Hesitation around 6krpm on track
05-13-2011, 04:01 PM
#62
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Location: Enschede, NL
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From: https://www.miataturbo.net/showthrea...995#post726995
Changed a couple of things before heading to the dyno:
- NGK race plugs (heat range 7)
- pluggen PCV
- breather on VC hot side
Turned out my sprak map was kinda lousy. I removed some timing before to combat the issue, but the curve looked choppy.
Had the boosted 4krpm+ range tuned on the SuperFlow with electronic detcans. Gained over 5 degrees some places. MUCH smoother curve now.
Was never able to reproduce the issue like before (need to find that old graphs where the dip is shown on the dyno). Maybe the ventilation changes made some impact with the new plugs.
Real test will be on the track later this month.
Changed a couple of things before heading to the dyno:
- NGK race plugs (heat range 7)
- pluggen PCV
- breather on VC hot side
Turned out my sprak map was kinda lousy. I removed some timing before to combat the issue, but the curve looked choppy.
Had the boosted 4krpm+ range tuned on the SuperFlow with electronic detcans. Gained over 5 degrees some places. MUCH smoother curve now.
Was never able to reproduce the issue like before (need to find that old graphs where the dip is shown on the dyno). Maybe the ventilation changes made some impact with the new plugs.
Real test will be on the track later this month.
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07-28-2011, 05:45 PM
#66
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Join Date: Jul 2010
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Total Cats: 2
That's a shame, I'm getting the same thing with my DIYPNP. I don't remember ever having revved past 6500rpm without experiencing this.. although I've been short shifting to avoid it most of the time.
Btw, from reading these forums it seems that misfiring should be visible on the AFR trace as a lean spike because of the unburnt O2? I've made my car misfire by bumping up the VE until it goes very rich (at ~2300rpm with no load) and it didn't go lean at all.
I'd discounted a problem with ignition because I didn't see the AFR go lean during the hesitation but now I'm not convinced that it would go lean if there was a misfire.
When my car does this I can't see anything in the logs that look suspicious at all - fuel and spark are consistent, the AFR stays flat. the car doesn't 'buck' as I would expect it to with a mis fire although I don't know whether it would buck at high rpm. It's not hard like the boost cut, it just feels like power drops significantly but smoothly, the return of power above the point is more abrupt than the loss of power.
I had a similar symptom around 5000rpm before I disabled the prediction in the ignition setup, wondering if there's something that causes the MS to get confused around 6500rpm resulting in the ignition being retarded in reality but fine on the logs? not sure that explains why it happens at 6500rpm and not 7000rpm though.
Going to take some time to work this one out I think.
Btw, from reading these forums it seems that misfiring should be visible on the AFR trace as a lean spike because of the unburnt O2? I've made my car misfire by bumping up the VE until it goes very rich (at ~2300rpm with no load) and it didn't go lean at all.
I'd discounted a problem with ignition because I didn't see the AFR go lean during the hesitation but now I'm not convinced that it would go lean if there was a misfire.
When my car does this I can't see anything in the logs that look suspicious at all - fuel and spark are consistent, the AFR stays flat. the car doesn't 'buck' as I would expect it to with a mis fire although I don't know whether it would buck at high rpm. It's not hard like the boost cut, it just feels like power drops significantly but smoothly, the return of power above the point is more abrupt than the loss of power.
I had a similar symptom around 5000rpm before I disabled the prediction in the ignition setup, wondering if there's something that causes the MS to get confused around 6500rpm resulting in the ignition being retarded in reality but fine on the logs? not sure that explains why it happens at 6500rpm and not 7000rpm though.
Going to take some time to work this one out I think.
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07-31-2011, 04:40 AM
#67
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Join Date: Jul 2010
Posts: 91
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My dwell was set to 3ms.
After reading this page...
http://www.diyautotune.com/tech_arti...azda_miata.htm
... I changed it to 5ms today (I have an '89 eunos roadster) thinking that this might help with this issue but instead it killed power between 4-6000 rpm.
Not sure why that is but I set it back to 3ms and the problem disappeared. Might try even lower dwell tomorrow just for the heck of it and see if it revs smoothly to 7000rpm
When it lost power it behaved a lot like what I'm seeing at 6500rpm, but obviously lasted a lot longer. The AFR's looked normal when this happened too.
After reading this page...
http://www.diyautotune.com/tech_arti...azda_miata.htm
... I changed it to 5ms today (I have an '89 eunos roadster) thinking that this might help with this issue but instead it killed power between 4-6000 rpm.
Not sure why that is but I set it back to 3ms and the problem disappeared. Might try even lower dwell tomorrow just for the heck of it and see if it revs smoothly to 7000rpm
When it lost power it behaved a lot like what I'm seeing at 6500rpm, but obviously lasted a lot longer. The AFR's looked normal when this happened too.
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07-31-2011, 05:37 PM
#69
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Join Date: Jul 2010
Posts: 91
Total Cats: 2
This morning after dropping my girlfriend off at uni I changed the 'Maximum Dwell' from 3ms to 2.5ms. I don't know how to explain it but the car now revs smoothly right up to the redline.
Spookyfish: I read about the changes you made to your ignition, I just thought it was curious that more dwell seems to make my car run worse, this is the opposite of what I've learnt to expect from reading these forums and the megamanual. I don't have the knowledge to explain why decreasing the dwell - to a value that should be well below spec for the 1.6 coils - has improved things for me.
If anyone can explain what is going on here then I'd be keen to know.
Sorry for hijacking your thread too btw, I guess it's entirely possible that we have two completely different problems with the same symptoms... It seems to be that way with cars I've found :\
Is there any risk with running a lower dwell setting? As I understand it the only issue would be a weaker spark and mis firing? but as i just pointed out there's a lot I don't understand here It concerns me a little bit that there is an 'Underdwell protection' option in tunerstudio..
Spookyfish: I read about the changes you made to your ignition, I just thought it was curious that more dwell seems to make my car run worse, this is the opposite of what I've learnt to expect from reading these forums and the megamanual. I don't have the knowledge to explain why decreasing the dwell - to a value that should be well below spec for the 1.6 coils - has improved things for me.
If anyone can explain what is going on here then I'd be keen to know.
Sorry for hijacking your thread too btw, I guess it's entirely possible that we have two completely different problems with the same symptoms... It seems to be that way with cars I've found :\
Is there any risk with running a lower dwell setting? As I understand it the only issue would be a weaker spark and mis firing? but as i just pointed out there's a lot I don't understand here
It concerns me a little bit that there is an 'Underdwell protection' option in tunerstudio..
Last edited by giblets; 07-31-2011 at 08:18 PM.
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08-08-2011, 06:51 PM
#71
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That was at 2.6ms and the hesitation at 6500 was gone but the low end/mid range dropped off.
I now have it at 2.7ms and the 'Maximum Spark Duration' is down to 0.6ms from 1.0ms and it's feeling strong and torquey across the rev range with no hesitation.
To be honest I have no idea what's doing on here because I thought that less dwell = weaker spark and more dwell just meant hotter coils? But I'm happy with how it's running currently.
I now have it at 2.7ms and the 'Maximum Spark Duration' is down to 0.6ms from 1.0ms and it's feeling strong and torquey across the rev range with no hesitation.
To be honest I have no idea what's doing on here because I thought that less dwell = weaker spark and more dwell just meant hotter coils? But I'm happy with how it's running currently.
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