Occasional rough idle?
#82
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This is Ken from the msextra/msefi forums. James, Phil, and to a lesser extent, I and a few others developed the ms1/extra code (James and I are currently developing ms2/extra, and have about equal parts in that).
James and I were there when we got Jerry's engine to stop doing the "miss" thing on idle. All we really did was change the number of squirts, and the engine started running better.
I think Jerry, and Lex are on the right track. In fact, I suggested the 4 squirts thing to Jerry on the phone today, and I do the same thing on my 4 cylinder engines. (You can't run more squirts than there are spark events, so 4 is the max on a 4 cylinder). Wiring of the injectors is also essential to getting a good idle and smooth running characteristics. The ms1/extra code does not follow any particular order to its squirts... it squirts simultaneous on crank, then switches to alternating (if you want it to) once running. That means that sometimes it'll be in the proper phase for the engine to run well, and sometimes not (depends on your wiring, and number of squirts). If the engine enters alternating mode with inj1 squirting on cylinders 3 and 4 instead of 1 and 2 (which can happen), the engine might exhibit the odd characteristics (cylinders were examples... not necessarily the actual setup) where if it enters alternating mode with inj1 on 1 and 2, it'll run correctly.
This is definitely not a code issue, as the miata CAS is the most simple example of a wheel that ms1/extra can run with. The wheel decoder just counts teeth, and passes the "trigger" teeth down into the distributor code. This means that everyone who runs ms1/extra, whether wheel decoder or distributor, is basically running the same core code. If this code were broken, it would be broken for everyone, and we have not seen reports of these sorts of problems.
We also put a nice tek scope on various parts of Jerry's MS, and did not see anything wrong, or out of the ordinary.
Long story short, this is a tuning issue. Jerry and Lex are on the right track.
Ken
James and I were there when we got Jerry's engine to stop doing the "miss" thing on idle. All we really did was change the number of squirts, and the engine started running better.
I think Jerry, and Lex are on the right track. In fact, I suggested the 4 squirts thing to Jerry on the phone today, and I do the same thing on my 4 cylinder engines. (You can't run more squirts than there are spark events, so 4 is the max on a 4 cylinder). Wiring of the injectors is also essential to getting a good idle and smooth running characteristics. The ms1/extra code does not follow any particular order to its squirts... it squirts simultaneous on crank, then switches to alternating (if you want it to) once running. That means that sometimes it'll be in the proper phase for the engine to run well, and sometimes not (depends on your wiring, and number of squirts). If the engine enters alternating mode with inj1 squirting on cylinders 3 and 4 instead of 1 and 2 (which can happen), the engine might exhibit the odd characteristics (cylinders were examples... not necessarily the actual setup) where if it enters alternating mode with inj1 on 1 and 2, it'll run correctly.
This is definitely not a code issue, as the miata CAS is the most simple example of a wheel that ms1/extra can run with. The wheel decoder just counts teeth, and passes the "trigger" teeth down into the distributor code. This means that everyone who runs ms1/extra, whether wheel decoder or distributor, is basically running the same core code. If this code were broken, it would be broken for everyone, and we have not seen reports of these sorts of problems.
We also put a nice tek scope on various parts of Jerry's MS, and did not see anything wrong, or out of the ordinary.
Long story short, this is a tuning issue. Jerry and Lex are on the right track.
Ken
#83
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Thanks for the clarification Ken, I am not sure if the miata has the same injector wiring as the fwd version of the BP, but check that as well, I had to change one wire on my stock injector harness.
If you are running big injectors on a turbo setup like myself, on the MSI I can't have 4 simultaneous squirts because the PW becomes too small ... although such a setup would be ideal in conjunction with lowering the rail pressure at idle and part throttle.
If you are running big injectors on a turbo setup like myself, on the MSI I can't have 4 simultaneous squirts because the PW becomes too small ... although such a setup would be ideal in conjunction with lowering the rail pressure at idle and part throttle.
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Well, if time/wife/mood permits, I'll rewire the injector outputs in the weekend. I'm pretty sure that I have them Bank 1-> 1&3, Bank 2-> 2&4, so I 'll rewire them as Bank 1-> 1&4, Bank 2-> 2&3.
Just a question though. When I have the said problem, the ignition is also affected - ie the bouncing revs problem when I pass the ignition control to the MS. As soon as resync, it goes away. My coilpacks are wired IGN1->1&4, IGN2->2&3 (for a wasted spark setup).
Jim
Just a question though. When I have the said problem, the ignition is also affected - ie the bouncing revs problem when I pass the ignition control to the MS. As soon as resync, it goes away. My coilpacks are wired IGN1->1&4, IGN2->2&3 (for a wasted spark setup).
Jim
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Well, I did wire it all by myself. You can tell that from my bloody scarred hands and rough fingertips (ain't wire stripping a bitch). ![](https://www.miataturbo.net/images/smilies/smile.gif)
My homemade PnP box - see the 4 switches on the top left? Yellow wire for #1 & #3 (INJ1) and orange for #2 & #4 (INJ2):
![](http://users.forthnet.gr/ath/twikicore/dsc00650_1.jpg)
Jim
![](https://www.miataturbo.net/images/smilies/smile.gif)
My homemade PnP box - see the 4 switches on the top left? Yellow wire for #1 & #3 (INJ1) and orange for #2 & #4 (INJ2):
![](http://users.forthnet.gr/ath/twikicore/dsc00650_1.jpg)
Jim
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No this change won't be too tough, but I don't envy the initial build
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Jerry a.k.a. 'FoundSoul'
DIYAutoTune.com
'91 Miata BEGi S3 GT2560 w/ MSPNP - 14.1psi - 253whp, 232wtq
'95 Miata n/a
A few other cars....
Jerry a.k.a. 'FoundSoul'
DIYAutoTune.com
'91 Miata BEGi S3 GT2560 w/ MSPNP - 14.1psi - 253whp, 232wtq
'95 Miata n/a
A few other cars....
#90
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Well, if time/wife/mood permits, I'll rewire the injector outputs in the weekend. I'm pretty sure that I have them Bank 1-> 1&3, Bank 2-> 2&4, so I 'll rewire them as Bank 1-> 1&4, Bank 2-> 2&3.
Just a question though. When I have the said problem, the ignition is also affected - ie the bouncing revs problem when I pass the ignition control to the MS. As soon as resync, it goes away. My coilpacks are wired IGN1->1&4, IGN2->2&3 (for a wasted spark setup).
Jim
Just a question though. When I have the said problem, the ignition is also affected - ie the bouncing revs problem when I pass the ignition control to the MS. As soon as resync, it goes away. My coilpacks are wired IGN1->1&4, IGN2->2&3 (for a wasted spark setup).
Jim
Ken
#91
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I believe the bouncing revs problem is probably because the stock ECU (as I understand it) varies the ignition timing and the pulse-width in an ocscillating fashion with the result of a stable idle... Take control of either fuel or spark from the stock ECU, and I'd expect weird things to start happening.
Ken
Ken
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I believe the bouncing revs problem is probably because the stock ECU (as I understand it) varies the ignition timing and the pulse-width in an ocscillating fashion with the result of a stable idle... Take control of either fuel or spark from the stock ECU, and I'd expect weird things to start happening.
Ken
Ken
Jim
#94
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The MS should really have an "idle" mode where these variables can be oscillated/varied only when the car is idling because otherwise most cars won't idle near stoich.
I'm no miata expert, but on most newer cars, if you leave the stock ecu in control of too much, you'll get weird results... I know that neons do the same thing because the stock ecu oscillates the ignition timing, AFR and idle valve with the result of a stable idle.
Ken
Ken
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I just tried the rewiring. Previously:
Bank 1 -> #1 & #3
Bank 2 -> #2 & #4
Currently:
Bank 1 -> #1 & #4
Bank 2 -> #2 & #3
Results: I first warmed up the car with the stock ECU and then switched to MS (fuel only) once the car was fully warmed up (coolant and IAT stabilised). At first it seemed like it worked. I restarted 6, maybe 7 times and it was smooth, around 14.0:1-14.3 AFR. I restarted several times again, and at some point, yes, the problem appeared again. It didnt matter how pich rich I made it (up to 12:1 at some point), it would still do the "slight misfire" thingy.
At this point, I'm just lost and dissapointed. I have a Hydra ECU which I bought on the cheap side to handle the idle and the VVT/VTCS and I'm afraid that it's going to replace the little squirt.
Jim
Bank 1 -> #1 & #3
Bank 2 -> #2 & #4
Currently:
Bank 1 -> #1 & #4
Bank 2 -> #2 & #3
Results: I first warmed up the car with the stock ECU and then switched to MS (fuel only) once the car was fully warmed up (coolant and IAT stabilised). At first it seemed like it worked. I restarted 6, maybe 7 times and it was smooth, around 14.0:1-14.3 AFR. I restarted several times again, and at some point, yes, the problem appeared again. It didnt matter how pich rich I made it (up to 12:1 at some point), it would still do the "slight misfire" thingy.
At this point, I'm just lost and dissapointed. I have a Hydra ECU which I bought on the cheap side to handle the idle and the VVT/VTCS and I'm afraid that it's going to replace the little squirt.
![](https://www.miataturbo.net/images/smilies/sadwavey.gif)
Jim
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I just tried the rewiring. Previously:
Bank 1 -> #1 & #3
Bank 2 -> #2 & #4
Currently:
Bank 1 -> #1 & #4
Bank 2 -> #2 & #3
Results: I first warmed up the car with the stock ECU and then switched to MS (fuel only) once the car was fully warmed up (coolant and IAT stabilised). At first it seemed like it worked. I restarted 6, maybe 7 times and it was smooth, around 14.0:1-14.3 AFR. I restarted several times again, and at some point, yes, the problem appeared again. It didnt matter how pich rich I made it (up to 12:1 at some point), it would still do the "slight misfire" thingy.
At this point, I'm just lost and dissapointed. I have a Hydra ECU which I bought on the cheap side to handle the idle and the VVT/VTCS and I'm afraid that it's going to replace the little squirt.
Jim
Bank 1 -> #1 & #3
Bank 2 -> #2 & #4
Currently:
Bank 1 -> #1 & #4
Bank 2 -> #2 & #3
Results: I first warmed up the car with the stock ECU and then switched to MS (fuel only) once the car was fully warmed up (coolant and IAT stabilised). At first it seemed like it worked. I restarted 6, maybe 7 times and it was smooth, around 14.0:1-14.3 AFR. I restarted several times again, and at some point, yes, the problem appeared again. It didnt matter how pich rich I made it (up to 12:1 at some point), it would still do the "slight misfire" thingy.
At this point, I'm just lost and dissapointed. I have a Hydra ECU which I bought on the cheap side to handle the idle and the VVT/VTCS and I'm afraid that it's going to replace the little squirt.
![](https://www.miataturbo.net/images/smilies/sadwavey.gif)
Jim
Were you not tempted by MSII?
Someon's going to end up with a very clean MS install!
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I'm not going to sell it, I paid like $600 for everything, start to finish, I can still get lots of things in my Innovate Datalog chain from the MS (coolant temp, intake air temp, knock, shift lights, baro readout, fuel pressure) plus a backup ECU "just in case". No one in their right mind would fork over $300 for a system that I claim to have problems.
The MS-II, I don't know. I still love the system for what it is and for how smooth it behaves overally - there were times that I would forgot than I don't use the stock ECU,p articularly in track days. It's just sad that a little problem like this can drive you nuts.
Jim
The MS-II, I don't know. I still love the system for what it is and for how smooth it behaves overally - there were times that I would forgot than I don't use the stock ECU,p articularly in track days. It's just sad that a little problem like this can drive you nuts.
Jim
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