Is anyone running their megasquirt without a BAC? Is it neccessary to have? My plan was to remove it and bump the idle up with the set screw to 950 rpm. I dont have p/s or a/c or a radio but I do have an e fan so i figured it would be ok. I know im gonna gey flamed for asking about removing because lots of guys like to keep it but with my front mount it is a lot more work to run air to the BAC to keep it working.

 

I did for a little while, but it was a bit of a pain, espec since just setting the idle with the set screw meant that when cold, it was very touchy and would die at stoplights and other return-to-idle conditions, and when warm it would idle at 1000 rpm or more. I have an FMIC and am running the BAC; the simplest way to get air to it would be to just slap a crank-case breather filter on the air line, since you don't need to worry about air through the AFM anymore. Just make sure that the BAC will be closed by the time you hit boost (if you have a turbo) so you don't bleed any of the boost off backwards through the BAC; alternatively you could slap a one-way valve in between the filter and BAC to prevent this backflow.

 

I dont have one either. But Im back to tuning again, so Im still really rough. When I was running before my issues with coolant arose, I was running NA and didnt have one. You just have to tend to the throttle in return to idle conditions. Like an carb'd Harley. And be patient while it warms up, cuz I would have to hold the throttle open until temps reached about 130*F before I could trust it not to stall. And I idle around 900-1000rpm. Thinking seriously about putting something back on it because I am an impatient basterd.

 

The majority of standalone users probably aren't running a BAC. But all the hoops you have to jump through to make the car run properly without the BAC seems like a lot of work compared to connecting two wires to the BAC and running an air line to the TID. Or as mentioned, just stick a filter on the BAC. However the sucking noises will start to drive you crazy.

 

Well then aaroncake, I have a question for you...

If BAC is an afterthought, like most of ours probably have been. Like mine, I have really considered putting it back on, and you have a DIY harness, but you have no available pins left on the db37, what should we do?

I have the DIY harness, and used FIdle for fan control and Ign output to my vr2. Every wire was used. As an afterthought, how would I wire up the BAC to ms with no exposed pins on db37?

I already have a transistor circuit from my fan before just waiting to be used going out to spr1 I think.

 

Most likely you should use fidle for the idle output, and connect it there, then use one of the other spare outputs that the ms2 supports as the e-fan output; such as one of the IAC pins. You just run it to one of the spare pins on the back of the MS.

Ken

 

The BAC only needs one wire for control, and another 12V ignition switched wire for power. You've used all 4 spare outputs and all 4 IAC wires?!

Generally I configure them to use the FIDLE wire for BAC purposes and then use IAC wires for other outputs (coils, fan) and then spare wires for CAS inputs.

 

Well, I know I used the FIdle pin for fan control because that was the only wire I had left. I know there are spares on the ms, but with the DIY harness, all wires were used and there is no pins exposed to add a wire to. Its different than the "build your own db37".

I used the IAC pins 25, 27, 29 for coils. And pins 31 and 36 for vr2. Those were the only options I had.

Can you somehow disassemble the DIY db37 to expose the pins where you could add a wire?

 

You can remove the clamshell cover from the DB37 and then add pins to the spare holes in the connector. These pins (get the solder type) are available at any Radio Shack or electronics store.

 

oh cool, so you can just push the pins into their slots and they will stay? and it has the little solider part on the back?


Ok Im done jacking this thread now, haha

 

It depends on the style of pins. In many cases, it is easier to solder the pins onto the wires then push them into the connector.

 

how would I make sure the BAC is closed OR where can I get a one way air valve ??

 

Plumb the BAC between the intake manifold and charge pipe off the turbo, as the OEM sets it up. There will always be higher pressure at the charge pipe then the intake manifold.

 

the BAC is closed when the idle PWM is at 0 (or up to about 15ish % i've noticed). If you've got a turbo car, then run an air hose from the inlet to the BAC (the single, large hose coming off the bottom) to the pipe right after the turbo as Aaron Cake said