Odd Fire TBI

**Willys43** · 08-09-2016

Originally Posted by skandolis

Very interested, lots of cool factor. what's the firing strategy,IE: will tach signals be right? is three cylinder firing possible on 7747? curious to learn how those things are gonna share fueling/mapping. I love oddball stuff, especially bringing it into the modern age........

Tach signal is picked up off of the distributor which still has six pulses so i think it will work. 1227747 ECU is software programmable for 3 cyl engine. I am using mapping for a stock 4.3. My 198 is a 3.2 which is almost exactly 74% of a 4.3 so I've reduced the base fuel pulse width of the 4.3 to 74%. It starts and I haven't got the foggyest idea what will happen next. Time will tell.

**lionelhutz** · 08-09-2016

Originally Posted by Willys43

It starts and I haven't got the foggyest idea what will happen next.

I love the 1 step at a time approach. No matter what system you're working with you've got to get it running before you can worry about doing anything more. It's the only way to learn and you're doing a good job on such an oddball system.

**1project2many** · 08-09-2016

Originally Posted by lionelhutz

I love the 1 step at a time approach. No matter what system you're working with you've got to get it running before you can worry about doing anything more. It's the only way to learn and you're doing a good job on such an oddball system.

Agreed. Getting it to run is a good plateau to rest on. Fuel pressure at 12-13 psi is good. I'd aim for as much common ground between the two systems as possible. Do you have the info to change the number of cylinders to three? I can dig that up...

**dave w** · 08-09-2016

Originally Posted by 1project2many

Agreed. Getting it to run is a good plateau to rest on. Fuel pressure at 12-13 psi is good. I'd aim for as much common ground between the two systems as possible. Do you have the info to change the number of cylinders to three? I can dig that up...

When I change the cylinder select value, Hex address 0016 changes. I think changing the Hex value to 03 would be the correct value?

See attached screen shot for an example of a 3 cylinder BPW (1.9 liters is half of a 3.8 liter V6 / figuring two 45 lb TBI injectors).

dave w

**1project2many** · 08-10-2016

knumcyl is a divisor and lower number of cylinders results in a higher value. Three cylinder is 96d or 60h.

**dave w** · 08-10-2016

Originally Posted by 1project2many

knumcyl is a divisor and lower number of cylinders results in a higher value. Three cylinder is 96d or 60h.

Interesting; see attached.

dave w

**Willys43** · 11-05-2016

Well gents I have never been able to stabilize the secondary computor. I finally abandoned the spark control and put an HEI dist with mechanically advanced spark. Starts and runs, first time every time.