Base Idle, Fast Idle, Non Idle - Best Practices Diesel

WILDEBILL308 wrote:
Mr.Mark, The heat grid is in the intake to help when starting. It heats the incoming air.

Holstein13, There is a difference between "operating temperature" and "safe to operate". You can start moving as soon as you have safe oil pressure as long as you don't use wide open throttle. So if you have a ways to go getting out of the campground and to the freeway you can start moving. Your engine will warm up faster. If you have a very short distance to where you will need full power like entering a freeway I would let it warm up some before moving. If you don't want to sit and bother your neighbors you can move toward the exit. I like to do a last check before leaving the campground and I haven't found any place where there isn't room by the exit to stop and do this. This gives your engine a little more time (at fast idle) to warm up.

Correct. The fast idle will get everything warmed up faster. as well as creating more amperage for anything that runs from direct battery/inverter power.

When I go to the Prevost class at the end of October in Vonore, TN, I'll ask about the engine heating/idling, etc., so that I can understand it better. Still learning as 'mechanics' is not my forte`.

Really looking forward to getting under the chassis looking at the lube points and what's what under there. We'll also learn about the norgren air valves, how to drain the air tanks, etc.

BTW, we only have air leveling and we have a Volvo D13. Prevost changed over in about 2012 from Detroit Diesel to Volvo.

MM.

Mr.Mark wrote:
Thanks for the correction Wildebill... 'heats air coming in'.

Holstein13, your coaches leveling system is on the air bags, right? Will your air leveling system adjust if your coach settles, lets say on a soft parking pad.

So, how can the air bags 're-level' if you don't have an aux compressor?

The chassis air brakes should definitely be separate than the house so your air wouldn't come from there.

On the Cummins engine, the heater is on the fuel rail. It heats the fuel rail and not the air. I'll bet you it's the same thing with the DD. Keep in mind that the incoming air is driven by the engine, hence no RPMs means no air and certainly no hot air. So I'm doubting this "heats air coming in" claim. Makes no sense. Your compression stroke is what creates heated air.

Yes, the coach will settle after a few days on air bags. But no, it will not re-inflate. In fact, that's how I discovered a slow leak in my front passenger air bag. It settled overnight. Now that it's fixed, I haven't noticed any settling at all after one night. I haven't tried two nights yet because I'll use jacks if I have to level for more than one night.

WILDEBILL308 wrote:
Holstein13, There is a difference between "operating temperature" and "safe to operate". You can start moving as soon as you have safe oil pressure as long as you don't use wide open throttle. So if you have a ways to go getting out of the campground and to the freeway you can start moving. Your engine will warm up faster. If you have a very short distance to where you will need full power like entering a freeway I would let it warm up some before moving. If you don't want to sit and bother your neighbors you can move toward the exit. I like to do a last check before leaving the campground and I haven't found any place where there isn't room by the exit to stop and do this. This gives your engine a little more time (at fast idle) to warm up.
Bill

According to my dealer, Spartan, and Cummins there is no more warm up time needed, period. I can go to full throttle immediately upon startup.

Now in practice, you are exactly correct. I start my engine, put it in fast idle, then exit the coach and walk around it to make sure the jacks are up, antenna down, everything unplugged and nothing sticking out. Then it takes a while to get to the highway and by that time everything is up to operating temperature. I drive very calmly to the highway.

But when I stop at a rest stop, everything is different. The engine is hot when I get there and after a very brief cooling period, I cut off the engine. By the time I'm ready to roll again (less than 30 minutes) I turn on the engine and floor it to get on the highway. No warmup or fast idle in that case.

Thanks for the correction Wildebill... 'heats air coming in'.

Holstein13, your coaches leveling system is on the air bags, right? Will your air leveling system adjust if your coach settles, lets say on a soft parking pad.

So, how can the air bags 're-level' if you don't have an aux compressor?

The chassis air brakes should definitely be separate than the house so your air wouldn't come from there.

Just curious.
MM.

Mr.Mark, The heat grid is in the intake to help when starting. It heats the incoming air.

Holstein13, There is a difference between "operating temperature" and "safe to operate". You can start moving as soon as you have safe oil pressure as long as you don't use wide open throttle. So if you have a ways to go getting out of the campground and to the freeway you can start moving. Your engine will warm up faster. If you have a very short distance to where you will need full power like entering a freeway I would let it warm up some before moving. If you don't want to sit and bother your neighbors you can move toward the exit. I like to do a last check before leaving the campground and I haven't found any place where there isn't room by the exit to stop and do this. This gives your engine a little more time (at fast idle) to warm up.
Bill

Mr.Mark wrote:
Holstein13, are you sure you don't have an electric auxiliary pump? I recall our previous Dynasty had one as I would hear it click on occasionally to keep the air bags up for leveling.

I know we have one on our current coach as 'air' is very important to our coach. We have air valves for everything.

-air operated tilt/telescope steering wheel
-air operated step cover floor slide
-air operated driver's seat
-2 air doors (like in star trek).
-air valves for sewer, fresh water release
-air flush toilets
etc.

Also, our engines have a heat grid to heat the cylinders. I have a coil icon that comes up on the dash if the engine is cold. I hold the start until the light goes out, then I'll start. Sometimes after the light goes out, it will come back on after starting for a few seconds as needed.

Yep, I'm 100% sure I don't have an electric auxiliary pump. The steering wheel, step cover, drivers seat and toilets are all electric. I don't have air doors and my sewer valves are manually operated.

Here's how my startup procedure works. When I turn the key to the on position, the electric fuel pump engages and the fuel rail begins to heat up. The system runs through all of its diagnostics as well. Once the fuel is hot enough and the diagnostics are complete, the engine light will extinguish and I turn the key on. (I can turn it on earlier if I wish). I then hit the high idle immediately but the engine warmup protection will not allow the engine to increase RPMs until the oil pressure is achieved. The engine maintenance light stays lit during this period (less than 10 seconds). I can proceed immediately after the light goes off.

There is no more warm up period for the ISX15 engine and probably all their engines. It's turn on the engine and go. I just got off the phone with Cummins and they confirmed no warm up and no idling. Just go as soon as the engine lets you go.

holstein13 wrote:

WILDEBILL308 wrote:

If you have air bag leveling you have a electric air compressor that keeps your air pressure up.
Most coaches have to use the engine powered compressor to build air pressure.
Bill

Actually, no I do not have an electric air compressor. My bags inflate off of the compressor attached to the engine. If I want to level the coach on air, the engine must be running. In practice, I simply hit the air level switch after deploying the parking brake. (Of course, I always activate fast idle as well)

The key is that air system retains all air pressure and does not purge. It inflates or deflates the bags as necessary all the while keeping the air tanks full and pressurized. Then I cut the key off. The next morning I've lost virtually no air and can drive off immediately.

Holstein13, are you sure you don't have an electric auxiliary pump? I recall our previous Dynasty had one as I would hear it click on occasionally to keep the air bags up for leveling.

I know we have one on our current coach as 'air' is very important to our coach. We have air valves for everything.

-air operated tilt/telescope steering wheel
-air operated step cover floor slide
-air operated driver's seat
-2 air doors (like in star trek).
-air valves for sewer, fresh water release
-air flush toilets
etc.

Also, our engines have a heat grid to heat the cylinders. I have a coil icon that comes up on the dash if the engine is cold. I hold the start until the light goes out, then I'll start. Sometimes after the light goes out, it will come back on after starting for a few seconds as needed.

Safe travels,
MM.

WILDEBILL308 wrote:

If you have air bag leveling you have a electric air compressor that keeps your air pressure up.
Most coaches have to use the engine powered compressor to build air pressure.
Bill

Actually, no I do not have an electric air compressor. My bags inflate off of the compressor attached to the engine. If I want to level the coach on air, the engine must be running. In practice, I simply hit the air level switch after deploying the parking brake. (Of course, I always activate fast idle as well)

The key is that air system retains all air pressure and does not purge. It inflates or deflates the bags as necessary all the while keeping the air tanks full and pressurized. Then I cut the key off. The next morning I've lost virtually no air and can drive off immediately.

WILDEBILL308 wrote:
Not hard to understand. When you start a cold engine and after oil pressure comes up when you go to fast idle the additional boost provided generates enough heat to get more complete combustion of the fuel.

"But here's what Cummins told me directly. My engine has a warm up protection feature that won't allow me to fast idle or use the throttle until the engine is ready to perform and everything is up to pressure and temperature to prevent harm. This is what's coming directly from Cummins."
Well that is easy to check. I bet starting with a cold engine, as soon as you can go to fast idle you can drive. It won't be at operating temperature.
Bill

I think I understand your point and I agree completely. If I understand you correctly, you are saying that a slow moving piston (base idle) provides just enough compression to ignite the diesel fuel in the combustion chamber, but not enough to get complete combustion, especially in a cold engine. While a faster moving piston (high idle) will generate more heat immediately and provide better combustion. If that is what you mean, that makes a lot of sense to me and supports my current belief that "best practices" are to start the engine and get it into fast idle as soon as the oil pressure is up or in my case, as soon as the computer allows it to go to fast idle (10 seconds, max (computer monitors oil pressure)).

The second point you mentioned was that the engine won't be at operating temperature and I also agree with that statement, but I wonder what does "operating temperature" really mean? Does it mean that you shouldn't engage the drive components while it's below operating temperature? Does it mean that the exhaust system won't work optimally? Does it mean that you shouldn't try to get maximum HP out of the engine during an acceleration to the highway? Or all of the above?

I seem to remember my dealer telling me there is no longer a warm up period. i.e. once the oil pressure is up, get going. Idling is worse than driving. Maybe this is the new "best practices."