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Old 03-02-2001, 03:11 PM   #1
munkis
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Thumbs down For those who wanted the 4.8v diodes :(

No Company anywhere makes a 4.8v diode, sorry. . 4.7 is as high as they go. I will question my mom about how involved it would be for her company to make them. Ill lets you all know.

Jay McDade
Auto Tech--Lincoln/Mercury/Jaguar
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Old 03-02-2001, 03:31 PM   #2
Patrick Olsen
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It's been a long time since I studied electrical engineering stuff, so I could be wrong on this. I'm pretty sure, though, that if you can't find a 4.8V diode that you could just get a couple of 2.4V diodes in series. I'm almost positive I remember studying circuits that used zener diodes in series to give the desired voltage drop.

Pat Olsen
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Old 03-02-2001, 03:38 PM   #3
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i think that you are thinking resistors, not diodes


[This message has been edited by Jaxx (edited March 02, 2001).]
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Old 03-02-2001, 03:54 PM   #4
iodine23
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Diodes in series work just like you said... so throw two 2.4's in series is like having one 4.8.

Are you trying to make some sort of voltage clamp I take it?
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Old 03-02-2001, 04:13 PM   #5
munkis
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yeah voltage clamp to stop the map/boost problem on 00-01 RS. Rallispec posted about, it they are using 4.7 volt diodes soddered directly into the ecu, on the map signal circuit, dont remeber the specifics, but they would have liked to use 4.8v diodes to gut more injector duty cycle, I dont know whey they dont use two 2.4, if they make them, maybe not enough room. Have to ask Rallispec about that. Since my mother workes at a large electronics company I thought maybe she could get them. Just trying to help out. But no dice.

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Old 03-02-2001, 04:59 PM   #6
iodine23
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It may be more of a pain to put the two diodes in series, because now you have to solder one end of each diode to the ECU and the other ends of each diode to the other diode.

If you use one diode you just jumper a connection with the diode to clamp to the voltage.
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Old 03-02-2001, 05:07 PM   #7
ludespeed
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I thought that 'in series' meant one attached to the end of the other, like flashlight batteries and parallel would be both diodes next to each other with the 'like' ends connected to the same points.
Anyway, I used a 4.7 zener on a MY01 and I opted to solder it to the wire going into the ECU and it works fine. I don't know about the rest of you but I don't want to go soldering on the ECU board. As long as the zener is VERY SECURE (completely taped to) the wiring harness, it will be trouble free.

But this discussion brings on another point. Someone said that the diode might 'wear out' eventually so I was thinking that if 2 4.7 diodes were run in parallel, wouldn't that make the unit twice as durable while still bleeding off anything over 4.7 volts?
Anyone know the answer to that?
Tom
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Old 03-02-2001, 06:33 PM   #8
wac
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Putting two zeners in series will work. You just have to connect them like a battery in series - cathode to anode. Then heat-shrink them together. Otherwise, a butt-splice connector will work just fine too.

However, the difference between using a single 4.7V zener and two 2.4V zeners in series can be insignificant. For example, a 2.4V zener is typically rated between 2.2V and 2.6V, while a 4.7V zener is typically rated between 4.4V and 5.0V.

Zener diodes don't wear out. At least not in an application such as this one. If you manage to dump too much current into a diode, it will usually fail shorted, so a parallel scheme will do you no good.

-WaC
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