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-   -   Recent 500 efi injector test vs another claimed replacement (https://www.offshoreonly.com/forums/general-q/376681-recent-500-efi-injector-test-vs-another-claimed-replacement.html)

Wildman_grafix 08-11-2022 11:46 AM


Originally Posted by articfriends (Post 4841233)
If you have mefi3, Id just use it and have it tuned. I recently dynoed a 540, AFR 325 heads, mefi3 controller, extrude honed/modified intake, a tb I bored out and made throttle blades for and with a fairly small cam from Bob M it made over 700 ft lbs of tq and 650 hp, Smitty

All that was done to the intake was extrude hone?

How big did you bore the throttles out?

That would be plenty for my 32,,,,,, I mean 27 fountain:evilb:

hogie roll 08-11-2022 04:17 PM


Originally Posted by compedgemarine (Post 4841185)
I am assuming (and I dont know that much about injectors) that the listing of the injector i.e. 42 lbs or 36 lbs is what they flow at 100% duty cycle? if so, no injector is ever run at that level in an engine so it would really be a meaningless number would it not? why are they not rated at something like 70% or 80% the way camshaft duration is rated at .050 to give a more accurate measure of what is useful to the engine.

Qstat is static flow, Qdyn was flow w at 2.5/10 ms pulse width. This was Bosch terminology. I don’t see any aftermarket companies showing dynamic flow.

The only time it would matter is when you’re trying to come up with a direct injector swap with out tuning.

compedgemarine 08-11-2022 06:40 PM


Originally Posted by hogie roll (Post 4841288)
Qstat is static flow, Qdyn was flow w at 2.5/10 ms pulse width. This was Bosch terminology. I don’t see any aftermarket companies showing dynamic flow.

The only time it would matter is when you’re trying to come up with a direct injector swap with out tuning.

which is kind of my point. lots of people dont know or dont have the ability to tune and are just putting in new injectors based off of advertising. those of use who build engines and/or understand them know the pit falls but most dont. seems to me that if they all listed the flow at x ms pulse width and psi you would have a better idea of compatibility. I am not that versed in injectors as most of what I deal with are old cars and carbs or big power and carbs. on my '60 caddy that I put an LS into I just bought new delco injectors that are the same part number as I took out since it does not have any mods. I looked at lots of injectors but did not feel comfortable that they would perform the same as the originals.

1BIGJIM 08-11-2022 08:40 PM

I’m so impressed thanks for sharing Smitty. Even an old guy like myself never stops learning. I had no idea until I read your threads. Priceless 😀

articfriends 08-11-2022 08:49 PM


Originally Posted by Wildman_grafix (Post 4841246)
All that was done to the intake was extrude hone?

How big did you bore the throttles out?

That would be plenty for my 32,,,,,, I mean 27 fountain:evilb:

Intake runners were cut down 1/2 to 3/4 inch, runners extrude honed, plenum ground out to meet the bigger tb. I been cutting the runners down 2, 21/2" , hand blending and port matching/touching up the ports where I can reach to get these mpis to pull 200 to 400 more rpms (tallking good heads, cam, exhaust, tb, etc) BUT I have yet to come anywhere close to the torque this motor made NA with a mpi. So time to digest the details of THIS build for future builds. It fell off a cliff after 5600 but with the power it made, who ncares This was also tuned on 89 octane fwiw, Smitty

Wildman_grafix 08-12-2022 07:38 AM


Originally Posted by articfriends (Post 4841310)
Intake runners were cut down 1/2 to 3/4 inch, runners extrude honed, plenum ground out to meet the bigger tb. I been cutting the runners down 2, 21/2" , hand blending and port matching/touching up the ports where I can reach to get these mpis to pull 200 to 400 more rpms (tallking good heads, cam, exhaust, tb, etc) BUT I have yet to come anywhere close to the torque this motor made NA with a mpi. So time to digest the details of THIS build for future builds. It fell off a cliff after 5600 but with the power it made, who ncares This was also tuned on 89 octane fwiw, Smitty

Good info thank you. I remember you saying you wanted to play around with the stock (sort of) intakes. Those results were on a MPI correct not a HP500EFI intake?

87MirageIntruder 08-12-2022 09:51 AM

It's concerning to me how much I read about injectors that are new and not up to par and or the spec that they are advertised to be. Seems like a lot of poor quality junk out there too. I guess it would be a good idea to have new injectors tested always before installation.

articfriends 08-12-2022 10:12 AM


Originally Posted by Wildman_grafix (Post 4841347)
Good info thank you. I remember you saying you wanted to play around with the stock (sort of) intakes. Those results were on a MPI correct not a HP500EFI intake?

502 mpi intake, I been playing with them for almost 18 years, made 1100 +hp with one at one point, never made 700 ft lbs of tq w one na though till now

articfriends 08-12-2022 10:15 AM


Originally Posted by 87MirageIntruder (Post 4841371)
It's concerning to me how much I read about injectors that are new and not up to par and or the spec that they are advertised to be. Seems like a lot of poor quality junk out there too. I guess it would be a good idea to have new injectors tested always before installation.

these 42 lb Lucas injectors were OK, they just had way different charteristics then 36 lb stock, 12% more static and 50, 60 % more in lower ms test.
I test every set of injectors I sell and have tested quite a few oem replacements thru the years

jeff32 07-27-2023 08:41 PM

Much more simple question here if you dont mind!!!!
how to remove and re install an injector on a motor? Simply pull hard enough till it pops out?
any seal / rubber/ oring mandatory to change before putting it back in?


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