1980 200sx 2.2 ohm resister

[WAGON JON]

Jon you have this right: http://dimequarterly.tierranet.com/dq/dq_1_1.pdf. The 200sx manual is better but this is a good quick reference.

 

I would have to trace back where the tach actually goes, but my first thought is that the 2.2k resistor helps protect the ECU. From the wiring diagrams I have seen, that is the input for the ECU where it measures engine speed (which may or may not have anything to do with the tach). Though I have never measured it, there very large pulses that come off the negative terminal of the coil (from what I have read over 100V). If I was designing something to interface with that, I would use something to drop the voltage to usable and safe levels for digital equipment....probably in the 5V range. Again, I have not verified the actual hookup and where everything goes, but until different information surfaces, I would NOT run your engine without sometype of 2.2k resistor there.

 

Although the Haynes manual says differently, the dropping resistors are typically used to match ECUs to low impedance injectors. Basically, one end of the injector is hooked up to positive, and the ECU sinks all that current to ground everytime it triggers the injectors. Because of the lower impedance of the injectors, WAY to much current is sunk through the system. I would image overheating injectors and fried ECUs.

 

 

Thank you for the info and the PDF file!

 

And yes, I went to the Junk Yard and found the infamous resister on a 720 pickmeup truck!

 

I figure if the factory is using it then it may be a good idea for me to use it too.

[Hardwyre]

Oh and a 2.2k 1W resistor from Radio Shack should do the trick. Like someone posted above, you can mix and match values to get the desired values. <BR><BR>It probably isn't critical in this application but there are MANY types of resistors with different properties and tolerances. Most of the time it doesn't matter, but you can get into some areas where the wrong resistor will cause problems. Since I am in the beginning stages of doing a similar upgrade, I will try to figure it out.

 

The problem is that Radioshack doesn't carry 1 watt resistors in the 2.2k ohm range. That's why there's the need to make a nicer version of this:

 

It's not as good as a solitary 1 watt resistor would be since current will still initially travel down the path of least resistance, but it ends up evening out as resistance rises as the resistors heat up, so the current ends up jumping from side to side, balancing itself. Note this trick only works with matching series.

 

Edit: Those are 10 ohm resistors, so don't use my color code :D

[datzenmike]

Thank you for the info and the PDF file!

 

And yes, I went to the Junk Yard and found the infamous resister on a 720 pickmeup truck!

 

I figure if the factory is using it then it may be a good idea for me to use it too.

 

My wiring diagram shows the 2.2K dropping resister connected to one side of a coil. The other side goes to pin 18 on the 200sx ECU and also to the dash tach. I know for a fact the tach won't work without this resister in line. If it's used by the 200sx yours should too.

[Sealik]

My wiring diagram shows the 2.2K dropping resister connected to one side of a coil. The other side goes to pin 18 on the 200sx ECU and also to the dash tach. I know for a fact the tach won't work without this resister in line. If it's used by the 200sx yours should too.

 

 

Ya...tac no workie with resistor MIA.

 

The ECU needs the pulse/signal from the coil to fire the injectors.....with the resistor gone..... no vrooom :D

For my application anyways.....

[brodster]

^^^^^

BTW I want to clarify something I had said (read this thread quick at work): I was assuming that it was being considered to directly bypass the resistor by just using a jumper. I thought that this is what was meant by not using the resistor. Doing that would most likely do serious damage to the ECU or tach input.

 

On the other hand, leaving it out should just do nothing: No signal to the tach or ECU. Looking over my 200sx wiring diagram, the resistor is in series with both components.

 

So to be clear: No harm but no run without the resistor. Bypassing the resistor, bad idea (probably).

[brodster]

The problem is that Radioshack doesn't carry 1 watt resistors in the 2.2k ohm range. That's why there's the need to make a nicer version of this:

 

It's not as good as a solitary 1 watt resistor would be since current will still initially travel down the path of least resistance, but it ends up evening out as resistance rises as the resistors heat up, so the current ends up jumping from side to side, balancing itself. Note this trick only works with matching series.

 

Edit: Those are 10 ohm resistors, so don't use my color code :D

 

We used to do stuff like that all the time in lab when we couldn't find the right resistor value. Gets the job done in most applications, but may be ugly as hell. (Your pic looks pretty though)

 

I was kind of wondering if radio shack didn't have a 2.2k 1 Watt resistor. Checked their website and they limited stuff. Digikey and mouser are always good, but if you can find a good model in the JY go for it.

 

On a quick thought, resistors do degrade over time. Probably not worth worrying about, but if there is a multimeter laying around, wouldn't hurt to verify it.

[Hardwyre]

We used to do stuff like that all the time in lab when we couldn't find the right resistor value. Gets the job done in most applications, but may be ugly as hell. (Your pic looks pretty though)

 

I was kind of wondering if radio shack didn't have a 2.2k 1 Watt resistor. Checked their website and they limited stuff. Digikey and mouser are always good, but if you can find a good model in the JY go for it.

 

On a quick thought, resistors do degrade over time. Probably not worth worrying about, but if there is a multimeter laying around, wouldn't hurt to verify it.

 

 

I have a few resistor packs on various projects; throw a little heat shrink tubing over them and they end up looking sophisticated and mysterious instead of shit. :D

 

Wish I could figure out what the post resistor value would be on a 12+ source with a 2.2k resistor. I guess it all depends on the amount of current being pulled by the ECU and tach. I want to say 5+ since that is typically the next step down, but who knows. It's can't be too much if a 1 watt resistor can sink it.

[brodster]

I have a few resistor packs on various projects; throw a little heat shrink tubing over them and they end up looking sophisticated and mysterious instead of shit. :D

 

Wish I could figure out what the post resistor value would be on a 12+ source with a 2.2k resistor. I guess it all depends on the amount of current being pulled by the ECU and tach. I want to say 5+ since that is typically the next step down, but who knows. It's can't be too much if a 1 watt resistor can sink it.

 

 

Heat Shrink FTW!

 

Yeah about 5 volts makes sense for that era of circuitry. That wouldn't surprise me. I may just crack open an ECU and check it out. But it could be determined by putting a scope on the input of the ECU. When I get closer to actually installing the equipment, I may just do this.

 

Also, you gotta keep in mind that when the primary coil of ignition coil is "chopped off", that there will be a huge voltage spike on that negative terminal. Like I said, I have never measured it, but I have seen scope shots showing it at about 300V.

[WAGON JON]

I used my Fluke multimeter it said 2 194

 

Looks pretty close to me

[elmerfudpucker]

Just snag one out of the JY. My 720 has one right behind the headlight on the drivers side.

[WAGON JON]

Just snag one out of the JY. My 720 has one right behind the headlight on the drivers side.

 

 

Yep! That is what I did!

[ggzilla]

The purpose of the resistor is not to get it to the certain voltage -- that's the job of a voltage regulator, which the ECU has. The purpose might be to protect the circuit from intermittent overvoltages (over the normal 14.5), pulses or spikes.

 

5V doesn't make sense. In the late 70s they probably would have used 5V chips (TTL or CMOS) but the ECU voltage regulator needs something a little higher than that.

[brodster]

The purpose of the resistor is not to get it to the certain voltage -- that's the job of a voltage regulator, which the ECU has. The purpose might be to protect the circuit from intermittent overvoltages (over the normal 14.5), pulses or spikes.

 

5V doesn't make sense. In the late 70s they probably would have used 5V chips (TTL or CMOS) but the ECU voltage regulator needs something a little higher than that.

 

 

Ggzila, do you have a schematic of the ECU by any chance? I would love to get my hands on that!

 

I agree that 5V off the top doesn’t make sense, but the input voltage to that pin, which is in line with the resistor, will be headed off to a digital signal in short time for the microprocessor. That will certainly be at logic level. And that vintage is probably in the 5V range. Maybe it would be accurate to say 5 to 20V range. Regardless, from a design perspective, I would think the 2.2k resistor is there to help lower the voltage to a particular range (but yeah maybe not a certain value).

 

Personally, I would imagine there would be some type of buffer stage on the input to convert the incoming pulse to something more usable and to interface with the digital inputs safely. It all depends on how much voltage the primary of the coil produces, which depends on dwell time, coil saturation, and the windings of the coil.

 

I don’t think you will see a voltage regulator handling the input signals. In my experience I have only seen and used voltage regulators purely for power supply regulation. (Unless you were referring to the buffer stage. Maybe just a semantics thing.)

 

Either way it is mostly speculation on my part as to what’s in that ECU. I have some ideas how I would go about designing it, but sometimes I am surprised when I pop open a circuit and start reverse engineering the thing.

 

Again if you do have a schematic I would love to see that, and not only for this particular topic. If I have time, I plan on tweaking the ECU with some piggy modules or my modifying the internals. And having the circuit will save tons of hours and possibly broken ECUs.

 

 

[datzenmike]

The source is the negative side of the coil. The matchbox holds this at ground to draw current through the coil to build the magnetic field. So much of the time it's going to be close to ground potential. When the dizzy is triggered the ground is removed to collapse the magnetic field. For this brief time the voltage available would be less than the battery due to the coils internal primary resistance.

[brodster]

The source is the negative side of the coil. The matchbox holds this at ground to draw current through the coil to build the magnetic field. So much of the time it's going to be close to ground potential. When the dizzy is triggered the ground is removed to collapse the magnetic field. For this brief time the voltage available would be less than the battery due to the coils internal primary resistance.

 

Mike,

 

The way I understand it is a bit different. You are right, during the dwell period the module (or points on old school dizzy) ground the primary of the coil so that a large current can be built up in the primary. However, the moment the module cuts the ground (or the breaker opens), the voltage on the negative terminal of the coil spikes positive. A few hundred volts is normal. I agree there is resistance in the coil; however, the inductance of the primary is what contributes to the primary voltage spike. I am not going to dive into equations, but the current through an inductor cannot change instantaneously. The voltage can change instantaneously and will. Before the switch, there would be +12V across the primary and the negative would be sitting close to ground. By nature the inductor will “try” to maintain the current as it was flowing before. Because the current path is essentially cut, the primary coil will generate a huge voltage to overcome the large impedance. So the positive side of the coil will be sitting at +12V, but the negative will be a few hundred volts above that. For a moment it would look like +12V and ~+300V batteries in series. The transformer action between the primary and secondary steps up the voltage to fire the spark plug.

 

There are also some other factors too: There will be some oscillation when there is a capacitor placed in the primary path. Eventually the energy will dissipate, and the voltage will flat line to +12V. The module (or points) switch ground back in and the process repeats.

 

This is of course a generalization, but most ignition systems use the same principle on a basic level.

 

 

 

[datzenmike]

Yeah, I can dig that. Inductances can do weird stuff.

[WAGON JON]

I got the system running! Took the car for a drive and there is a 3300 bog. At 3500 it clears up and runs fine. The question is, what do I need to do to tune this out? Any takers? Also, I have 3 ECU's and I tried all of them. Each of them have the same 3300 bog. That may indicate accessory parts like the AFM or TPS.....

[brodster]

Good to hear you got it fired up!

 

This 3300 rpm bog is probably beyond my expertise. The others will give you better advice. But... You get a bog at 3300 rpm at all different type of engine loading and throttle positions?

[WAGON JON]

Yeah all loads.

[Sealik]

I got the system running! Took the car for a drive and there is a 3300 bog. At 3500 it clears up and runs fine. The question is, what do I need to do to tune this out? Any takers? Also, I have 3 ECU's and I tried all of them. Each of them have the same 3300 bog. That may indicate accessory parts like the AFM or TPS.....

 

Maybe have a look at the AFM...where the wiper arm sweeps the electrical board.

Could be an anomaly in it. Rev the engine up to 3300 and see where the arm is in relation to the board...pitted maybe. I've shifted the board and gave the arm a fresh track....tune up, so to speak.

Also...the spring gets weak over time and could be reclocked....CCW (more tension)

I marked the original position before I moved it.

If you do intend to move the wheel...hold onto it when you loosen the phillips screw...it's under tension from the spring.

My AFM is rotated 180 degrees...so it's a little easier to work on.

 

 

Vroommmmm.

Also has a VG30E TB on it... :D

 

http://youtu.be/B5GYm-Z2UdE

[brodster]

Yeah all loads.

 

Just to make sure we are on the same page, by all loads we are meaning that you ran it through 3300rpm in different gears or different throttle positions? Are you accelerating through 3300 RPM slow, mildly or as hard as you can? Did you decelerate and accelerate through 3300 rpm? Any problems there? Just trying to isolate the problem.

 

Maybe the car isn't even drivable right now. Hopefully I didn't miss that.:D

 

Maybe have a look at the AFM...where the wiper arm sweeps the electrical board. Could be an anomaly in it. Rev the engine up to 3300 and see where the arm is in relation to the board...pitted maybe. I've shifted the board and gave the arm a fresh track....tune up, so to speak. Also...the spring gets weak over time and could be reclocked....CCW (more tension) I marked the original position before I moved it. If you do intend to move the wheel...hold onto it when you loosen the phillips screw...it's under tension from the spring. My AFM is rotated 180 degrees...so it's a little easier to work on. Vroommmmm. Also has a VG30E TB on it... :D http://youtu.be/B5GYm-Z2UdE

 

Which engine setup do you have a VG30E TB on? I have an L20b that I am going to run with a stock L18e manifold. Just trying to find a good TB that will bolt on. Have the orginal one and a 280zx one. I know those both bolt on just fine.

 

With the AFM, I haven't looked inside, but that seems like a good thing to check.

[Sealik]

Just to make sure we are on the same page, by all loads we are meaning that you ran it through 3300rpm in different gears or different throttle positions? Are you accelerating through 3300 RPM slow, mildly or as hard as you can? Did you decelerate and accelerate through 3300 rpm? Any problems there?

 

Just trying to isolate the problem.

 

 

 

 

Which engine setup do you have a VG30E TB on? I have an L20b that I am going to run with a stock L18e manifold. Just trying to find a good TB that will bolt on. Have the orginal one and a 280zx one. I know those both bolt on just fine.

 

With the AFM, I haven't looked inside, but that seems like a good thing to check.

 

My engine is a Z24

The EFI is out of a 81 Z20E...so I had to reclock the AFM.

Was at 3 after the swap....but now I'm about 12 teeth/notches CCW. :blink:

[WAGON JON]

"Just to make sure we are on the same page, by all loads we are meaning that you ran it through 3300rpm in different gears or different throttle positions? Are you accelerating through 3300 RPM slow, mildly or as hard as you can? Did you decelerate and accelerate through 3300 rpm? Any problems there? Just trying to isolate the problem."

 

Yeah Brodster, all loads in all gears and even cruzing on the freeway. Accelerating and decel too. I did move the TPS all the way to one side and it almost fixed the problem. It isn't as noticeable any more....but it is still there!!! Ug!! :angry:

[Hardwyre]

Yeah Brodster, all loads in all gears and even cruzing on the freeway. Accelerating and decel too. I did move the TPS all the way to one side and it almost fixed the problem. It isn't as noticeable any more....but it is still there!!! Ug!! :angry:

 

Check your AFM for worn sweep traces. Also, have you cracked open the TPS and seen if it's contacts are spaced properly? If you adjusted the TPS all the way to one side, you're only masking the problem because how it's running rich which is hiding what is most likely a lean issue.

 

TPS adjustment guide (mine; there are others): http://forums.hybridz.org/index.php/topic/86041-tps-throttle-position-sensor-adjustment-preguide-76-280z/

 

If the carbon trace on the AFM is worn in one little spot, it'll throw off the fuel mapping for that spot, usually WAY to the lean side.

 

Here's some more information on the AFM: http://www.atlanticz.ca/zclub/techtips/afm/index.html

[WAGON JON]

Thank you good sir for the info!