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I use Bosch injectors and a custom tune with the kit that I offer. All testing/tuning was done by me on my dyno and fuel injector flow bench. I have been running them in my own personal boat. I also spent a whole lot of time trying to source an exact replacement, it's not going to happen. Fuel control is much better with a modern injector. Start up and idle is much smoother than even an engine with known good stock injectors. I don't even like wasting anyone's money flowing and cleaning a set of stock injectors. It's been years since I've seen a set flow properly, and even if they do pass the flow test it's only a matter of time until they don't. |
So im sitting here drinking coffee pondering WHY these aftermarket injectors way outflow the mercs even though they are supposed to be equal sized. So i just headed out to shop and tryed a couple things on flow bench. Ive never tryed lowering the pw to minimum to see if i could tell a injectors dead band/latency (the time it takes for coil to try to open/close the injector where no flow actually occurs). So i lower the pw ms to .7 at 2400 at 3 bar (43.5 psi)w the 38, 42 and two 500 efi injectors in machine, no flow, .8, no flow, .9, no flow, 1.0 ms, aftermarket just start to spray a tiny bit intermittently, 1.1, they all start to flow intermittently, lower pressure to 36 or so, they just about flow same. Go to 1.2, run 60 second test, the 38 and 42 still outflow the 500's by same amount. If they flow much better at minimum pw because of much shorter dead band, they should REALLY kick the 500 injectors ass at these pw's but the difference is really the same.
So i go to other end of spectrum, 22.20 ms of pw at 2400 for 75 seconds, this should be pretty close to driving these injectors at a "static" test, ie, open maxed out. Same differences, i really expected the "gap " to close up but it DIDN'T. This is all useless info as it answer's nothing but still the same, interesting and thought id share! |
These minimum pw test DO confirm a few suspicions and observations ive seen riding around in peoples boats tuning them. Ive chased afrs at really light throttle settings, pw ms numbers were in the 1.3 ish range, change to 1.2, afr changes from 12.2 to 14, well, yes, if dead band is about 1.0 ms, a .1 change on 1.3 or 1.4 is a HUGE % of , again, i already knew this, the flow bench just confirms it, Smitty
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At Bosch we developed to a standard “dynamic” flow of 2.5ms on a 10ms period. We would set the spring force on the line while measuring flow in real time to target the same “qdyn” we could hold this number to +_3%. This was calculated by measuring 30 pieces then applying statistical analysis. Some of this would have been the measurement capability variation. Also parts can vary from test to test themselves. These were Bosch EV14s. Id bet graduated cylinders measure a better than flowmeters. At the time (10 years ago) denso made the best injectors. They had a machined or turning process on the main body of the injector and could hold +-2% qdyn on my tests. Sorry I don’t remember the standard test pressure or our minimum suggested turn down for durations. |
Sounds like Jason at MDG is your best bet at this point!!! |
Originally Posted by articfriends
(Post 4626152)
Yes, the 500 efi injectors are NOT 32 lb, im sure, however, the dead band is in excess of 1 ms and the aftermarket ones much shorter for them to outflow them by so much at every rpm/pw setting on my machine. Its not just these particular ones either, ive tried others in past. I also have some 50 lb delphis and flowed them against a couple of different 48 lb standards, holleys, racetronix house brand ,etc and they come up low. Thanks for sharing John, Smitty
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