Okay a lot of you are going to think this is dump but I'm sick and tired of how loud my car is after all the mods, I hate having a car that sounds like it make 1000hp when it only make like 400. After talking to a lot of muffler manufacturers if I want to lower my db's I need to have a smaller tailpipe outlet, I've tested the theory and its correct, I went to AutoZone and picked up two slip on down size pipes, 2 1/2 to 2 1/4, the db drop was very noticeable.

My plan is since my muffler is a 3" in and two 2 1/2" out, I would put an electric cut out on one tail pipe to close it and at say about 75% tps to ground a relay to open the second pipe.

It looks like the U19 chip is a ground control for relays, f1,f2,f3 and f4 pins to the ecu, I have f3 open and I was thinking if I could setup a Scalar to ground after a set TPS %.

If someone could piont me in the right direction I would really appreciate it, I just dont know where to start or how to patch the bin file.

 

Pin F3 is operated off of the U19 and is not used on most 8d code.
It is the A/C clutch control.
The code address that operates it is $002F, bit 2
There is already code to turn this off at high RPM in AUJP and I think ANHT as well. not sure of others.
I think the Vette bins use the A/C control but AUJP does not have it wired to work from what I have seen.
I'd have to look at the code some more to see if it could be modified to use it.

Pin F8 is the second fan control output. Address $4004, bit 1
Lot of code to change there to only use off TPS% but is another option.

Pin F4 is Air Divert, address $4004, bit 4

These are based on AUJP addressed usage, other bins may have them slightly different.
What bin are you looking to use?

 

Thanks for the response JP, Yes I believe F3 in not used in my setup, looking at the diagram it looks like C9 is used for A/C request, need to look at the car to verify. I use the S_AUJP bin, I was thinking of using it as a ground above a set TPS threshold but I could use it in revese also, now I just need to look at the code and see if I can figure out how to get it to work, thank you so much for the location.

 

Look at the AUJP disassembly that is commented on Moates site. its commented and relocatable so you can add code without adding up the junk to be sure its not broken. AUJPJP2.zip or something like that.
Its also on my website (follow sig to links page IIRC)
If you find a way to get what you need let me know.
That setup might work for a N2O solenoid control as well

 

You could also do this off a simple vacuum switch like the 700R4 TCC uses. I like the code way of doing it but some like a simple mechanical way.

 

True, I've thought of this in the past and/or using and rpm activating switch but then I wouldn't be learning anything new.