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Author Topic: What does "more torque" do to a car's performance?  (Read 73934 times)

Offline Nizzle

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Re: What does "more torque" do to a car's performance?
« Reply #50 on: 09/05/2012 09:24:15 »
peppercorn, before as well as after chipping I was obsessed with getting maximum range out of one tank of gas, so my driving style was similar, with the exception that I'm accelerating a bit faster and smoother to cruising speed after the chipping, because the chipping made that possible :)
My previous post was not a comparison pre- and post-chip. It was a comparison in cruising speed 120Km/h vs. 110Km/h on motorway, both post-chipping. The range increase of this test is however much bigger than the range increase of chipping..
Oh well, up to now, I'm convinced that chipping my car was a good idea. There may be some placebo effect, although there's hard data as well, and I believe that in ~ two years (conservative estimate), I will have return on investment followed by actual profit afterwards...
 

Offline peppercorn

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Re: What does "more torque" do to a car's performance?
« Reply #51 on: 09/05/2012 10:06:54 »
Apologies for my misunderstanding :)
Although I guess it'd be good if you could separate the two changes (chipping and speed reduction) for a side-by-side comparison.
Still even if it takes the remaining lifetime of the car to get RoI then in my book it was probably worth the 'experiment'!
 

Offline syhprum

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Re: What does "more torque" do to a car's performance?
« Reply #52 on: 10/05/2012 22:03:04 »
I always understood that at modest speeds drag increased as the square of the speed it is of course the power required that increases as the cube of the speed.
 

Offline Geezer

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Re: What does "more torque" do to a car's performance?
« Reply #53 on: 10/05/2012 22:56:10 »

I always understood that at modest speeds drag increased as the square of the speed it is of course the power required that increases as the cube of the speed.


Quite right! I thought that was what I said, but I didn't.
 

Offline techmind

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Re: What does "more torque" do to a car's performance?
« Reply #54 on: 30/08/2012 00:20:02 »
Thanks for your nice graph, Lmnre, but won't the fuel efficiency depend (non-linearly) on the demanded torque - at any given rpm speed?

Surely the efficiency should be a 2D (3D?) plot of efficency versus engine speed (rpm) and torque (or power)?

I would really like to see a 3D plot for my (petrol) car engine...
I'm not doing badly though, to get about 40mpg out of the car even for my daily commute, about 5-6miles each way, on 30-50mph roads, over half of which is 'urban' driving. And that's with fairly "enthusiastic" acceleration when it's safe and inoffensive to do so. :-)
 

Offline William McCormick

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Re: What does "more torque" do to a car's performance?
« Reply #55 on: 30/08/2012 04:50:35 »
Hi,

Next week, i'll be "eco-chipping" my car. I'll have experts rewrite my motor management software to make it more fuel efficient, with a 5-10% increase in range with a full gastank by optimizing valve timings in the 1500 - 2500 rpm range. They will also make my acceleration pedal feel more like the "old mechanical systems" instead of the current "drive by wire", and they will also increase my torque from 350 to 400 Nm, but my BHP/kW will remain the same (since increasing BHP without informing the taxation authorities is illegal here).

So my question is: "What performance differences can I expect with this Torque increase while my maximum Power stays the same?"

For good performance torque, is usually king. If you have a lot of horse power, but you have to make it 3,000 or 4,000 rpm, that is time. When you want to get on the parkway, you do not want to wait for the engine to hit 4,000 rpm, and then go.

With torque, you just go. Many of the state trooper, state police cars used to be equipped with what some dealers would call a parkway rear. Parkway rears are not popular with most amateur street racers. Because they heard that, at the race track, they use much higher gear ratios. Higher number of drive shaft revolutions to tire rotations. But what they don't realize is that at the drag strip or even the small oval tracks, the race engines are fully or nearly fully revved, to the maximum sustainable RPM's the engine can handle. They channel the full horse power, through the clutch. The average street car would last about a month doing that.

The average driver and car, even the guy who likes to move, will benefit from the parkway rear, and high torque. Because the automatic transmission is usually designed to make the most of the parkway rear. You get really good acceleration, because, you have the torque, and since the drive shaft is not turning very fast, you can stay in first gear to 50 or even sixty miles an hour. Giving you a wild acceleration curve.

To give you an example the older 1986 five speed mustangs were very fast, off the line, they were the car to beat. But a larger heavier thunderbird of the same year with a parkway rear, could stay with the Mustang off the line. It would hang three car lengths back, until the cars hit about 70 miles an hour, and then the Thunderbird would, literally wall all over the Mustang. The Thunderbird used to get about 17 miles to the gallon all around. And as much as 27 highway doing 70 miles an hour. Top end was off the odometer.

Some of the higher end vets would also walk all over both of those cars. But the average stock vets would get beaten by the Thunderbird.


                      Sincerely,

                            William McCormick 
 

Offline peppercorn

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Re: What does "more torque" do to a car's performance?
« Reply #56 on: 30/08/2012 19:56:51 »
Thanks for your nice graph, Lmnre, but won't the fuel efficiency depend (non-linearly) on the demanded torque - at any given rpm speed?

Surely the efficiency should be a 2D (3D?) plot of efficency versus engine speed (rpm) and torque (or power)?

This may not be precisely the comparative plot you're looking for but most manufacturers will (eventually) publish one of these: a Brake Specific Fuel Consumption (BSFC) chart.

They can be particularly useful for understanding where the sweet-spot is for a vehicle w.r.t. throttle setting, engine load and revs; which is sometimes counter-intuitive.
 

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Re: What does "more torque" do to a car's performance?
« Reply #56 on: 30/08/2012 19:56:51 »

 

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