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Fast idle?

Over the past few years there have been several mentions of using the cruise control to set the engine at a fast idle. I've not been successful in making that happen. Is it possible on our coach? If so, what is the procedure?

Re: Fast idle?

Reply #1 –
I don't think the GV's have that ability.
1993 U300 40ft GV SE
Build # 4344

Re: Fast idle?

Reply #2 –
Actually, some GV's do have the capability, but may depend on what type of cruise control you have, and what type throttle control.

On our coach, which has the combination Bendix air activated cruise control and throttle control, it is pretty simple.  With engine at idle, and air pressure up, I turn on the cruise control.  Then I repeatedly click the "resume" switch, until the idle rpm starts to increase.  I think I can set it at any rpm I want - more clicks for more rpm, but there may be a upper limit.  To get it back to normal idle, I can either turn off the cruise control, or touch the brake.

Other systems may work differently.  For Bendix system info, scroll down to page 3, "Throttle Control Mode" in below linked document:

http://www.wanderlodgeownersgroup.com/downloads/BendixCruiseCtlManual_Parts.pdf
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Fast idle?

Reply #3 –
"...and air pressure up, ..."  That might be my problem. I was hoping to be able to raise the air pressure more quickly with a faster idle.

Re: Fast idle?

Reply #4 –
I start the engine then turn on the cruise, push the button and engine rpm goes from 750 to 1100.
Used this feature to increase the rpm while recharging the dash AC system.
Of course you have to have some amount of air available as it is an air activated throttle and cruise on our 95 GV.
Justin & Cathy Byrd
1995 U280 "Old Faithful"
36' Build #4673
C8.3 Cummins
Allison MD3060R 6 speed - retarder
Powertech 10KW  4cyl Kubota

Re: Fast idle?

Reply #5 –
On our coach, the throttle starts working at about 60 psi system air pressure.  After that point, the "fast idle" mode can be used as desired.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Fast idle?

Reply #6 –
David,
Your electronic 6V92 uses the engine computer for the cruise control - not the Bendix system.  I have tried the fast idle with the cruise control buttons to no avail on my coach.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: Fast idle?

Reply #7 –
David,

I had the same problem until I discovered that running a manual cylinder cut-out test using a Pro-Link 9000 you can choose to set the idle at 1000 rpms.  You can then hold it there until pressing the function key stops the test and the idle resumes at 600 rpms.  You don't have to wait and can idle up right after starting and the oil pressure is up. 

It makes for airing up much more quickly and using it for a couple of minutes to cool the turbo before shutting down.  I believe you can add a mechanical type fast idle but I haven't seen one.  Before I had my Pro-Link, I would just lay something heavy like a small tool box on the throttle.

Maybe Pierce or Caflashbob or one of the truckers on the forum can tell us how to do it!

Jerry
The selected media item is not currently available.
Jerry and Cindy Maddux
1993 U300/36WTBI DD6v92TA
build 4271  "Miss Lou"
1995 suzuki sidekick 4x4 toad
Gulfport, Ms

"Pride of Ownership"

Re: Fast idle?

Reply #8 –
Cat 3126= No fast idle :'(  :'(

John
John and Stacey Smith
Motorcade NO: 11973
1997 U295 CSGI 40'..Build No. 5036     
920 Watts on the roof..CAT Power w/fuel Inj. Programmer
2021 GMC Sierra AT4 1500
EX..2015 Jeep Wrangler Sahara
Ex 1990 U280 RSAI 36'..Build No. 3638

Re: Fast idle?

Reply #9 –
Clueless as a newbie to Air brake system, is three minutes too much to wait, as the engine warms up slightly. How much time are we talking about to reach operating temps,? The
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Fast idle?

Reply #10 –
On my Cummins 8.3 ISC 350, I observe the following after startup:
 
    Upon starting, idle speed is about 700 RPM.
 
    After turning cruise control on, and pressing the set button, about 800 RPM.
 
    After then pressing the resume button, about 1200 RPM.
 
Is this normal behavior?
 
Thanks,
 
Trent
Trent and Jean Eyler
2000  U295  4003  WTFE  ISC  350
Build#5603 MC#17385

Re: Fast idle?

Reply #12 –
That is the normal behavior on our coach. However, you have more control than just that. You can set the idle pretty much anywhere you want, though I generally never set it higher than the 1200 that the resume button actuates. If instead of just tapping the resume button which instantly sets the idle at 1200 once the cruse is on, you push and hold it, the idle will increment gradually upwards and stay where it is when you release the button. Likewise, when the idle is set higher than 800 by using the resume button, you can gradually lower it by pushing and holding the set button.
Don
Quote from: TulsaTrent –
On my Cummins 8.3 ISC 350, I observe the following after startup:
 
    Upon starting, idle speed is about 700 RPM.
 
    After turning cruise control on, and pressing the set button, about 800 RPM.
 
    After then pressing the resume button, about 1200 RPM.
 
Is this normal behavior?
 
Thanks,
 
Trent

The selected media item is not currently available.
Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson

Re: Fast idle?

Reply #13 –
Ok.  From what I'm reading here , our coach should have the cruise idle function thing. Haven't been able to get it to work yet but I haven't tried the bumping the resume function either. I'll be trying that.

 Thought I'd use it for coolant flushing when we get back home. Topped it off with a different color before we left for the FMCA ralley and now at the ralley their telling me that's a no no.
Robert and Susan
 1995 36' 280 WTBI 8.3 3060r
 1200 watts on the roof, 720 Ah of lithium's
 Build # 4637. Motorcade # 17599
        FMCA  # 451505
        18  Wrangler JLUR

Re: Fast idle?

Reply #14 –
Quote from: Bob & Sue –


 Thought I'd use it for coolant flushing when we get back home. Topped it off with a different color before we left for the FMCA ralley and now at the ralley their telling me that's a no no.
Not sure you can go by color anymore. It is not the color it is the chemistry that matters. Ethelyne Glycol comes in different colors. Not sure about OAT based coolants.

Roland

1993 U280 4341
2010 Jeep Liberty
The Pied Pipers

Re: Fast idle?

Reply #15 –
Quote from: coastprt –
David,I had the same problem until I discovered that running a manual cylinder cut-out test using a Pro-Link 9000 you can choose to set the idle at 1000 rpms.  You can then hold it there until pressing the function key stops the test and the idle resumes at 600 rpms.  You don't have to wait and can idle up right after starting and the oil pressure is up. 
It makes for airing up much more quickly and using it for a couple of minutes to cool the turbo before shutting down.  I believe you can add a mechanical type fast idle but I haven't seen one.  Before I had my Pro-Link, I would just lay something heavy like a small tool box on the throttle.
Maybe Pierce or Caflashbob or one of the truckers on the forum can tell us how to do it.
Jerry
Jerry,

I wish I could. When we received four of our first 8V-71s (non-turbo), we all went to a Detroit seminar where our new engine's operating procedures were focused on. After that, we never left the cab without switching the fast idle on. So, why? The first reason is the 2-cycles don't like prolonged idling and may have less than optimum oil pressure after a lengthy period. The second is that during a fire, it's very possible the engine was operating at maximum throttle pumping large volumes of water. The noise was incredible with the fan, blower, engine and Waterous fire pump making so much noise that it would go through headphones. Anyway, after pumping for an extended period, going back to idle dropped the oil pressure way down to a point where it was marginal. The fast idle feature allowed the engine to have plenty of oil pressure as well as efficiently circulating coolant. So how did it work? Since these were mechanical engines, there was a switch on the dash that operated an air solenoid on the governor housing which, in turn, moved the "rack" a small amount and would give us the 1000 RPM fast idle.

Since our 92 series are electronic and no longer have a rack, the fast idle is accomplished by a ECU command from the Pro-Link. It could be done pretty simply without the Pro-Link but I have not looked into it. Probably the reason it was not fitted as OEM is that if it's accidentally operated while in gear, it would overpower the parking brake in a nano second and also the service brake.

On a slightly different topic, you 2-cycle Detroit owners probably notice how slowly your coach comes off a stop sign with the 4.xx first gear compared to the 6.xx first gear in the six speed varieties found in the later coaches. While following a U320/M11 on a recent trip, they were a half block down the road by the time I had cleared the intersection when the light turned green. It's partly because the the DDEC II ECU has a smoke control built in and until it sees 2 psi, it won't give the injectors much fuel. The other reason is the poor but necessary first gear ratio in the four speed Allison. But, using one of the extra wires from the front to back, you can install an easy fix to get you off the line and across the intersection much faster. I understand that the latest firmware updates on the Pro-Link may allow you to turn off the smoke control but here is an easy way to get around it by fooling the ECU so it thinks it has 2 psi at the sensor: BNO BBS - BNO's Bulletin Board System: DDEC - engine slow accelleration Just a fixed value or variable resistor.

Going back to the original post, I noticed while parked at a couple of truck stops on our latest trip, that after parking, most fast idled their rigs for about 20 minutes before shutting down. Good idea for extending turbo life.

For 92 owners, here is a site with an excellent description with illustrations of just about all the components of the engine. PDF at: http://avtec.edu/sites/default/files/DDC%2092.pdf

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Fast idle?

Reply #16 –
On our '95 once the air is up to appx 60psi, hitting the resume bumps the rpms up to about 1500 IIRC.  From there each hit of resume raises the rpms eventually to WOT@2700 and the coast button lowers it back down incrementally.  Turning the cruise off returns it to low idle. 
Dave and Kelli
1997 U295 40' Build #5188 CSGI
1995 U240 36' Build #4621 SBID-SOLD
2006 Jeep Wrangler Rubicon
 

Re: Fast idle?

Reply #17 –
     Cummins 555 usually idled at around 650 rpm, in the trucks we had the Cummins motor came with a dash mounted hand throttle that screwed out and the recommendation was to wind out the hand throttle to 800-825 rpm. The fast idle sounds good until you factor in Fuel Wash, this is when the rpm on a cold engine pushes raw fuel past the piston rings washing the oil film from the cylinder and contaminating the oil. When warming up remember that there are at least 4 dis-similar metals in the cylinder, heads, cylinder sleeve, piston and rings. Think Bi-Metal strip they will all expand and contract at different rates so warming up aggressively can put you in a 'Trick Bag' before you know it.
Cooling down is another important procedure because post oilers are rarely installed the temp of the turbo at shut down can be such that the oil for the turbo bearings is boiled off or toasted.............Turbo Failure 
88 Grand Villa 36' ORED 3208 (throwaway)Cat.
 Build # 3150
Happiness is the maximum agreement of reality and desire.