ddnspider

iTrader: (26)

You should be getting the AFR and timing reasonable and unplug the IAC, start the car and adjust the screw until it barely idles/stalls. Then leave the screw alone and plug back in the IAC and adjust AFR and timing from there. If you're in the 14's/15s, leave AFR alone and keep increasing timing until you see a negligible decrease in MAP. At the beginning you should see map drop with each degree of advance added. When it starts to take 2 or 3 degrees of advance to drop the MAP 1 kPa, then back the timing up a degree or 2. That should be your sweet spot. And with no knock sensors it would still be really tough to get the thing to knock at idle. It such a low load. You can idle at 16:1 with 25 degrees advance and it probably wouldn't knock.

Rx7TyreBurna

iTrader: (1)

Thanks ddnspider!
I think I am going to try that later today.

I also want to try and understand how adjusting the timing like that, advancing, changes the manifold pressure. Advancing timing, decreases MAP to a point.....

Great tips! Very appreciated.

As I tune more and learn more... i see the value in things like the stock PCM, and the newer Megasquirt 3 platform that has more inputs and outputs. haha!

ddnspider

iTrader: (26)

Adding timing increases the efficiency of the motor by creating torque. This will increase vacuum with the throttle blade closed which will lower the MAP. Lower the MAP, the better the car will idle. Big cam cars will idle from 55-75kPa, stock cars will idle in the 40kPa range.

Rx7TyreBurna

iTrader: (1)

Ahh, okay. That makes a lot of sense.

Was googling like crazy to try and understand why.

I think the struggle in my mind is to fully understand and comprehend the kPA reading, and what that really means engine wise.
Looking at:
https://www.avweb.com/news/pelican/P...-182081-1.html

Lots of stuff to read. Love learning all the new stuff.

Again, it's greatly appreciated ddnspider.

ddnspider

iTrader: (26)

NP. I highly recommend Greg Banish's books and DVD's. Does a good job explaining stuff. Also the Master EFI Tuning book is really good.

Rx7TyreBurna

iTrader: (1)

I did grab his Engine management advanced tuning book, and his high performance fuel injection systems book.
Slowly making my way through the engine management advanced tuning book. It's added a lot of base understanding. But, only about 30 or so pages in.

I was poking around the megasquirt system last night, and did find that there is a specific 'Idle Advance' tuning area. It looks like I can set an Idle advance in relation to RPM or manifold pressure, or both. I was wondering if there would be an advantage to utilizing that, over keeping just a base map in the appropriate pressure / RPM range. I can't think of a time where I'd be around idle, and would want to utilize base timing, rather than an idle specific timing.

I figure they threw the feature in there for a reason. maybe figure out what I need to idle at, and then utilize the idle advance feature to add the timing I need, and let it do the taper. It does have specific pre-requisites that are set. Like... only apply idle advance when throttle is less than 2%, RPM is less than 1k, manifold pressure is X, etc.
The settings allow a slope for advance, to slowly taper down. It can be an adder to base timing, or be utilized as face value.

Is there any advantage to utilizing a system like that?

ddnspider

iTrader: (26)

That sounds like the difference between base timing table and hi/low octane timing tables. I always make my high/low/idle timing tables match for the cells around a stopped idle. Outside of that as soon as the car is moving you'll be in the high/low octane tables. Id only touch as many tables as required to get the car to idle and drive the way you want. When you start messing with too many tables you can throw things off and make it worse.

Rx7TyreBurna

iTrader: (1)

It's idling pretty good right now. ~19-20 degrees of timing, idling around 55 kPA @ 750-800 RPM.

I went to 21 degrees of timing, and saw 49 or so kPA. So, dropped from 21 to 19 @ 700 RPM, 20.8 @ 1100 RPM for my cells.

IAC isn't hooked up yet though. I think it's almost to the point where I say it's idling well, and start moving to other things.

A log from the idle and tune attached.

I do have a question out on the Megasquirt forum, asking about why my MAPdot is changing, even though car is off.

Rx7TyreBurna

iTrader: (1)

I was very tired tuning last time. LoL.
I realized that... I should be shooting for the 49 kPA, not the 55 kPA.... Need to get it in my head that lower number = more vacuum.

I'll tune more tomorrow, and hopefully post some stuff up.

Luke19901

you could use purely the spark idle control to maintain idle RPM. I've seen several LS combos tuned with aftermarket engine management using only spark corrections, no IAC

don't be afraid to idle an engine with a decent cam on the richer side of stoich if its more stable there

Rx7TyreBurna

iTrader: (1)

Thanks! I know for a bit I was running way too rich, I think. The plugs were covered in black. lol

Rx7TyreBurna

iTrader: (1)

Video of it running the attached tune. Almost 26 degrees of timing at idle. But, it's not hunting like it was before, and seems pretty stable. Going to test adding a degree or so, but overall it seemed to be running pretty well. Don't have a log for the video, but will try and get some logging done this weekend.
3k rev limiter is enabled right now, to prevent myself from being dumb with the car. Going to get driveshaft made soon, and should be able to drive it around in a few weeks. Hoping to get a few miles on it, then change oil.