Misc Q's about sometimes untouched ECU params

[crcain]

My first question is about ignition advance attack and decay rates. Some ECU's might call it something different, but it's my understanding that this allows you to control how quickly ignition angle can increase or decrease.

So perhaps between 500 and 1500 rpm, you don't want the ignition angle to be able to jump from say 5 degrees to 35 degrees instantly. Maybe you want it to increase a bit slower? Can anyone shed some light on this feature and when you would want to use it?

[crcain]

Bump!

Here is an example, is it ideal when your idling at say 5 - 10 degrees advance, and you step on the throttle, is it ideal to go from say 5 degrees to 35 degrees almost instantly? Would this not create a bit of jerkiness?

[David Buschur]

For your example you posted, I don't know anyone who sets up a map that way. Any extremely fast change in any parameter generally is not the correct way to do something, in my opinion.

[crcain]

For your example you posted, I don't know anyone who sets up a map that way. Any extremely fast change in any parameter generally is not the correct way to do something, in my opinion.

Ya I guess that was a bad example. I just checked my main ignition map and the cells around idle, and then what my idle ign map looked like, and at most there might be a jump of like 5-10 degrees coming out of idle ign map and into the main ign map.

I dunno.. the point of my question was, does anyone on this board use an ECU feature to limit the maximum rate of change for ign timing in their ECU?

[tkklemann]

For your example you posted, I don't know anyone who sets up a map that way. Any extremely fast change in any parameter generally is not the correct way to do something, in my opinion.

The Mitsubishi OEM Ecu can and will do that.. FWIW...

I do agree with you on it not being correct...

[crcain]

You guys aren't answering my basic question though... is there any need to tell the ECU to limit the attack or decay of ignition angle under certain conditions?

For example. I could say under vacuum and between 1000 and 2000, don't advance ignition faster than 10 degrees / sec.

[David Buschur]

I am unfamiliar with any setting in any ECU that has a limit like that. It's actually an excellent feature, would have saved me some money if it was on the AEM EMS so when you lose a cam sensor the timing doesn't advance instantly.

I just took some time to look at the stock timing maps I have and I don't see anywhere in EVO8-9 maps where the timing takes huge jumps from one cell to another. Do you have an example of a stock map that does?

[crcain]

I am unfamiliar with any setting in any ECU that has a limit like that. It's actually an excellent feature, would have saved me some money if it was on the AEM EMS so when you lose a cam sensor the timing doesn't advance instantly.

I just took some time to look at the stock timing maps I have and I don't see anywhere in EVO8-9 maps where the timing takes huge jumps from one cell to another. Do you have an example of a stock map that does?

I haven't looked at any stock ECU maps to see... I really just always wondered about this because the autronic has it, and I wondered if people used something like this.

I can say from my own map, if I come out of the idle ignition map, and into the main timing map, I could get a jump from around 5 to 12 degrees. And my car has always been a bit "lurchy" when tipping in from idle. I might do some logs and tinker with it a bit. I'd like to do some logs on the stock ECU as well and see how quickly it ramps up from idle when you tip in to get an idea on how mitsu does it.

Dave, sort of off topic, but have you done testing on the dyno to tune EVERY load cell for minimum timing for best torque?

[03whitegsr]

Not exactly what you are looking for, but I have heard of this being used as a mild form of traction control on drag cars that are not allowed to have traction control implemented...

[David Buschur]

Make up your mind, haha. You said from 5 to 35 degrees, now you are saying 5 to 12 degrees, big difference in the two.

Yes, I've spent considerable time setting up the base timing curves I run. Truthfully now I have one basic timing map that is used in most cars for the low end vacuum areas, this is for EVO's obviously.

[crispeed]

The Mitsubishi OEM Ecu can and will do that.. FWIW...

I do agree with you on it not being correct...

So do many aftermarket ecu's.

My first question is about ignition advance attack and decay rates. Some ECU's might call it something different, but it's my understanding that this allows you to control how quickly ignition angle can increase or decrease.

So perhaps between 500 and 1500 rpm, you don't want the ignition angle to be able to jump from say 5 degrees to 35 degrees instantly. Maybe you want it to increase a bit slower? Can anyone shed some light on this feature and when you would want to use it?

If I'm not mistaken you're asking about 'Transient throttle acceleration ignition adjustment' and 'Transient throttle acceleration decay rate'.
Use mainly for adjusting timing during transient throttle or acceleration pump conditions. Helps reduce knock when the throttle is moved very quiclky like between shifts or just off idle conditions. It can also help with improving throttle response only during the above conditions.

[crcain]

If I'm not mistaken you're asking about 'Transient throttle acceleration ignition adjustment' and 'Transient throttle acceleration decay rate'.
Use mainly for adjusting timing during transient throttle or acceleration pump conditions. Helps reduce knock when the throttle is moved very quiclky like between shifts or just off idle conditions. It can also help with improving throttle response only during the above conditions.

Hmm, well know I just want to see how you mapped yours Thanks for your explanation. I'll do some fiddling with this when I get a chance.

Make up your mind, haha. You said from 5 to 35 degrees, now you are saying 5 to 12 degrees, big difference in the two.

Yes to be honest, without looking at my map, I thought that is what my map did.. come out of idle ignition straight into 30+. But then looking at it, it doesn't get to 30+ degrees till much later in the rpm/vacuum area.

[Dave W.]

I know that the 1G DSM ecu has a feature that limits the change in timing to around 22 degrees per iteration. Why it does this is open to interpretation. IMHO it could be there in case the CAS skips a beat and goes out of sync. In reality there's no reason for timing to jump by 22 degrees, rpm can't increase that fast under normal conditions, load can't change that fast.