Any questions you have before you begin buying, building and installing.
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By PeterJones
#51711
Is the location of the injector in the throttle body (ie relative to the inlet port/valve) significant? Every factory individual throttle body that i've seen has the injector on the top of the TB, pointing toward the back of the inlet valve. I'm looking at adding FI (Speedy of course) to a Suzuki GS1100 (air cooled 4 cylinder from the early 80s), replacing the four carbs with a TB from a late 90's Suzuki GSXR750. Ignoring for a minute the considerable amount of work just to make it fit, when this manifold is installed on the GSXR, the injectors are on the underside, pointing more or less to the top of the port. As I have to make adapters to go between the head and the TB I can mount it either way up. I am sure Suzuki knew what they were doing when they built the GSXR engine, but, can anyone suggest if there is an advantage over the more conventional orientation?

Pic of GSXR750 engine
Attachments
gsxr750.jpg
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User avatar
By PSIG
#51716
There are dozens of factors that drive injector placement. Unfortunately, you don't know the ones that drove the engineers to place them in any particular location. You're also at a disadvantage of likely not having a research lab to test fluid dynamics. Injectors may be placed based with more weight on appearance, or how they made the air filter housing, or that they found less fuel reversion in that location. :? Some previous thoughts on this topic here, that may help with brain food.

Where this leads you in DIY is to making a list of factors you are aware-of (vaporization, wall-wetting pros and cons, your injector spray pattern, airflow reversion, injection timing, etc), and hoping others you missed are not critical. Then, take your best shot and put them where you think will work best. Every conceivable location has been used by someone at some time. While placement can make large differences in some cases, most of the battle is usually just getting fuel into the tract and then into the cylinder, however you can.

Carburetors had few choices, but you do. Take your best guess and keep going. Data gathered later may guide you to issues or solutions you can apply when you know better what happens in your specific setup. Do your thing! 8-)
By LAV1000
#51718
Peter,
Those injectors placements have a small angle compared to the airflow.
Can't you use them upside down compared to the OEM set up ?
Throttle diameter, don't go much bigger then your current oem carburators.
Intake manifold and or valve can only take so much, there is no point in getting bigger.
Since you have to adapt spaces between throttle bodys check for a modulaire setup (4 singles bolted together).
I know Triumph did on there EFI motorcycles and maybe BMW on there K-series.
User avatar
By PeterJones
#51722
This TB assembly is made of four individual TBs mounted on a bar and the fuel rail. I will have to reduce by a few mm the space between 1 & 2, and 3 & 4 and increase about 10mm between 2 & 4. At 40mm internal diameter they probably are a bit big (Carb size is 34) but I have to work with what I can get.
I'll try it right way up (injectors on top) and see what happens.
By LAV1000
#51725
When you need to redo the fuel rail, check for a "dash-6" type.
Fits lovely whit M14 (metric) banjo bolts.
Attachments
DSC_9912 (2019_08_05 13_57_12 UTC).JPG
DSC_9912 (2019_08_05 13_57_12 UTC).JPG (3.22 MiB) Viewed 4865 times
User avatar
By PeterJones
#52916
I've got the TBs mounted with the injectors down because there's a lot more room under there. Next question - the wiki says this about coils "There are many dual pole, wasted spark coil packs available both with and without built in igniters.
Either are suitable for use with Speeduino, but use of coils with built-in igniters is recommended" - but so far I havent been able to find any. Any suggestion, either part numbers or model of donor car or whatever, would be greatly appreciated.
User avatar
By PeterJones
#52933
Thanks for that. I hadn't considered something like this, thinking more of two separate coils, each with dual outputs, much the same as the standard dumb Suzuki coils as there isnt a whole lot of room between the frame rails under the tank. I'll see if I can find one of these in the local pick-a-part and see it will fit.
User avatar
By PSIG
#52942
Just to expand options; this one I've used has multiple features I like, is the GM/Daewoo/Isuzu/Suzuki UF-356. It is a "smart" two-coil 4-output waste-spark linear coil pack, with a physical size and shape for different mounting options, using LS-style HV wire terminals (available everywhere). Under $20 from various online sources or wrecked vehicles. The passive ("dumb") version is the UF-503, using a 3-pin connector, for reference and to avoid buying the wrong pack. There are many other options, so take your time at the wreckers, and get the connector while you're there. ;)

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