Did a little poking around, and you’re right, but only when it comes to downshifting “at speed,” like trying to hit 2nd gear when you’re doing 50 mph, at least according to this guy. I’d never noticed the effect, apparently because in more normal driving, there isn’t much of an effect. According to him, it’s not strictly necessary, but it does produce a smoother downshift under those conditions.
I think I’d still say that there’s no point for most drivers ever to double-clutch, unless they’re in full “boy racer” mode, since in routine driving, it doesn’t do anything beneficial.
On the other hand, if you’d ever driven a car without synchromesh (I’m old enough to have done so), you wouldn’t have a moment’s doubt about it. In a car like that, it’s very difficult to downshift without double-clutching, even in routine driving.
By the way, gang, before trying to push-start your car, you might want to check the owner’s manual. If the car’s battery is dead, that also means that the car’s computer isn’t getting any power, and push-starting the car could damage the electronics.
Also, if your car has a catalytic converter (almost all cars do), repeated attempts to push-start the car may result in unburnt fuel getting into the converter, and shortening its life. A catalytic converter is a very expensive piece of hardware, so damaging it is a certified “bad thing.” If the car is just suffering from a dead battery, a single push-start probably won’t do the converter any harm, but if there’s some other problem, and you try push-starting it several times, you’re in danger territory.
Given the high cost of repairs, you’re always better off getting a jump-start from someone (cables between batteries) than push-starting the car, if at all possible.
We live in Honolulu so unfortunately we are not near Las Vegas (or anywhere else) and finding a) someplace flat and b) an empty parking lot are pretty tough. We had one session at a reasonably deserted lot before the mall opened and she did well, starting up in first and taking it around in circles, also reversing some (Mom has heart attack at this point, but survives without saying anything).
We will work our way up to second gear and beyond next time around, I hope.
She was actually with me once when I had to push-start our old car - I made her do the pushing and it worked just fine. I definitely want her to have these “old-fashioned” skills.
Oh, and this is no hot little Porsche or other racy type cool car, so forget the double-clutching. It’s a Subaru station wagon - real soccer mom material. Thirty five years ago, I learned on a Plymouth 3-on-the-column wagon that was slightly smaller than the Titanic, so I don’t wanna hear no complaints from her.
The tips have been great, and very much appreciated.
Early Out is correct on the push-start. If the battery is completley dead then push-start will not work. You need enough power to power the fuel pump, and the ECM (Engine Control Module). These take alot less power than cranking over the engine, but still require some power. Not to sure about damaging stuff. Car computers these days are fairly well protected, but I would be careful.
Thanks to all for the how-tos on push-start. I am going to practice a couple times on my truck to see if I can get it down just in case I ever need to do it.
In my case no cat because my truck is a diesel so no worries about frying that. Don’t think any diesel has a cat except maybe in CA. CARB is strict there.
As Ender_Will mentioned you want the car in the lowest gear to ease the rotation of the engine. If someone is pushing you aren’t going all that fast (maybe 3 mph). The less resistance to turning over the engine the better. Each higher gear makes that turning more difficult so first gear is best.
Think about it…if second gear was better than first than why wouldn’t fourth gear be better than second?
Actually that’s an interesting point I’d be curious about an answer to it. Certainly in the old ‘mechanical’ days push starting was no sweat but can the same be done in the days of fuel injection and computers controlling the operation of the engine?
In the case of downshifting, depress/disengage the clutch, shift to neutral, release/engage the clutch, hit the gas (this increases the transmission gear speed), then depress/disengage the clutch, shift into the target gear, and release/engage the clutch again. The whole process happens pretty fast. This allows you to downshift earlier than you would otherwise be able.
Thanks Fuji for the explanation. This brings up another question: In my car, a '93 BMW 325 if that matters, I can’t notice any difference in smoothness of downshifting if I double clutch or merely hit the clutch, give some gas to bring up engine RPMs, select lower gear, release clutch. Is this due to my being horrible at shifting, really good at shifting, not sufficiently attentive to notice the difference, the German’s engineering being so good there isn’t a difference, or something else entirely?
Dunno what you folks are thinking with regards to torque and push-starting. At any given speed, the engine will turn over slower in 2nd gear than it will at 1st. Therefore, you have a mechanical advantage (i.e., greater torque) in 2nd as compared to 1st. The engine, of course, faces the opposite situation - mechanical advantage in lower gears, not higher. Anyways, if you’re moving too slowly when you pop the clutch, engine compression is more likely to stop you in your tracks if you use 1st, hence the doctrine of using 2nd in push-start situations. Use of even taller gears gets chancy because it’s harder to avoid an immediate stallout once the engine fires, at the vehicle won’t be moving fast enough for the engine to reach idle rpm and you may not get the clutch back in fast enough.
And what the heck is all this about ECM’s and fuel pumps and stuff?
Gorsnak, who drives an old diesel Rabbit with a mechanical injector pump and bugger all for electronics. On the other hand, if the battery doesn’t have enough juice to cycle the glow plugs, you may as well not bother pushing, either, unless the engine’s already warm (which, thankfully, it was both times I needed to pushstart - turns out I had a bad connection on the starter solenoid).
Pushing and popping. Heh, I used to have an 87 camaro with no starter. Had to push and pop the damn thing every time. Usually tried to park facing uphill. That way I could leave the door open, push the clutch in with my right foot, and push backwards with my left foot before popping. Worked like a charm for 2 years.
Of course, I had already replaced the Catylitic Converter with a chunk of straight pipe.
Just keep practising.
Go to a quiet car parking lot and just let her drive around in first gear, changing from first to second and back down again.
It’s a matter of repeating the motions of clutch down, gear change, clutch up, over and over again until they become so automatic she doesn’t have to think about it.
And if she is stalling, it’s either the clutch up too fast or not enough acceleration, and practice will get rid of both.
Is your car diesel or petrol? I learnt in my mother’s diesel citroen, it was big, heavy and old, but it had a really easy clutch. She bought a petrol Fiat Punto last year, and although I like being able to overtake and park more easily, the clutch threw me for a while, I would often stall at hills and junctions until I got used to it.
It’s like riding a bike, really hard until you can do it, then so easy you don’t know how you couldn’t.
Good luck!
No, a higher gear is actually better for push starting than a low gear. With a high gear there is less resistance to turning the engine. There would be more resistance if we were the engine trying to make the car go, but we’re not, we are the car trying to make the engine go.
The reason 4th gear isn’t better than 2nd is that at the speed we can push a car, 4th gear does not have the engine turning at high enough revolutions to prevent it from stalling once it starts.
How 'bout one more push start story. Recently I’ve been considering buying an old VW bug. I’m about to test drive one with the owner in the passenger seat. I start it up and while I’m putting it in reverse to back out of the driveway the engine stalls. As the car is rolling backwards at about walking speed I pop the clutch, re-engage the clutch and blip the throttle to keep the engine going all while I continue backing out of the driveway and turning the car in the direction we want to go. The owner turns to me and says “I guess you’re familiar with VW’s after all!”
