EOC bump starting -> synchro wear?

[theholycow]

Cool, sounds great to me.

[MrChoi]

im asking myself this question: is it worth gaining 1% FE by roll starting? will you even gain 1% FE by doing this?

to me its not worth saving a few pennies in gas in the expense of "re-syncro-ing" the tranny.

when i do a roll start im usually on a hill and not moving. i put the car in second gear.
no wear to syncro's since car is stopped.
then let the e-brake loose, at this time the car will start to roll if you are off the brake. ( <very important to be off the brake)
then let the car gain some kinetic energy and let the clutch go to spin the enigne on.

any of what i said make sense? i hope so.

[MrChoi]

Originally Posted by Jay2TheRescue

Not an option on all vehicles. On all of my vehicles if the transmission is not in park the key will not turn to accessory. Also, in Accessory on all of my vehicles the steering wheel is locked.

-Jay

usually only applies to automatic transmission and you cant roll start in an auto.

[theholycow]

Key starting is unpleasant and causes a series of error beeps. I worry that those beeps mean that it's logging data about what I'm doing, to be used against me in the event of a warranty claim on my leased car. No, they are not the seatbelt chime or any other normal beep. Yes, it's unlikely to ever cause me any trouble, but I prefer roll starting. I don't expect to have to re-synchro the tranny even if my fear of synchro abuse is confirmed. I do appreciate the opinion of someone with the same concern, though.

Oh, and Jay...I've never driven an automatic that can't kill the engine with the key in D. It's necessary for safety in the event of brake failure or engine fire. Restarting with the key won't work in moderm GMs unless you're in P or N, but does work fine in N at speed. I still strongly recommend against EOC in any automatic not approved for towing (usually behind an RV) with the drive wheels on the ground, since heat will quickly destroy the transmission without the input shaft pumping the fluid.

[white90crxhf]

Originally Posted by theholycow

When I neutral coast with the engine on, I can rev-match before stepping on the clutch, so when I shift it goes right into gear.

When I bump start during EOC, not only can't I rev-match, but it's got a lot more RPM for the synchro to make up, and I can feel it in the shifter. The synchro has to accelerate the clutch from a dead stop to 1500 or 2000 rpm. Is this going to wear my 5th gear synchro really terribly?

why not just stop bump starting? id rather change my starter than my syncros.

[Jay2TheRescue]

Originally Posted by theholycow

Key starting is unpleasant and causes a series of error beeps. I worry that those beeps mean that it's logging data about what I'm doing, to be used against me in the event of a warranty claim on my leased car. No, they are not the seatbelt chime or any other normal beep. Yes, it's unlikely to ever cause me any trouble, but I prefer roll starting. I don't expect to have to re-synchro the tranny even if my fear of synchro abuse is confirmed. I do appreciate the opinion of someone with the same concern, though.

Oh, and Jay...I've never driven an automatic that can't kill the engine with the key in D. It's necessary for safety in the event of brake failure or engine fire. Restarting with the key won't work in moderm GMs unless you're in P or N, but does work fine in N at speed. I still strongly recommend against EOC in any automatic not approved for towing (usually behind an RV) with the drive wheels on the ground, since heat will quickly destroy the transmission without the input shaft pumping the fluid.

What I was saying is that on many GM cars the accessory position is past the lock position. It can only be accessed by putting the vehicle in park. I can shut the engine off while in gear though. I do not shut off the engine while gliding for several reasons though.

1. Loss of power steering and power brakes. My truck weighs 3 tons. I need power steering and brakes.

2. All my vehicles are 10 years old & up, and the lowest mileage one has 150,000 miles on it. What if I'm ready to restart, and the vehicle isn't?

3. Safety reasons. What if I need to hit the gas to avoid something, or swerve to miss someone/something. No engine, no PS, no PB.

Years ago my mom's old 1988 LeBaron (Luxury version of the Dodge Aries K-car sedan) had the FE gauge. I used to do engine off glides on hills just to see the gauge at 99mpg. That was a small K car though. I could easily steer and brake without power assist. Also it was relatively new so I was quite confident that it would start quickly if needed.

-Jay

[dosco]

Originally Posted by MrChoi

no wear to syncro's since car is stopped.

There's the point. If the car is moving, and you are using the transmission, the synchros are wearing. If you're concerned about synchro wear, don't drive the car.

[theholycow]

Old bump...

I wondered if maybe my 5th synchro was starting to feel weird, so I tried the 4th synchro for comparison. They feel the same. Then, when I went to put it in 5th it went right in like a perfect double-clutch shift...and I realized that I can use any synchro to spin up the input shaft/clutch plate then drop it in 5th without wearing the 5th synchro at all.

So, now I can spread out the synchro wear across a few gears. Wait at the 4th or 3rd gate for a second then stick it in 5th.

[bowtieguy]

i did EOC and bump start for the first time today w/ my wife in the car. she had no idea when i restarted.

i asked her if she felt it and she said yes. but, what she felt was my first shift after restarting. we did it a 2nd time to confirm.

[theholycow]

Nice job!

I haven't tried with my wife or even let her know I'm doing it...