Use IGF or Tach for fueling only piggyback?

coyoteboy · Post by **coyoteboy** » Sun May 07, 2006 4:04 pm

(MS1, code v3, board v2.2 on a toyota '91 3sgte)
Well since my daughterboard for ignition seems to be taking forever to get sorted i thought I'd set this MS up as a piggback just in control of the fuelling. This allows me time to get used to tuning the fuelling side and to calibrate my knock circuit etc when its created with the protection of the stock knock sensing/timing. So a couple of questions:

Since i wont be using the dizzy signals for timing I will have to use the normal coil -ve. But then i have an ignition amp fed with IGT and with IGF feedback (stock toyota ECU uses it to be sure ignition has occured) and with an output to the dash. Can anyone see a reason not to use the IGF to trigger the fueling? I cant decide whether to go with IGF or dig around the back of my dash for the dash's RPM signal, more of a pain. Any thoughts either way?

Will the stock idle control deal with not having control of the injectors? I presume yes.

Ive checked around and some people suggest i wont be able to share sensors with the denso unit, am i right in thinking I'll just have to remove the MS bias resistor and recalibrate it as per many other piggybacks ive read about?

Cheers all!

J

suberimakuri · Post by **suberimakuri** » Tue May 09, 2006 5:00 pm

You'll want to use the Tach signal.
I used to run my gen 2 3sge with ITB's like this... just make sure you have the knock sensor connected to the standard loom or else it will not advance as much as stock setup.

To tee into the water and air temp sensors, you may have to remove the MS' onboard bias resistors.

coyoteboy · Post by **coyoteboy** » Wed May 10, 2006 2:23 am

I'm have to track down the tach signal then, no idea where it is so might take some time

Any reason *not* to use the IGF? Its a nice clean 5v signal every time spark occurs?

I'm not running the stock IAT as its before the turbo and would give wildly inaccurate readings but I've done as you say for the CLT.

I've only disconnected the fuel pump and injectors, and ive shorted the fuel pump speed relay to give max speed at all times. I'm leaving the NB 02 on the stock ECU, and the knock signal, and im running the MS with wideband only for now.

Cheers
J

suberimakuri · Post by **suberimakuri** » Wed May 10, 2006 1:52 pm

Sweet.

The ECU uses the IGF to confirm that spark is happening as it should be.
I would be wary of frying an ignitor or ecu if you were tapping into this... in theory you should be ok, but I don't like it.

However, depending on whether your motor is quad coils or distributor based (gen 2 na distributor based) there should be a tacho signal coming off the ignitor. This is normally a thin black wire with red dots every couple of inches.

If you have a diagnostic plug on the loom, that also has a tacho signal on it you could use.

coyoteboy · Post by **coyoteboy** » Thu May 11, 2006 2:11 am

Its gen2 yup, tacho signal comes from ignitor as you say, I'll trace it through the bulkhead and tap into it somewhere nearer to the ECU (MS is being mounted on top of the stock ECU and sharing power connections). Much obliged,
J

lmr052 · Post by **lmr052** » Thu May 11, 2006 4:12 am

I don't believe the tacho wire goes near the ECU. I believe it goes to the tacho! Connectng into the diagnostic connector should be the simplest.... or the back of the tacho.

Regards, Richard