Hello my old 2005 Super Duty diesel used to have high idle when it got real cold out here in Massachusetts. I noticed my 2017 does not do that so I'm assuming the 2017 s do not have high idle when you first turn them over in the morning. Is that the case with everybody else?

take care
Eddie

 

I'm sure this is a dumb question, but what is the purpose of the high idle? Warm the truck up faster? I have seen a thread on adding a fast idle to one of the upfitter switches, so I guess that means the answer is no? We just bought our first diesel last week, so lots to learn.

 

The Diesel engine does not burn much fuel at idle, so therefore requires a long warm up time. The primary purpose for most people is to help it warm up faster. There are also other applications, where the PTO on the transmission is being used (Think work trucks with an overhead bucket), that the higher RPM give more power to the PTO.

 

Roger that, thanks.

 

I installed the new switch I have a link for here https://www.dieselpowerproducts.com/...werstroke.aspx

I installed it in about 45 minutes. It worked great. I also had mine working in my 2010 F250 but had to hook up the up fitter switches to make it work. The 2017 can use this product and it is plug and play. Great product and easy to install with directions.

 

Mine has high idle. I flip my #4 upfitter on, set parking brake, and it idles up to 1400 RPM's.

High idle helps warm it up faster, but more importantly it's much better for the longevity of the EGR system.

 

Define "cold." I've had two 2017 diesels and they absolutely and automatically idle higher at cold temps immediately after startup. We had 12F last week for a low, and in the morning the truck was idling around 1000 RPM instead of the usual 6-700. It gradually idles back down. Actual cold temps (below zero) would result in even higher idles.

There is a modification one can make using a resistor, an upfitter switch, and a specific wire in the blunt-cut bundles. I did this on my 2016 diesel. The value of the resistor determines the idle speed when the switch is flipped on. Some people use a rheostat instead of a resistor which allows for variable idle speed. In order for it to actually work, the truck must be in Park with the parking brake set. Once the brake is released, the truck idles down.

As for the purpose of high idle...the primary purpose is to power PTO-driven applications as someone above mentioned. Most people who wire in the mod here are using it for the purpose of preventing wet stacking, lessening the impact of extended idling on the DPF, having hotter heat, or better A/C.

Diesels don't warm up slower because they are burning less fuel. They warm up slower because they have much larger amounts of oil and coolant compared to an equivalent gas engine. The biggest problem a diesel has is that it uses compression ignition...meaning the heat generated by compressing the diesel fuel is what causes it to actually ignite. There is no "spark plug" electrically igniting the mixture. Only heat. That is why glow plugs are used to start an engine when cold. On a typical warm day, you'll barely see the glow plug light come on before it goes out on the dash gauges. But on a very cold morning, you might wait 2, 3, or more seconds before it extinguishes and then you can start the engine. Of course, many people with an ignition key starting system don't wait at all and the engine still starts. But if you have push-button start or if you remote-start the engine, the delay is forced by the computer.

Nevertheless, a certain temp needs to be reached for diesel to ignite under compression. Obviously, low idle speed will produce the least amount of heat while wide-open throttle would produce the most. So...we have an absolute temp that needs be be met in the cylinder for diesel to ignite...and we have an absolute value of heat produced by compression in a cylinder. What changes is the block temp. If the temp is -40F, the truck would have to compensate for a 100-gree difference compared to the same truck operating in 60F temps. The engine fan is also constantly cooling the engine block and coolant. I've operated in cold enough temps (-15F or so) where the engine temp gauge has shown fully warmed up during a highway run, but when stopping and idling for 10 minutes, the gauge would actually register a decreasing engine coolant temp. The 6.7L Powerstroke has a complex cooling system with four thermostats between the two independent cooling systems to try to maintain the best possible temp. The main cooling system, for example, can close the 201F thermostat and still keep the 194F thermostat open. This still allows engine cooling but at a lower volume to prevent over-cooling.

As the engine loses temp in bitter cold conditions while idling at normal low speed, what happens is the diesel does not combust as cleanly and fully. This creates soot (visible black particulate matter) which must be trapped by the DPF...filling it sooner and requiring sooner regenerations. It also eventually leaves a sheen of unburned diesel on the cylinder walls, which is the phenomenon known as wet stacking...which can be harmful to the engine.

Our 6.7L diesels have good computer management will can vary idle at any time and will idle up in cold temps and extended idling. But some choose to install the high idle switch which will, in fact, provide better heat and A/C performance, and less DPF usage.

 

Last winter, in January and February, I started my truck in temperatures of -25 F. It was plugged in and it did high idle itself to somewhere between 900 and 1000, but never higher. I'm wondering where you're getting the info that it will idle higher without additional components installed.

 

Just my own personal experiences. I've had it idle as high as 1100 on its own when the temp was -15F but that was on a 2016.

 

I've seen about 1200 (by the stock tach) after extended idling with a cold engine, ambient temps around 50 F.

 

It was about 25 degrees. 2005 would high idle at 32f

 

Assume that's something that you performed as a mod? Didn't come out of the box like this, correct?

 

Temps have started edging to the single digits here, and I've seen several variations of high idle after I remote start. It seems to vary from 800-1.2k RPM, and I can't really figure out why it differs from start to start.

I also have supplemental heating pads on the oil pan and transmission when I plug in, but I doubt that really plays any part.

 

Its pretty straight forward, the computer in the vehicle managements and engine controls are looking at outside air temperature, intake air temperature, oil temperature and coolant temperature. I believe they also look at voltage and assess whether ramping up RPM for the alternators are needed, ie charge protect. For example with teh diesel supplemental heater running. this would depend on your temperature settings in teh truck, defrosters on windows on, seat heater loads ect, climate control auto setting, seat and steering wheel auto settings. All these demands will drive up the idle speed. the good thing is if needed it will, the thing a hi idle switch does is demand a increased idle speed whether or not its needed, whether the engine is warm enough to hi idle or not. My 2005 did also have this mod done, I am so far resisting the urge on the new truck, as i used it less and less frequently recognizing that the internal controls can do their thing better than I can. I dont really want to leave my hi idle on for remote starting becuase it ramps up right away versus the above conrtols give it a bit before that starts happening. Cold starts for me are the most often reason, but also to cool the cab down in summer, cool the seats, run accessories is another good reason to have hi idle.

 

My 2005 was pure stock, High idle would kick in after a minute or two. My 2017 does not high idle. Jus was wondering if this is something they changed.