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Subaru ECU cold start logic is, well, questionable at best. As a side note, if your car is stalling that frequently, I would suggest adjusting the clutch engag

Subaru ECU cold start logic is, well, questionable at best. As a side note, if your car is stalling that frequently, I would suggest adjusting the clutch engagement position. Sounds like its either very low or way too high.

msandford 11y ago
It's definitely driver error and not the car's fault. I try not to rev too hard and slip too long, and it occasionally results in a stall. I'm spoiled from having driven a number of very powerful manuals. Big engines mean a lot of rotating mass which means that no revving is needed, just pop the clutch and go. That extra rotating mass also means that the ECU has more time to notice the drop in RPM and give it a little extra gas to bring idle back up. Not so in the Subaru. It's a very light engine and seemingly a pretty light flywheel too.
- jaytaylor 11y ago
  Just out of curiosity- Do you recall the approximate weight of flywheels in referenced "big powerful manuals"? IIRC the Subaru flywheels for the Impreza weigh in at about 20 lbs - and this is likely similar or identical to what is used in the Foresters.
  - msandford 11y ago
    No idea, but one of the cars that I learned to drive stick in was a friend's 2003 Mustang Cobra. All cast iron engine and something like 400WHP. I don't know that the weight of the flywheel was everything, the crankshaft weighs a lot and I think even the moving mass of the pistons and rods translates into rotational inertia. Finally having 8 cylinders versus 4 means that your engine response time is theoretically twice as fast. When the clutch engagement time is say 1 second and your engine is idling at 900 rpm you're only doing 1.5 rev/sec. In a four stroke, four cylinder engine that means you're getting on average 1.5 combustion events per second. In the 1 second engagement, you get 1 or 2 combustion events. In the 8 cylinder you get at least 2 and probably 3. I thought about doing the math for how much energy is in a cylinder firing versus stored in the rotational inertia of the moving parts, but honestly I don't know that I really care. I know anecdotally that big engines make it easier to get cars moving for some reason, and that smaller engines make it a little more difficult. I just speculated as to why I thought that might be.
    - digitalneal 11y ago
      I'd gamble it has more to do with the fact you have to overcome the resistance of 2 extra axles and mechanical differentials of the AWD forester that is making it appear to be a bit more difficult than the lazy v8 2WD Cobra. With that said, check out where the engagement of your clutch is. I've had people complain about grabby clutches(stalling) only to find out the engagement point is almost at the top of the throw (Former Subaru tech)
sliverstorm 11y ago
You could just start the car in neutral, then the clutch engagement zone doesn't matter...

msandford 11y ago

It's definitely driver error and not the car's fault. I try not to rev too hard and slip too long, and it occasionally results in a stall. I'm spoiled from having driven a number of very powerful manuals. Big engines mean a lot of rotating mass which means that no revving is needed, just pop the clutch and go. That extra rotating mass also means that the ECU has more time to notice the drop in RPM and give it a little extra gas to bring idle back up. Not so in the Subaru. It's a very light engine and seemingly a pretty light flywheel too.

jaytaylor 11y ago
Just out of curiosity- Do you recall the approximate weight of flywheels in referenced "big powerful manuals"? IIRC the Subaru flywheels for the Impreza weigh in at about 20 lbs - and this is likely similar or identical to what is used in the Foresters.
- msandford 11y ago
  No idea, but one of the cars that I learned to drive stick in was a friend's 2003 Mustang Cobra. All cast iron engine and something like 400WHP. I don't know that the weight of the flywheel was everything, the crankshaft weighs a lot and I think even the moving mass of the pistons and rods translates into rotational inertia. Finally having 8 cylinders versus 4 means that your engine response time is theoretically twice as fast. When the clutch engagement time is say 1 second and your engine is idling at 900 rpm you're only doing 1.5 rev/sec. In a four stroke, four cylinder engine that means you're getting on average 1.5 combustion events per second. In the 1 second engagement, you get 1 or 2 combustion events. In the 8 cylinder you get at least 2 and probably 3. I thought about doing the math for how much energy is in a cylinder firing versus stored in the rotational inertia of the moving parts, but honestly I don't know that I really care. I know anecdotally that big engines make it easier to get cars moving for some reason, and that smaller engines make it a little more difficult. I just speculated as to why I thought that might be.
  - digitalneal 11y ago
    I'd gamble it has more to do with the fact you have to overcome the resistance of 2 extra axles and mechanical differentials of the AWD forester that is making it appear to be a bit more difficult than the lazy v8 2WD Cobra. With that said, check out where the engagement of your clutch is. I've had people complain about grabby clutches(stalling) only to find out the engagement point is almost at the top of the throw (Former Subaru tech)

sliverstorm 11y ago

You could just start the car in neutral, then the clutch engagement zone doesn't matter...