Any questions you have before you begin buying, building and installing.
By Michael1
#48513
Hi, i have two tbi feeding a large single plenum . So i think i need to wire the injectors parallel.
Then the injectors need to be set to 8 sqirts per cycle? Correct?
That is a lot......?
Would it make sense to use bigger injectors to get cycle duty down ?
Regards
Michael
#48519
I dont know how to post pics..... :D
But i have a long plenum and the tb are on each end.
So with the fireing order it might be tough to feed all cylinders.
It is a Ford V8 Flathead engine with an aftermarket intake.
User avatar
By PSIG
#48521
@Michael1 — Upload photos in the Attachments tab below the posting text box and Insert Inline, or upload to any other site and link to them here.
  • How many injectors?
  • Fuel-only or fuel+ignition?
  • Describe your trigger system and if you are using a cycle signal ("cam" sensor).
Helping us with minimal (or more) info allows us to help you better.
#48523
Hi,
Fuel an ignition.
36-1 trigger wheel.
I can ad a cam signal if it is easier.
The pic is nearly my set up . My intake is a Eddi Meyer and has one long plenum
Two injecotors. One in each Ducati TB.
Pics are easy to upload once you know how to do it :D
TIA
Michael
Attachments
IMG_9556.JPG
IMG_9556.JPG (237.06 KiB) Viewed 2762 times
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By PSIG
#48528
I would agree with @theonewithin, that 4-squirts alternating typically works well on a typical V8 TBI, and is likely where you should begin. However, yours is not typical TBI, and injects below the throttle plate, rather than above. TBI injectors above the plate enables fuel to be collected on the plate and walls, where intake pulses then collect and vaporize fuel into and through the manifold to the active cylinders. The result is better vaporization and delivery to the cylinders that need it.

Your TBI design is fashioned like ITB with injectors below the plate, which are designed for individual cylinders, injecting directly to the active port or intake valve. This limits the more even distribution of fuel, with (potentially) more of the fuel going to the first active cylinder and less evenly to following cylinders. Therefore, it will likely run (and maybe very well) on 4/alternating, but may require 8/alternating in order to distribute fuel more evenly. 4-per-injector at 8/alt will require more time (due to added dead-times) from your injectors. However, unless you calculate it, I would just try what you have and avoid over-sizing as it can then cause idle and cruise instability. If they are too small, then you have some run-data in order to select specific suitable options.

While a lesser concern, your firing order and cylinder layout draws fuel to ends of the engine alternately. This may mean you will need a cycle signal, in order for the injections to occur on the same relative cylinders every startup. Else it could randomly fire injector 1 near cylinder 1 this time, but injector 1 for cylinder 8 next startup (360° offset), with slightly different running results due to different effective distribution.

These comments are based on my previous experience with V8 TBI, also realizing that every setup and hardware responds differently. So, I'm commenting just to make you aware if you weren't, and side-step issues when and if you ever have them. Final suggestion; "doing it" and reading real-world hands-on results beats guessing or theorizing every time, and much quicker too. ;) Start simple, do it, and see where it leads you. Do your thing! 8-)

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