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Discussion Starter · #1 ·
I recently posted a message at various forums asking about how to get the most low end torque out of my '79 ZX, and I've gotten alot of responses telling me that I shouldn't be worried as much about low end torque but rather the high end. I want my 280 to be a real street fighter in a small package. So I was wondering, should I concintrate on the low or high end?
 

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Discussion Starter · #2 ·
> I recently posted a message at various
> forums asking about how to get the most low
> end torque out of my '79 ZX, and I've gotten
> alot of responses telling me that I
> shouldn't be worried as much about low end
> torque but rather the high end. I want my
> 280 to be a real street fighter in a small
> package. So I was wondering, should I
> concintrate on the low or high end?

for street use low end torque is always much more useful. high end horsepower is great for the freeway or the racetrack. it's just more difficult to make low end out of a small displacement motor like the l28. the 3.1 liter engine build is a good way to build low end, as well as raising the compression ratio and installing a better cam.
a good person to talk to is bob hanvey. he's built some strokers and has done the p-79 head modifications. you can view his site at <A HREF=http://www.geocities.com/MotorCity/Track/6997>http://www.geocities.com/MotorCity/Track/6997</A>/. he also post here quite a bit.
 

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Discussion Starter · #4 ·
Re: Try this comparison

here's another comparo. the new honda s2000 vs. the bmw m roadster. i chose these two cars because they make the same amount of horsepower, but in two different ways. they also weigh close to the same. let's start with the honda- now depending on what you read, this car makes 240 hp @ 8500 rpm and 159 lb-ft torque @ 7500. the car has a curb weight of somewhere between 2500 and 2800 lbs. the 0-60 time is between 5.5 and 6 seconds. i haven't read about a quarter mile time yet. the bmw on the other hand makes 240 hp @ 6000 rpm and 236 lb-ft torque @ 3800 rpm. the 0-60 time is between 5.1 and 5.3 seconds. the 1/4 mile time is 13.7sec/ 101 mph. also bear in mind this car weighs almost 3100 lbs, at least 300 lbs more than the honda. looking at the numbers, the bmw should win anywhere on the street and in a drag race, but the honda should pull higher top speed numbers.
 

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Discussion Starter · #7 ·
Re: Exactly my point!

> OK, the Honda: [email protected], 159ft/[email protected]
> Look at where peak torque is. When you
> shift, you are going to fall WAY below the
> peak torque. You'll probably fall around
> 5500-6000 when you shift. This is not very
> good, and hurts acceleration. But the Honda
> still has 0-60 of 5.5-6.0 why?? This is due
> to the HP. Because once it is in a gear, it
> can stay in that gear for a long time, this
> makes up for the utter lack of torque. I
> would bet You can probably hit 40mph in 1st
> gear. Probably hit 60mph @6500-7000rpm in
> 2nd. This proves the importance of gearing.

A couple of things, if you want acceleration, shift after your peak torque not 500-1000RPM before it. Also, your HP peak is where you'll experience the best acceleration for a given speed, so if you have a smooth torque curve then you also want to shift at your HP peak. In the case of the honda, a good idea would be to shift a bit after HP peak so your revs don't fall too far below the torque peak in the next gear. Simply: HP peak = best acceleration for a particular speed, torque peak = best acceleration for a particular gear.

> Now the BMW: [email protected], 236ft/[email protected] So
> if you shift @6000, you drop to @4000, which
> is right smack in the 'sweet spot' of the
> torque curve. So the BMW is making peak
> torque at a very useable rpm. The BMW will
> require shifting sooner than the Honda, but
> will pull harder in each gear compared to
> the Honda.

> So, the moral of the story is:
> The BMW needs to shift to stay moving, while
> the Honda can stay in a gear for a long
> time, but suffers when you shift. Great
> example of hp vs. torque.

But considering the BMW has more torque, the BMW would be geared lower and probably finish its gears at about the same speed as the Honda, I suspect the BMW would be slightly faster(assuming equal weights) because of the wider torque curve the figures indicate.

Project#2501
 
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