That's exactly how crate engine controller will work with the pressure sensor in AC system and PWM fan control. Will modulate fan output only enough to control pressure. This is how Jackass, Red Devil, Mayhem and Camaro XV are set up.

I hate listening to a car and all you hear is the fan screaming.

Ok Charlie - next time we'll use small words and speak slowly (or buy you enough margarita's you won't care). I get this same abuse from my wife and kids - now you too?

I don't know what your talking about - there were tons of women in Rolla, just not many of them.

Exactly! We've got an analog input (ECT goes from 180 to 181, or refrigerant goes from 175 to 176), but a binary response: the fan goes from 0 to full speed.

How about this question: do Jackass, Red Devil, Mayhem, and XV use a trinary (or binary) switch? Let the ECM manage the fan, but the fail-safe requirement when the refrigerant gets dangerously high is still allocated to the binary/trinary switch?

I'm from the age: If it has spark and fuel it should run.

I thought we were about the same age....

This discussion "sparked" my interest, "fueled" my knowledge and I'm so full of "....." I gotta run.

Yes - compressor controlled by Vintage Air (including bi/trinary switch), with PWM fan controlled by ECM.

Typically fan request for AC pressure never more than 30-40% (and only that high on very high demand AC environment). At that level, can barely hear fan running.

At full tilt (90% DC for most PWM fan controllers), an 850W fan tends to make a little noise - but only see that level during track use due to ECT, IAT or oil temp. I'm ok with fan making some noise then - especially if controlling temps.

Excellent. I think I have a plan then. Great stuff, great discussion.

thanks!

Very interesting read!

Would this type of setup work on my C5 LS1, MarkVII, VA in my Nova? Or is my old school PCM not capable?

Thanks guys,

Dhamen

No real easy answer to your question and I'm no expert by any stretch but here is what I "Think" I have learned that may offer some insights:

So far, I have found evidence of 3 GM ECM types or series that have been used in applications that used some sort of PWM control of cooling fans and/or fan clutches as follows:

E38 ECMs have been used in C6 Corvettes and use PWM control of the cooling fan using the fan control module.

E40 ECMs have been used in some Trailblazer SS applications and use PWM control of the fan clutch.

E67 ECMs have been used in C6 ZR1s and use PWM control of cooling fan using the fan control module.

There may be more. These are just the ones I have found in my research so far.

Here are pics of these three ECM types:


E38
http://i1140.photobucket.com/albums/...ps9ed02ff9.jpg


E40
http://i1140.photobucket.com/albums/...ps2d322fe2.png


E67
http://i1140.photobucket.com/albums/...ps1d165872.jpg

You will notice the easiest way to tell them apart is by the arrangement of connectors and fins.

I have been told the ECM itself is analgous to your desktop computer. By that, I mean within reason, each computer of the same type or series is theoretically "capable" of doing the same job as long as the right software programs are loaded into them. In other words, two computers that are made the same are only capable of running the same operating system or programs if the same software is loaded into them.

Following that logic, if one computer (or ECM) of a specific model number has the internal hardware to do a job in one application, it should be able to do it in another application provided the right software is resident inside, that software is enabled, and it is wired to the correct inputs and outputs.

So, using deductive logic, (which you should treat as suspect until you or someone who has actually done it validates or disputes it), would suggest that if your ECM is one of these types, it should be "capable" of PWM control of cooling fans because it has been used to do so in other applications.

The next challenge would be to find out if your ECM has any software inside that can be enabled to provide PWM control or if it would be possible to load that software into your ECM and then turn it on.

If all that looks possible, you would then need to figure out if you have wires in your harness for the appropriate input and output pins, whether the fan control module will work in your application, if you have the right input sensors, etc.

Like I've said earlier, first time retro-fits are like the old whack-a-mole game. Solving a problem in one area can cause another problem to pop up somewhere else in the system. It can often be an interative process with inherent tradeoffs.

Unless you are a gluten for punishment or just like the challenge of figuring things like this out yourself, getting the advice of or hiring a professional is highly recommended. That is exactly why we plan to follow Dave's trail as much as possible.

I am definitely not a professional or experienced resource. I'm just a fellow newbie trying to validate what I think I am learning as I go.

Good luck!

Thanks for the reply. Maybe when I get further in my project I'll play with it and see what I can get done.

BTW your engineering degree is showing. :D

Here's the report back from ISIS:

So does anybody know: does the GM E67 use J1939 protocol over CANbus?