Felt like rev limiter at full throttle at 4500rpm, help me figure out why? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 05-08-2013, 03:15 PM   #1
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Default Felt like rev limiter at full throttle at 4500rpm, help me figure out why?

To catch you all up - I built a MS3x and forgot (had the dumb) that I should use the expander to run a bunch of stuff and tried to use the main board to control A/C without having the proper circuits and so I smoked my EMS.

This thread isn't about this - but I wanted to explain why I don't have the ability to test hypotheses at the moment. I am however driving myself nuts trying to figure out what was causing a problem when I was auto-tuning on Saturday.

While I did my route around town (about 20 miles) I varied my driving from idle to probably 6200rpm. I drove a bunch normally to flesh out the cells that I used the most, and when I felt like that was starting to really come together I started doing pulls from 2000 rpm on in 4th gear or so. Then I repeated it in 5th, 6th, etc. I figured that different loads on the engine would tickle new cells and get me an overall better tune.

When I got near home, I started to really push it from stop signs. That is where I started to see problems. I would accelerate quickly to about 4200 rpm, and then it would stutter like I was hitting a rev-limiter. I pulled over and checked my rev limiter and it was set to 6500 or so (maybe even higher), going off of memory. I did this multiple times. When I crept up slowly (part throttle?) I could go above 4500 rpm, so it was not a true rev limit.

Also of note, standing still and in neutral I could rev higher than 4500 without a problem.

Can you guys take a look at my MSQ and look to see if anything sticks out at you? Mind you, I cannot test until my MS3 daughtercard comes in the mail and put it all back together. I am just trying to roll this around in my head and not knowing is bothering me.

DISCLAIMER (to people like me who are idiots)! DO NOT USE THIS MSQ TO RUN YOUR CAR. It still has the wrong inputs and outputs for A/C and a couple other things. When I get it all together and running I will update the MSQ in this thread and also post a log.

Applicable data:
2001 NB
Using factory crank and cam sensors
Using MAP, no MAF
2001 has variable throttle (If I am understanding the term properly)

Thanks all!
Attached Files
File Type: msq lookyloo.msq (156.9 KB, 51 views)
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Old 05-08-2013, 03:36 PM   #2
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VR conditioner pots need adjusting. Do a compostie log to see which sensor is dropping out and then adjust the pots on the circuit accordingly.
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Old 05-08-2013, 03:55 PM   #3
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Crap... that is a pain in the butt to do while the ems is in the car. Thx for the heads up. I will put the VR pots back to the settings recommended by Frank and start over. I adjusted them to the point that they are when I had a million other problems in my way. I have since fixed most of those problems and it likely wasn't a VR pot trim problem to start with (but is now).

When I get it all together I will give it a shot.
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Old 05-08-2013, 04:17 PM   #4
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do 7 CW on the mainboard pot and 3 turns CW on the expander pot.
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Old 05-08-2013, 04:53 PM   #5
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Does everyone with an ms3 need to deal with this pot adjusting ------ry? I'm not looking forward to crack my case open every time something goes fucky. If my rev-built ms3xxx ever gets here of course.
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Old 05-08-2013, 05:31 PM   #6
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I started messing with my pots when I couldn't get a tach signal over a year ago. I have since replaced my "jumper harness" between the stock harness and the megasquirt with one that I did a MUCH better job building and that's when I was able to get it to fire. I never turned my pots back down to the recommended values but since it fired I didn't mess with it. I should get my parts by this weekend and I will let you know what I find.
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Old 05-08-2013, 06:20 PM   #7
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Wow, glad I switched to DTA a year ago. Back in the MS1 days ppl would say: check you overboost settings...
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Old 05-09-2013, 11:07 AM   #8
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Quote:
Originally Posted by Oscar View Post
Does everyone with an ms3 need to deal with this pot adjusting ------ry? I'm not looking forward to crack my case open every time something goes fucky. If my rev-built ms3xxx ever gets here of course.
Not always - and if you start with an MS3-Pro, it uses a self adjusting circuit that doesn't need trim pots.
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Old 05-09-2013, 11:12 AM   #9
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Quote:
Originally Posted by Oscar View Post
Does everyone with an ms3 need to deal with this pot adjusting ------ry? I'm not looking forward to crack my case open every time something goes fucky. If my rev-built ms3xxx ever gets here of course.
the 99+ sensors tend to need one extra turn CW each past the documented suggested point it seems. This is only becoming something that I've seen happening with people who I've built a 99+ unit for. This is a set and forget sort of thing otherwise.
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Old 05-09-2013, 11:54 AM   #10
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Quote:
Originally Posted by Oscar View Post
Does everyone with an ms3 need to deal with this pot adjusting ------ry? I'm not looking forward to crack my case open every time something goes fucky. If my rev-built ms3xxx ever gets here of course.
Neither the Enhanced MS2 nor the Basic MS3 need ANY kind of adjustment.
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Old 05-09-2013, 11:56 AM   #11
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Are you turbo? I had this same issue and Overboost protection was turning on too early. I raised the limit and fixed the problem.
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Old 05-09-2013, 03:46 PM   #12
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Quote:
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Are you turbo? I had this same issue and Overboost protection was turning on too early. I raised the limit and fixed the problem.
No turbo.
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Old 04-23-2014, 08:24 AM   #13
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OP, did you find the cause of the issue?
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Old 04-23-2014, 10:46 AM   #14
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Uh yeah read post #2.
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Old 04-23-2014, 11:42 AM   #15
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Not exactly correct (in this case) Nuge. I remember this being a ground issue. Let me check my records.
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Old 04-23-2014, 12:06 PM   #16
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I want to say that my cam sensor wasn't reading reliably until I added grounds from the ECU to the engine block.
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