cruising and engine

[azharj]

One of my friend told me not to use crusing whilel uphill roads, as it damages the engine. Cruising is only for non hilly roads. Is it a truth or myth?

[wiswind]

This is something that you will have to decide when you are going up the hill.
What you want to avoid is having the transmission shifting down and back up over and over.
If the transmission is doing this, I would press the O/D button on the end of the gear select lever to keep the transmission from shifting into 4th gear (Overdrive).
This is particularly important when towing or you have a lot of weight in the vehicle as these conditions will cause the "hunting" on hills, and the transmission is working harder.

Shifting between gears generates more heat than staying in gear.
When the vehicle is constantly shifting between gears to try to maintain a set speed, it is worse than just having the motor run at a higher RPM in the lower gear to start with.

In other words......pay attention to what your vehicle is doing at the time as there is no hard fast rule.....like always turning the O/D off when towing or not using cruise control on hills.

Although 1 fast and hard rule about cruise control would be to NOT use it on slippery roads.

[azharj]

Though delay but thanks.
Dear now-a-days I have to travel a very steep hilly road abour 2 miles, once a week. Many German (BMW), Japnies Camery, Corrolla Toyota Honda even korian Hyandi cars Less than 2000 cc. overtake my car with quite an envying speed.

But,

1. If I am in drive mode with cruise on at 50 mph then 3rd and 4 shifting starts RPM go to 3500 and 2000 and coolant needle starts going up, so I have to putt AC off.
2. If I drive at 50 mph with overdrive off (light on), with cruise on RPM go to 3500 and coolant needles starts going up I have to putt AC off.
3. If I further reduce speed to 30mph with cruise on, OD off (light on) then I feel as if 2nd and 3rd shufting starts. RPM going to 3500 and 2000 and coolant needles starts going up I have to putt AC off.
4. If I place manual the gase paddle cannot be maintained and the car comes to 20 mph and shifting 1st and 2nd gear again RPM in the same varriation 2000 to 3500 and coolant needles starts going up I have to putt AC off.
5. If I try manually at 50mph same RPM varriation and coolant needles starts going up I have to putt AC off.

Any expert opinion??
Should I avoid this steep by extra travelling of 25 km??

[tomj76]

I don't know how steep a grade you're attempting to climb. That has a big impact on the issues you describe. When traveling uphill the engine needs to provide the normal energy to overcome friction and air resistance, plus the energy needed to lift the vehicle to the top of the hill. Traveling fast means that you need more horsepower from the engine, which in turn means that you need more cooling from the radiator.

The radiator also cools the transmission fluid by passing it through the tanks on each side of the radiator. A great deal of transmission heat is produced if the torque converter clutch (TCC) is not engaged. The TCC will only engage in 3rd gear and O/D, and only if the engine load is low enough.

When I climb steep grades (5-10%), I usually regulate the engine RPM instead of the road speed. I work to keep the engine in at least 3rd gear with the TCC engaged as I climb the hill by watching the tachometer. You can tell when the TCC engages because the engine RPM will drop as it locks the crankshaft rpm to match the transmission input shaft (at 60 mph in O/D, it's about a 300 rpm drop). I don't normally disable the O/D traveling uphill (I do disable it when traveling down steep hills), but rather based on the grade I can tell if the engine will be able to maintain the speed with reducing the gear and TCC lockup, so I adjust the throttle to keep it in the best gear possible.

This is a lot like driving a manual transmission up steep grades since you'd want to avoid constant down/up shifting as you climb, so you choose the best gear to minimize shifting and keep the engine RPM low as well.

Finally, the climbing capability of a vehicle is fundamentally based on the weight to horsepower ratio. The cars that pass you easily likely have much lower weight for the amount of horsepower delivered by their engines. Small engines can be boosted with turbo chargers which makes the perform like a much larger engine.

[azharj]

Thanks for good advice. I try to keep my RPM 2500 and use 3rd gear at this part of uphill it is 10 % grade