which engine--minivan?

Emergency situations occur regardless of what kind of engine you have or
how you normally drive. When they *do* occur -- say, a truck doesn't see
the red light at the intersection you've just entered -- you'd better hope
you're in the 200hp minivan and not the 83hp item.

-Stern

 

Apparently.

 

I find that hard to believe

Reason why is because I thought the slant 6 was a taller engine, thus with
bigger connecting rods. I was incorrect.

If memory serves, you're an engineer, right? Mechanical engineer? The
extent of my technical background is made up of a couple of
Physics/Chemistry background classes with some Calculus and some C++
classes and such. So I am always glad to learn new stuff from people.
I've heard it said that the first step to knowledge is to admit you know
nothing. Memorable quote from a computer science book I read about 5 years
ago: "with the internet, we are quickly becoming a global village filled
with village idiots."

 

No paper necessary - I see it in my mind's eye from your excellent
verbal description. Thanks for the education.

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

The 2.2/2.5 shares *many* design aspects with the slant-6, which is not
surprising since they had the same daddy.

Naw, I just play one on the radio ;-)

Also: "It has been said that a million monkeys with keyboards would
eventually reproduce the world's great works. The internet has proven this
is incorrect."

-Stern

 

My point is that the gearing doesn't cause an increase in power. The
engine running faster is what changes the power output. Gearing can
ONLY affect torque intrinsically, it can't affect power. Power is
constant through any set of gears, neglecting that which is lost through
friction in the gears.


Matt

 

Actually, longer connecting rods for a given stroke does have a
beneficial affect, but it isn't huge typically. You are wasting less
effort pushing against the cylinder wall and more pushing against the crank.


Matt

 

That is the underlying premise behind genetic evolution. It is as
flawed there as it is with respect to the internet.


Matt

 

Well ... ... actually longer rods actually reduce torque by changing
(reducing)the rod angle to crankshaft(relative to the piston travel)just
after TDC .... what they do is move peak torque further up the rpm range (
usually increasing horsepower), however that peak torque is reduced...
shorter rods produce more torque at a lower rpm as the rod angle is greater
as the piston move down from TDC..


Ted

 

Sorry, none of the above is correct. Go back to some basic engineering
texts and let us know when you're ready for a quiz.

-Stern

 

Sorry,, I cede... should study first then put foot in mouth..... only
quoting what I remember from school a *long* time ago,, probably wasn't any
research to back it up then,, just some body's explanation at the
time...don't remember

So after reading the text's I could find quickly online (stuff that didn't
seem like it had an agenda anyway) It seems,, ( first look anyway) there
really hasn't been a lot of research done on this..

Thought this article was pretty good..
http://www.chevytalk.com/tech/engine/rod_angle.html checked lots of others,,
but didn't see *anything* with any real documentation to back it up either.

As for the quiz,, it won't be in this lifetime I'm afraid I've already been
at it too long and I "ain't even close" to learned in any field or even as
smart as 90% of the people I know..

But I do appreciate the education.. I will let this rest now,, Thank you.

 

Why do you get such poor mileage out of your vans? I average 19-20 "mixed", 25
"highway" and 17 "city". I've never gotten below 16MPG on a tank...ever that I
can remember (and I check mileage at every fillup). Ironically the very best
was 28 on a 470 mile trip to Myrtle Beach doing 70-75 most of the way...got
there on one tank with gas to spare.

| GEEZ what do you do drive downhill with the wind at no more than 50?! My
| vans have always given "real world" avgs. of 15-17 (in town) and 20-22
| highway if not pulling boat. If pulling than only about 17-18. Reason for
| range is winter to summer. Now I know I can look at the trip computer at
| various times and see as much as 28-30 but that's not "real" mileage. I'm
| talking averages. Recently replaced my 93 (3.3 T&C) with a 4wd 1/2 ton
| suburban with a 350 and don't find it too much different than the 99 T&C. 13
| in town and 18 on road.
| Larry
| | > (Fredisg) wrote in message
| | > > Hi,
| > >
| > > If I were to purchase a used 2002 or 2003 town and country or caravan,
| which
| > > engine is the most reliable? 3.3? 3.8? any others?
| >
| > I have been amazed that my 97 3.8 Caravan gets 27-28 miles per gallon
| > and my 3.3 '92 Caravan got only 23-25 on the highway. In fact I
| > (three peple plus luggage) just completed a 5000 mle round trip to
| > Alaska in the '97 and got over 30 mpg average because we were obliged
| > to drive at less than 62 mph.
|
|

 

|
|
| But you got to admit, there's a lot of variation in people's driving
| habits. What I mean is, if you gave someone a minivan with 200HP they
| might be so easy on the throttle that they don't drive any faster or
| accelerate any faster than a minivan with 83hp. Someone who is a more
| spirited driver will feel the difference in HP, but a person simply
| cruising around the neighborhood dropping the kids off at soccer or
| going to the bakery might not care that their van has 83HP.
|

If the road to the bakery was on a 15%-20% grade I bet they'd mind.

 

Once again, that is true *IF* you are looking at the HP at a given
ENGINE RPM (NOT vehicle speed). *BUT* my point was that if you look at
the HP at any given VEHICLE SPEED (NOT engine rpm) (as the vehicle is
accelerating from, say, 0 to 60), at that given vehicle speed, there is
more HP being produced than at the same VEHICLE SPEED, as evidenced by
the higher rate of acceleration at any given speed.

Stated another way, at a given vehicle speed at WOT, if you freeze it in
a moment of time, with the lower gearing, there is more HP being
produced by the engine at that vehicle speed than with the higher
gearing at that vehicle speed (which you say in your next line below).

Remember HP is a product of torque and rpm. With the lower gearing,
you're at the higher HP part of the curve at a given vehicle speed
precisely *because* rpm is higher at essentially the same torque (once
again, until you get into the higher rpms where things start tailing
off).

AHA! So if you have lower gearing, for a given vehicle speed, you *DO*
have more power (until super high rpm). That's all I'm saying. I think
that once you think it thru you'll see that we're in violent agreement.

Lower gearing will mean more power at a given vehicle speed (at the low
and mid part of the curve) because of the truth of your immediately
preceding statement ("The engine running faster is what changes the
power output").

You haven't said anything wrong. You're only limiting your vision to
looking at HP in relation to engine rpm. Expand your vision to look at
it in relation to vehicle speed, and you'll see what I mean.

I challenge you to plot out a typical power curve: HP vs. engine rpm.
STEP 2: *NOW* replace the horizontal scale labeling with *vehicle speed*
instead of engine rpm for some arbitrary real-world reasonable gearing.
STEP 3: *NOW* duplicate that plot, but divide all the numbers on the
horizontal scale (vehicle speed) by 1.2 to represent 20% lower gearing.

You should immediately see that for a given vehicle speed, HP will be
greater (remembering to ignore the top end of the scale where the curve
drops off).

But again, do not take this to mean that I disgree with you when you say
that, relative to engine rpm, HP output will be the same regardless of
gearing (for a given engine rpm) - basically, a naked engine dynamometer
test. That will always be correct. You, so far, are refusing to look
at vehicle speed. I am looking at HP in relation to engine rpm (which
you are also doing), *AND* in relation to vehicle speed (which so far
you are not doing) and simply stating what is true for *both*
relationships (the two graphs I talked about).

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

Haha! Bravo, Matt! 8^)

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

Naw, I just play one on the radio ;-)


Are you a radio host? Or SW user? I listen to SW on my Sangean SW
receivers (ATS505 that receives SSB and a 602) but I don't have a
transmitting SW radio.

 

Because in a family of five, we owned 2 K-cars, therefore we were bound to
use one for our family trips. That car got us where we wanted to go, for a
number of years, didn't see a need to buy a beefier vehicle, although we DID
opt for the 2.5L and not the 2.2L engine.

Have you ever come across those asshole drivers that you want to get past,
but they make it difficult? Normally we would drive at a mire mild 105-110
km/h speed.

Meh, that car's transmission never "skipped a beat"

 

I understand what you are saying, but the point is that the power
increase doesn't come from the gears themselves, which is what you said
originally. The gears themselves can't MAKE power. They can MULTIPLY
torque, however. This is a very common missunderstanding and I was
simply correcting it. Read any good text on gearing or mechanical
engineering and you will see this principle.

I know what you are saying about the gearing allowing the engine to run
faster at a given road speed which allows the ENGINE to produce more
power at a given road speed, but the GEARS aren't producing the power.
That is the fundamental point. If you look at the power going into the
differential and look at the power coming out of the differential (or
transmission, same thing), the power coming out equals the power going
in (minus losses due to friction), no matter what the gear ratio between
output and input. However, if you look at the torque going in and
coming out of a gearbox, it is proportional to the reduction ratio.


Matt

 

Please provide quote(s). If I really said that, then I failed to
include the full context in a particular sentence because it was the
20th time or so that the context of vehicle speed vs. engine speed had
been stated, and was, by then, understood (either that, or I didn't
state what I intended because *never* would I say or imply that gears
produce power taken in full context).

If I contradict that *anywhere*, please quote, with context.

As an engineer, I certainly understand the law of the conservation of
energy. Gears cannot produce power. However, they can and do cause
better effect (acceleration) by moving the speed of the engine up higher
into its power band where - yes - more horsepower is being produced (by
the engine - not by the gears themselves). Did the engine produce more
power? Yes. Did the gears produce more/any power? No. But they put the
engine at an operating point where it can produce more power. That is
not the same as saying that gears produce power. They can result in
more power (from the engine), but they cannot produce it. Again - on
that, we are in violent agreement.

I never said that gears produce power (unless I *really* screwed up in
which case you will show me where that occurred). I was careful to
qualify my statements (how many times did I say "relative to vehicle
speed not engine speed" or the equivalent? If I failed to do that at
some particular point, please show me where.

Consistent with everything I think I said (unless I plain screwed up
somewhere and did not properly convey what I intended - again - show me
where, and I will honestly assess what I said).

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

A theory is not proven - for sure. It is only "not" disproved. Hence we keep
reading statements couched with phrases such as "suggests..." and "apparently
indicates...." Not exactly "for sure 100% true" statements. So far, the "works"
written by the aforementioned simians has not happened. That does not mean it
will not happen in the future.