Date: Fri, 22 Jun 2007 14:56:58 -0400
Reply-To: Jim Akiba <syncrolist@BOSTIG.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Jim Akiba <syncrolist@BOSTIG.COM>
Subject: Re: Timing Chains, Belts, Gears, etc
In-Reply-To: <467C17E2.2010405@videotron.ca>
Content-Type: text/plain; charset="us-ascii"
Ben you can't be backing up your generalization with one example from a
motorcycle engine? As to why it had a large effect on the bike, the cam
gears for a bike are much smaller than for a car engine. Belt stretch will
then translate into much higher cam gear angle changes and much greater slop
in valvetrain timed events. This is what you're seeing with the bike. It
does not translate as readily to car engines.
Power transmission via belt vs. chain translates even less.
Camping sounds good, and is a refresher. but my true passion lies in the
means and technologies that allow us to do such things, which is why I'm
here, typing my reply, happy as a clam.
Jim Akiba
From: Ben [mailto:huotb@videotron.ca]
Sent: 2007-06-22 2:42 PM
To: Jim Akiba
Cc: vanagon@GERRY.VANAGON.COM
Subject: Re: Timing Chains, Belts, Gears, etc
Well, thell that to Honda engineers! In 93, when i ask what was the problem
with my bike (low power band) this was the answer from Honda Canada. They
have done excessive testing way before we, or other company did so about
engine configuration (we all agree that Honda tried almost all possile
engine configuration).
The same CB 1000R when back the next year with a T-Chain, more torque in low
RPM, problem with the chain. So you draw your own opinion about that my dear
Jim. I'm far from being an Engineer, but i know and i read a lot about the
subject..
But on another hand, i was liking the fack that i had no chain or belt,
another exemple is my 1983 CX650 Turbo, drive shaft instead of a chain
(engine to wheel), what a pleasure to drive, but again, poor handling
because each time you punch the bike, the rear was raising (torque/drive
shaft). Some like Harley wnet with belt with good success.
I often state motorcycle company as example, why, because they have to to
the long way against competition, they try hard and they try everything. Of
course, it would be nice to have a gear driven cam to crank engine, but
company are staying away from those for different reason, i'm sure that one
is a power related one.
I said SOHC for low coast, good power and fuel economy, again, i fully agree
that power wise, DOHC is the way to go, again, the Honda S2000 with 2000CC
as 250hp, no turbo, no nothing!
As for GM..... oufffffff, sorry here but you guys loose me big time. Wile
every company were working on smaller efficient 4cyl, those company were
still "fiddling" with old V8 :-)
Jim, your conversion is quite something and i have great respect for what
you do, BUT, i now ( for now) drive a Subi, and i have the right to say that
i'm more than happy and T-belt change should NOT be a concern at all wile
thinking about a conversion. Subi have been in Westy way before anything was
tried there, why, it's a boxer engine!
Anyway, you guys do what you have to do, me, i'll go camping with that nice
engine in the back of my van....
Ben
Jim Akiba wrote:
There is nothing about the inherent design differences in driving the
camshafts that will produce more power/torque in and of itself. I don't
believe that the flexibility of a timing chain produces more power/torque.
It will help dampen power pulses from the crank however, which contributes
to longer wearing on valvetrain parts. The valve timing event placement is
what will determine the output characteristics of the engine. The primary
reason for not using timing gears on OHC engines is because of the distance
between the crank and cams. The number of parts and rotating mass are
somewhat prohibitive, and belts do have benefits mostly in cost of
production and maintenance. The trend toward light chains however is
continuing, and as Toyota demonstrated this year, if you can lower the
spring rate on the valve springs and not sacrifice sealing or return
speeds(they did so iva much lighter valves), you can run a much smaller,
lower mass timing chain, which we will start to see more of in the next 5
years. With older pushrods engines, timing gears are much more common. I
have a set of timing gears on my 302, but they don't make sense for the
majority of OHCs.
As far as "almost all went back to SOHC 4 valves per cylinder" this is true
of Honda, but not generally speaking. Also most DOHC 4 valves are simpler
than SOHC 4 valve which usually require rockers or oddly shaped lobes to
achieve, and the SOHC lacks any ability to alter the power making
characteristics without a cam change. Through phasing changes and tuning
alone, power adders can be made much more effective on DOHC engines.
" So, now you may have to spend 600$-1000$ for a
heas gasket job, a new T-belt, guide and maybe a tensionor after 100k miles
of driving your Westy!" Ok, but you also already spent the money to convert
it... and you still have an engine with 100k more miles on it. If you had
gone with a conversion based off a world engine, you would spend the $600 on
another engine with 10k miles on it, swap it in(just install work) and never
get into the engine at all, and then everything is low miles all over again,
for the same cost as maintaining your older Subaru.. and with far less risk,
skill, knowledge, tools, time required. This is one of the additional
benefits to owners that vanaru is going to achieve with their new
conversion. Maybe you should have waited Benny ha. As far as who drives
that much? Our Colorado customer Jason has put just under 30K miles on his
westy inside of his first year of owning our conversion. So it can happen
very quickly if people are really out there driving.
Jim Akiba
-----Original Message-----
From: Benny boy [mailto:huotb@VIDEOTRON.CA]
Sent: 2007-06-22 12:13 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Timing Chains, Belts, Gears, etc
Hi (longish and boring stuff for those who don't like engine stuff)
Gear Driven (cam to crank) gas engine have NO good torque/HP and poor torque
curve, i know, i have owned a Honda CB 1000 with that system. That bike had
NOTHING before 6000-7000 rpm, i said nothing. It felt like something was
wrong, to tight. The funny thing is a broke one gear teath on the crank...
The relation between the cam and crank have big variation in engine power
curve and torque. With a belt, that very slight flexibility produce torque.
We all know the story about DOHC VS single VS 4 valves per cylinder, many
went DOHC with as much as 5 valves per cylinder (Yamaha Genesis), in cars,
almost all went back to single (SOHC) 4 valves per cylinder. It was the
best simplicity VW power VS fuel consumption. Chain, he he he, anyone here
who have owned a Honda CX bike will stay away from timing chain, binder
problem.
My ZR 600 broke a chain because of a faulty bender, now, get that chain out
of there... no easy way, that engine need to go on the surgery table.
Now, let me do my corruptor thing about T-Belt change, that kind of pis****
me off (he he he), i had a few p-mail about that subject, and i find that a
bit... sorry to say, stupid. Most modern engine have T-Belt, they all need
preventive change at 60k miles. In the case of a Subi, it's a joke, no more
dificult than on Honda or Toyota, what the big deal on those???? On your
wasser, you may go on 4 head gasket change in that 60k miles, you may even
need new heads or a total rebuilt, so tell me, WHAT is the big deal on
timming belt? Sorry guys but a timming belt does't break, that's urban
legend.
Now, another thing, about Subi head gasket problems... i have did my
research way before i choose that path. The early 2.5L DOHC big scary flat
four had """some""" problem (even, now we nead to undersand what "some"
mean), even "Some" late 2.5L had heads gasket problem, Honda 1.6L and 1.7
also have their share of ealy head gasket problem, now let see how bad this
is! Fist of all, most problem found were in general between 60k mile and
100k miles, on top, it is easy to see the problem as occasional overheating
occur, so that said, ok, let say you need head gasket job, first there is NO
need for new heads, it can be easily done with the engine in the "Van", no
rusty bolt, no damage water jacket, no bent push-rod, bottom end O-ring
replacement, pushrod seal.
Now, how many of you will reach 60k-110K miles with your westy in the next
few years? Also, in general, people have done more than 150k miles before a
head gasket job was needed on most Japanese engine, and that is TOTALY
normal on most 4cyl engine. So, now you may have to spend 600$-1000$ for a
heas gasket job, a new T-belt, guide and maybe a tensionor after 100k miles
of driving your Westy! Very far from a total Wasser engine rebuilt or
re-seal each 30k-50k miles.
I "would" take a Honda/Subaru belt or head gasket job anytime over a Wasser
head job. 1/5 of the price on the Japanese engine and my hands stay way
cleaner.
NO one here will ever convince me otherwise. But don't get me wrong, a well
maintain Wasser still as in place in the back of our Vanagon, i will give a
honorable mention to that engine who worked so hard over the years to get us
there, where we wanted to go.
Ben
http://www.benplace.com/vw2.htm
On Fri, 22 Jun 2007 06:52:56 -0500, John Rodgers <mailto:inua@CHARTER.NET>
<inua@CHARTER.NET> wrote:
Just reading the post about "New Engine Conversion" - and I wonder -
besides cost, is there any reason why engines have not had meshed gears
to drive the cams. Piston type aircraft engines all have gear driven
cams. No body wants to try to pull over and park on a cloud when a
timing chain fails.
Just curious.
John Rodgers
88 GL Driver
|