Got my Scangauge-pretty eye opening - Page 5 - Fuelly Forums

Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

Reply
 
Thread Tools Display Modes
 
Old 05-23-2008, 04:42 PM   #41
Registered Member
 
Join Date: Apr 2008
Posts: 1,259
Country: United States
Location: wiliamsburg virigina
So you propose using the brakes on a 5 mile downslope. Go ahead you might not have them when you need them. In the VA mountains they have a place for the big rigs to run off the road when their brakes fail. Loose gravel to slow them down.

If you know how to change gears and rev match you are causing no additional wear to anything, and you have the brakes for stopping when things get real rough.

I almost got killed by an idiot in a Subaru on route 50 in the mountains of western VA. Long downhill grade, max speed 35 mph. In neutral you would be going 80, through a guard rail and over an 800 foot vertical drop. I was 200 feet from a curve going uphill and a big rig came around the corner. The Subaru lost it and came all the way through my lane within 2 feet of the guardrail before he managed to save his arse.

Had I been 200 feet further down the road he would have knocked me off the cliff.

I dont wear out brake pads or clutches.

The advice stands, if you want to see what happens when your brakes go out have at it just stay away from me.

regards
gary
__________________

__________________
R.I.D.E. is offline   Reply With Quote
Old 05-23-2008, 04:50 PM   #42
Registered Member
 
Join Date: Apr 2008
Posts: 1,259
Country: United States
Location: wiliamsburg virigina
Also no gas due to fuel shutoff. I guess you gentlemen would rather burn up your brakes and waste gas idling. If you were towing a large load and not using lower gears they have places on the grades, I am taking about for you to run off the road when your brakes fail. Some of the grades are soo severe you can acclelerate in neutral down the grade faster than you can accelerate with max power on flat ground. Engine braking (while I definitely prefer to avoid it) is your safest bet. This is about 3000 feet of elevation in 4 or 5 miles, with some areas requiring braking every few seconds.

regards
gary
__________________

__________________
R.I.D.E. is offline   Reply With Quote
Old 05-23-2008, 05:17 PM   #43
Registered Member
 
theholycow's Avatar
 
Join Date: Apr 2008
Posts: 6,624
Country: United States
Send a message via ICQ to theholycow Send a message via AIM to theholycow Send a message via MSN to theholycow Send a message via Yahoo to theholycow
Quote:
Originally Posted by R.I.D.E. View Post
So you propose using the brakes on a 5 mile downslope. Go ahead you might not have them when you need them. In the VA mountains they have a place for the big rigs to run off the road when their brakes fail. Loose gravel to slow them down.
You didn't say anything about 5 mile slopes or mountains in the post I quoted. Once again, with more of it included, here's what I quoted:
Quote:
Originally Posted by R.I.D.E. View Post
When they get too steep to stay at speed in high gear (downhill) with fuel shutoff you may have to use a lower gear to keep your speed down. It may also be better to climb in a lower gear if they are steep enough to keep you from manitaining speed uphill in highest gear. Always use highest gear when practical, and go as fast downhill as you feel is safe.
I did mention brake fade (and mountains), suggesting that you should indeed downshift more for that.

Quote:
If you know how to change gears and rev match you are causing no additional wear to anything
You are wrong. When you rev match nicely, you do avoid extra wear on the clutch and synchros. That is correct. However, by using a lower gear for more engine braking, you do increase engine wear. 1000 rpm for one minute is 1000 revolutions of wear. 3000 rpm for one minute is 3000 revolutions of wear -- that's three times as much. A hundred thousand extra engine revolutions worth of wear per day wouldn't bother me, but they would bother some people.

Rev-matching also costs gas that you won't spend if you leave it in whatever gear you're already in. It's well worth spending in extreme conditions such as long steep mountainsides, but using brakes is more appropriate in more common conditions which can still easily include needing to slow while already in DFCO. Granted, the steep mountain road is not extreme to you and is very common for you, but it is not that way for the general population.

Quote:
I almost got killed by an idiot in a Subaru on route 50 in the mountains of western VA. Long downhill grade, max speed 35 mph. In neutral you would be going 80
Why are you talking about neutral?

Quote:
Originally Posted by R.I.D.E. View Post
Also no gas due to fuel shutoff. I guess you gentlemen would rather burn up your brakes and waste gas idling.
Why are you talking about idling?

Quote:
Some of the grades are soo severe you can acclelerate in neutral down the grade faster than you can accelerate with max power on flat ground.
Why are you talking about neutral?
__________________
This sig may return, some day.
theholycow is offline   Reply With Quote
Old 05-23-2008, 05:33 PM   #44
Registered Member
 
Join Date: Apr 2008
Posts: 1,259
Country: United States
Location: wiliamsburg virigina
I am talking about some of the most severe grades I have seen in close to a million miles of driving, since 1966.

Use your brakes loose your brakes.

The drum brakes fade out first then you loose the rear brakes, and loose control when you try to stop on what's left of the front.

Blind corners almost vertical cliff above and below you, absolutely no margin for error.

At 2500 rpm 1 mile a minute, 2500X250,000=62,500,000 revolutions for 250 k miles. In reality it would be closer to 100,000,000 unless you spend every minute cruising the interstate.

Highest mileage I have seen on an original (never rebuilt) engine is 864,000. Nissan Maxima diesel. Say 300,000,000 revolutions.

I have seen 540,000 on an original (never rebuilt) NAP Z 2 liter 4 cylinder. Thats close to a 1/4 billion revolutions. Say 200,000,000 revolutions

Engine braking using no fuel and also creates no combustion pressure which is when your real wear occurs. You can see it when you tear down a worn out engine. The greatest wear is at the top of the top ring location. Thats where combustion pressure is greatest.

regards
gary
__________________
R.I.D.E. is offline   Reply With Quote
Old 05-23-2008, 05:40 PM   #45
Registered Member
 
Join Date: May 2008
Posts: 85
Country: United States
What does this have to do with my post again???
__________________
bkrell is offline   Reply With Quote
Old 05-23-2008, 05:40 PM   #46
Registered Member
 
Join Date: Apr 2008
Posts: 1,259
Country: United States
Location: wiliamsburg virigina
The guy in the Maxima was driving 90,000 a year, thats 1500 hours at 60 MPH average, for over 9 years. 42 weeks at 40 hours a week at 60 MPH.

The compression was 225, should be 425. Engine would start when boosted and restart until it cooled down. Then it would only restart when boosted again. The customer was griping at the mechanic and service writer telling them they didn't know what they were talking about.

Its only advice gents, present yours and let the reader decide which he likes better.

regards
gary
__________________
R.I.D.E. is offline   Reply With Quote
Old 05-23-2008, 06:07 PM   #47
Registered Member
 
Join Date: Mar 2008
Posts: 408
Country: United States
Quote:
Originally Posted by R.I.D.E. View Post
So you propose using the brakes on a 5 mile downslope.
No one here proposed "using the brakes on a 5 mile downslope."

Quote:
In neutral you would be going 80
The comment you're responding to didn't suggest using neutral.

Quote:
I guess you gentlemen would rather burn up your brakes and waste gas idling.
The comment you're responding to didn't suggest idling.

You're talking about the danger of brake fade. That danger is real. But the comment you're responding to already acknowledged that danger. You're acting as if it didn't.

This isn't the first time I've seen you implicitly misrepresent what the other person has said. I don't know if this is intentional on your part; it could be that you just didn't read the prior comments very carefully.

Quote:
Highest mileage I have seen on an original (never rebuilt) engine is 864,000.
Some engines last a long time. Some don't. An engine spinning at high rpm is subject to more wear than engine spinning at low rpm. Engine braking isn't free, and engine braking in a lower gear costs more than engine braking in a higher gear (assuming the same vehicle speed).

Also, most people do not have perfect shifting technique, so clutch and synchronizer wear also need to be accounted for. Those parts are hard to get at. Brake pads are not. Fuel required for rev-matching also needs to be accounted for.

Engine braking has a place, but it can also be overused. In a situation where the brakes are adequate for the amount of deceleration that's required, and brake fade is not a concern, it's preferable to rely on the brakes.

Quote:
The guy in the Maxima
The guy in the Maxima has nothing to do with this thread.
monroe74 is offline   Reply With Quote
Old 05-23-2008, 06:38 PM   #48
Registered Member
 
Join Date: May 2008
Posts: 85
Country: United States
I'm not sure what any of the last few posts have to do with this thread.
__________________
bkrell is offline   Reply With Quote
Old 05-23-2008, 06:47 PM   #49
Registered Member
 
Join Date: Apr 2008
Posts: 1,259
Country: United States
Location: wiliamsburg virigina
I had one hijacked also bkrell, no more from me. Hope my imput helped you.

regards
gary
__________________
R.I.D.E. is offline   Reply With Quote
Old 05-23-2008, 06:57 PM   #50
Registered Member
 
Join Date: May 2008
Posts: 85
Country: United States
No, I sincerely appreciate EVERYONES' input. Just trying to get the proper frame of reference and figure out what it means for my circumstances.
__________________

__________________
bkrell is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Saturn TDI for S-Series cfg83 Diesels 14 10-02-2007 02:24 PM
Anyone have experience making their own solar panels? MetroMPG Electric and Solar powered 17 08-29-2007 06:43 PM
Hovercraft 88HF General Fuel Topics 2 06-21-2007 11:41 PM
Belated Intro GasSavers_brick Introduce Yourself - New member Welcome 4 12-22-2006 07:48 AM
Atlanta Auto Show GasSavers_DaX General Discussion (Off-Topic) 26 05-07-2006 06:02 PM

Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 10:44 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.