Fuel Injector Flow Testing

I also ordered some fuel injectors. This is where it got a little interesting. I decided to get them flow tested. I read a few posts from Noobz about getting new injectors flow tested and the more I thought about it the more it seemed like a really good idea. I felt knowing what they are actually flowing would allow me to organize them in the fuel rails so the left and right bank have even flow. That way the AFR reading I'm seeing from my wideband in the left bank should be very similar to right which is not monitored. It would also let me catch any defect.

This quote is what really got me thinking about it.

Noobz347 said:

On a side note: The 19 lb injectors used in this setup are being pushed way beyond spec and it is a [really] good idea to have them all flow tested and adjusted so that they all squirt the same.

It only takes one weak injector to throw the whole damned thing off.

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Chances are if I went lean it wouldn't be all the cylinders evenly lean and destroyed together. It just takes one lean cylinder to stop the party.

I found a local fuel injector cleaner and flow test shop. He's a racer and was really great to work with and super fast turn around time. 7 bucks per injector to flow test.

I'm using a FMU which raises the fuel pressure under boost. So I had him flow them at the standard 43.5 psi and also 90 psi so I can see how consistent they are when being pushed.


The first set of injectors I got from LMR. They are the pink 24lb injector. This pic taken after getting them back from flowtesting. (They shipped from LMR loose in a ziplock bag.)






I wasn't thrilled with the results.




The flows were pretty inconsistent with each other and one of them had a higher resistance. Had I not got them flow tested I would have never know. I definitely didn't have the warm and fuzzies about using them.


I asked the owner of the shop if he knew of a place where I could order a set of new, not re manufactured OEM quality injectors. He recommended Fuel Injector Connection. I gave them a call and I ordered a set of flow matched, new, authentic Bosch 24lb injectors. Again I took them to be flow tested.






This time the results were great. This is what I expected to see from a quality injector. They flow nearly identical.


I should be able to get this wrapped up this weekend. Then I'll do a little "tuning" with the FMU. I'm having a local machine shop make me some calibration disc sets in sizes Vortech doesn't make.

Noobz347 said:

I am tickled effin pink that you did all that and posted the results here.

I am going to steal your post and make it a sticky someplace. The last time I had injectors flow tested was 2000-something and [wished] I had thought to keep all the documentation.

That matched set is pretty sweet. I am 100% convinced that, that is the way to go.

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Ive been told by my friend in Alabama that word is spelled just like it sounds... pank. .

Feel free to do whatever with the info. Maybe it will lead to some good conversations.

Your advise to get injectors flow tested was solid. Somewhere I saw you mention you had brand new ones flow tested as well but couldn't find that particular post to qoute it.

LMR advertises the pink injectors to be flow matched at 3-5%. So most people would have just tossed them in, myself included.

The static test is when they open the injector and just let it flow for two minutes. Which would be similar to running it at 100% duty cycle. They were almost 15% apart from the lowest flowing injector to the highest. That seems significant.

The dynamic test is when they operate the injector at a duty cycle similar to normal driving. That test for the pink ones was almost 10% variance. Again it seems significant.

So if I happened to grab three of the highest flow injectors and the lowest flowing injector and put them all in the same bank I wouldn't expect it to work out very well.

Mac131 said:

The LMR ones seem solid at 43 psi but they sure lose consistency at 90. I wonder if that much pressure is outside of their specs?

Edit. Just saw how far off injector 1 is at 43 psi...still 24# but lower than the rest.

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The flows report is a little odd to read. I should have mentioned more detail about how it's organized.

The flow is measured accurately in CC/minute (the first 3 digit #). Then converted to what lb/hr class it would represent in two digits with no decimals. The lb/hr is not the accurate number to use for any calculations. For example If you do a calculation you would see 268 CC/Min = 25.523809523809526. On the report it would be listed as 26 lb/hr because it's technically closer to 26 than 25.

cc/m to lb/hr calculator

-So the CC is the number to pay attention to and the number the variance percentage is based on.

-The variance % is the number to look at to see how closely they are matched as a group.

-The CC flow # would be what to use to see what each injector is flowing individually when deciding on individual placement in the rails.

So the pink ones at 43.5 psi have a 14% variance static and 9.6% variance dynamic. Oddly they actually flowed more evenly matched when pushed to 90 psi as that variance dropped to 5.9 / 6.5.

In contrast the flow matched set from Fuel Injector Connection measured 1.1% and 1.2% variance respectively for both 43.5 psi tests. Which is better by a wide margin.

I can't blame LMR. They are just selling someone else's product who tells them what they are rated at. I'd guess they have a big box of them and grab 8 per order. You get what you get. Someone else might get a better matched set. Or maybe a worse one. Its pretty much luck of the draw, literally. They are just a reseller.

Fuel Injector Connection is an injector specialist and flow matches each order in house. It's their business so I expected alot from them and they delivered a really nicely matched set.

In hindsight I should have reached out to the local injector shop that did my flow testing BEFORE I ordered and learned more about it. I knew i was going to take them to him to test them anyways when I ordered them. Should have called him first.

Seperate but related, I should also mention there are two FIC's to avoid any confusion there.

Fue Injector Connection sells OEM new and remanufactured injectors, performance injectors and flow matches in house from various manufacuted like Bosch, Siemans Deka, Denso etc.

Fuel Injector Clinic makes their own branded injectors based off modified Bosch's.

Oh nice!

Yeah, I wonder how many ghosts get chased trying to straighten out drivability issues when it's really just a bad match of injectors. After putting in a brand new set of injectors it's probably the last thing you'd think of as the problem. They're brand new, can't be that...

^^ Right.


I got a little injector maintance flyer from the shop that flow tested mine. The * asterisk bold statement near the bottom is particularly telling.