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Engine Dies when braking with clutch in

 
Old 06-10-2019, 09:13 PM
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Default Engine Dies when braking with clutch in

Hi Forum!

I have the following issue with my MS3Pro.

If I depress the clutch and start braking at the same time, the rpm drops and does not catch idle. I haven't been able to figure out correctly what's the issue.

Specs:
1999 Mazda Miata Stock
Flyin Miata HappyMeal with lightweight flywheel
MS3Pro PNP

Any ideas why it could be happening? Besides that, the car run great!

I'm attaching the currentmap and the log. It happens at around mark 390. For some reason if I add a marker and save, the marker gets lost.
Attached Files
File Type: msl
2019-06-10_17_modified.msl (438.1 KB, 9 views)
File Type: msq
CurrentTune.msq (273.2 KB, 10 views)
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Old 06-10-2019, 09:22 PM
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Mine does the same thing, but only when I have my headlights on.
Looking forward to seeing the answers.
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Old 06-10-2019, 10:27 PM
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Tune your initial value table?
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Old 06-10-2019, 10:56 PM
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I took a look at your log and what stuck out as strange for me is that your pwm idle duty was at 31.8% when your rpm was dropping down to idle, and then after restarting the car you idle with the valve open at about 27.5%. 31.8% is a good bit higher than 27.5% I would think that would be enough to catch the engine as it slows down. I noticed you are using the last value option for your initial pwm idle duty. Perhaps your engine needs more idle valve to catch it, if that is the case I would recommend changing to use the initial table, and use MAT in the table lookup. I'd also recommend adding more ignition advance in your 700rpm column. As we know, adding more spark advance will increase the rpm, so this will also help catch the engine.

As an example, I made those changes to your tune, which you can compare with your original tune.

In regards to what borka was talking about, I too have struggled with this. So far I have found that running more timing at idle has helped compensate for the extra load from the headlights. I also enabled table switching to make basically an idle only spark table. Currently it is set up to swap to my normal spark map when the tps is over 0.3%, otherwise, it runs on a different spark map that mostly focuses on the idle. Since doing this the car only almost stalls about half the time now with headlights on, whereas it used to be every time. I am also curious to see how other people have dealt with this.
Attached Files
File Type: msq
asalinas' tune.msq (273.2 KB, 4 views)
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Old 06-10-2019, 11:19 PM
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I use the Idle Advance table and it helped smooth out my idle without needing to use a second spark table. Copied curlys table exactly with a 10 degree advance across the board and my car seems to like it. I have only stalled once since and I think I may have modulated the clutch wrong or something like that when it did stall.
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Old 06-10-2019, 11:21 PM
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Thanks a lot for the suggestions. I will try with the initial values and a little more advance and I'll report back!
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Old 06-10-2019, 11:25 PM
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Unless ms3 works a little different from ms2, which is what I have. The adaptive idle only works once you've entered closed loop idle. Can't enter closed loop idle when the engine blows right past your idle speed and isn't stable, which is currently the case for OP.

For my car if I am in closed loop idle and then turn on the headlights, the car is fine and compensates with more idle duty and spark advance. The problem I have is trying to get into closed loop idle with the headlights on and not dipping down into the 500-600 rpm range.
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Old 06-10-2019, 11:34 PM
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Originally Posted by dglb99 View Post
Unless ms3 works a little different from ms2, which is what I have. The adaptive idle only works once you've entered closed loop idle. Can't enter closed loop idle when the engine blows right past your idle speed and isn't stable, which is currently the case for OP.

For my car if I am in closed loop idle and then turn on the headlights, the car is fine and compensates with more idle duty and spark advance. The problem I have is trying to get into closed loop idle with the headlights on and not dipping down into the 500-600 rpm range.
That was one of my main concerns. From the logs it seems that the engine doesn't even enter CL Idle so it just dies.

Maybe it has something to do with the "Slow deceleration threshold" in the engine states?
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Old 06-10-2019, 11:43 PM
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Oh, yeah don’t use closed loop with an ms2, problem solved.
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Old 06-11-2019, 07:22 AM
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Just a random thing to check that I had a problem with... My vacuum line to the ECU was routed under the clutch pedal. This caused the vacuum line to get pinched when my clutch was all the way to the floor.

Just something to check if your logs show high vacuum.
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Old 06-11-2019, 07:42 AM
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With ms1 I had dashpot settings that needed to be altered. I cannot remember what adjustments I made in ms3 but will look when I get in front of a computer. Lightweight flywheel exacerbated the issues.
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Old 06-11-2019, 10:31 AM
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You should increase your dashpot adder. You are at 3.1%, try 6ish until you can get everything dialed in. It is a band-aid, it slows your decel (RPM drop) by artificially opening your idle valve.
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Old 06-11-2019, 11:36 AM
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Ok I'll actually be useful. I finally looked at your log and your afr is in the 18s before it dies, I'd add fuel in the decel rows so it doesn't go so lean.
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Old 06-11-2019, 05:00 PM
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Just a random data point.. If nothing else works check the crankshaft end play.
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Old 06-11-2019, 11:40 PM
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Originally Posted by Chiburbian View Post
Just a random thing to check that I had a problem with... My vacuum line to the ECU was routed under the clutch pedal. This caused the vacuum line to get pinched when my clutch was all the way to the floor.

Just something to check if your logs show high vacuum.
WE HAVE A WINNER!

I can't believe it was something that simple. I've been chasing my tail for two weeks trying to fix what I thought was a tuning issue, when was just the line getting pinched by the clutch pedal.

Now I can properly tune my initial values, so thanks everyone for all the suggestions!
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