Some more bump starting discussion

[CO ZX2]

Originally Posted by MetroMPG

If you start engine-off coasting, Alex, your MPG is going to go throught the roof

DITTO to that.

"do something, even if it's wrong"

[cfg83]

AlexK -

Originally Posted by AlexK

From a conservation of energy standpoint, letting the clutch out slowly wastes energy (slows the car down while the transmitted torque builds up enough to overcome the compression and start the engine). It also wears the clutch pads. Popping the clutch wears the clutch less and saves energy but jolts the drivetrain more. My experiment showed me that the jolt isn't too bad in my car.

Maybe this should be in it's own topic. Do you guys double clutch when shifting from neutral to say 5th gear after a P&G cycle? I do to save wear to the synchros in my transmission.

No, I try to match RPMs. I usually am pushing the accelerator when I engage the clutch to try to make it a smooth transition.

You can't double clutch when the engine is off, so there will be some synchro wear happening.

I am obsessed with FE but more obsessed with mechanical wear. From my experiences with many cars, the transmissions and drive trains break before the engines wear out (with proper oil changes). I need to decide if the increased wear and hassle is worth the FE benefit.

I don't know how to describe it properly, but I do the following :

1 - EOC'ng between 25 and 35 MPH, key already in "start" position.
2 - Push clutch down with foot
3 - Put in 5th gear
4a - Let up on clutch quickly, but not all the way, just enough to "tap the flywheel", is how I like to think of it.
4b - Push clutch back in right away to let engine turn over and start revving.
5 - Re-engage 5th gear and be on my merry way.

When I do it right, there is almost no bump in the start.

I agree that this should be it's own topic. There must be different drivetrain MPH+Gear sweet spots for each car, with the caveats noted so people can do this with full knowledge at their disposal. If we know the caveats, we can predict the sometimes possible negative results (i.e. strange noises coming from the tranny, wiggly engine from worn motor mounts, or ???), and adjust accordingly.

My assumption is that I will be getting a new clutch earlier than normal because I am engaging 5th gear like mad. The thing is, it's become a hobby for me at this point, a way to turn an awful commute into something creative, so the potential cost is ok because my eyes are wide open, so to speak.

I don't know anything about the mechanicals. I only have surface knowledge. My only barometer is how "violent" the bump-start feels. Also, when I tap it wrong, it doesn't turn over, and I have to do it again .

CarloSW2