uskrewed

No, it isn't some trendy title.... I was just curious about the negative effects that popping your clutch to restart your engine has on your tranny/synchros/clutch. I used to coast with my engine off to save fuel, sometimes I'd drop down to 40mph and pop it in 5th and sometimes I'd slow down to 10mph and pop it in 5th then shift to 2nd and keep driving - but that was with my old beater. Now that I have a new car I haven't even tried it because I didn't want to do anything to damage my baby.

So anyone know the verdict? how bad is it for you to pop your clutch?

rangerryda

iTrader: (1)

Definitely not recommended at all. Wearing out the clutch prematurely is the first thing and they're not easy to swap out in our cars compared to most FWD's. I don't know if you are aware but when slowing down... if you are still in gear and have your foot off the gas, absolutely NO FUEL is going in the motor. If you put it in neutral and coast, you are using fuel. My advice, just leave it in gear when slowing down. Then again, you could cut a hole in your floor and use flintstone power up to 10 mph lolz. jk

uskrewed

I thought the ECU just changes to a learn burn of like 17.7:1 instead of 14.7:1 also if you're in gear you slow down a lot faster than if you coast in neutral

draxcaliber

you always coast in gear, never in neutral. when coasting, as stated before, there is no gas going to the engine, whereas if you coast in neutral, your engine uses fuel to make the engine idle, so it doesn't die, this is the same idle as if the car was standing still, no difference.

you downshift exactly the opposite way you upshift, choosing an appropriate gear for the speed. do not shift to overdrive at 10 mph. for example, going 50 mph in 5th, you see a red light up ahead, downshift to 4th, 40 mph, downshift to 3rd, 30 mph, downshift to 2nd, and do not shift to neutral until you are about to stop.

you leave the car in gear should you need to start moving again, and so that the cars handling is more predictable, or should you have a heart attack or something, the car will engine brake until it stops instead of rolling in neutral until something stops it.

also, your brakes are vacuum powered, therefore they are stonger when engine speed is higher.

mcbrew

Actually, it is pretty much the opposite. The more open the throttle, the less vacuum you have. Of course, you have a reservoir of vacuum to hold you over for a while... and it takes a relatively small amount of vacuum to add boost to the brakes.

It is true that our engines (and most modern engines) will completely cut fuel delivery when in an overrun situation. This is when you are coasting in gear above idle speed. The engine is being turned by the wheels. There are a lot of people who don't believe this, but anyone who has installed an EGT gauge can prove it -- coasting down a long hill, you will see EGTs drop down close to ambient air temp. In other words, there is no combustion going on.

It is true that zero fuel (in an overrun) is less than a little fuel (idling in neutral), but you will not go nearly as far in gear due to engine braking. Which one is better depends on the situation and the terrain.

As far as the original question, I can't give any hard data, but it doesn't seem to me that starting the engine by popping the clutch is much more damaging than normal clutch usage. Apparently, some new cars don't recommend it because it "confuses" the electronics. I've pop-started a lot of cars and there has never been any immediate damage. That includes diesel Mercedes... let me tell you, it's not easy to pop start a car that has a 23:1 compression ratio!

rangerryda

iTrader: (1)

Diesel = Tank. Doubt you'll ever break that car lolz

engifineer

Since your brakes are vacuum powered, you have no brake boost when the engine is off. Coasting with the engine off is a BAD idea any way you look at it.

As far as coasting in neutral, you have given up 1/3rd of the control you have over the car. You have steering, brakes and throttle as forms of control on a car. And when push comes to shove, the throttle can get you out of a lot of trouble in some situations. Coast in gear. A very small savings in fuel economy is no good trade off for unsafe driving.

uskrewed

Steering on our car is electric, and loss of brake boost just means you have to push harder and it's not like the boost goes away the second you turn off your car. As far as going faster goes I'm sure the half second it takes me to pop the clutch wouldn't make any difference because of the slow acceleration rate in 5th gear.

Anyway, I wasn't trying to argue semantics or ethics, I just wanted to know if anyone knew the damage caused to my car by popping it's clutch. thanks to mcbrew for giving some insight on the situation

draxcaliber

dude, it does make a difference. it is just a waste of clutch and synchro wear. you aren't supposed to pop the clutch into 5th gear when decelerating. why on earth would you shift into overdrive gear to slow down?

more to the point, if you leave the car in 2nd gear while coasting the a stop, eventually the car will start idling again, and will not stall. so you can coast to an intersection in 2nd, and if you don't touch the gas or the brake, when the rpms get to about 1000 rpms, it will start to idle, and actually keep the car going on its own.

but hey, if you wanna drive like an idiot, and think popping it into 5th gear is fine. more power to you, i look forward to you trying to get toyota to replace your transmission underwarranty. i bet the owner's manual says what the proper wheel speeds are to have which gear engaged.

pickledchang

i remember dating this girl that drove her 5spd in a similair way... yeah, i dumped her shortly after that.

popping the clutch to start up the car should only be used when your battery dies on you. makes me wonder how much longer it will be until some fancy electronics take away that feature too.

uskrewed

lmao @ you dumping a girl because of that, way to be petty.

rangerryda

iTrader: (1)

He never said it was because of that...

Long story short, on your car, don't pop the clutch. It just doesn't make any sense no matter how you look at it. If you want better fuel economy, buy a Prius.

pickledchang

...if you only knew the half of it.

Nateson

My first car was a 1968 Mustang, and would always start in the driveway. When I got to where I was going it didn't want to take me home. Various issues with that car. Anyway I was good at push starting my car.

I found out later that push starting puts a strain on your timing belt. So when you turn off your car at speed and coast, then pop the clutch to start it back up, you are endangering breaking the timing belt (or chain) or screwing up your timing. I got away with it, but it could have been costly. I only found out about this when I had a ninja 250 a year ago.

Just think of it this way, when you're at speed and want to start you car, you have the momentum of the vehicle going what ever speed and your engine is at a stand still. When you pop your clutch its up to your engine to suddenly get up to speed. So the crank shaft starts spinning and turns the timing belt for the cams. If your belt slips, then your cams are off time. Then bad stuff happens! bent valves... detonation what ever. You may get away with it too, but be careful.

uskrewed

Thanks for the info, Nateson - it's exactly what I was asking about.

rangerryda

iTrader: (1)

Not to mention oil pressure.

engifineer

Your cams are turned by the timing belt which is turned by the crank, regardless of whether you pop the clutch to start the car or if you start it with the starter. In either case, you are suddenly spinning the crank to start. So the timing belt is not seeing something different than normal. There is possibly a slight bit more shock load when push starting, but an electric motor (aka starter) with direct drive to your crank (via the flywheel on a manual) is a pretty abrupt start since electric motors apply all their tq all at once.

I would be more worried about shock load to the clutch if it is done all the time.

Nateson

When you start your car it's not rev-ed very high. If you are coasting down a hill at 70 mph in neutral and miss shift to 2nd rather than 4th for engine breaking, you can slip the timing. Cars are meant to take a bit of abuse, but 2nd maxing out around 60mph you would bang off the rev limiter and could possibly screw your timing. I understand the 2zz motor was susceptible to this. It is more common in motorcycles but not exclusive. Just be careful.

bwhite

Wow !! from dumping a gal to all kinds of BS!!

I'm a MECHANIC, and have been for many more years than some of you have lived, and turning the engine over with a starter (that turns the crankshaft) or via a transmission (manual) that also will turn the crankshaft is not putting any more strain on any timing chain or belt at all..... period. I have absolutely NO RESERVATIONS WHATSOEVER at starting the car with a manual tranny by Push-starting it.

and... if the gal that got dumped because she started it without using the starter is reading this... Baby.... you lost a hunk of garbage when you got dumped !!! Wayyyyy to go...... c'mon over to our neck of the woods and I'll hook you up to some REAL men. Tough, but warm 'n way SMARTER than you had before .

pickledchang

i can see how pretty much everyone on a car forum would/could call themselves a 'MECHANIC', but to be a mechanic longer than some of us have lived, and youre 23? wow, so youve been working on cars since the age of -3? it sounds a little desperate down in yer neck o' the woods, especially if a girl who cant even turn a computer on is so appealing. oh, and a word of caution, she watches you while you eat. have fun.

however, im not sure how good the attention span in your neck of the woods is either, but if you read the original post, it discusses restarting the car while in motion. and if youve done it, youll feel the car jerk, which causes stress on the tranny and engine. if it was good for the car and saved fuel, than wouldnt manufacturers have made a feature that turns off your engine on the freeway when you take your foot off the gas? i guess thats why down in yer neck of the woods there are so many broken cars in the front yard.

and here i was having a bad case of the mondays... thanks for the laugh.