mountain driveing and your safety

J

james melberg

New member
Oct 2, 1999
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> Jim downshifting to a lower gear has its
> disadvantages to. It means that gas
> is still going into the engine and washing the
> cylinder walls down resulting
> in increased wear.

Tom,

Jim speaks the truth. In the mountain states, all
serious down grades have LARGE signs indicating all
trucks and large vehicles should down shift. As a
former Coloradan who lived at 7500 feet and worked 1.5
miles away at 5600 feet, it is the only way to go.

Besides, how are you planning on keeping gas out of
the engine? Are you going to shut the engine off and
coast? I sure hope not. Also, your brakes will not
have sufficient time to cool between applications on a
six to seven percent grade four or five miles or more
long.

I am really surprised that some of the other
"mountaineers" who are regular contributers to the
list have not commented.

Another Jim

75 PB in MN (original)

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Besides, how are you planning on keeping gas out of the engine? Are you
going to shut the engine off and coast? I sure hope not. <

Jim,
I wondered about this too. Since at least the carb's idle circuits
would continue to bleed fuel into the intake manifold even if the
throttle valves are closed, I'm sure gasoline continues to get to
cylinders. But since the ignition system is still operating with the
spark plugs are firing, wouldn't that keep the unneeded fuel burned and
exhausted out the tail pipe? It seems to me that would limit the amount
of fuel washing the cylinder walls receive while using engine braking on
long downhill grades.
Phil Stewart
'76 Transmode, TN
 
>But since the ignition system is still
> operating with the
> spark plugs are firing, wouldn't that keep the
> unneeded fuel burned and
> exhausted out the tail pipe? It seems to me that
> would limit the amount
> of fuel washing the cylinder walls receive while
> using engine braking on
> long downhill grades.
> Phil Stewart
> '76 Transmode, TN
>
>
Phil,

You got it!

Jim

75 PB in MN (ex CO)

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Tom,
I believe the manifold vacuum would be be higher and I suppose that would tend
to pull more fuel in. But shouldn't that fuel also be burned by the
combustion process in the cylinders? What would be good to see would be some
data from an on-board exhaust analyzer that would compare the amounts of
unburned fuel going out the tailpipe when engine braking down steep grades as
compared to using wheel brakes for vehicle speed control.
Phil Stewart
'76 Transmode, TN

> just a thought. When using the engine for braking on a steep hill is the
> manifold vacuum low or high and what effect does that have on the amount of
> fuel being delivered to the cylinders?
>

> >
> >

> >>But since the ignition system is still
> >> operating with the
> >> spark plugs are firing, wouldn't that keep the
> >> unneeded fuel burned and
> >> exhausted out the tail pipe? It seems to me that
> >> would limit the amount
> >> of fuel washing the cylinder walls receive while
> >> using engine braking on
> >> long downhill grades.
> >> Phil Stewart
> >> '76 Transmode, TN
> >>
> >>
> >Phil,
> >
> >You got it!
> >
> >Jim
> >
> >75 PB in MN (ex CO)
> >
> >__________________________________________________
> >Do You Yahoo!?
> >Send instant messages & get email alerts with Yahoo! Messenger.
> >http://im.yahoo.com/
> >
> >
 
I have used engine braking for all the years I have been RVing. In my C class
and my previous trucks with trailers and campers. Any truck driver who knows
what he is doing will always use gearing to stay slow on down grades. It is the
safest way to go down. If you need to stop quickly you still have a lot of
brakes, because you haven't been using them. I have never, never had any
problems as a result of downshifting on steep down hill grades. Some of those
vehicles I had went hundreds of thousands of miles with no problems. One of
the first rules I learned while driving trucks was, Never go down a hill in a
higher gear than what you could go UP the same hill in. What the manifold
vacuum is or what fuel is delivered is unimportant. The fuel getting through
will get burned off on the way down.
This is an important issue. It is a lousy thing to not have brakes going down a
steep hill. Any modification on your braking system won't be worth beans when
they fail because they were overheated. No brakes is no brakes and if you are
already going to fast the transmission will not allow you to shift down past a
certain point. Now what do you do. Look for an emergency off ramp and hope
nobody gets in your way. Darren

> just a thought. When using the engine for braking on a steep hill is the
> manifold vacuum low or high and what effect does that have on the amount of
> fuel being delivered to the cylinders?
>

> >
> >

> >>But since the ignition system is still
> >> operating with the
> >> spark plugs are firing, wouldn't that keep the
> >> unneeded fuel burned and
> >> exhausted out the tail pipe? It seems to me that
> >> would limit the amount
> >> of fuel washing the cylinder walls receive while
> >> using engine braking on
> >> long downhill grades.
> >> Phil Stewart
> >> '76 Transmode, TN
> >>
> >>
> >Phil,
> >
> >You got it!
> >
> >Jim
> >
> >75 PB in MN (ex CO)
> >
> >__________________________________________________
> >Do You Yahoo!?
> >Send instant messages & get email alerts with Yahoo! Messenger.
> >http://im.yahoo.com/
> >
> >

- --
Darren Paget
76 Experimental
Another Fab Day
http://www.TZEplus.com
 
. Any truck driver who knows
> what he is doing will always use gearing to stay slow on down grades. It
is the
> safest way to go down

A truck driver from Canada driving a large loaded grain truck and
trailer hadn't learned this lesson. He came down a very steep grade 9 miles
long into Lewiston on Hwy. 95. When he got almost to the bottom he didn't
use the slow down gravel spot. went over the top and through the cement
abutments across a wide grass divider across 4 lanes of traffic hit a truck,
through a chain link fence across 2 lanes of traffic across a parking lot
and wiped out the front of the IDAHO STATE POLICE OFFICE. Luckily now one
was injured seriously, both truck drivers went to hospital and were released
the same day. The truck was mechanically sound just driver error.
Marlene Meineken
 
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