brians356

I live on a hill and some time ago commenced roll starting my 92 Civic VX rather than using the starter. However, I am now wondering if this is wise. Does the ignition system (or fuel system, for that matter) suffer any ill effects from a roll start?

I recently replaced a bad igniter, which got me thinking ...

tony_2018

I don't see an issue, but roll starts, to me that is, are meant as an emergency usage

Former User

I agree

hondamark35

both methods of starting are perceived by the ECU/ignition identically.

key is in "ON" position: yes. crankshaft/camshaft is spinning: yes.

ECU: send signal to igniter/ICM to fire the coil.

that is all.

NotARaCist

iTrader: (1)

The transmission and clutch, however, don't appreciate it. IF you can start the car normally, you really should.

TomCat39

I had thought about this aspect and began to wonder which is harder on the drive train... Rolling start, popping the clutch in low gear or dumping the clutch at 5000 RPM to drag race....

This made me forgo the comment of the added stress to the drive train.

tony_2018

Yeah, which is why I stated that that rolling start procedure should only be used during emergencies, bad starter and you need to get to the parts store to replace yes. If its a bad ignition switch ( AFTER THOROUGH DIAGNOSTICS ) than ghetto rig a push button. I'm not going into details on that one as its kind of a security issue.

hondamark35

technique does become a factor. poor execution could accelerate wear on drive components

FabricGATOR

As opposed to starting to roll by releasing the clutch with a running engine in first gear, you want to "Roll Start" in high gear.

Think about it... if your doing 30 mph and you downshift to 1st, the wheels are going to try to make the engine turn really fast 1500 2000 RPM?

On the other hand, the starter turns less than 500 rpms to get her running, so if your rolling downhill at 5mph and pop the clutch in 5th, the engine turns easier and at lower RPMS.

I am constantly teaching the kids how to take it easy on the equipment...

TomCat39

Engine will turn faster but you are putting even more stress on the transmission as the ratios are much larger, it's not actually easier. It's quite a bit harder.

The easy way to test this try pedaling a 16 speed bicycle in top gear from stop, and then try it in first gear from a stop, which needs less energy (force) to get going?

The ideal gear is second as it gives plenty of engine speed to start and is the least stressful on parts for the engine speed.

I still use first or reverse as my car starts real easy and it's the gentlest on the drive train. I still need enough battery to disarm the immobilizer/alarm though as push starting it otherwise is futile.

94EG8

5th is the easiest to start the vehicle and the easiest on the driveline. You just have to be quick to keep it from stalling. Pop the clutch in 5th, as soon as you see the tach jump shove the clutch in.

TomCat39

How is it the easiest on the driveline? It takes the most force to overcome the large gear ratio to get everything spinning. It's also why once it does spin it spins everything faster. However the initial resistance is much more over the smaller ratio.

More force does not equal gentle or more gentle.

94EG8

You're thinking about this backwards.

You're not trying to move the car, you're trying to turn the engine over with the car. Or if you want to use the bicycle analogy the bike is already moving, you're trying to move the riders legs.

Using 5th turns the engine over slower, but due to the gearing it takes much less input force.

If you really want to prove it try it. You'll feel the difference. You'll note that when popping the clutch in 1st there's quite a shock, but when using 5th almost none. You can pop start a car in 5th at a normal walking pace.

Also, if you want to go a bit further, if you try pop starting a car in 1st moving at a high enough rate of speed you will tear the hub out of the clutch disc. You can do it in 5th at any speed though.

tony_2018

So it looks like a roll start from 2 or 3rd gear? Maybe depends on conditions (uphill/straight away or downhill )

TomCat39

I guess so. I'll have to think about it more.

Unfortunately the bike analogy doesn't work for the reversal as the bike isn't hard geared to make the pedal turn when the bike moves.

No the consensus is highest gear so 5th, or 4th.

I still am struggling with wrapping my mind around it as I can only imagine the forward direction based off a bicycle and this is the reverse.

I suspect another factor that is coming into play is where the big gear is and where the small gear is in the chain of force transfers.

I still struggle to see how a non 1:1 ratio would resist less to change when a clutch is released over a closer to 1:1 ratio. But that is the general consensus.

tony_2018

Only one way to find out........

94EG8

3rd. It's a reasonable compromise between a gear so low it's hard to turn the engine over, and a gear that's so high if you don't immediately depress the clutch you'll stall.

Assume it's a fixed wheel bike for this example.

When the smaller gear is on the side where you're inputting power it is easier to turn and the output side turns fewer revolutions than the input side.

slogfilet

iTrader: (1)

Say you're riding your bike at about 15mph... just coasting. Suddenly, your bike becomes a fixie! Would you want it to suddenly become a fixie in the lowest gear, or the highest gear? Which would give the least shock to your legs?

TomCat39

Yeah, I think that's what I was overlooking. A prime example of this setup is motorcycles. The small gear is typically on the motor and the large gear is on the wheel. I believe it reduces the amount of torque the engine has to produce to get the wheel turning...

Thanks for explaining that so my brain could wrap around it.

It helps when you don't just repeat the same answer over and over hoping for me to come up with a different result. I appreciate the different angles being provided until a connection is made.

94eg!

iTrader: (2)

The higher gear gives the road more of an advantage over the engine.

The determining factor is just how fast you can get the car moving before popping the clutch. If you can't it rolling fast enough (usually a when pushing) you won't turn enough rpm with 5th to fire the engine.

I drove on a dead battery for a week once by backing up hills every time parked. I also used to sneak out of the garage to not wake the baby early in the morning (loud exhaust) by letting the car roll out of the driveway and down the street. I usually used 3rd gear. lol