How does this target AFR table look?, VE table results after autotune Options

[rwilner]

I'm going to use the autotune feature of Microsquirt to set my fuel map (VE table). This system will automatically adjust the VE to achieve the mixture as defined by the target AFR table.

This is a 12x12 table. The Y axis is MAP reading (load), and the X axis is RPM. This table was auto-generated by this microsquirt calculator.

What do you guys think? Is this a solid target AFR table or are adjustments needed?

[McMark]

You should do your own safe testing, because I haven't.

Here's what I see in the factory manuals...



Which I read to be:

+0° vac. adv. at 100 mmHg (33.8 kPa) and below
+11-14° vac. adv. at 200 mmHg (67.7 kPa) and above

What's your idling kPa?

I'm not proposing that adding 14° of vac. adv. is a good idea. Just suggesting that, based on my interpretation, the stock dist. adds that much. I wouldn't go over you max. adv. (28°), but bringing your 100kPa @ 1200rpm bin up to quite a bit and then linearly degrading with dropping kPa.

Something like the following, might be helpful. I distributed 14° between 45kPa and 100kPa, without going over 28° at any point.
8-22-26-28-28-28
8-20-24-27-28-28
8-18-22-25-28-28
8-16-20-23-26-28
8-14-18-21-24-28
8-12-16-19-22-26.5
8-10-14-17-20-24.5
8-8-12-15-18-22.5

And again, the above suggestion is based on speculation, not experience. Try it at your own risk and always listen for sounds of pinging or other problems. And only add as much advance as makes power. Watch your CHT & EGT.

[JamesM]

You should do your own safe testing, because I haven't.

Here's what I see in the factory manuals...



Which I read to be:

+0° vac. adv. at 100 mmHg (33.8 kPa) and below
+11-14° vac. adv. at 200 mmHg (67.7 kPa) and above

What's your idling kPa?

I'm not proposing that adding 14° of vac. adv. is a good idea. Just suggesting that, based on my interpretation, the stock dist. adds that much. I wouldn't go over you max. adv. (28°), but bringing your 100kPa @ 1200rpm bin up to quite a bit and then linearly degrading with dropping kPa.

Something like the following, might be helpful. I distributed 14° between 45kPa and 100kPa, without going over 28° at any point.
8-22-26-28-28-28
8-20-24-27-28-28
8-18-22-25-28-28
8-16-20-23-26-28
8-14-18-21-24-28
8-12-16-19-22-26.5
8-10-14-17-20-24.5
8-8-12-15-18-22.5

And again, the above suggestion is based on speculation, not experience. Try it at your own risk and always listen for sounds of pinging or other problems. And only add as much advance as makes power. Watch your CHT & EGT.

Mark, I had initially gone the same route and tried to translate the factory information into an advance table but then realized a couple things. One is that both vacuum advance and retard need to be taken into account and two is that the factory chart is listing the vacuum at the distributor ports which is not the actual manifold vacuum as these ports go to various locations on the throttle body so they dont translate directly into a table based on manifold vacuum. Also as far as the 2.0 motor goes, there was ZERO vac advance from 74 onward. even though the port was on the dizzy. I would say stick with the RPM only advance right now as that table appears to be close, if not exactly the same as specs I have seen Jakes RPM advance curve listed as and any adjustment beyond that should probably be done on a dyno.

I am not sure running near full advance at low RPM, WOT conditions is a good idea.

[rwilner]

One is that both vacuum advance and retard need to be taken into account

This is an interesting point. The MS takes into account only Manifold Pressure "position", i.e. the instantaneous MP, to calculate advance. However, the factory arrangement takes into account MP"change in position", i.e. whether it's increasing or decreasing, to calculate advance. In this way, the factory setup is actually more sophisticated than MS! (IMG:style_emoticons/default/blink.gif)

two is that the factory chart is listing the vacuum at the distributor ports which is not the actual manifold vacuum as these ports go to various locations on the throttle body so they dont translate directly into a table based on manifold vacuum.

This is also a great point. For the manifold vacuum sense pickup, I've connected the port on the plenum just downstream of the throttle body to the MPS. Is this the best place to measure manifold pressure? Would it be better to use one of the ports further down on the plenum (ex. where the vaccum elbow connects), or better yet to install a nipple someplace special?

[ChrisFoley]

This is an interesting point. The MS takes into account only Manifold Pressure "position", i.e. the instantaneous MP, to calculate advance. However, the factory arrangement takes into account MP"change in position", i.e. whether it's increasing or decreasing, to calculate advance. In this way, the factory setup is actually more sophisticated than MS! (IMG:style_emoticons/default/blink.gif)

Analog vs digital. The sampling rate of MS should be fast enough that instantaneous mp measurements are sufficient to at least be the equal of an electro-mechanical device connected to a pcb filled with resistors and transistors.
Ie., the MPS "sophistication" was needed to overcome the shortcomings of rudimentary electronic circuitry.

[rwilner]

Analog vs digital. The sampling rate of MS should be fast enough that instantaneous mp measurements are sufficient to at least be the equal of an electro-mechanical device connected to a pcb filled with resistors and transistors. Ie., the MPS "sophistication" was needed to overcome the shortcomings of rudimentary electronic circuitry.

Chris,
Let me see if I understand your point:

For the MS, each value of KPa and RPM will result in a single commanded advance. This advance is commanded instantly because it's done digitally in software (at least, it is with my crank-fired setup).

For the factory setup, each value of KPa and RPM will result in TWO possible commanded advance values, based on whether manifold pressure is increasing or decreasing. The retard was needed because the elecro-mechanical limits of the system did not enable the "advance only" numbers to be achieved fast enough under decreasing MP conditions.