Questions about resistors, gonna try an experiment Options

[jsayre914]

I was reading the D-Jet Brad Anders and came across the part about the aux air regulator. I will quote from his site:

Does Yours Close Too Fast?: If you'd like for the AAR to stay open longer, try adding 2.5 ohms (four 10 ohm/10W power resistors in parallel) in series with the heater. This will reduce the heater power from ~14W down to ~10W, and cause the AAR to close more slowly. Should add a few minutes to the fast idle part of the cycle. Please exercise caution - that resistor pack can get hot, make sure it is safely secured.

My 2056 runs pretty rich on cold start, the aux air valve is working as it should, I tested it 14.2ohms and put it in the freezer, it opened all the way, then put it in a ziplock and submerged it in boiling water and it closed all the way.

I noticed that the idle drops pretty quick, like within 2min it is below 1000rpm. I was going to try to slow down the aar closing so i could get a good 5min or so before it drops. I tried to just unplug it because the valve will close by itself with just the heat from the engine. This kept the idle up for more much more than 5 min.

So teach me how to drop the voltage from 14.4 to about 10v

I dont want to melt anything, start a fire, or screw with the same circuit the fuel pump is running on. What do i buy, where do I buy it and what do I have to do to make my idea work.


(IMG:style_emoticons/default/popcorn[1].gif)

I have an 250ohm resistor in the garage from a 2.0 liter cht sender that would fit perfect in line, would that work (IMG:style_emoticons/default/rolleyes.gif) (IMG:style_emoticons/default/beer3.gif)

[Dave_Darling]

250 ohms is a whole lot more than 2.5 ohms. I suppose if you get 100 of them together, you can wire them up in parallel... At 250 ohms, you would get something on the order of 0.5V to the heating element, which will take approximately forever to heat up to the point where the valve closes.

(Note that you'll always have heat coming from the motor itself, so that places an upper limit on the amount of time the valve can be open.)

If you put 2.5 ohms worth of resistance in there, it will have about 1 amp running through it. That's a lot of power, and you need to make sure to get a resistor that can deal with it. I don't think there are many 2.5 ohm - 6.25 Watt resistors out there, so your best bet is to put together what Brad said.

Find a handful of 10 ohm-10 Watt resistors. Hook them together in parallel. That being, all of the one end of the resistors are hooked together, and a wire goes from there to the connector on the AAR. All of the other ends of the resistors are hooked together, and a wire goes from there to the power wire that plugs into the AAR wire. Yes, insulate the connections.

Dissipating 10W of power means the resistors will get kind of warm. You might want to make the wires somewhat long, and put the resistor pack away from stuff that can easily melt or that you're going to be putting your hands near.

--DD

[Mike Bellis]

Your 250ohm would most likely prevent it from working at all. High power resistors are cheap enough to buy a few and experiment.

Just remember resistors in parallel effectively half the resistance. It's more complicated if you use different values.

Resistors in series are additive.

You can also make a series-parallel resistor circuit that gets even more complicated.

I buy mine from www.mouser.com

[Tom]

Taking the values you have given, your current is about 0.8 amps and your power is about 10 watts now. Adding 3 ohms will lessen that to about 8.5 watts 0.7 amps.
I = V/R for amps and P = I X E for power in watts.
I = current in amps V = volts R = resistance P = power in watts E = volts in the power formula
You can get metal can type resistors in 3 ohms 10 watt and 5 ohm 10 watt sizes. The metal can ones ( see pic) can be mounted to a metal bracket and assist in heat transfer.
The 3 ohm 10 watt sounds like about what you want, with the 5 ohm 10 watt will give you and even longer high idle and use only 7.5 watts.
At mouser, look under "chassis mount resistors".
Tom

[worn]

I was reading the D-Jet Brad Anders and came across the part about the aux air regulator. I will quote from his site:

Does Yours Close Too Fast?: If you'd like for the AAR to stay open longer, try adding 2.5 ohms (four 10 ohm/10W power resistors in parallel) in series with the heater. This will reduce the heater power from ~14W down to ~10W, and cause the AAR to close more slowly. Should add a few minutes to the fast idle part of the cycle. Please exercise caution - that resistor pack can get hot, make sure it is safely secured.

My 2056 runs pretty rich on cold start, the aux air valve is working as it should, I tested it 14.2ohms and put it in the freezer, it opened all the way, then put it in a ziplock and submerged it in boiling water and it closed all the way.

I noticed that the idle drops pretty quick, like within 2min it is below 1000rpm. I was going to try to slow down the aar closing so i could get a good 5min or so before it drops. I tried to just unplug it because the valve will close by itself with just the heat from the engine. This kept the idle up for more much more than 5 min.

So teach me how to drop the voltage from 14.4 to about 10v

I dont want to melt anything, start a fire, or screw with the same circuit the fuel pump is running on. What do i buy, where do I buy it and what do I have to do to make my idea work.


(IMG:style_emoticons/default/popcorn[1].gif)

I have an 250ohm resistor in the garage from a 2.0 liter cht sender that would fit perfect in line, would that work (IMG:style_emoticons/default/rolleyes.gif) (IMG:style_emoticons/default/beer3.gif)

I am having trouble understanding the purpose for this. By the time the AAR normally closes your cylinder heads are pretty hot. Why not simply adjust the idle up? Or does it drop and then come up some after it gets warmer? Good luck. Reading up about electronics even in a simple way can open big doors.

[ChrisFoley]

I'm working on a (csob diy) hand throttle kit which would eliminate the need for the aar.

[jsayre914]

I'm working on a (csob diy) hand throttle kit which would eliminate the need for the aar.

I did that already. It works, but it gets to be a PITA espically when you first start the car on a cold morning then hop out for a min. if you dont pay attention to the sound of the car it soon gets well over 2k rpm (IMG:style_emoticons/default/blink.gif)

Joe hand throttle kit

[ChrisFoley]

Mine will be more like the 914-6 hand throttle.
Its a lever on the tunnel which actuates a pushrod against the throttle mechanism in the footwell.
It doubles as a cruise control. (IMG:style_emoticons/default/unsure.gif)
Much simpler and smoother than what you created I think.

[jsayre914]

Now I got another idea that might bring the same result. What about adding an additional air regulator side by side ? Then have a splitter before and after so the car has twice the air flow all the way across the warmup cycle. (IMG:style_emoticons/default/smoke.gif) Its Friday, my brain is dead. (IMG:style_emoticons/default/smoke.gif) (IMG:style_emoticons/default/smoke.gif) (IMG:style_emoticons/default/smoke.gif)

[McMark]

It shouldn't be running rich. I think you're attacking this from the wrong end. Do you have a wbo2 sensor?

[Spoke]

So teach me how to drop the voltage from 14.4 to about 10v

Very easy to drop the AAR voltage as Brad and other have said.

The AAR is a resistor of 14.2 ohms. So add a resistor in the circuit to drop voltage:


14V ------ RESISTOR ------- AAR ------GND

Resistors in series share the total voltage such that the amount of voltage across each resistor is proportional to the resistance divided by the total resistance in the circuit.

Thus, AAR voltage is:

V-AAR = 14.2V x AAR/(RESISTOR + AAR)

The current is voltage divided by total resistance:

I = 14.2V/(RESISTOR + AAR)

We need to know the current to calculate the power dissipation in the resistor. Power dissipation in the resistor is I x I x R.

Let's let RESISTOR be 0, 1, 2, 3, 4, 5, 6 ohms and plug into above formulas. Let battery voltage be 14.2V.

You can see below that 6 ohms will drop voltage and provide 10V across the AAR. This will slow down the opening.

Wattage of the 6 ohm resistor is less than 3W. Best to find a resistor that is 2x, 3x, or higher wattage like this 50W resistor from Digikey. It's in stock for about $5.

6 ohm, 50W