My friends lettin me use his ms v2.2 , he got it from TERRH , so it was on an rx7 before......I've basically got everything figured out, but theres a couple things i need to sort out before i can start puttin it in

FIdle solenoid--- is that what is used to control the BAC? or what does it need to be connected to if anything?

TPS wires------ the 5 Vref and signal, what is the 5 Vref go too? its the S5 TPS
would it be the signal for the full range and the 5 Vref to the narrow band?

and if anyone has a basemap that'll atleast get it started that'd be nice

I wanna get this in soon!!!

 

The idle solenoid is connected to the BAC. It doesnt NEED to be connected to anything, but in cold weather starts it can come in very handy.

The 5v reference signal is just 5v from the MS that is applied across the TPS that you'll be using (since I think MS will only work with one, I suggest using the one thats triggered off of the cam) so that the MS can read it. I dont know which wire specifically this needs to be on.

 

Terrhs ECU is configured for fuel and ignition. Why are you using it fuel only?

FIdle as various uses depending on how it's set up. It cannot control a BAC directly. The little signal transistor needs to be replaced with something that can handle the current, and a few other changes need to be made.

5V is provided by the 'Squirt. The MegaManual contains instructions on finding the wires you want to connect to on the TPS.

 

i'm not sure my buddy had just said it was fuel only i'm only goin to use it for a little bit, my car runs and drives beautifully right now but it goes pig rich when the secondaries come on, this is just a temp job to try it all out

I'm still in the process of readin through the mega manual, be expecting an email aaron lol

my cars on the road now, it drive awesome , clutch makes me look like a tart though hahahaha OS giken twin disk

i probably wont even run the BAC, ....how cold are we talkin , cuz my car wont ever be goin out in the winter

 

I suggest you run the BAC. It's quite useful in that it allows the ECU to control the idle under various loads. For example, without it the idle will droop when the e-fan activates. With the BAC, the ECU can keep the idle steady.

Can you post a good high res picture of the front and back of the Megasquirt circuit board?

 

yeah i didn't get a chance to go pick it up today, i'll check for the ignition circuits

i need to see if it has the resistor changed for the stock IAT

aaron what are you doin next weekend lol.....

my car is runnin so nice right now, it goes crazy rich after 4200rpm lol i dont want to disconnect the extra secondaries incase it goes lean

i have my WB and everything so i'm hopin theres not to much down time from the time i put the MS in, i have the long weekend to get it goin decent enough to drive to work and back, its fuel only , wiring it in is easy enough, i'll just have to work my way through the settings to get it to start, idle and drive decent
in 3 1/2 days

 

Don't bother with the stock IAT or ECT. Use the GM sensors. They are easier to replace and connectors are more available.

 

Aaron,

I am a bit stumped on this part. Will the BAC be all I need or do I still need to set up a "Fast Idle Solenoid"?

-billy

 

The BAC is a bosch 2-wire PWM idle valve. You need to follow the instructions to set it up as such. This includes replacing one of the transistors on the board (at least with V3) with a higher capacity one and such, so no, the BAC is not the only thing you'll need

 

The BAC takes the place of the fast idle solenoid. Instead of the 'Squirt just providing low level signal (actually an open collector...) to activate a relay which then activates the ground, the BAC gets driven by a PWM signal. You replace the little signal transistor with a power transistor, remove a few other components (check the Megamanual) and then set the idle control up as PWM. You can then use the BAC as both the fast idle solenoid and to control your idle via closed loop.

 

Thank you.

-billy

 

not trying to hyjack the thread, but where can I find more info on how the BAC operates and under what circumstances? Would be usefull in a Half bridge project I have.

Thanks in advance!

 

The BAC operates all the time. It's a PWM valve the ECU uses to adjust the amount of air bypassing the throttle body, and thus the idle. An example is when the A/C is switched on. The BAC opens up a little to raise the idle of the engine.

 

But ...

do you let the OEM ecu operate it? or you use the Mega to do it? Cause the megasquirt I cant ... right?

 

the megasquirt operates it with closed-loop idle control. It doesnt get a signal specifying that the power steering pump or AC is in use, it just responds to the dip in idle speed, but it works pretty well once you get all the constants set

 

now you lost me.

how does the megasquirt achieve that, without a IAC valve?

I would love to have closed loop idle control considering the half bridge ITB engine Im putting togheter. The thing is, I got a MS1 v2.2 board, and I read you can operate a fast idle valve and not a IAC valve.

Thats why Im confused...

 

"If you plan on controlling your BAC valve on a v2.2 board, you'll want to get a ztx688 transistor, and replace Q5 with it. Also, you'll want to get a 1/2 watt 510 ohm resistor, and replace R16 with it."

How does the BAC valve exactly operates? The more I read, the more confusing it sounds

 

An IAC valve is a BAC valve, and vice versa. Two names for the same thing.

With MSnSE you can run a simple fast idle solenoid, or a solenoid based PWM IAC/BAC. The only thing you can't run is a stepper IAC/BAC.

 

the 2-wire or 3-wire BAC's on RX-7's are just on-off valves... meaning that if you feed it 12v its open, 0v and its closed. However, by quickly blipping it 12v and then going back to 0v repeatedly, you can get it to stay at a position between fully open and fully closed. This blipping is called pulse-width-modulation, or PWM, and the amount of time you're at 12v respective to the amount you're at 0v is the duty cycle (12v all the time is 100% dc, constant 0v is 0% dc etc) This way, with the same on-off valve, you can control it much more precisely.

You need to replace those components though, since they cannot handle the current that the valve draws.

 

That is exactly what was stumping me. I wondered how it would be controlled. The duty cycle make perfect sense now. The only thing that I wonder is what is an acceptable duty cycle for the stock BAC. To high and you risk burning it up prematurely, correct?

Also, I was only able to find a 560 Ohm Resistor for R16 locally. I hate paying shipping on $.90 items.


-billy

 

Now it makes perfect sense to me. Thanks guys!

works exactly like a fuel injector