injector firing for a TBI

maztah · Post by **maztah** » Tue Jan 10, 2006 8:48 pm

i am using 2 injectors from a usual port injected toyota engine
and applied those 2 injectors to my efi TBI engine

is it more ideal to simultaneously/alternately(half of the time on 1 injector, half of it on the other) fire them per engine cycle (180Â° revolution) or only one injector will fire per engine cycle?

the injector's flow rate is 14.5 lbs/hr and the engine is 1.3L 4 cylinder

other ideas on injection timing for TBI are gladly welcomed

thank you

Bernard Fife · Post by **Bernard Fife** » Tue Jan 24, 2006 4:41 pm

applied those 2 injectors to my efi TBI engine ... is it more ideal to simultaneously/alternately(half of the time on 1 injector, half of it on the other) fire them per engine cycle (180Â° revolution) or only one injector will fire per engine cycle?

maztah,

This depends almost entirely on the details of your setup. You'll have to experiment to see what works best at idle, at mid-rpm, and at high-rpm, and come to some compromises.

For example, on my TBI, I found 4 squirts alternating worked best overall. But this was a compromise between fuel distribution and duty cycle. It was also dependent on having 8 cylinders, a fairly large common plenum, and a large number of other factors.

I certainly couldn't have guessed beforehand from first priciples which squirt settings would be ideal.

Lance.

mtnguide · Post by **mtnguide** » Wed Jan 25, 2006 1:27 am

First post here. I'm no expert on this stuff, but I'm working on the same issue. I just finished a MS I for Chev 262cid V-8 with Ford CFS 2 barrel TBI and started playing around in MegaTune. It seems you can get some useful baseline info on duty cycle and PW by setting engine constants and adjusting the stim RPM and TPS within your engine's operating range. Playing around with # of squirts and simultaneous-alternate you can see what MS might do in a very general way. It's helped me identify what flow rate or injector size/fuel pressure I'll likely need to keep the duty cycle down.

whittlebeast · Post by **whittlebeast** » Wed Jan 25, 2006 4:01 am

See if this excel spreadsheet helps

http://www.ncs-stl.com/fuel/ReqInjectors.xls

AW

mtnguide · Post by **mtnguide** » Wed Jan 25, 2006 11:45 am

whittlebeast wrote:See if this excel spreadsheet helps

http://www.ncs-stl.com/fuel/ReqInjectors.xls

AW

Thanks for the help. This spreadsheet answered all of my questions. Very nice.