How to smoothly bump start / clutch start an engine

[KJSatz]

I just read this after a 250-mile drive to school when I did EOC 4-5 times and bump start...I made sure to shutoff while the tach was falling so hopefully the injectors were shut off even before I turned the key. Your post makes me feel better about it. Anyone else want to corroborate to make me feel even better?

[bkruger]

Wow, for the past week or so, I've been bumpstarting when I EOC but it was actually....bumpstarting. I didn't know it would work without a kind of a slowing down then a jerk on. I'll practice more once I get that kill switch installed (if only there was a relay diagram for my model). Reading this probably saved me a lot of drivetrain damage.

[newtonsfirstlaw]

Originally Posted by NoCO2

How does this method effect clutch wear though?

It obviously depends on how often you bump start. I did it compulsively, probably 50-100 times per commute.

I have also noticed that some cars (such as a Mira) aren't very bump-start friendly, for whatever reason. On other cars I have driven (e.g. early Suzuki Swift, carb model), the wear on the clutch would be imperceptible (as judged by loss of kinetic energy in the car). On a bump-start friendly car, it could probably be done with abandon.

I bump started for 2 years like this on the Mira and the clutch is on its last legs.

However, if I had restricted the bump starting to the largest hills (e.g. glides of maybe 20 seconds plus) instead of every opportunity to glide (even several seconds), I would have had the lion's share of the benefit and maybe the clutch would have lasted 10 years.

There is something to be said also for getting the clutch fully engaged before major acceleration, rather than a gentle easing out until 2000-2500rpm, and avoiding engine braking since the loss is in the form of kinetic energy, and brake pads are cheaper than clutches. As it is, a dedicated hypermiler will probably have brake pads lasting the life of the car, so you may as well use them for something.

[noxman]

I read , that bump mode isn't ideal for car catalyst.
Because sometime can unfired fuel mixture get to catalyst and damage him.
(I guess, when the car don't start at first bump)
I have catalyst and now for 1 month trying bump mode. But i'm afraid from braking my catalyst.

What do you think, how solve this problem?

[Snax]

You are at no more risk of damaging your catalytic converter with a bump start vs. a keyed start with any modern fuel injected vehicle. There is potential for damage with a carbed vehicle if the motor is allowed to turn over without the ignition on since the fuel flows regardless, potentially doing exactly what you suggest. Serious indiscretions there are usually followed by a large bang!

It is however worth noting that frequent engine off operation may allow the converter to go below it's optimal operating temperature, rendering it less effective during the cool times.

[noxman]

Thank you. Next question. I heard , that V-belt can be breaking. So its danger use bump mode. Is that correct?

[Snax]

If that is the case, it's probably best not to use the starter either.

[Jammer]

"select a higher gear than you would otherwise be in for the vehicle's current road speed"

Well I had posted a long reply saying that this method was not allways the best option in my Cobalt. However I just got in from testing the method as described here and it went pretty well.

So, as they say: Never-mind.

[user removed]

Assume you car goes 70 MPH at 3000 RPM. At 7 MPH bump starting in the same gear is the same RPM as cranking the engine with the starter, about 300 RPM.

regards
Mech

[taredog]

Have to put in my thoughts.

There should be no bump involved. Do not "pop" the clutch. Think of the way you go up through the gears when accelerating. Unless you always give your passengers whiplash and chirp the tires when you shift up. Gentle is the word and use the same gear you would use when accelerating at the speed you are at. Having knowledge of what is actually happening when the tranny is in or out of gear and what happens when you push the clutch in helps. Oh and how the engine is involved in all that.

I have used this technique a lot over the years due to being too poor to waste gas, having a dead battery and no funds to replace it or just having to drive a POS the wouldn't idle well.

As far as reverse tourque harming the drive train, if done correctly it is the same as taking your foot off the gas when decelerating. In other words the clutch is designed for reverses in forces. That's why many clutch plates have springs in them.

As to EOC, I never thought about the pilot bushing (is it really a bearing now in cars/light trucks?) but you should never keep the clutch depressed for long periods of time. Shift to neutral and let the clutch out. Less wear on the through out bearing.

I have known and ridden with people who pushed the clutch in every time they let up on the gas. Why? They were told to by someone. Believed the car would stall otherwise, even at speed. Never was successful at converting any of these people.

So do your EOC right, enjoy but know you didn't invent it. Been around since there were cars with clutches.

And be gentle restarting it using the proper gear and don't "pop" the clutch.