Turning off ignition at stoplights = starter wear?

[GasSavers_DaX]

Civic starters are in abundance, and you can rebuild them with new brushes, so I shut off at stop lights every chance I get.

[VetteOwner]

usually its not so much the motor part of the starter iself its more of the soliniod that kicks the drive out to enguage the starter.

[omgwtfbyobbq]

Originally Posted by JanGeo

Every time the piston rings stop moving they make contact with the cylinder walls and cause wear. They stop at the top and the bottom of the bore all the time that is why there is usually more wear there. Bearing surfaces will be exposed to the same added wear every time you stop and start the engine and the oil will be hot - could be really hot - hotter than the coolent thus thinner when you hot start every time increasing the wear.

I'm pretty sure that once everything is warm the wear is minimal. If manufacturers were shying away from automatic engine stop/start systems, I'd be a bit more inclined to believe ya.

Originally Posted by JanGeo

Plus you thermal cycle the Cat and exhaust system every time you stop the engine and start it again.

How does the cat cycle again every time you restart when everything is already warm?

[thecheese429]

Originally Posted by omgwtfbyobbq

How does the cat cycle again every time you restart when everything is already warm?

when you stop the engine the cat cools down from operating temp, and when you start it back up, it gets red hot again. I guess it depends on how long the engine is off and just the car and cat you have.

[omgwtfbyobbq]

Originally Posted by thecheese429

when you stop the engine the cat cools down from operating temp, and when you start it back up, it gets red hot again. I guess it depends on how long the engine is off and just the car and cat you have.

As per the thread title, stoplights. I'm pretty sure the cat won't cool down noticeably during a minute or so.

[JanGeo]

Oh yeah it will cool off - I think it runs at 700C - it will radiate a lot of heat. What I tried once was to stop the engine at a red light because I just took off with a cold engine and didn't want to sit for a minute with .4gph burn rate. When I started up again the engine ran like crap for 20 seconds, had no power.

As far as the cylinder bore wear, rings are really hard metal like chromium steel and are much harder then the cylinder bores. Newer engine designs have less spring tension in the rings and oils have improved a lot in the last 10 years but there used to be a lip that formed at the top and bottom of the bore from increased pressure of combustion which cause more pressure sealing on the rings as well as there was less oil at the top of the cylinder bore lubricating the rings. Yeah there is oil up there or else you would not need oil sprayed from the wrist pin to lubricate and cool the pistion and rings. Also adding some lube to the gas INCREASES TOP CYLINDER LUBRICATION and reduces friction so yeah the rings are causing drag on the bore. The oil ring is scraping excess oil off the bore but not all of the oil is removed and it also deposites it there too since the oil ring piston groove has holes drilled through the piston into the inner of the piston where the oil spray is coming out of the wrist pin as well as up from the splash from the crank. Some engines have a Silicon Steel bore which is really hard and very slippery which reduces friction and wear but most have steel liners and have very fine hone marks when new that require some break in.
A more detailed expaination is available at the Synlube site - which by the way coats the bore with a solid lubricant to reduce friction even further and improves ring seal reducing blowby.
The page has clear explanations of how the engine operates and even lists the losses in the engine from various factors like friction and pumping losses. good reading but you may want to turn down the speaker volume.

http://www.synlube.com/howsyn.htm

[omgwtfbyobbq]

Originally Posted by JanGeo

Oh yeah it will cool off - I think it runs at 700C - it will radiate a lot of heat.

The average light off temperature at which the catalytic converter begins to function ranges from 400 to 600 degrees F. The normal operating temperature can range up to 1,200 to 1,600 degrees F.

From here. So it's gonna drop ~600F sitting at a light?

Originally Posted by JanGeo

What I tried once was to stop the engine at a red light because I just took off with a cold engine and didn't want to sit for a minute with .4gph burn rate. When I started up again the engine ran like crap for 20 seconds, had no power.

That's why yer supposed to do it when the engine is warm, ie what automakers do w/ hybrids and even normal vehicles with the engine stop/start system.

Originally Posted by JanGeo

As far as the cylinder bore wear, rings are really hard metal like chromium steel and are much harder then the cylinder bores. Newer engine designs have less spring tension in the rings and oils have improved a lot in the last 10 years but there used to be a lip that formed at the top and bottom of the bore from increased pressure of combustion which cause more pressure sealing on the rings as well as there was less oil at the top of the cylinder bore lubricating the rings. Yeah there is oil up there or else you would not need oil sprayed from the wrist pin to lubricate and cool the pistion and rings. Also adding some lube to the gas INCREASES TOP CYLINDER LUBRICATION and reduces friction so yeah the rings are causing drag on the bore. The oil ring is scraping excess oil off the bore but not all of the oil is removed and it also deposites it there too since the oil ring piston groove has holes drilled through the piston into the inner of the piston where the oil spray is coming out of the wrist pin as well as up from the splash from the crank. Some engines have a Silicon Steel bore which is really hard and very slippery which reduces friction and wear but most have steel liners and have very fine hone marks when new that require some break in.
A more detailed expaination is available at the Synlube site - which by the way coats the bore with a solid lubricant to reduce friction even further and improves ring seal reducing blowby.
The page has clear explanations of how the engine operates and even lists the losses in the engine from various factors like friction and pumping losses. good reading but you may want to turn down the speaker volume.

http://www.synlube.com/howsyn.htm

O.K.
How do warm stops/starts at lights result in more than minimal wear?

[GasSavers_Minger]

You don't have to crank (is that the right term?) for as long to get it to restart.

[JanGeo]

When my engine is warm it doesn't burn a lot of gas so there is no point in shutting it off for 20 seconds - typical length of a red light. It's when it is cold and racing that I get the most savings. Also often hot starts - which I don't do so I am not sure - from the few times I did do them have random crank time from starting right away to cranking a lot. Hybrids are setup to start and run at a high RPM right at startup so the ECU is programmed to handle the fuel injection under those rapid start and run conditions and they also have a much more powerful starting motor connected directly to the crank at all times so there are no gears engaging and wearing. I just don't think a pennys worth of gas is a big deal to stop and start the engine for a typical light.

[GasSavers_RoadWarrior]

And if you're interested in emissions, a coffee shop chain did a study that suggested drive throughs were more emissions friendly than park and walk in operations, due to the emissions puff from restarting an engine (even if it remained fairly hot) being worse than emissions from idling a warm motor, I think the breakeven point was at about 10-15 minutes. One might say that they were biased, but if you look at how ECUs handle starting, they do just hose fuel into the motor until it catches, some fire all injectors at once in batch mode until they pick up the crank position signals and determine the motor is running over 700rpm or so, and THEN they look at whether the CTS is reading hot enough to pass to closed loop. So for about 15 seconds, warm start to idle smoothing out... your ECU is dumping fuel in there at about 10 or 11:1 or worse. And this is the best case, if your motor cooled off just enough, it could be doing this for a minute or two.

Then... it is always said that it takes about 15-20 minutes of running to put a start back into the battery. Now if your ECU controls alternator field current according to demand (Very common since the late 80s) that means it's running at full output, i.e. full drag, for 15 mins after you start, which is probably a 2HP drain on power.

Anyway, I typically reckon on a 1 minute service time for each car at the drivethrough and 5 minutes for each locomotive at the head of a train at a railroad crossing (1 loco pulls 40 cars IIRC, so if you see a "triple header" it's likely pulling 120 cars, and they move at little more than walking speed in our city so take a good while to go past) So if there's 5 cars ahead, I'll pull through and idle, if there's one loco pulling the train, I'll figure it's only gonna be 5 mins or less... if there's 12 cars, or 3 locos at the head of the train, I'll pull up and turn off the car.

At intersections though, I figure it's not worth turning the vehicle off for 2 mins.