8708 $A8 Does it have VATS?

[EagleMark]

Does the 8708 $A8 have VATS? The XDF does not show it but since it's hardlty ever used who knows if it needs to be added?

Trying to fire up the kids 22RE Toyota to 8708 DIS conversion. We have spark but no clicking of injectors...

Here's the long project thread:
http://www.gearhead-efi.com/Fuel-Inj...RE-with-GM-ECM

[EagleMark]

I can't even find a dissasembly, IIRC this was the reason I did not want to start with this mask ID...

So any other ideas for a mask for four cylinder 8708 DIS for this conversion? May be easier and better option?

[RobertISaar]

doesn't look to be.

generally, the VATS register on a 7727/7730 type ECM is 3FF8, i see 2 references to it in A1(which most certainly does have VATS), but 0 in A8.

[RobertISaar]

So any other ideas for a mask for four cylinder 8708 DIS for this conversion? May be easier and better option?

assuming no goofy hardware is inside of it that absolutely requires the 1X signal for injector firing, you should be able to run nearly any mask you want that would run on a 7727/7730. the only issue i can see with going that route is that the code will need to be inspected and changed in a place or two for the alternating injector driver scheme to work, assuming you have them wired that way.

[EagleMark]

Well then I got something else wrong...

Is there another Mask that would run this 8708? The reason I wanted to stay with it is it has jumpers wired external already for Low injectors which the Toyota motor has.

At this point changing to 7727 would be a lot of work as there are some pin out differences in the 2... or from what I've seen is!

[EagleMark]

assuming no goofy hardware is inside of it that absolutely requires the 1X signal for injector firing....

That may be it then. I have the 1x wire run and there is an empty spot on this TBI DIS but it is not wired as per the factory set up.

[RobertISaar]

other than the dual injector drivers and the FMD2 chip that controls one of them(and possibly extra SRAM), the 8708 more or less is a 7727....

i don't see any reason why 7727 code couldn't run in it and act exactly like a 7727. the second driver is about the only tricky part i can think of.

[RobertISaar]

now that i think about it, i seem to remember uncovering an option bit for the 1X signal to be ignored....

[EagleMark]

now that i think about it, i seem to remember uncovering an option bit for the 1X signal to be ignored....

In what ECM/Mask?

So what needs to be done to make a 7727 run these Low injectors?

[EagleMark]

Hooking up the 1X signal wire from 8708 ECM to IIRC a 7727 type TBI DIS (that has that hole plugged) did not help. Still have spark, still no injector click...?

Going to go over the wiring and see if I messed something up...

[RobertISaar]

A8. i have 8009(0009), bit 5 marked as the 1X ignore bit. cleared = 1X shouldn't be used for any purpose that i've seen.

to make a 7727 run 4 low-ohm injectors in peak/hold mode, you would basically copy the 8708 injector driver setup. 2 drivers, 2 sense resistors..... to make them run in an alternate fashion, you would need the FMD2 chip present as well.

to make all 4 fire at the same time.... FMD2 wouldn't be needed, would have to tie in the 2nd driver's gate pin to the 1st driver gate pin, though this MIGHT defeat normal peak/hold operation. i'm not 100% on how GM setup the current-limiting when in hold mode.

[EagleMark]

A8. i have 8009(0009), bit 5 marked as the 1X ignore bit. cleared = 1X shouldn't be used for any purpose that i've seen.

to make a 7727 run 4 low-ohm injectors in peak/hold mode, you would basically copy the 8708 injector driver setup. 2 drivers, 2 sense resistors..... to make them run in an alternate fashion, you would need the FMD2 chip present as well.

to make all 4 fire at the same time.... FMD2 wouldn't be needed, would have to tie in the 2nd driver's gate pin to the 1st driver gate pin, though this MIGHT defeat normal peak/hold operation. i'm not 100% on how GM setup the current-limiting when in hold mode.

I'm going to give the Ignore 1x bit and give it a shot!

Making a 7727 run the Low injecotrs is way to much~! I'd change injectors first, they are available from newer Toy 22RE

[1project2many]

AMDD is used with 7749 without 1X signal. Mask is $5C.

Toyota made high impedance injectors from low impedance parts by installing resistors in series. IIRC, Honda does the same thing.

[EagleMark]

AMDD is used with 7749 without 1X signal. Mask is $5C.

Toyota made high impedance injectors from low impedance parts by installing resistors in series. IIRC, Honda does the same thing.

Would AMDD and $5C work in 8708?

[EagleMark]

I did get it to fire up but not running, something is off.

Also have a relay that is buzzing?