Low End vs High End torque

[KarateBoy]

i know that torque plays a big role in acclerating but what is better low end 2K-3k revs or high end 4K-6K. I would think that high end because then you are using your peak Hp and Peak torque- or something near it. Or is this just a matter of preference. Also how can you increase the torque of a car?

[crisis]

Originally Posted by KarateBoy

i know that torque plays a big role in acclerating but what is better low end 2K-3k revs or high end 4K-6K. I would think that high end because then you are using your peak Hp and Peak torque- or something near it. Or is this just a matter of preference. Also how can you increase the torque of a car?

Depends on the application. Low end torque gets you off the mark quicker but high end torque would probably pull higher ks. Off road driving I would definitely prefer low torque where the motor didnt have to be stressed to maintain momentum through sand and over hills etc. Also driveabilty around town is helped by lower torque. Henk will be able to inform you of the advantages (yes I said it) of diesels in this regard. The length of intake runners has an effect of where the torque is maximised but it will take one of our more technically informed members to explain the finer details.

[KarateBoy]

i understand the point of off roading but what about "sport car" wise like a supra, skyline, 350z, etc... would high end torque be better there and when you're in 1st i doesn't take long for a car to rev up from my experiences. But i want to hear more about this so lets keep the good replies coming

[Matra et Alpine]

Originally Posted by KarateBoy

i understand the point of off roading but what about "sport car" wise like a supra, skyline, 350z, etc... would high end torque be better there and when you're in 1st i doesn't take long for a car to rev up from my experiences. But i want to hear more about this so lets keep the good replies coming

It's generally accepted that a torque curve leading the power curve is better.
The where you want torque is about drivability for speed.
WRC are now playing with 4-speed boxes because they have managed to increase the torque across the range enough to save them a grea. The theory is avoiding a gear change will make stage times quicker as the driver won't change gears as often.
Because of the way torque ss developed/measured, I don't think you can expand torque beyond the upper power band, but I'll need to think about that overnight to remember why
Simply put you can always use a gearbox and clutch to 'exchange' power for torque. An extreme example of this was the 12 geared bikes raced on the isle of Man TT in the 60s. These had a tiny usable power band and next to no torqu, so riders used gears to keep the engine in that narrow band.
On the example you quote of quick spin up in first then you could utilise a higher first gear if the engine had enough torque. My father had a BMW 325i for a while and as at the time he was in his 60s he found it too harsh and difficult to control acceleration in 1st and got into the habit of driving off in 2nd then changing to 4th. Drove 10s of thousands of miles in that car for a couple of years and I don't think he ever used 1st or 3rd and there was not a single grumble form it
Of course if you start modifying gearboxes to get the best acceleration then you're likely going to lose some of the flexibility in the original gera rations shoen by the manufacturer

[henk4]

Originally Posted by crisis

Depends on the application. Low end torque gets you off the mark quicker but high end torque would probably pull higher ks. Off road driving I would definitely prefer low torque where the motor didnt have to be stressed to maintain momentum through sand and over hills etc. Also driveabilty around town is helped by lower torque. Henk will be able to inform you of the advantages (yes I said it) of diesels in this regard. The length of intake runners has an effect of where the torque is maximised but it will take one of our more technically informed members to explain the finer details.

Too much honour here, and beware the converts have a habit of becoming the real fanatics.

But anyway yes, the diesel will provide you with low end torque, but everything is relative because power development normally stops above 4000-4500 revs so the actually usuable rev range is not so big. When going up the gears I hardly ever rev above 2300-2400 as full torque sets in at around 1700 revs, although you need to rev a bit further from time to time to clean the engine internally. 150 kph comes with 3100 revs in 5th gear.
I just read the story about Matra's father's BMW and I could probably do the same. Idling (1000 revs) only will bring me into 3rd gear, by just feathering the clutch. I could probably do without 2nd and 4th gear.

[fpv_gtho]

Originally Posted by crisis

The length of intake runners has an effect of where the torque is maximised but it will take one of our more technically informed members to explain the finer details.

ive seen somewhere how it all works with the intake runners, its something like pressure waves reverberate throughout the intake runners and whether its a short or long runner determines where the torque comes on in the rev range. you can get the best of both worlds here with a variable inlet tract, or just a 2 stage system like what Ford implement on the Falcon's 6