High Idle switch

[Haywire6000]

I was wondering if there was a way to setup a "High Idle" switch on my 1993 Ranger. I searched and didn't find anything....

 

[RonD]

Fuel injected engines(i.e. computer controlled) don't easily allow that.
Computer needs to control idle to balance the air/fuel mix.

But you do have throttle control via the gas pedal or cruise control type actuator.
You could install a manual choke cable, attach it to the throttle linkage and use that to set higher RPMs.

If you feel like doing a little modifying you could modify a cruise control actuator with a vacuum solenoid, solenoid would be controlled by switch on dash, when you turn it on actuator pulls throttle open a "preset" amount to set higher idle.

And the always good, "brick on the gas pedal" still works

Someone that programs/tunes Ford Computers "may" be able to to use and unused pin on computer(EEC-IV) to trigger a higher idle, high jacking IAC(idle air control) Valve, that could get you up to about 1,500rpm, maybe a little higher.

What's the purpose of this?

 

[bobbywalter]

you can use a dpdt switch to isolate it and run a pwm controller, i had a similar setup for running my weldernator with my 302....back wheni was running one of those.

with a piggyback setup you can run the idle at different settings as well...like with an ol tweecer or a moates 1/4 horse ect. and it can run up to 3k or more...


the easy way is to valve a vacuum leak.

i initially just disconnected my iac and cranked the tb manually with the screw as it was easy to turn by hand.

not sure, but i assume like me, you doing it for your on board air, welder or power source needs.

 

[Haywire6000]

Yes to the power part. haha. I currently don't like running all my lights at idle because the voltage dips under charging..... Granted I don't need to run them at idle often but in case I need them for something it would me nice to not have to sit in the truck holding the RPM's up so she keeps charging.

 

[RonD]

If you just have Stock electrics then you have a failed field in the alternator, that's the only reason voltage would drop below 13.5v at idle.
Alternators have 3 fields that generate AC voltage, each field has a set of diodes to convert AC to DC, 1 field or it's diodes can fail, this doesn't reduce voltage/amps by 1/3 because of voltage regulator, but at idle the alternator simply can not produce the 13.5v needed.

If you have added electrics, then just get an alternator with a more amps.
1993 Ranger will have 95 amp, 130amp can just bolt in and use the same wiring, although adding a larger gauge B+ wire is a good idea, depending on how many electric add-ons you have.

Good read here on what you have and what will bolt on: http://www.therangerstation.com/tech_library/alternator.shtml

 

[Haywire6000]

Already did the 130 AMP swap... Just with the factory lights running plus the 6 100 Watt lights and two 55 watts... She doesn't care to much for them all running at idle.

 

[RonD]

I can see why
600 watts at 13.5volts is 44amps(50 amps at 12v)
110 watts at 13.5volts is 8amps(9 amps at 12v)

So the add-ons are 52amps and you only increased stock alternator by 35amps.

You could go to bigger alternator(best choice), or smaller pulley on current alternator(which mimics higher engine RPMs).
Overdrive alternator pulleys are common now because underdrive crank pulleys are popular and you often need to increase alternator RPMs when you install an underdrive crank pulley.

You would need to measure current crank pulley diameter and alternator pulley diameter.
Most car builders spec a 1 to 3 ratio stock, so 6" crank pulley would mean a 2" alternator pulley, if engine was idling at 700rpm then alternator would be spinning at 2,100rpm.
measure your pulleys and then divide crank(6") by alternator(2") to get ratio(3) so 1 to 3, or 3 to 1

Hook volt meter up to battery terminals, start engine and check voltage, should be above 14volts, wait for battery to recharge, a few minutes, when voltage is down to 13.5 or 13.6 recharging is done and you are ready to test.
Turn on everything, lights, heater fan, radio, doors open
Battery voltage should now be down below 13.5v
Increase RPMs slowly until battery voltage is at 13.5 again, thats the RPM you need for alternator to power the system with everything on.

If that is 1,200rpm at the crank(tach) then 130amp alternator needs to be spinning at 3,600rpm to service amp draw, assuming 1 to 3 ratio.
3,600 divided by 700(target idle RPM) = 5 to 1 ratio
6" crank pulley with 5 to 1 ratio(6 divided by 5) = 1.2" pulley on alternator
Getting very small so hard for belt to grip, and then you also have the problem of maximum RPM for alternator.
At 5 to 1 ratio, engine at 4,500rpm means alternator would be spinning at 22,500rpm(4,500 x 5 = 22,500)
Not good for alternator or its bearings, you want to stay under 20,000rpm, under 17,000 is even better.
Stock 3 to 1 ratio with engine at 4,500rpm is 13,500rpm at alternator.

Get a bigger alternator, you may still need to decrease alternator pulley size(overdrive it) but not by much.
Running engine at higher RPMs increases fuel use of course, but it can also cause overheating if cooling system is even slightly out of spec, and if you are not in the vehicle at the time.......................

 

[Haywire6000]

I thought about picking up a 200 AMP. The overdrive pulley idea did cross my mind.... Now I just need to get one.

 

[RonD]

The overdrive pulley for a 130amp alternator probably wouldn't work with your current amp draw with everything on.

Alternators basically can't produce any amps until they are at 1,000rpms(alternator pulley/shaft speed)
And get to maximum output at about 3,500 rpm
But they do get to about 50% at 2,000rpm

Stock alternator, 95amp, would have been at 47.5amps at idle 700rpm(engine crank), this would be the stock lighting and power use minimum required.
Current 130amp alternator is at 65amps when idling at 700rpm, you took away 50 of those amps with add-on lights that only left 25 amps for stock electrics, so...........dimming lights would be expected.
200amp alternator would be at 100amps at idle, 50amps for add-on lights and 47.5 amps for stock electrics = 97.5 amps, so will be close but should be OK.

All the above has a few assumptions, good alternator for one, lol, and the alternators pulley size which can be different from model to model, and the RPM vs Amp output specification for that model alternator, while average is 50% of the amps at 2,000 rpm it could be 40% or 60% it is a best guess without the data.

 

[bf750]

go LED

 

[RonD]

go LED

lol, but then you got all those extra amps and need to add an air compressor or Dual 15" sub woofers, so back to dimming lights again

 

[WarHawk-AVG]

Add a second battery, this way much more AH storage before volts droop, however you will need to charge longer if you drain them too low

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[holyford86]

I have a 200 amp alt, and 2 batteries wired through an isolator, the 200 amp alt doesnt put out 100 amps at 850 rpm idle, but at 1500 rpm it puts out about 195 amps. I have a high idle setup rigged to the shifter with a bicycle brake handle and cable to throttle body and have never had an issue. The setup hates the winch under full load though, which is to be expected because it draws around 400 amps full load. Led lights are the way to go to save amperage for other things though.

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