Basically then, what I would want to do with an FI engine (say turbo in this case) is to bore out to get higher displacement....and possibly destroke a little to a displacement slightly higher than stock (1.8L to 1.9 or 2.2L to 2.3)...So it would go from (for example) 1.8 liters to 2 - 2.1 Liters from boring out and whatever else that can be done here... and then destroked from 2-2.1 back down to the 1.85-1.95L range... This would probably work fine for street emmission and still give us some better numbers eh?

Would that not work the best in our case...and also because extra torque isn't really utilized well "off the line" in our front-wheel drive cars? (wheelspin in excess)... (I'm implying that we should do this instead of increasing stroke and displacement because we wouldn't utilize that torque very well whereas we can rev higher with this plan)...

We would be revving high, creating a decent amount of torque, and a really good top end HP curve right?

Any opinions on the best NA or FI solution on this matter? (I suppose you'd have to differentiate for race and street cars or whatever)

 

In a word, yes. However, destroking endeavor's are limited to the few B-series cranks that are available. I'm not sure what's out there that would destroke a B18. If you've got cash to burn, I think Crower does custom cranks for a couple grand a piece.

The most common method is a B20 block & B17 crank, which yields close to a 1.75 r/s, with a good bit more displacement than a B16 (I want to say 1.8 liters, but I'd have to look it up). The B20 block is also popular because there's room in the sleeves for some boring. Or, do a resleeve & bore it out as much as you can to get that displacement back. Just don't forget to rework the head for the new bore size.

The only tricky part is sourcing a B17 crank. They weren't the most common engines ('92-'93 USDM GS-R, I think). Put a B16 head on it, and you've got the holy grail of B-series engines . . . good for 9,000 rpms with cams, or as much boost as you want to build it for.

Most of this stuff, by the way, I picked up by looking around on the Endyn site & discussion boards http://www.theoldone.com There's good info over there, despite all the controversy.

Too bad stuff like this is out of my league financially. Even doing most of the labor myself, I bet I'd be out 3 or 4 grand - before digging in with the turbo.

 

HP = ((TQ * RPM) / 5252)
derived from
TQ = ((5252 * HP) / RPM)

horsepower is just derivation from the torque at a certain rpm

 

For the most part, displacement and volumetric efficiency dictate torque output, not increased rod length alone. As mentioned, optimum rod/stroke ratios increase dwell at top dead center, paying dividends in brake mean effective pressure (bmep), which translates to torque.

That said, the horsepower vs. torque debate is actually quite simple.

History lesson: Back in the day, James Watt reached the epiphany that basic torque measurements of his nascent steam engine did not accurately portray its work potential as RPM fluctuated. Consequently, Watt invented the rate of torque delivery as HP.

What's all that mean? Keyword: rate, measuring anything (pay, velocity, torque) in increments of time. Just like pay and velocity rely as hours ("X" dollar/hour; "X" MPH) as incremental units, Watt decided to measure the rate of torque production in minutes. Consequently, Watt declared a total of 33,000 ft. lbs of total torque produced in one minute as one horsepower. Dividing that figure by 6.28 (2 x pi) yields 5252 - the constant from which HP is calculated as a function of torque.

This formula should make more sense now:HP = RPM X TQ/5252

Now apply Watt's dilemma to the internal combustion engine. For the sake of simplification, image a motor with a completely flat torque curve with an operation range between 1000 and 7000 RPM generating 100 lbs/ft of torque. Anywhere between those two figures, torque output is identical. However, torque is an instantaneous reading that does not even acknowledge the existence of time.

As time elapses, and RPM increase, instantaneous torque production does not change whatsover, but total torque produced proliferates dramatically. Per the HP formula, at 1K RPM, the above motor generates 100 lbs/ft of torque and 19 HP. Now, at 7K RPM, the motor still produces the same 100 lbs/ft of torque, but 133 HP. The instaneous rotational force/torque the motor produced did not change at all, but thanks to multiplication via RPM, the total torque output at 7000 RPM in one minute of time yields far greater power.

Now can you feel the difference between 19 and 133 HP? You bet your sweet ***

Recite this mantra 10 times: [/i]HP is nothing more than total torque produced in one minute of time[/i]. Keep the debate simple Watt must be rolling over in his grave.







[Modified by Jim S. '95 Z28, 12:50 AM 12/1/2001]

 

Right. And that's why a stock b16a will outrun a stock b18a, all else being equal.
Also, the motor has similar torque to my old d16, but the d16 was just slow.

I thought about this a little, and how it related to my mountain bike.

I stopped my bike and put it in its shortest gear. Then, I jumped hard on the pedal. The front tire would actually lift up for a split second because of the torque on the rear wheel. I didn't yank on the steering bar or anyting.

If I tried doing this while the bike was slowly moving then nothing would happen. Try as I might I couldn't get the tire to lift (without yanking on the steering bar). I didn't get any weaker. My leg could still put the same torque on the pedal, but not fast enough to keep up with it. That's why you need power, not just torque.

You have to push something hard to accelerate it, but you also have to keep up with it as it's accelerating.

Anyone see any flaws in this analogy? Is it correct?

 

i agree with your bike analogy... you do need power to get things started. the reason it's easier to switch gears on a bike once you get it going is that you have momentum already.

 

Please pardon my "domestic ignorance." Presumably, the B16A is a del sol VTEC motor; the B18A a RS/LS/GS Integra motor? If so, then the statement's correct. 160 HP beats 142, although it sacrafices some low/mid-range torque, via winding out additional RPM with minimal torque loss up top. B18C vs B18C5? Same deal: the cam specs of the latter afford bonus ponies up top, while sacraficing some midrange torque/HP.

Yes and no. The analogy somewhat assumes peak torque and HP at the same RPM. "Wheelies" on a bike are not the most precise method of gauging TQ/HP production. To assume both occur at initial "launch" since the front tire lifts is inaccurate. As a cyclist continues to pedal, although torque drops, no thanks to less-resilient-then-IC-motor-human-legs, total torque and the rate of delivery increase, reflecting an increase in HP. In this example, fractions of HP

Likewise, all motors produce peak torque at peak volumetric efficiency. However, HP always peaks much higher in the rev-band than torque. Consequently, although torque continues to drop off after the peak, multiplication via RPM achieve gains in power production. That is, until VE drops to the point of diminishing returns.

Case in point, my motor (not stock) reaches a peak of 418 lb/ft of RWTQ at 4000 RPM, translating to 318 RWHP. From there, volumetric efficiency and torque steadily decline, but power still increases. By 6200 RPM, the torque drops down to 369 lb/ft, yet churns out 118 additional RWHP for a total of 436.

Still gotta watch out for those pesky Supras, though


[Modified by Jim S. '95 Z28, 9:00 AM 12/1/2001]