Let it warm up or drive it right away?
09-05-2007, 12:00 PM
#46
Rennlist Member
rnln: You've got it, except that it's OK to run the engine up to about 4K revs before an up-shift. This insures that the engine will be in operating range after you shift. If you up-shift at only 2.5K revs the engine will have to work too hard in the next higher gear (lugging - your item #2), and you don't want to do that. Lugging is hard on both the engine and transmission, forcing each to operate outside of a desirable rpm range.
09-05-2007, 06:46 PM
#48
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rnln: You've got it, except that it's OK to run the engine up to about 4K revs before an up-shift. This insures that the engine will be in operating range after you shift. If you up-shift at only 2.5K revs the engine will have to work too hard in the next higher gear (lugging - your item #2), and you don't want to do that. Lugging is hard on both the engine and transmission, forcing each to operate outside of a desirable rpm range.
09-06-2007, 01:49 AM
#49
IIRC, BA has said that teh max stress on the valve train is at or near idle. The idea of faster motion makes for more wear is _generally_ true tho.
A comment on what really happens when an engine is lugged:
http://content.hamptonroads.com/stor...8031&ran=43046
A comment on what really happens when an engine is lugged:
http://content.hamptonroads.com/stor...8031&ran=43046
09-06-2007, 03:51 AM
#50
RL Technical Advisor
The more I know, the more I find out how much I DON'T know. Ultimate knowledge appears to occur just before your funeral.
09-06-2007, 07:58 AM
#51
Burning Brakes
09-06-2007, 11:39 AM
#52
Rennlist Member
A good example of lugging would be to drive the car normally up to 15 mph and then put the car into 5th gear. Your engine will probably lug.
The greatest chance for lugging is when the engine is too cold or is very hot.
If you wanted to discuss what might cause misfires and pre-detonation, that would be quite a lengthy response, but I would be happy to share if you wanted to know
To be honest, I've experienced lugging in older, carburetted engine more frequently than fuel-injected engines. Also, you might find lugging is much easier on a high-compression engine than a low-compression engine.
09-06-2007, 12:17 PM
#54
Burning Brakes
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I know what lugging means now. Thanks. In the past, I had a car which can lug anytime, yes anytime it wanted even at higher rpm :lol:
Thank you everyone for explanation.
Thank you everyone for explanation.
09-06-2007, 03:38 PM
#56
Rennlist Member
"The more I know, the more I find out how much I DON'T know. Ultimate knowledge appears to occur just before your funeral."
When I need a subtle reminder of how much I don't know, I watch JEOPARDY! with my wife!
When I need a subtle reminder of how much I don't know, I watch JEOPARDY! with my wife!
09-07-2007, 01:25 AM
#57
- Talking about mechanical stresses, not frictional losses. What you say is nonetheless, generally true -- that is why Bruce's comment that mechanical stress on the valve train was greater at idle than at higher engine speeds stands out in my mind.
Certainly, no one would want to take a cold motor to red line tho, and that is the context of the discussion.
Certainly, no one would want to take a cold motor to red line tho, and that is the context of the discussion.
09-07-2007, 04:06 AM
#58
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- Talking about mechanical stresses, not frictional losses. What you say is nonetheless, generally true -- that is why Bruce's comment that mechanical stress on the valve train was greater at idle than at higher engine speeds stands out in my mind.
Certainly, no one would want to take a cold motor to red line tho, and that is the context of the discussion.
Certainly, no one would want to take a cold motor to red line tho, and that is the context of the discussion.
10-05-2007, 07:14 AM
#59
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...just to throw a spanner in the works as it were, whats everyone's procedure for the reverse?
i.e. after you've been out and driven it hard for a fair bit. do you let it idle for a bit or switch it straight off - or doesn't it really matter?
i usually let it idle a bit, check the oil level manually and then top up (or not) and then switch off and put a cover over the car.
I'm often paranoid this cover will catch fire from the heat off the license plate panel and engine lid, or the cover will trap moisture with the car still hot. (maybe this is a little OT)
i.e. after you've been out and driven it hard for a fair bit. do you let it idle for a bit or switch it straight off - or doesn't it really matter?
i usually let it idle a bit, check the oil level manually and then top up (or not) and then switch off and put a cover over the car.
I'm often paranoid this cover will catch fire from the heat off the license plate panel and engine lid, or the cover will trap moisture with the car still hot. (maybe this is a little OT)
10-05-2007, 08:35 AM
#60
Burning Brakes
...just to throw a spanner in the works as it were, whats everyone's procedure for the reverse?
i.e. after you've been out and driven it hard for a fair bit. do you let it idle for a bit or switch it straight off - or doesn't it really matter?
i usually let it idle a bit, check the oil level manually and then top up (or not) and then switch off and put a cover over the car.
I'm often paranoid this cover will catch fire from the heat off the license plate panel and engine lid, or the cover will trap moisture with the car still hot. (maybe this is a little OT)
i.e. after you've been out and driven it hard for a fair bit. do you let it idle for a bit or switch it straight off - or doesn't it really matter?
i usually let it idle a bit, check the oil level manually and then top up (or not) and then switch off and put a cover over the car.
I'm often paranoid this cover will catch fire from the heat off the license plate panel and engine lid, or the cover will trap moisture with the car still hot. (maybe this is a little OT)
Keith
'88 CE coupe