Flow rate of +40 injectors and 5277895 (TII-TIV injectors)

As many of you know, the actual flow rate of MP+40 injectors can vary by quite a bit. In the past, I had many NOS +40 injectors batched. They ranged in flow from 520-560cc/minute. They were NOT batched together whatsoever by MP, so you could have a set flow as much as 40cc/minute difference. Some of our vendors do batch them, so depending on where you buy from, you may or may not have a balanced set. This is not really new news to many.
What is sort of surprising at least to me, is I also just had had a set of 4) 5277895 current TII-TIV injectors cleaned and refurbished. I always send at least one extra injector to Mr. Injector in case Bill finds any with external leaks. If leaking externally, they cannot be cost effectively rebuilt. I was always under the impression that OEM injectors that came out of the same vehicle would be a batched set and flow very close to each other. What I didn't realize is that the same exact part # (in this case 5277895) after refurbishing, can flow different amounts. So after sending in 6) 5277985 injectors, 4) flow 360CC/minute, and two flow 376/CC minute.
So in a nutshell, not only do the +40's vary by a lot, the 5277895 injectors (and probably many more) can vary too. Unknowingly placing the least flowing injector in the best flowing cylinder and you could get a stacking effect going on. So the moral of this story is don't assume a given injector is going to flow x amount, unless it has been flowbenched.
Todd

None are close. It could be that they never were or it could be a result of 30 years of use. I send them in 20 at a time and let Bill match them.

Andy and I were talking about this today. Thanks for the info and note Todd!

I sent 4 sets of the ‘895’ injectors to Mr Injector for refurbishing/flow matching a few years ago. He did a great job and thankfully none were bad. I’ll have to try to find the flow sheets I got with them..

I also sent 2 sets of injectors for the older log TI and 7 out of the 8 turned out to leak externally! I don’t know if they are an inferior design compared to the later units or what. I’m glad I sent them to him and found out though, rather than risk just using them and having a potential fire.

Thanks for the reminder, Todd

Shall we muddy the waters a bit more?:-)

Not only can/will injectors vary in max flow rate within a batch/size, but their rate @ a particular duty cycle can vary, even if they are "batch matched" (did I coin a phrase there?).

A friend of mine that worked at Cosworth back in the mid-nineties who informed me that they had a person who's job is was to "dyno" injectors and not only match the total flow rate, but also the rate at various duty cycles in order to have truly "balanced" injectors.

I imagine that job has gone away, or gotten much easier these days in that one could "inform" the electronics running things as to the individual flow curves of each injector and let it figure things out, or just let it figure things out based on O2 pulse feedback and a simple algorithm...

Muddy enough yet? :D

Mike

if one were inclined to do so you could buy a cheap megasquirt a 12v power supply that can deliver around 30 amps and a 100 cc graduated cylinder, put all that together and you have an injector flow test bench that is extremely accurate.

I actually have a video of me doing that exact test on youtube i did years ago. in the video im using the fuel system of the car to run the test but you can just take a fuel pump and a gas can and have a test bench that you can use to flow and clean injectors.

https://www.youtube.com/watch?v=20Fisp92iHM&t=6s