Batch injection with siamese ports, injector timing

Converting To Delco ECU From Carby Or Other Injection Systems
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Re: Batch injection with siamese ports, injector timing

Postby Charlescrown » Fri Jul 06, 2018 3:47 pm

I would still consider 3 injectors and place them as far away from the ports as possible to get better fuel mixing. I am using 12P on a TBI with 2 injectors and it works a treat.

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Re: Batch injection with siamese ports, injector timing

Postby Jayme » Fri Jul 06, 2018 3:55 pm

Holden202T wrote:the problem with the grey motor though is the head only has 3 small holes for the inlets, so they might not even work like this unless the injector is almost in the head itself!

2yxnc51.jpg


plenty of room there to drill the injector into the head :P as long as you dont hit a water jacket :P

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Re: Batch injection with siamese ports, injector timing

Postby FBUTE » Fri Jul 06, 2018 7:58 pm

I had originally tried to get 2 injectors on each inlet runner but they simply arn't wide enough so went with 1 per inlet .My thinking at the time was that as all the injectors squirted together(hope i have this correct)then it may still work.Also have made a straight fuel rail for simplicity so mounting 3 in a line was easier .I was aware there would still be a question of getting enough fuel out of the three injectors only and pulse width etc.Im not sure if its relevant but this setup uses 3 Toyota 4AGE 20 valve throttle bodies.Yes the idea of putting the injectors in the head had gone thru my mind ,something for another engine maybe.Really appreciate everyones input on this,thanks.

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Re: Batch injection with siamese ports, injector timing

Postby VL400 » Sun Jul 08, 2018 2:10 pm

Another issue with siamese ports is AE, rather than fuel sitting waiting for the valve to open on each cylinder the first to open gets most or all of it (and pulls more of the condensed fuel from the intake), then when the shared cylinders intake valve opens there is bugger all left sitting waiting.

There are two modes of AE in operation all the time, one that extends the regular pulsewidth (the manfuel items in 11/12P) and another that adds fuel between normal openings (called async and is dTPS AE ie in carb tuning the throttle pump) which is the one that can cause issues with lean cylinders on throttle changes.

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Re: Batch injection with siamese ports, injector timing

Postby v6bucket » Mon Jul 09, 2018 8:02 am

VL400 wrote:Another issue with siamese ports is AE, rather than fuel sitting waiting for the valve to open on each cylinder the first to open gets most or all of it (and pulls more of the condensed fuel from the intake), then when the shared cylinders intake valve opens there is bugger all left sitting waiting.

There are two modes of AE in operation all the time, one that extends the regular pulsewidth (the manfuel items in 11/12P) and another that adds fuel between normal openings (called async and is dTPS AE ie in carb tuning the throttle pump) which is the one that can cause issues with lean cylinders on throttle changes.

Would this still be an issue if the injectors were moved further away from the port(similar to a carby), or would it introduce other problems?
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