Setting Decel, basic questions

[AbeFM]

How do I set up DECEL well? Everytime I let off the pedal, it's pop-pop-pop-pop at a couple of hz, pretty loud and annoying. I turned the decel down from 80 to 50, and everything was great. Then when I bumped up my fuel tables richer, it all went poppy again. I set the decel down to 30%, and then I noticed my tip ins were terrible.

Maybe I could make up for it with more accel enrichment? It's port injection, so I can't imagine there's a huge lag time for the fuel to be delivered.

Whatever is it, it's either really annoying popping everywhere, or hard to drive because the tip in is stuttery. Do I have the right idea about trying to bring it back with accel enrich, or am I just stuck between the two? What's the point of fueling on decel anyway?

Sorry for the basic quesitons! Running b17 on a miata + turbo.

[md95]

Have you tried using "over run fuel cut". This cuts fuel when you let off the gas and just engine brake it. You want to set it to trigger at maybe 4-5 kpa less than your highest idle map value. For example, if you idle at 30 kpa, set the over run to 25 kpa. You have to know your closed throttle adc, and set that perameter in the overrun settings for maybe 5 adc above that closed adc value. Set the rpm threshold to around 1700. Set the delay to 1.5-2 seconds. These work well for me, and when you let off the gas just cruising, it cuts all fueling and you dont get the pops out the exhaust. I dont think i've ever played around with decel settings much, i just use the default.

[AbeFM]

Set the rpm threshold to around 1700. Set the delay to 1.5-2 seconds.

Ah! That makes excelent sense, just what I'm looking for, thanks!

I'm still a little curious why there's fuel on decel, but I guess that's when you're in light decel.

I'm also curious about the quoted settings above: That's so it only does it above 1700 rpm? So you'd get some pops those last few feet? Also, the delay? I guess that makes sense, since I don't get popping right on lift, generally.

I thought maybe overrun was for like diesels with a sticking fuel valve or something, which didn't make a lot of sense.

[muythaibxr]

In ms2/extra you don't use the ADC values anymore, it's % throttle.

Ken

[md95]

Set the rpm threshold to around 1700. Set the delay to 1.5-2 seconds.

Ah! That makes excelent sense, just what I'm looking for, thanks!

I'm still a little curious why there's fuel on decel, but I guess that's when you're in light decel.

I'm also curious about the quoted settings above: That's so it only does it above 1700 rpm? So you'd get some pops those last few feet? Also, the delay? I guess that makes sense, since I don't get popping right on lift, generally.

I thought maybe overrun was for like diesels with a sticking fuel valve or something, which didn't make a lot of sense.

Opps, yeah TPS position is in % now..so set it for like 5%. This means overrun wont trigger unless TPS is 5% or less. The rpm threshold means it wont trigger below what you set. Its best not to set it too low, but high enough for a higher gear trigger when you are going slower(like 3rd gear at 15-20 mph). The time delay can be as low as 1 second, but i think i have mine at 1.5 or 2 seconds. You dont want it to activate too quickly, you will just have to play around with some of the settings to what works best for your setup. You want it so just a light tap of the gas brings fueling back on(this is the TPS setting, if you set it too high, you can get weird lean stumbles) For the kpa settings, know your highest idle kpa, and then watch the kpa gauge as you engine brake. You want that kpa setting to be just a few kpa higher than what you saw. maybe like 4-5 kpa. So if your idle kpa is 30, and your engine braking kpa is 20, a setting of 24 kpa would be fine. This means pressure has to be 24 kpa or less to trigger overun.

You have to be careful with the kpa settings..if you use fast idle control, some engines will pull more kpa at fast idle. If the engine runs at 2000 rpm, and pulls 23 kpa, then it would trigger overrun, causing it to have this mean cycle up and down in rpm. This is why you want to set the kpa to just a few above your engine braking kpa. I beleive there is a coolant temp value you can set too, so maybe setting this to closer to full warm(160), may help in that respect.

[hassmaschine]

I wouldn't set it for 5% - I typically only use 2-3% throttle while cruising, so overrun fuel cut would be constantly activating. I was only able to use it with either 0 or .5% TPS.

[md95]

I wouldn't set it for 5% - I typically only use 2-3% throttle while cruising, so overrun fuel cut would be constantly activating. I was only able to use it with either 0 or .5% TPS.

This value needs to be adjusted for your particular setup really..A higher compression engine will cruise with less throttle than a lower compression engine..My engine is 7.8:1, so just cruising takes a little bit of throttle, usually around 10% or so. Each setup is different. I use:

1600 rpm
23 kpa
2% throttle
140 degrees coolant
2.0 sec delay

Works very well for me, very smooth transitions.

[hassmaschine]

makes sense, my motor is ~10:1 so it takes very little throttle to cruise (even typical acceleration is under 10%).