Climbing short steep hills

[cathy]

If I drive 1 mile 10%+ freeway grades daily as part of a commute, does it drastically shorten life of the engine? Does car use boundary lubrication always? (say 40mph-50mph uphill)
What would be the best solution to reduce engine wear?

 

[Burt]

A guideline for industrial engines is not to run them continuously at more than 90 percent of rated power capacity. I assume that similar is true for cars. Most all the wear is cold starts or when you push the engine to its output or rpm limits. But look forward to comments of others. You might be a good candidate for a plug in hybrid because it will shut off the engine during coasting and recharge when braking.

 

[ueberooo]

Originally Posted By: Burt
A guideline for industrial engines is not to run them continuously at more than 90 percent of rated power capacity. I assume that similar is true for cars.


So, if your car has say 200 hp, then don't run it continuously at 180 hp? That translates to perhaps something like don't run it to redline minus 500 to 1000 rpm. I don't know of anyone in real life (who still is alive) that would continuously drive like that, although I have seen some really crazy stuff in movies (eg drive, the bjourne insanity, etc).

Quote:

Most all the wear is cold starts or when you push the engine to its output or rpm limits. But look forward to comments of others. You might be a good candidate for a plug in hybrid because it will shut off the engine during coasting and recharge when braking.


I agree, I would try to keep it at least 1000 rpms from the redline (which is like 6000-something)). In my car the fuel efficiency at near wide open throttle peaks somewhere before 3300 rpm (the peak torque point) then starts to decline more and more rapidly after that peak torque point; therefore I rarely take it above 5000 (and generally under 4000 to maximze fuel ef).

If you have an automatic transmission you have less ability to control this, but I believe most automatics will go reasonable on the rpms unless you have the gas pedal almost all the way down to the floor.

For the first few minutes of driving (say 3 minutes), I try to keep the rpm's below or not much above 2000. So, after the first mile or so of a cold startup i'm really careful and aware of this. The second mile, i try to keep it under 2500; and after that I drive it as I normally would.

If your up hills are pretty much immediately after startup, then I would consider letting it idle for a minute or two and have it get a headstart on warming up.

Good point also on the hybrid; many of these have regenerative breaking and would be ideal for hills and stop and go driving.

 

[eljefino]

Don't lug. An automatic would have you covered. 3rd gear on a stick shift at 4000-4500 RPM wouldn't break anything. Freeways are generally engineered to avoid the steepest worst grades.

 

[demarpaint]

Originally Posted By: eljefino
Don't lug. An automatic would have you covered. 3rd gear on a stick shift at 4000-4500 RPM wouldn't break anything. Freeways are generally engineered to avoid the steepest worst grades.


+1 Lugging an engine is probably one of the worst things you can do.

 

[ueberooo]

Quote:
+1 Lugging an engine is probably one of the worst things you can do.


I've heard somwhere that it's just about impossible to technically really lug an engine these days. The computer may not let you do that and not inject enough fuel to do damage.

I go by my manifold pressure gauge to maximize fuel economy. I try to get power anywhere in the range of 1200 rpms to 4000 rpms when driving for economy. I vary the gear (thus rpm) by how much power i actually want/need and will try to be in the gear giving the best fuel economy; thus, I won't be at 1200 rpm's anywhere close to an open throttle (being closer to 2000 rpms at half to near idle throttle would give much better economy when that sort of lite power is demanded), but wouldn't hesitate to drive it at 1200 near half air density all the way down to idle air density (which is at about 1/3 atmospheric pressure) if even less than lite power is needed to keep a coast going.

What sort of conditions are you thinking of when you refer to 'lug'ging?

like forgetting to engage the clutch while in gear and coming to a stop, and going well below the idle rpm (~800)? I've done that a few times, and the violent shaking tells me that probably wasn't great for the car.

what are lugging rpms in your opinion?? I've heard oil pumps may not perform optimally under 1500 rpm, but after idling for like 2 seconds i don't see that should be a problem, there should be plenty of oil everywhere.

I don't have much fear of low rpm's but maybe it's a question of what is considered "low" rpm and how it's driven there.

 

[demarpaint]

^^ I don't think you can lug an AT, although some of these newer 8 speed units sure feel like they're being lugged at times.

A standard transmission can be lugged, as you mentioned coming to a stop and forgetting to clutch, or shifting too soon into a higher gear and being too lazy to downshift again into the right gear when clearly the engine is straining.

I drove with someone who was taught to drive stick and get out of first gear and into the higher gears as soon as possible. By the time he was doing 25 at the end of an acceleration ramp he was in 5th gear, floored wondering why his car couldn't get out of its own way. I'm glad he had an open mind, and I was able to reprogram him before he ruined an engine and his clutch.

 

[Eddie]

I don't think the industrial engine guidlines apply here. Most industrial engines run at a lower rpm and put out less HP/CuIn than auto engines. The best pulling rpm for an auto engine is at the maximum BMEP which is at or close to the maximum torque. For heavy climbing I would hold maximum torque if possible. Ed

 

[KrisZ]

Originally Posted By: cathy
If I drive 1 mile 10%+ freeway grades daily as part of a commute, does it drastically shorten life of the engine? Does car use boundary lubrication always? (say 40mph-50mph uphill)
What would be the best solution to reduce engine wear?


The boundary lubrication is a last form of defense and metal to metal contact is next, so be design it's not there to protect the engine for long periods of time. If your engine was in boundary lubrication for most of its commute, it would be toast by now.

However I would let the car idle in the morning for few minutes to get the oil heated up a bit and keep the RPMs between 2k-3k during the climb.

 

[rslifkin]

If the engine is warmed up by the time you hit the big hill, provided you aren't lugging it, pretty much nothing you do while climbing the hill is going to hurt it. Even 90 seconds of WOT at near redline (say, 500 rpm below) is very unlikely to hurt it (assuming the engine is healthy).

 

[SwampSurvivor]

I would think, if the engine is up to temperature, that it would be very good for the car. Probably would clear out some carbon.

 

[Clevy]

What engine. Where's the torque peak. If it's an auto transmission find the gear that holds you near the tq/peak rpms and still maintains close to the speed limit.
Ive had my mustang rev at 4200rpm for hours driving thru the BC mountains and it didnt even hiccup once we hit flat ground,so I doubt any damage van occur.
If the oil is in good shape in a healthy engine high rpms won't kill it. Just make sure the engine is up to operating temp before you go full torque.

 

[mechtech2]

Originally Posted By: cathy
If I drive 1 mile 10%+ freeway grades daily as part of a commute, does it drastically shorten life of the engine? Does car use boundary lubrication always? (say 40mph-50mph uphill)
What would be the best solution to reduce engine wear?


Do absolutely nothing about it.
Just drive the car when and where you want to.