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pete c · 02-13-2012, 10:34 PM

I have a few questions about the different techniques and overall economy.

I realize that engine off coasting down to the high gear min speed results in the best FE, but there are other factors.

Pop starting causes some clutch wear and the sudden quick spin up of a hot engine might result in some engine bearing wear.

When my glide ends at something under 25 mpg, as when coming up to a stop sign or light, I will pop start in 5th, then immediately clutch to a lower gear or neutral. Doing this means a much smoother gentle start which is obviously easier on the drivetrain.

This has me thinking that maybe a better technique might be to coast down to maybe 15-20, pop start in 5th, shift to third, accelerate ,skip back to 5th.

It does add a few gentle shifts, but, it eliminates the shock of instantly popping an engine up to a higher rpm.

Another option would be to just engine on coast or maybe engine off coast, start with the starter.

My guess is that with a diesel, engine on coasting might be just as good since diesels at idle use next to nothing for fuel. With a gasser with it's pesky stoichiometry concerns, engine on coasting more wasteful.

02-13-2012, 10:34 PM	#1 (permalink)
pete c Master EcoModder Join Date: Oct 2011 Location: ellington, ct Posts: 830 Thanks: 44 Thanked 104 Times in 80 Posts	E on/off coasting questions I have a few questions about the different techniques and overall economy. I realize that engine off coasting down to the high gear min speed results in the best FE, but there are other factors. Pop starting causes some clutch wear and the sudden quick spin up of a hot engine might result in some engine bearing wear. When my glide ends at something under 25 mpg, as when coming up to a stop sign or light, I will pop start in 5th, then immediately clutch to a lower gear or neutral. Doing this means a much smoother gentle start which is obviously easier on the drivetrain. This has me thinking that maybe a better technique might be to coast down to maybe 15-20, pop start in 5th, shift to third, accelerate ,skip back to 5th. It does add a few gentle shifts, but, it eliminates the shock of instantly popping an engine up to a higher rpm. Another option would be to just engine on coast or maybe engine off coast, start with the starter. My guess is that with a diesel, engine on coasting might be just as good since diesels at idle use next to nothing for fuel. With a gasser with it's pesky stoichiometry concerns, engine on coasting more wasteful.