Hi Bob,
Good to know someone is reading my rants ;). Like you say, most of the current
high-RPM engines use some kind of variable intake tuning to broaden the
performance (I won't call it torque or power) band: Yamaha with the dual-runner
setup, Toyota with their TVIS (like on my '85 GT-S), Honda uses their VTEC
variable valve timing thing, and so on. The best one (and most unmaintainable)
I've seen is what Mazda was using on their GTO rotary a few years back, where
they had carbon fiber ramstacks that slid in and out according to the engine
RPM. Mark commented that he'd seen V-8 engines that made lots of power at high
RPM, and so have I, but I'm sure that same engine would not do so well putting
around downtown (not without a lot of the technology you mentioned). The nice
thing about a big engine in a small car is that 'not so well' is usually still
perfectly acceptable.
My point (other than to tweak the big-v8-is-best gang) was that the smaller
engines are generally set up in a higher state of tune than most V-8's, and that
results in them being more finicky to drive. It has also resulted in a lot of
development being directed at solving the driveability "problems" associated
with these engines. You are right when you say that you can drive them at 2500
rpm and below, but if you need to go anywhere quickly, you'll need to get the
RPM up to where you're making some power, and some people resent the fact that
they have to row the gearbox all the time even when they're not pretending to be
Jacques Villeneuve.
#2:
I knew that the farm implement thing would get someone going. I agree that the
transmission is a fine piece of work (can we get an all-aluminum case for it?)
and well-matched to the engine, but the shifting action is, well, a little heavy
for everyday traffic-jam use. Compare it to a mid-seventies Toyota Corolla or
Celica gearbox if you ever get the chance.
#3:
Well, I'm not sure that I was making a statement on that subject one way or the
other in my post. I'll guess that most people associate low-rpm performance
(what they call 'torque') with around-town traffic-light situations, and
high-rpm performance (what they call 'horsepower') with racing, and so everyone
says 'torque is king for street cars'. Not true, since you can use rear-end
gearing (and that shift lever thing) to optimise the engine RPM for the driving
conditions you encounter most often.
Warming things up from the Great White North,
Theo Smit
tsmit@novatel.ca
B382002705
> -----Original Message-----
> From: Bob Palmer [SMTP:rpalmer@ames.ucsd.edu]
> Sent: Thursday, February 04, 1999 2:08 PM
> To: Theo Smit; 'Mark Radelow'; johnson@ids.net; JPKKMK@aol.com
> Cc: tigers@autox.team.net
> Subject: RE: Rather have a Big One
>
> Theo, et Listers,
>
> While I think you are generally correct Theo, you've managed to hit at
> least three of my "hot" buttons with your latest posting. In the order in
> which they appear, let's start with your statement: "Any piston engine
> built to develop maximum power "well above" 5000 rpm is not going to
> perform worth beans at 2500 rpm and below." Now I haven't ever driven the
> Honda 2.0L/240HP screamer, but the 3.0L DOHC Yamaha motor in my SHO is
> probably the sweetest engine I've ever driven. You can rev it up to 7,000+
> rpm and still lug it around at ridiculously low rpms, way below 2500,
> without it ever complaining. It puts out 220HP at 6,400 rpm and max torque
> at 4,800 rpm; probably not too far different from the rpm points of the 289
> in my Tiger. And, cruising at 75 or so with the air conditioning running it
> gets pretty close to 30 mpg. The SHO engine is naturally aspirated, has
> four valves per cylinder of course, and has two intake runners for each
> cylinder; a long one, and a short one that opens up above 4,000 rpm. I
> don't think the valve timing changes with rpm, but I assume there's some
> dual pattern setup at least. This whole package comes about as close as I
> can imagine to having your cake and eating it too. And, of course, this is
> not the only modern engine out there with these kind of manners. To get my
> 289 to run this well over the whole rpm range I'd probably want to start
> with a set of Gurney-Westlake heads, fuel injection, dual runners, etc.,
> etc., and lots of $$$$$. BUT, it could be done, and be very driveable, and
> make 400+ horsepower, and even get decent mileage too (20+). So, in
> summary, I think you're way to pessimistic with the referenced statement.
> Even just a roller cam will give you a motor that runs well over quite a
> broad rpm range; i.e., just like a new 5.0L.
>
> On to hot button #2: What's this about the toploader being a farm
> implement? Hey, I love this brutish piece of machinery. Can't imagine
> having a wussy tranny behind a big bore motor; just doesn't fit. Kind of
> Zen thing you know. And hey, this tranny is so good, they even make
> adapters to put it behind Chevys! Sure, it takes a firm hand to use it, but
> it downshifts a 7000+ rpm just as easy as at 2500. And, of course, it's
> probably the most rugged tranny you can find in a passenger car or truck.
> You're absolutely right about the Mazda tranny though; that's what's in my
> SHO. BTW, the new 5-speed boxes are a lot smoother shifting, although I
> haven't tried the Tremec which I believe is more like the toploader (so of
> course this is the one I want).
>
> And finally, I'll bait you with this question: Just where in the rpm range
> does the important parameter go from being horsepower to torque? The answer
> is nowhere, but for some reason most people talk about torque in the low
> rpm range and horsepower in the high rpm range. Just seems unnecessarily
> confusing to me. Just look at the horsepower versus rpm curve and it tells
> you everything you need to know.
>
> Just tryin' to stir up some trouble in San Diego,
>
> Bob
>
> At 11:07 AM 2/4/99 -0700, Theo Smit wrote:
> >The funny thing about engine power is that you can't make it everywhere. Any
> >piston engine built to develop maximum power "well above" 5000 rpm is not
> going
> >to perform worth beans at 2500 rpm and below. And that means you can't use
> 2.88
> >gears anymore. Not having 2.88 gears means you get to row the gearbox driving
> >around town, and let's face it: The toploader shifts like a farm implement
> >compared to any Japanese transmission (okay, not Mazda's :) built in the
> >last 30
> >years.
> >
> >And what's GOOD power in a V-8? 1 hp / cu.in? You won't get much over that
> >using
> >factory heads, even with porting and oversize valves. Even making 400 hp
> out of
> >a 302 only gets you 1.3 hp / cu. in., and I would like everyone who has a
> real
> >400 hp Tiger that is pleasant to drive around town to share their secrets,
> >please. The only thing that saves high-RPM V-8's is that even if they are so
> >tightly tuned that they only make 60 ft-lb of torque at idle (compared to say
> >300 at peak), that's still enough to move a Tiger off the line with
> reasonable
> >vigor. With a smaller engine, having that kind of peak to idle torque ratio
> is
> >going to make the car hard to drive. Not that it can't be done, you just
> >have to
> >drive like you're on a mission everywhere you go.
> >
> >Theo Smit
> >tsmit@novatel.ca
> >B382002705
>
> Robert L. Palmer
> Dept. of AMES, Univ. of Calif., San Diego
> rpalmer@ames.ucsd.edu
> rpalmer@cts.com
|