Overboost spark cut

Testing and development of Megasquirt 3

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Nightstalker1993
Helpful MS/Extra'er
Posts: 75
Joined: Tue Jun 03, 2014 11:09 am

Overboost spark cut

Post by Nightstalker1993 »

Hi yes, it's gonna be about cut x sparks from y events again....

Anyway, just wondering if we can get that feature back from the firmware 1.2.x as the current spark cut is very violent when it kicks in, whole engine rocks on it's mount when the spark cut activates whereas previously on 1.2.x with the correct cut x sparks over y event setting, the power cut would be more tame and less hard on the engine mounts. I use the overboost protection as a safeguard when tuning the boost control settings and hit the overboost protection quite frequently and really I can hear my engine mounts cry everytime it does :lol:

I apologise if I ask too much about this, but it is one feature that I truly love and miss.
wes kiser
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Re: Overboost spark cut

Post by wes kiser »

Fundamenttally the "x from Y'" cuts completely eliminates any safety/protection you gain from overboost.

This is a load safety, not overspeed. Those firing cycles are at the boost level deemed "unsafe/undersirable." If you feel the engine can safely operate at the overboost condition (the "x-y" cycles certainly were), then temperoraily raise the overboost while tuning this setting.

If you want an actual safety, perhaps you should request have some "overboost retard" feature whereby it retards the spark map by some amount. This could already be done in the table though for temporary tuning.
86 Rx-7, swapped to 2.3 ford turbo (BW EFR 6758), ms3/ms3x sequential fuel /waste spark, ls2 coils
88 Tbird 2.3t, Microsquirt Module (PIMP), TFI ignition
Nightstalker1993
Helpful MS/Extra'er
Posts: 75
Joined: Tue Jun 03, 2014 11:09 am

Re: Overboost spark cut

Post by Nightstalker1993 »

wes kiser wrote:Fundamenttally the "x from Y'" cuts completely eliminates any safety/protection you gain from overboost.

This is a load safety, not overspeed. Those firing cycles are at the boost level deemed "unsafe/undersirable." If you feel the engine can safely operate at the overboost condition (the "x-y" cycles certainly were), then temperoraily raise the overboost while tuning this setting.

If you want an actual safety, perhaps you should request have some "overboost retard" feature whereby it retards the spark map by some amount. This could already be done in the table though for temporary tuning.
Well in my opinion the overboost protection trigger is not just to protect the engine, but most importantly to alert the driver that something is not right and previously with the x-y function, whenever the overboost protection kicks in, I will immediately let go of the throttle and tend to the cause of the overboost(boost control tuning etc). Well, now with total spark cut it's also a similar story but just that when it comes in, it comes in really hard :lol:

And wouldn't overboost retard actually raise the boost even more? All the engine will do is reduce in engine power, raise the EGT and possibly make even more boost :?
jsmcortina
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Re: Overboost spark cut

Post by jsmcortina »

Sounds like you've set the overboost hysteresis too low. Setting it to a larger number will give more time for the driver to react to the boost-cut.

James
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