ECU P4120534 Super Stock / Pro Stock / Nascar

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HiPoVALIANT

Similar yes but no, not at all like your Grandma's
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I was reading a thread the other day and some specs for a few ECU part numbers were posted as part of the discussion.

Years ago I bought a 4 pin ECU new in the box from a Chrysler dealer to carry in my car as a spare. Thinking that an ECU is an ECU.

After reading the specs in the thread I checked mine and discovered that I have been carrying around a P4120534. “Racing applications only to 10,500 rpm’s. Not for prolonged use under 2000 rpm.” What?

Anybody using one of these without any issues in a relatively mild street only car? I would assume likely not but what are the why nots?

Confused. Please advise if I should be buying a more appropriate ECU to carry as a spare.
 
I have that on the wall in the shop. I have tested it. The damn thing works and only retards 1 degree in 10,000 RPM.

I think they were worried about hear building up in the unit during street driving. I'm not going to say to use it on the street, but if I didn't need a two step, or a start retard or other timing retards, I'd use it on the street.

I've boxes by other manufacturers on the street that said not to.

Again, I'm not advising you to do it, I'm just saying I would. But I ignore very good warnings all the time so I'm used to failure.
 
That number comes up as the Chrysler Chrome box.
The description you give is like the Gold box.
(Gold box to 12500 rpm)
I used the Chrome box in an everyday driver. No issues.
The Gold box is a racing box to be used with a high power coil.

Does your car idle and drive under 2,000 rpm’s?
 
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That number comes up as the Chrysler Chrome box.
The description you give is like the Gold box.
(Gold box to 12500 rpm)
I used the Chrome box in an everyday driver. No issues.
The Gold box is a racing box to be used with a high power coil.

Does your car idle and drive under 2,000 rpm’s?
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Wondering if you are referring to the Chrome/Blue unit (Low RPM). Little difference between the Gold/Black and the Chrome/Black. Apparently both are race only ECU's. Still want to understand what is at risk in using on a street car. What is the difference between the racing ones and other more typical units?
 
I said what I said and I don’t understand what your saying. Or is it that on me?

You asked a question I gave an answer.
Now you want to split hairs on what box I’m referencing when via the chart it is quite clear. But you also ask me about color. Never mind me! What colors are your non pictured box? I’m not a mind reader nor clairvoyant enough to see where your box is. How am I supposed to know?
 
I think hes wondering why it would not work under 2k. Is it the race dwell that the box gives or is it the low resistance coil that its designed to use? Maybe using it with the stock coil is not good for it.
 
Still want to understand what is at risk in using on a street car. What is the difference between the racing ones and other more typical units?

I am guessing that prolonged low RPM dwell builds heat that the boxes cannot handle. The thing is, "Ma said it" I guess you'd have to ask them.
 
That number corresponds with the chrome box which is fine for the street. I think someone got the description mixed up on what you read.
 
The ECU spec chart I copied to this thread was submitted by @halifaxhops in another thread. Unquestionably a knowledgeable guy. I was surprised to see that there were several types of “Chrome Boxes” listed there. Only one recommended as suitable for street applications (Chrome/Blue NO fins).

So I gathered that one has to be careful about the generic term “Chrome Box”. I do like the chrome case but apparently there is more to it than just pretty. So I checked out my chrome spare. Turned out to be the Chrome/Black P4120534 (racing applications).

@yellow rose has one he has tested. His comment is above in this thread and does prove the spec to be accurate.

I’ll be buying a standard street use application ECU to replace my spare.

If anyone chimes in that is happily (long term?) using a P4120534 ECU in their street driven car I would appreciate knowing what the coil/ballast combination being used is.

Thanks to all who have commented.
 
Accel supercoil. Yellow one. That's what my dad has in his setup.
 
Accel supercoil. Yellow one. That's what my dad has in his setup.

Thanks. A low resistance coil as expected. Any idea what ballast (ohms) was used? I'm trying to figure out how many amps the ECU would be getting. Stock ECU's are apparently spec'd to receive 4-5 amps max. Don't know about the racing application ECU specs.
 
15 year with the MP Chrome box & the MP recommend coil and ballast firing a MP distributor. Used as a daily driver racking up 15K miles a year easy. Stop and go traffic in and out of NYC sitting in 2-1/2 rush hour traffic in the winter and summer as well as vacation trips as far south as Summit Racing in McDonough Georgia for the **** and giggles of it.
Longest constant drive time, 16 hours. Caught behind an accident going to Winder Ga.
 
Confused........
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If I'm reading this right, that 534 ECU should be fine when used for basic applications as long as you are not running the 560 coil and the .25 Ohm ballast. IMO, One might want to carry a spare set.... JIC!

Figure 17-3..........
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View attachment 1715475726

If I'm reading this right, that 534 ECU should be fine when used for basic applications as long as you are not running the 560 coil and the .25 Ohm ballast. IMO, One might want to carry a spare set.... JIC!

Figure 17-3..........
View attachment 1715475721

I think you are right on. Thanks.

I have discovered that the 4120534 OEM version (rare today) and the specs we have been looking at, is a completely different animal than the later USA, Mexico, Chinese mfg stuff (Mopar Performance). What else is new right?

@yellow rose I sure would like to see a picture of the 4120534 10,500 RPM genuine article you have hanging on the wall.

So this explains why today and for many years, people are running the Chrome/Black boxes in street cars without issues. Confusing that Mopar kept the same part number when the deliverables are not comparable.

Mine, while it was mfg in the USA is the later, less robust modern version of the original 534. So come Spring I will run it, with just a 3.0 coil without a ballast or a 1.5 coil and 1.5 ballast combination.
 
I think you are right on. Thanks.

I have discovered that the 4120534 OEM version (rare today) and the specs we have been looking at, is a completely different animal than the later USA, Mexico, Chinese mfg stuff (Mopar Performance). What else is new right?

@yellow rose I sure would like to see a picture of the 4120534 10,500 RPM genuine article you have hanging on the wall.

So this explains why today and for many years, people are running the Chrome/Black boxes in street cars without issues. Confusing that Mopar kept the same part number when the deliverables are not comparable.

Mine, while it was mfg in the USA is the later, less robust modern version of the original 534. So come Spring I will run it, with just a 3.0 coil without a ballast or a 1.5 coil and 1.5 ballast combination.


I'll take one and post in in this thread Wednesday. And if I remember, I'll post some rocker shaft pictures in that other thread for @Rumblefish.
 
I've run 2 with no issues. I even left the stick coil and ballast! I didn't know any better and car ran fine I think.
 
And here I thought a chrome box was a chrome box. I had no idea there were so many part numbers.
 
And here I thought a chrome box was a chrome box. I had no idea there were so many part numbers.
Yup Rusty. I too was surprised that Chrome ECU's involve more than just being pretty! One has to be cautious with choices.
 
Yup Rusty. I too was surprised that Chrome ECU's involve more than just being pretty! One has to be cautious with choices.


I looked at that chart above and I'm now confused.
The first one posted show the 534 as a chrome box, but I'm about 97% sure I have a gold box with that part number on it.

I know that gold box I have was used on the street. I was thinking about it last night laying in bed and I'm thinking where did I get that box? I never bought one of those.

Then I realized the car I have now came with that box on it. My cousin owned the car then, and he wanted a two step so we took that off and bought a Mallory box.

Of course, my cousin was like a fart in a skillet and we never got around to getting a two step in the car.

So that particular gold box was used in the street. For quite a while.

Now I can't wait to see what I actually have.
 
I looked at that chart above and I'm now confused.
The first one posted show the 534 as a chrome box, but I'm about 97% sure I have a gold box with that part number on it.

I know that gold box I have was used on the street. I was thinking about it last night laying in bed and I'm thinking where did I get that box? I never bought one of those.

Then I realized the car I have now came with that box on it. My cousin owned the car then, and he wanted a two step so we took that off and bought a Mallory box.

Of course, my cousin was like a fart in a skillet and we never got around to getting a two step in the car.

So that particular gold box was used in the street. For quite a while.

Now I can't wait to see what I actually have.

Well confusion reigns here. It is entirely possible that the robust OEM 534 ECU unit was not chrome but gold. Either way no idea why Mopar continued to use the part # for Mexican/Chinese made "Mopar Performance".

Looking forward to seeing an actual OEM 534.
 
The 534 ECU, .25 Ballast, less the T-drive dist and wiring (in use) that came in my distributor kit back in the '80s. The 306 coil was a separate purchase from kit.............
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All right. Here are the pictures of the gold box I have. I thought there was a part number on it. There isn't. But I did research the best sink on it, and I believe this is the 1980's gold race box.

I also know this was used on a street/strip car. I also know I've personally tested it, and it's only losing 1 degree across 10,000 RPM. I also ran it to 12k and it didn't lose any more.

IMO, even this box is usable for a street/strip car. Regardless of what Chrylser said at the time.
 
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