What is the ideal RPM level from which you should change gear? I know this could vary from car to car, petrol to Diesel. When I'm driving normally and dont need to accelerate hard, I usually change gear at about 2500 rpm. This has been the same for my past car, a petrol, and my current focus diesel tdci.
I came across a website and noted that for diesel cars the an ideal rpm would be between 3000-3500rpm, and about 4000 during the initial run in phase. The reason was that in diesels revs are needed to blow out the soot created by the diesel engines. Is this correct, and am I driving too sedately at 2500rpm, which seems ample, without labouring the engine and enough for most situations.
It's entirely dependent on your engine. The redline usually indicates peak power (though not always) and the furthest point you should rev your engine. Changing too early or too late both put different types of wear on your engine, the kindest thing you can do for your engine is to vary the load on it, ocassionally let it rev and blow away the cobwebs.
For normal driving, the key thing is that when you change up a gear that there are enough revs so that the revs don't jump too low. You'll know this by how smooth the car feels. Note that the jump from 1st to 2nd will be larger than the other gears (usually) so more revs are required for that gear.
Generally, for a petrol around 2500-3500 revs is ideal, 500 less for a diesel.
As Crankcase says, it's a good idea to regularly (once a week) stretch the engine to the red line to clear things out a bit - but not if your cambelt change is overdue!
I agree with the comments above. but if you are going to give the revs a good blast make sure the engines nice and warmed up and don't over rev when starting off the oil needs time to warm up and lubricate all those inmportant parts inside the engine. Lesson over now lets aim for that red line
Originally posted by Wilko: I agree with the comments above. but if you are going to give the revs a good blast make sure the engines nice and warmed up and don't over rev when starting off the oil needs time to warm up and lubricate all those inmportant parts inside the engine. Lesson over now lets aim for that red line
Yeah, that's one of the little details I love on my 205 Gti, not just a water temp gauge, but also oil temp and oil pressure gauges so you can tell when it's just the right viscousity to safely floor it. All cars should have these gauges!
Cool. How long does it take after the coolant shows full operating temp does the oil take to reach full pressure? I've heard there's around a five minute gap from when the car says it's warmed up, to when the oil really is. True or false?
Originally posted by OilBurner: Cool. How long does it take after the coolant shows full operating temp does the oil take to reach full pressure? I've heard there's around a five minute gap from when the car says it's warmed up, to when the oil really is. True or false?
Oh it can more than 5 minutes to properly warm, depending on the oil you use, especially if you're starting the car up for the first time on a cold morning. You're actually looking for the reverse with oil pressure, the pressure goes up with RPM (oil pump speed), you want to see the pressure drop slightly meaning the oil us warm and more liquid.
IF you drive a Diesel remember is it a turbo or not, with a turbo u can kinda keep going a bit more. But if its not a turbo diesel then the acceleration dies off after the peak torque.
Originally posted by HP75: I came across a website and noted that for diesel cars the an ideal rpm would be between 3000-3500rpm, and about 4000 during the initial run in phase. The reason was that in diesels revs are needed to blow out the soot created by the diesel engines. Is this correct, and am I driving too sedately at 2500rpm, which seems ample, without labouring the engine and enough for most situations.
Don't know where they get that figure, most diesels you don't need to get as high as 3k to make decent progress as the max torque is from about 2/2.5k. If you look on Honest John's bit on running in a diesel he says the following:
"For the first 1,000 miles do not exceed 3,000rpm, but make sure you reach 3,000rpm regularly. For the next 1,000 miles (to 2,000 miles) do not exceed 3,500rpm, but make sure you reach 3,500rpm regularly. For the next 1,000 miles (to 3,000 miles) do not exceed 4,000rpm, but make sure you reach 4,000rpm regularly. For the next 1,000 miles (to 4,000 miles) do not exceed 4,500rpm, but make sure you reach 4,500rpm at least a couple of times a week. After that, no limit, but make sure you continue to hit 4,500rpm through the gears several times a week. The benefit of this is it helps to self clean the injectors, it blows any accumulated soot out of the exhaust system and it helps to free off the piston rings, making the engine more efficient and less likely to use engine oil."
Personally I've never pushed the engine that hard in normal driving, though I do give it a late-night thrash every few weeks to clear the soot out, my car now has 55k miles and uses no oils so I must have done something right!
Bear in mind that many modern diesels have a particulate trap in the exhaust that you should follow manufactureres instructions for that!
b308, that was the exact paragraph I got the figures from but I've mis-interpreted. It still says you need to reach 4500rpm several times a week. That is redline speed for my tdci and I never get near that even at hard acceleration. I just dont drive like that - feels like I'm thrashing the car.
thrashing is when you regularly exceed the 'red line' on the rev counter...without checking the oil first!
in the bad ol' days, valve bounce would set in just after the red line...and most cars' inductions were strangled at that point anyways.
there is no problem regularly taking the engine up the rev counter...especially when overtaking.
more damage occurs to an engine that spends its lfe permanently kept at low revs....its a throwback to WW2 cars!
however, what you need to find out is whether it is WORTH taking the engine to the red line during acceleration?
If the red line occurs after peak power has been developed, its pretty much a waste of time.
as an example of using low revs/high gears, on my old Volvo 740, which is a 2 litre...generally I keep the revs BELOW 2-2500 rpm, changing up early, etc, setting off in 2nd gear, etc...using the low-end torque of the motor....this is when I'm in a general traffic flow..it keeps the fuel consumption reasonable...and in this type of car is quite a relaxed form of progress..I suspect a diesel will be much the same?
However...when I want to get a move on and eat beemers....I use the lower gears for acceleration....getting to a spit 'n 'f@rt off 60 in 2nd gear...with the engine JUST off the rev limiter!
for overtaking, I drop down to whatever gear is going to give me the best acceleration, and is USEABLE given my starting speed.....and rev to the point where I detect that the rate of increase in speed has slowed....coming off the power band..time to change up to the next gear...
Originally posted by HP75: What is the ideal RPM level from which you should change gear? I know this could vary from car to car, petrol to Diesel. When I'm driving normally and dont need to accelerate hard, I usually change gear at about 2500 rpm. This has been the same for my past car, a petrol, and my current focus diesel tdci.
I came across a website and noted that for diesel cars the an ideal rpm would be between 3000-3500rpm, and about 4000 during the initial run in phase. The reason was that in diesels revs are needed to blow out the soot created by the diesel engines. Is this correct, and am I driving too sedately at 2500rpm, which seems ample, without labouring the engine and enough for most situations.
Originally posted by HP75: What is the ideal RPM level from which you should change gear? I know this could vary from car to car, petrol to Diesel. When I'm driving normally and dont need to accelerate hard, I usually change gear at about 2500 rpm. This has been the same for my past car, a petrol, and my current focus diesel tdci.
I came across a website and noted that for diesel cars the an ideal rpm would be between 3000-3500rpm, and about 4000 during the initial run in phase. The reason was that in diesels revs are needed to blow out the soot created by the diesel engines. Is this correct, and am I driving too sedately at 2500rpm, which seems ample, without labouring the engine and enough for most situations.
Change gear? Whats that? and how does it work?
LOL!
Mind you, I must be getting lazy as I quite fancy the idea of an auto ...... or is it that I'm getting old?!
Officially, my car develops peak power (115ps?)at 1850rpm but the redline starts at 4500rpm. So, what does this mean, do I still take it to 4500rpm? Someone please explain! :-)
Originally posted by HP75: Officially, my car develops peak power (115ps?)at 1850rpm but the redline starts at 4500rpm. So, what does this mean, do I still take it to 4500rpm? Someone please explain! :-)
Not simple to explain - its how you drive the car - a petrol engine tends to deliver its power higher up the rev range, therefore to keep the engine delivering the power you need you will inevitably rev it high.
If your red line is at 4.5k its sounds like a diesel, most modern diesels deliver their maximum power a lot lower, as someone else said, around 2/3k, above that the power tails off quickly and you are not gaining anything by revving it to the red line.
The two types of engine develop power in a different way and need to be driven differently, hence racing car drivers like Tiff struggle so much when they test diesels as they do not respond well to "foot to the flooor" driving styles that they use in a racing car.
QJ gives a lot of good advice in the previous thread, all I would add is to drive you car around and find out when it delivers the power and adjust your driving style accordingly. In fact that applies to any car if you want to make smooth, quick progress as I've no doubt Palmira would confirm!
Forget the max revs - if you want to drive on them buy a GTi petrol!
Very cleaverly, if left to it's own, my car will change up at 6700rpm (peak power) and start again at 4200rpm (peak torque) without having to lift off the gas. All very cleaver these fly-by-wire throtles and robotised 'boxes.
