GM TBI injector settings

[toyotaspeed90]

I posted about some issues I'm having in the 'build' section....

I'm wondering if my GM TBI (low ohm) injector settings are wrong, among other things. In doing some reading I understand more, but I don't quite understand the difference in 2 constant settings.....

I see there is the "injector opening time", and then there's the PWM time - which seems to indicate how long, at full power, the open to close time is.....

why would these 2 numbers not match?

http://www.msextra.com/doc/ms1extra/MS_ ... #constants

I tried to open the DIYAutotune msq for the TBI conversion, just to see the constants - and Tunerstudio gives umpteen errors then grays everything out, no matter what I do.

So - for those who have MS1 with GM TBI injectors, what are your opening times/PWM.


I have a V3 that just destroyed one of it's injector circuits upon cranking and the flyback circuit is fine.

[Matt Cramer]

The "opening" time is actually the dead time; opening time minus closing time. The PWM time is something you'd typically want to match actual opening time and is likely to be a bit longer, at least in theory. In practice, it often gets left at the default value of 1.0 ms unless somebody determines there's another issue.

[toyotaspeed90]

I was hoping someone would have been able to share their injector settings...... seeing as it seems it's one of the more common MS1 uses..... I may have to dust off the old laptop and try to open the MSQ file in Megatune...


On another note - the rewiring of the fuse panels in the truck (to just clean up some of the general absurdity of the wiring) is done and I'm about ready to install the other injectors and test - but I want to redo how the injectors are wired.

Currently all of MS is wired through 3 main fuses and 3 relays....

Relay 1 is 20A fused - it receives 12V switched - it splits out 3 ways - one to megasquirt (which has it's own fuse at that point), then acts as 12V switched to the other 2 relays
Relay 2 is (currently) 10A fused - it runs to the injectors
Relay 3 is 20A fused - it receives the negative signal from MS to fire the fuel pump and runs the fuel pump

Past MS installs I've used a relay board. In looking at the tracers - there's 1 relay that powers both injector banks, but it splits off to 2 fuses.

I can easily rewire part of it, but given how I've wired this all, it would actually be easier to add fuses on the 'ground' side. Since 12V passes through the injector until the ECU closes the circuit, the fuse on the "ground' side should act as the same protection, right?

[slow_hemi6]

I was sure DIY Autotune had a walkthrough of using a tbi on a smallblock on their site. Should have a .msq on there you could look at.

[toyotaspeed90]

That's the file that Tunerstudio gets upset about - and I'll have to throw on a thumb drive, get the really old tablet (Fujitsu 3200) going, and open it in Megatune.....