Thursday, April 06, 2006

Wrench Spinnin' - Theoretical-style

AnalogKid is looking at a new (to him) set of wheels. Apparently he's a fan of high-winding, small-displacement, powerful motors. There's certainly no shortage of 'em coming out of Japan.

Rivrdog disagrees, via comments, advocating in favor of low-rpm grunt engines that don't have to wrap their elbows around their assholes to get something done (my interpretation).

Well, in fact, they're both mostly right. Thing is, the Kid's talking apples, and Rivrdog's talking oranges.

AnalogKid likes to go FAST. Rivrdog likes to go ANYWHERE. Since we're talking about four-wheeled passenger vehicles, not helicopters, the two are pretty much mutually exclusive.

NOTE: I'm staying out of the diesel end of things here - that's not an area I know enough to talk about. I've heard wonderful things, but I don't have enough understanding to comment with much intelligence, much less any authority.

Something to remember: T=T, and H=H. As in Torque=Tugging, and Horsepower=HaulingCookies. Two very different requirements.

Something else to remember: Horsepower=(Torque*RPM)/5250. Yes, this means Torque=Horsepower at 5250 rpm, always. It also means that high horsepower usually comes at higher rpm. This is variable, based on many different engine design decisions.

It also means different engines are made for different purposes.

But, something is ALMOST univerally true, that AK either doesn't understand, or doesn't believe:

There really IS no replacement for displacement.

I admit, I loves me some big fat V8s. But I also love the little 1600cc aircooled engine in my 1970 Beetle, and no, it ain't no "flower power" Bug; it's built to run autocross, and run it hard.

The Japanese did some REALLY cool things with small engines, cranking out almost unbelievable horsepower/cu.in ratios... thing is, those developments usually scale pretty well.

If you figure out what makes a 2.5L V6 run so hard, and do the same thing, but tack another two cylinders on the front of it, you're going to have a winner. The V8 WILL produce more power, every time.

Comparing old-tech V8s to new-tech I4s or V6s is comparing apples to oranges.

Engines are, basically, just big air pumps. The more air you can move through them, the more power they can make. Efficiency does play a big part here, but you can make big engines work about as efficiently as small ones, and the big ones can move more air, thus making more power (given approximately equal volumetric efficiencies).

Of course, there's also the question of application. Rivrdog wants a grunt motor. AK wants a fast screamer. There's places for both, just like there's places for a snubnosed .38 Special, and places for a .308 boltie. They're meant for different jobs, and neither can do the other's job well.

For example: I've got a '79 GMC 2wd 3/4 ton pickup, with a 454 in it. This truck is NOT fast, even with a Gear Vendors overdrive in it. The overdrive means I'm not dangerously slow on the interstate, that's about it. But... I'd be whatever amount of money AnalogKid wanted to bet, that we could tie that truck and his choice of ANY Toyota (4wd and AWD included) back-to-back, with any (Toyota-based) engine he can imagine, and I'd drag it backwards through a cloud of its own tire smoke. More than likely, I'd never go over 1500 rpm doing so.

On the other hand, take that same fasty-fast Toyota of The Kid's, put it on a road-race course with the old GMC, and if it's more than a mile-long circuit, I'm quite sure he'd do two laps before I finished one.

Difference in purpose, difference in results.

When you're buying a new car, or a daily driver in general, you have to think about what you want to do. Compromises MUST be made, even if you're building your own engine - no one engine will do EVERYTHING well.

Thus, we have guys like me, who have vehicles specialty-tuned to particular endeavors, just as avid shooters have specific guns tuned to specialty shooting scenarios.

3 Comments:

Blogger Rivrdog said...

"There really IS no replacement for displacement."

OOOOOH-Rah! I recognize Gospel when I see it!!!!!

My favorite all-time is the Mopar 318" V-8 smallblock, with an RV cam and a large 2-barrel.

Not a gas-sipper, but a LUGGER.

The actual best smallblock was the IH 348 in/cu. It was built to grunt, and this doughty engine pulled 42-pax school busses around before IH came up with the 9.0liter diesel V-8, then the DT466, a modern turbocharged 6 cylinder diesel thumper. Hooked to an Allison tranny, it can and does pull everything from class seven light 5th-wheel tractors to class-8 semitractors in local service.

I had a '72 (or was it a '74?) IH Scout II with the 348 in front of a beefed Chrysler 727 auto tranny. I actually did pull stumps with it, using log-truck binder chains. With 4 wheels on the pavement, and the wide, sticky tires I had on it, the tranny could be "feathered" to keep it just below the tire-smoking range, and it would pull stumps without me chopping the roots first.

Except for an accident where I broke a 9300# chain and the end came through the heavy tailgate like a shotgun slug, I had a perfect record of stump-pulling with it.

IH built them tough. The hydraulic lifters in that 348 were 1 1/2 times the diameter of those in a Chevy smallblock. When I had to tear down the top end to change lifters, I discovered this. Also discovered that they were 3X as expensive, but after grinding the racer's flat on them, and putting them back in with a new high-volume oil pump, I was secure in the knowledge that the cam gallery was ALWAYS awash in 15-40 Delo, and enough of that extra oil would get by the valve guides to give a decent top-lube to the cylinders, just what you need when putting the grunt down on the pavement.

The SUV was never designed for it, but I did haul a 10,000# trailer on the highway once....

9:25 PM  
Blogger Aaron Neal said...

Weeellll, Rivrdog... I think you kinda missed my point.

Carbs are finished. Stick a fork in 'em, they're done.

Here's why: A carb can only have one fuel/air ratio mapping.

Electronic Fuel Injection (EFI), however, is only limited by the programmer's patience.

EFI is where we're headed. It's more versatile, gives greater power throughout the powerband, and greater power in different situations.

Example: My '02 Silverado, with an EFI-equipped 325, vs my '79 GMC, with a Quadrajet-equipped 454.

At LOW rpms, <2000 or so, the 454 is gonna out-grunt the 325. But not by much. Get over 2500 rpm, and the 325 is gonna smoke the 454 hands-down. Especially since the 454 starts running out of breath around 3800 rpm, and the 325 will wind to 5k pretty easily.

The 454 wins down low, but only by a little, because we're comparing apples to oranges. If the 454 had heads, intake, cam and EFI like my 325, oh holy shit... get outta the way. But (for now), it doesn't, so it only beats the 325 in one narrow application.

BUT... if I were to rebuild the 454 with the 325's technology, it would have enough grunt to pull the Moon (provided I could get traction), and run down the highway faster than I want to go (and that's saying something... I'm currently on probation for speeding).

But yeah, the truism still holds - given equivalent technology, there STILL is no replacement for displacement. Just gotta make sure you're comparing apples to apples.

9:44 PM  
Blogger Rivrdog said...

Sure, I'm talking old tech, but unless we are Ahnuld Der Terminator, we can't afford a barnful of Hummers when we feel like getting into the dirt.

I realize that there are new V-8s out there, all "Inspritzmotor" and digital chips, and I also realize that a chip can make a digital engine do handstands, changing from a revving fool of high-hp on the pavement to a lugging dumkopf that just won't quit in the dirt.

Doesn't Dodge advertise a 500-hp pickup? Sure, with bucks, you can do anything.

My purpose in scribbling these screeds is to provide ideas to the guy (or gal) who wants a vehicle for standby use, and one that will do the job in the dirt, but one that doesn't require a 5-figure investment under the hood.

Sure there are digital crate engines. There are levered-out diesels, with huge dollars in their bolt-on Gale Banks and Bullydog gear.

I'm taling about putting together a pickup or van with a reliable CARBURATED grunt engine for under $5,000 TOTAL.

And yes, it might still have it's factory stock 8-track in it.

10:31 PM  

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