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Re: [GMCnet] Gas Prices- At What Point Do You Park It? [message #116509 is a reply to message #116489] Fri, 25 February 2011 13:19 Go to previous messageGo to previous message
USAussie is currently offline  USAussie   United States
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma:
Senior Member
Gord,

Oops!

Forget about the horsepower, look at the torque. A lot of the motorcycle
engines you've cited don't produce torque until they're running at a
gazillion RPM.

What big European sedan were you thinking of, I checked and the VW V10TDI is
a diesel not gasoline.

Regards,
Rob M.
USAussie - Downunder
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426


-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Gord Hubbell
Sent: Saturday, February 26, 2011 3:59 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Gas Prices- At What Point Do You Park It?

Hi Craig,
Considering the 455 is a cast iron lump that hasn’t really changed in
decades and relies on its displacement to do its work, it’s not
difficult to find many other engines which have moved forward in leaps and
bounds in their technology…after all, they have had decades to make
these improvements. What’s a 455 – 7.5 liters correct? It
seems a *really* good 455 is making 400 hp or 53 hp per liter. That’s
a really good one; I doubt many out there come anywhere close.

Current “modern” engines are now easily exceeding 100 hp /
liter, some designs (i.e. motorcycle engines) are doubling that @ 200
hp/liter and they’re still not using all the tricks in one package.
Oh, don’t think I’m pondering a motorbike engine in a 12k#
motorhome, but it’s just to say the technology is there and it works.


Craig, you seem to have some good savvy with engines (great!) so let’s
look at the sum total increase of your percentages? Let’s not forget
that those 0.1% increments have been occurring constantly for a couple of
decades? Proper multiport fuel injection is known to be a 10% increase in
horsepower *and* economy – that was proven when MPFI became
commonplace for many engines in the 80s. They downsized the engine’s
displacement, improved the economy, yet gave the consumer even more power
than they had prior. Manufacturers ran 5 valves per cylinder for quite some
time with great success too but that’s fallen back just the same way
the V12 engine is now a dinosaur compared to a V10 – and the main
reason for performance gain? Reduce the friction. Imagine, you spend
millions developing 5 valve heads then realize that the friction caused by
that 5th valve doesn’t equal the gain had you left it at 4 bigger
valves. Ditto to twin-cam engin
es – many manufacturers still use DOHCs but others that are really
working to get the most out of a given engine have gone back to a SOHC
– main reason…friction.

The biggest area of advancement to my understanding has been with
metallurgy, specifically in the design of pistons, piston rings and
connecting rods, as this is where a lot of work has to be done, done well,
and done for a long time between changes. Piston rings and pistons account
for incredible amounts of power loss (friction) – so much so that that
is why v12s are basically history…knock 2 cylinders off and the 10
remaining can actually make more total output.

100,000 mile intervals between tune-ups or even changing a sparkplug? We
all know what the computer or in some cases *computers* have done in regards
to maintaining optimal fuel / air mixture ratios, and then look specifically
at fuel injection management and the incredible tasks which can now be
performed regardless of vehicle location (altitude, barometric pressure,
load…) and at an adjustment rate we can’t even imagine.

Compare this technology to a 4 barrel carburetor? That’s apples and
oranges Craig – meaning, it’s really just not fair to compare.

Yes, these days the changes made to a modern engine design are becoming
perhaps a little less – they’re on the top of the curve so to
say, but they’re still being made and I bet there’s hundreds of
engines on dynos right now getting the life kicked out of them to try to
make things better.

Drag and resistance of the motorhome – well, that’s sort of a
constant now isn’t it. I for one would be removing all sorts of
‘shhhtuff’ from my coach (if I had one! :( ) because I would
want to get that resistance down as much as I could. BTW (fyi) we tested a
racing motorcycle at Brainerd Minnesota in the late 80’s and picked up
2 mph on their lengthy front straight by cleaning and waxing *all* the body
work – an incredible gain for just a couple of hours of elbow grease.
Imagine not only the frontal area of the motorhome, but *all the sides and
roof*? Sure, air hits the front, but it then drags down the sides, top and
no doubt, the undercarriage, so there’s a lot to think of in all those
areas. ;)

Transmissions – well Craig, given closer ratios and multiple speeds,
they can only make it easier for any engine / engine management system, to
select the optimal ratio depending on the load. I’m sure you’ve
been stuck behind an older 18 wheeler at a traffic light as the driver rows
his way through the multitude of gears to get the thing to speed again?
More ratio selection is better, especially as today these are now automatic
or semi-automatic. A three speed automatic transmission regardless of the
final drive ratio is (speaking honestly) an absolute has-been, sorry.

Ok so, maybe if and when I swap out the original power unit and replace it
with something that is rated at 24 mpg in a big heavy European sedan,
I’m not going to get 24 mpg, but I am certain it will be an
improvement over the 10 mpg that the 455 delivers now. Will it be worth it?
Yup. If I could gain a couple of miles per gallon, have the fun of making
something interesting and unique, have something that is technologically
current and at least making an effort to be environmentally responsible,
I’d give it a go without a question.

Perhaps I’m missing the point of the GMC Motorhome and the group? If
like certain old cars people want to have them remain “original”
in so far as to say, their power plant, I guess I’m in the wrong
place?

Thanks Craig!

Gord

p.s. If anyone tolerates motorbikes, here’s a little video which shows
the extent some manufacturers (Yamaha in this case, and they develop / build
engines for Ford BTW), are currently at so far as getting power from a drop
of gasoline. This technology is going hand in hand with automotive engines
albeit slowly. Hope you can envision the hours and millions of dollars which
have gone in to the *design concepts*, not necessarily the motorbike itself
. :)

http://www.youtube.com/watch?v=nJKkvbsojWI


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Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426

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