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Acceleration settings MAP or TPS

Road Tuning

Discussion and questions related to the course Road Tuning

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Hi, I've done a installation for a megasquirt2 ECU and some times the engine goes off when for example I am driving on the road, and stop, the idle speed goes down and i think it is for the MAP aceleration, the image shows the parameters of aceleration and it modificates the values when the map sensor measure positive and negative values, any issue. Someone ideas, tips or recommendations?


Attached Files

Nah, don't worry about using the accel enrichment. The accel enrichment page you've shown above is only for the split second that the throttle position is changing quickly. The settings you've shown shows no 'enleanment' (decel fuel amount is set up 100).

In the situation you're describing, you need to make changes to the fuel and ignition maps below the idle area and change the way that closed loop idle speed control and idle adaptive timing curve functions (only available on MS2E). If you're plain MS2 and not MS2E, we can work with that too but the 'dashpot adder' function provides more air to the engine as it's settling back to idle to make the transition easier.

What you want to do is make more torque below the idle point in comparison to the idle point. What this entails is:

-making the fuel map slightly richer below idle, (I don't know what engine and where idle is so I'll just say 500 RPM as an example if you're idle is at 900 RPM) through either the fuel map itself or the target AFR map if incorporate AFR is on and

-adding a few degrees of timing below idle.

What you'll have is a valley of timing and fuel around idle with idle being the lowest point. MS allows you to move the RPM columns so it's easier to have the first one at 500, the second at idle (750/800/900) and then wherever your columns are from there. In saying that, you want another at 1100 or 1200 so that you can stabilise your fueling and timing around the idle area. You don't want the rise too sharp to the right of the idle RPM because more RPM will get you more timing which makes more torque and it keeps wanting to increase in RPM.

Are you running MS2E and do you have a PWM or stepper idle control? If you do, this will make fixing your issue way easier. However, the above should be able to solve most idle issues on a factory engine.

Hi Ken, thanks for your suggestions, I'm going to apply them, I'm using the MS2E, the idle speed is configurated in open loop, and have a PWM idle valve, can you give some help in the configurations for closed loop? there are many settings (Attach file) , I'm going to search information for configurate it, but if you can give some suggestions I 'll be grateful.


Attached Files

Before you enable closed loop, be sure to have a smooth idle. If you don't, turning on closed loop idle control can make the idle worse as it tries to fix up RPM error. If it's not quick enough, it can lag behind actual RPM and make the oscillations worse.

There's not much you should need to adjust with on that screen except for the sensitivity. You will have to 'tune' this by setting it to a small value and increasing it to a point where the idle hits target RPM relatively quickly but not a value so high that it starts to oscillate. You can use advanced mode and use the PID control if you are confident in doing so. I have left mine in basic mode and set the sensitivity low at 400. What I have done is increased the dashpot adder to 15% and am slowly bringing it down. The car has a lightweight flywheel so I'm okay with it settling at 1500RPM before slowly coming down to target but it's something I'm slowly decreasing. MS3 doesn't have the extra closed loop PID activation as that's done elsewhere. You shouldn't have to touch them but you may want to set the TPS activation to 0.2% or so if you get variances in this figure between starts.

The main thing is to have the fuel and spark maps give you a stable idle. The closed loop idle control just makes it slightly smoother and hits the target RPM better. I wasn't using any electronic idle control (just coolant temp based idle up) until I turbo'ed it and added the lightweight flywheel. I could probably get away without it if I had to but it makes it easier to 'catch' the RPM as it's dropping.

Ok Ken thanks for your answers, I have done the modifications in map base of fuel and ignition like your first recomendation, and the engine now goes so good, rigth now I don't have the problem, I will review the settings for closed loop.

Thanks very much!