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High Idle & MPG Fooler

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Has anyone tried a stacked rotary switch similar to the switch on the bottom of pg 3 of the attached link to get everything into one switch with multiple positions for each of the functions/combinations needed to get both the High Idle & MPG Foolers into one pkg? I haven't sat down and sketched it out to see if it's even possible, just thought I'd check before playing it all out. It would require more then one of each resistor but they're cheap and would reduce the wires through the firewall to 4 and just one switch. No idea how many "stacks" the switch would need or number of "load" terminals for all the possible combinations involved but I'll work that out. It is more complicated then the original design but would result in a cleaner install. Would definitely need an index list for all the positions. Input on the concept would be greatly appreciated. http://www.alliedelec.com/images/products/datasheets/bm/NKK_SWITCHES_OF_AMERICA/70192244.pdf

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I bought a rotary switch from Radio Shack, was going to put multiple resitors on it for MPG / IAT fooler. Got the one toggle installed, never went back, yet! I start with the grids on for easy starting (wife uses truck sometimes too)... switch off once running.

I'd really like to see a video of a cold start then the sound when hitting the switch..

Anyone got a schematic of their toggle setups? Or how they wired in the IAT fooler?

O.k. I am diesel stupid. lol Been a mechanic for 30+ years and this thread i cannot figure out. Is this thread about trying to make the engine idle higher on warmup?Mitch:banghead:

It to fool the ECM that the conditions are colder than typical and force the ECM to start the high idle software for faster warm up times.

WOOHOO!!!!:hyper: I was right. So, does this benefit work also in colder weather?

WOOHOO!!!!:hyper: I was right. So, does this benefit work also in colder weather?

The engine has set points where it goes into high idle or 3 cyl high idle. It does this automatically if the IAT sensor detects such frigid conditions. The fooler reroutes the wires through a resistor to simulate the cold conditions, so it will work the same be it -100F or 200F, it replaces the sensor completely.. The resistors for the 3 cyl high idle simulates 10F or something and the high idle simulates 30F or something based on their resistance. The MPG fooler simulates a HOTTER temp than it really is. The 24V bases it's timing on a number of variables and the IAT is one of them. When it is cold it seems to put the engine into a really advanced mode and this seems to have a negative effect on mileage. The consensus is that it does this for emissions.. By fooling it into thinking it is summer, it stays put using a better timing table which is more efficient. His writeup on it: http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/26-engine-systems/51-high-idle-mod
  • Owner

For MPG's the average range of high point is 100-140*F IATFor high 6 cylinder you need 32*F in the manifold with grid heaters active. Like ISX got a video measuring his grid heater and it con produce 400-500*F easy. So reaching 32*F on a cold morning can be tough hence the fooler. Then 3 Cylinder is set at 15*F with grid heaters running. So it got to be really cold to reach this one.

Have you tested it at 160 170 180?

No. That is well above the normal spectrum for sure. But I could twist it up and see what happens. :think:

Well yeah the normal spectrum is also under 12V MPG....get out of the norm :thumb1:

So basically, I should do this mod to help fuel mileage?:think:

So basically, I should do this mod to help fuel mileage?:think:

The high temperature IAT fooler is ONLY intended for that. It serves no other purpose. Maybe some guys will list their gains they personally saw.

So, to do this I just need to unplug the IAT and plug in selected resistor? And this blocks the heater from coming on? So I need a switch to use the warmer and then switch to resistor?

If you are just putting in the 100-140F resistor then you would use the regular sensor for cold starting since the engine will NOT use the grid heater if it thinks it's 100F+ outside. Ideally you would run it regular for a couple minutes and then switch it over to the resistor.

  • Owner

ISX is correct. So you would build a ECT fooler but with IAT plugs and the change the resistor to the value you selected. So then you leave the switch normal IAT for start but once the engine is started and ran for a short period you can flip on the fooler. Now If you happen to attempt to start the truck with the fooler enabled then you will not get grid heater. Even if you turn the key off and the fooler off it will still hang on the previous value for quit a bit.

Thanks! Sounds simple enuff!!! I will build me a fooler!:hyper:

Just a thought....why couldn't I use a manual idle cable. Like a choke cable just to get high idle,as you can see I have too much time on my hands here.I also saw a plug and play 3 speed idle box,don't know if it will work on the cummins yet. Gonna call and ask this week if I remember.

  • Owner

Just a thought....why couldn't I use a manual idle cable. Like a choke cable just to get high idle,as you can see I have too much time on my hands here.I also saw a plug and play 3 speed idle box,don't know if it will work on the cummins yet. Gonna call and ask this week if I remember.

Because of safety factors.

With the high idle flash and box you still have all the safety system in place. The high idle will cancel with...

[*]Touching the throttle

[*]Touching the brake pedal

[*]Placing the trans in gear (auto)

[*]Speed above 0 MPH

[*]Coolant above 170*F

With a choke cable to hand throttle you can't use the exhaust brake as a warm up aid because the throttle is above 0% so exhaust brake is canceled. (virtual loading)

Then also there is no 3 cylinder mode with choke or hand throttle which creates more heat than 6 cylinder. (virtual loading)

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