes, that helps. Thank you. So you're running a MAP sensor... But if you have it connected to the original stock source, it's a ported vacuum. Can the 123 deal with that? And what MAP sensor are you running?

 

Oh, and I added fixed dwell to my device today. Seems to work as intended.

[Zed Head]

10 initial + 18 vacuum + 20 centripetal = 48.  34 is just initial + centripetal.  High PRM cruise could get both vacuum and centripetal max'ed out maybe.  What's also interesting is that the PCM/ECM/computer "learns" and holds on to variable to optimize certain things.  The O2 sensor feedback probably comes in to play along with EGR.

Anyway,  finding 50 degrees on a Hyundai is one of those things you probably would never know without the scanner.  My point.  Once you see it then you can try to figure out why the automotive engineers made it happen.

Edited April 19, 2020 by Zed Head
max'ed

[Captain Obvious]

23 hours ago, 240260280 said:

My solution was to run the choke cable to where the (removed) vac advance was and use this to retard the timing to 5 at start then move the choke lever to off to bring the advance to 20 after it started.

Cool mod.   What's old is new again.

http://modelabasics.com/Ignition.htm

 

[Captain Obvious]

@jonbill, Did you put the Speeduino together as a kit, or buy something turn-key?

@AK260 I was looking through some of the speeduino and megasquirt documentation and saw they often use the MPX4250A sensor for MAP. Is that what you used?

Nevermind... It's probably built into the 123 device. You didn't put it in.

 

Edited April 21, 2020 by Captain Obvious
I'm distracted

[jonbill]

[mention=32065]jonbill[/mention], Did you put the Speeduino together as a kit, or buy something turn-key?
[mention=32052]AK260[/mention] I was looking through some of the speeduino and megasquirt documentation and saw they often use the MPX4250A sensor for MAP. Is that what you used?
Nevermind... It's probably built into the 123 device. You didn't put it in.
 

I bought it as a kit and assembled it myself. I sourced sensors, injectors, trigger wheel, coil pack and igniter separately. And tuned it myself too (mainly tuner studio autotune did it actually)
FWIW including buying ITBs, I reckon total cost was about £2000.

[AK260]

10 initial + 18 vacuum + 20 centripetal = 48.  34 is just initial + centripetal.  High PRM cruise could get both vacuum and centripetal max'ed out maybe.  What's also interesting is that the PCM/ECM/computer "learns" and holds on to variable to optimize certain things.  The O2 sensor feedback probably comes in to play along with EGR.
Anyway,  finding 50 degrees on a Hyundai is one of those things you probably would never know without the scanner.  My point.  Once you see it then you can try to figure out why the automotive engineers made it happen.

From what I understand, modern cars are able to run super lean on the cruise and can get into AFRs of 18-20ish for fuel economy. Some are able to tolerate 60+ degrees of timing while cruising! To an L series owner that seems horrific but to modern head designs, coupled with knock /EGT / O2 / MAF / Air temp sensors and super fast ECUs etc it’s just BAU.

[mention=32065]
[mention=32052]AK260[/mention] I was looking through some of the speeduino and megasquirt documentation and saw they often use the MPX4250A sensor for MAP. Is that what you used?
Nevermind... It's probably built into the 123 device. You didn't put it in.
 

No siree, I most certainly didn’t. The interesting thing is, having looked a little under the hood of the device and the app, it would be SUPER simple for them to add a data logging function to the app and if it took a signal from an O2 sensor (which is merely a 0-5v signal), it could provide a proper ECU-esque solution off a dizzy with 3D spark tables. In fact they use the GPS on the phone to get speed so they could just store the data and overlay on google maps for track days etc. But I guess they want to keep it simple for obvious reasons. :(

I know this is off topic but out of interest, is anyone aware of a successful aftermarket knock sensor solution for the L series!? I know the 280zx had the first of such things but I’d love to get one on mine.

JB started to build one but the filtering / testing was too hard without potentially damaging the engine. You need to detect the exact frequencies involved when knock happens - who wants to volunteer their engine for some Fast Fourier Analysis!? ;)

[240260280]

7 hours ago, AK260 said:

 

From what I understand, modern cars are able to run super lean on the cruise and can get into AFRs of 18-20ish for fuel economy. Some are able to tolerate 60+ degrees of timing while cruising!

 

My Honda hits a/f ratios of ~ 25:1 but advance is only around 31degrees then.

 

[Captain Obvious]

Well that, and it's a shoe.  

[Captain Obvious]

7 hours ago, jonbill said:

I bought it as a kit and assembled it myself.

Nice! I didn't even know they were available like that until I started poking around. I thought they were all built at "the factory". Glad to see they aren't. Adds credibility to the open source and community "heatkit" vibe. Good work.

[Captain Obvious]

7 hours ago, AK260 said:

To an L series owner that seems horrific but to modern head designs, coupled with knock /EGT / O2 / MAF / Air temp sensors and super fast ECUs etc it’s just BAU.

 

 

Yup. Moore's Law in action. Coupled with the rise in fuel prices and the desire to reduce emissions?

I found a few references to knock sensors being added to cars which did not originally come with one. But they were vague and I didn't find anything that came to successful fruition. Granted, I didn't look very hard though.

So the 280ZX had a knock sensor? Is that the turbo version? I don't think the NA had one.