Bought some "flow matched" decapped truck injectors off of Ebay. The seller was an American individual with other feedbacks on LS parts etc, seemed reputable, no idea though really. Only has like 2 digit feedback so he's not a bulk pusher of anything. Seemed like "just another LS guy".

A mechanic friend of mine used a cheapie Autool CT150 flow bench and tested all 8 injectors in a variety of ways. Did not clean or do anything to the injectors, straight from the seller as I got them. I am only maybe 530HP and likely not growing, so am only really looking for relative measurements for injector placement (fat one on 7 for example), peak flow numbers arent' what I'm seeking.

But, the data we found is nothing like his flow numbers relatively speaking. One injector in particular shows to be by far the lowest flowing in the group from our test, by over 10% from these tests (more in some tests), and the Ebay seller's flow numbers show this numbered injector to be I think the second highest flowing. A home-made or cheap chinese injector tester surely would be able minimally prove fattest injector relatively speaking, right?

To verify results, I moved a few injectors around (leads/everything else stayed with the graduated cylinder, moved just the injector around) and results were perfectly repeatable within say 1ml and correct measurement followed the injector around the bench tester positions. This tester can do all sorts of different tests at different pulses etc.. and I was able to show one injector consistently lower on every style of test.

So the question: Trust the cheap chinesium tester I witnessed with my own eyes or trust the sheet the seller included that showed actual static and dynamic flow numbers?

I guess they could "both" be right, maybe seller's test was wide-open-something-or-other which gives different results..? I don't know the science behind testing injectors. I am leaning towards trusting the local chinesium tester.

 

The Autool is certainly crude with lots of potential for variation (especially with high flow injectors) compared to a professional bench, so definitely would not trust overall numbers. But since the one part doesn't correlate to the seller's flows in terms of leanest, and the lowest value seems to follow that injector, does make one wonder if that data is accurate too.

Question would be, what bench was used to flow match the injectors? Are they flow-matched by modifying the injectors, or are they sorted (or combination)? If the injectors were modified, did they go through a break-in process before verifying the flow? You could always have them sent to a 3rd party for verification.

BTW, did you try flowing just one injector at a time in the same position, without the others running at the same time? With high-flow injectors there could be pressure waves affecting total output that won't show up on a gauge. And/or the pump might not be keeping up in general.

 

Nope, didn't try that. All I did was put all 8 injectors in (4 at a time), ran whatever tests the tool does and wrote down the numbers from the graduated cylinders. I ran different tests, and did each one 3 times. Then, I took the one injector that was showing the lowest and moved it around among the 4, trying to trick the tool. But the low flowing injector kept the low number wherever it was placed, and it was constantly repeatable for all tests.

I understand the tool's actual volume measurements are suspect, but in relative terms this tool seemed spot on. The injector I moved around not only continued to show the lowest among the 4, the number it showed on the graduated cylinder was like within 1ml every time regardless of position, some tests took it to 90+ ml (the high flow one for example) while others were only 70ish ml, but consistency was absolutely there. In that sense the tool was pretty impressive.

I didn't ask the seller for any additional information because to be honest, I don't feel I can trust anything from an anonymous person on ebay. In this case I totally thought I'd be able to back up his numbers with this tool. I guess that's the risk with buying on ebay.

I think what I might do is do some math on a real life situation, at 6000rpm in the car, and see which of the 10 tests might come close to replicating that environment, and whatever injector in this tool shows the most output is going in the car's Cylinder #7, then 8 and will go right down the line cylinders 6,5,4,3,2 and 1 where 1 will be the lowest flowing.

 

I have the same machine and for what it cost, I think it works well.

That being said, I also never test more than 2 at a time, and do that only after dialing in the fuel pressure before doing any actual testing/recording.

I'd try running the best flowing injector and the one that is showing low, and try to get them equalized as best you can. That machine can reverse flow an injector, and has the ultrasonic cleaner, which should get them closer to one another. I've "fixed" a few sets of uneven flowing stock injectors, by "backflushing" them and running them through the ultrasonic cleaner.

 

I think that's good advice, and will give that a shot. I am going only to use 2 injectors at a time, and will take the highest flowing and each other one, one at a time, and see if I can backflow/clean the lower one to bring it closer to the high one. Actually sounds like a fun test.

I wonder if anyone has ever modified a higher flowing injector to try to bring down its flow rate to match others, like intentional closing holes on in the basket or something.

 

That is backward thinking. Normally you would want to get rid of any restrictions (crud, corrosion, etc.) that would decrease flow.

 

How close do the decapped injectors need to be percentage-wise to be considered usable when arranged fat-to-lean?

Cleaning didn't help.

I just took the lowest flowing injector and did the ultrasonic cleaner with seafoam and backflow cleaned it a few times and tested it again with no change.

One interesting point is that I have reduced the testing down to just 2 injectors at a time and using the default fuel pressure the milliliter number was still within, say, 1 ml from the measurement using all 4 injectors. I expected it to be higher or different because with 4 injectors the fuel pressure gauge clearly bounces around, but with 2 injectors the gauge was steady. But it was I believe no significant different in the ml measurement.

So I at least trust these measurements relationally speaking injector versus injector, meaning regardless of the lb/min of flow I think I can demonstrate with good confidence that the injectors are x% apart from each other. But this is about as good as it's gonna get.

So my question to you all, is this set usable if injectors are arranged fat-to-lean rear-to-front on a 10PSI turbo L33 daily driver that's tuned very rich in PE and Boost tables?

Here are my numbers for the same test repeated now at least 12 times per injector sorted highest to lowest with an 8 ml delta which I think means 11% among the 8 ( 69-11%=61.41) and about 10% relative on each bank.

For anyone who is familiar with this machine I used test #10 at 1500 samples.(top left is Cyl 1 and lower right cyl 8 of my placement plan if I decide to use them)
=========================================
8(63) 2(61)
7(65) 3(63)
4(66) 5(66)
1(69) 6(67)

61 ml
63 ml
63 ml
65 ml
66 ml
66 ml
67 ml
69 ml

 

I stopped reading after that...

 

Come on man that's an unnecessary and useless response. I thought we were all on the same team modding cars and having fun and the OP has been a member longer than most people on here (including you) so clearly not a troll or anything just a person trying to do something on the cheap and experiment.... I'd think all of us on here could respect that. He asked a legitimate question and not everyone wants to pay $1000 for a set of id1050x injectors.
To the OP - I've used decaps and they work fine albeit I did it myself and had them flowed and cleaned but you take your chances with some people on the internet so it is what it is. If you plan to run them I'd say %10 seems like a lot to be off between them so get a hold of the seller and see what his tests showed, maybe he'll explain it or offer a swap to a different set. Or since your buddy can flow them decap some yourself and get a set that's as close as possible and send those ones back.

 

LOTS of variables there, and many that a simple flow machine isn't going to give you. Larger pulse widths are one thing, smaller pulse widths at light part throttle and idle is a totally different thing. A good flow matched set of injectors will only have a deviation of 2%-3% across the entire pulse width range. The larger the injector the more important it is...

They don't flow like **** because they are dirty...

I wouldn't even consider it but you will get 10 more people on here that say decapped injectors are the way to go and it worked great for them when in reality they just don't know any better the difference between those and a quality set.

 

Thanks everyone for the input. So between your answers and my Googling I agree that 11% is too risky. But I have a plan.

The seller has offered partial refund and letting me keep these (for less than $10 each), so "for now" I am going to plop them in and just see what I can accomplish on the IDLE tuning. If these seem like they'll work better than the Deka 80's for the idle tuning, I think I will just buy maybe 5 more truck injectors and decap them myself and try to get a set within 5% or so for eventual WOT tuning.

I guess I shoulda mentioned the reason I am trying this. I already have the car all tuned on flow matched Ebay Deka 80's that are confirmed genuine, the car with a nearly bone stock L33 at around 11psi ran 11.48 at 123 mph ON 87 PUMP GAS with the Dekas lol.. so I have a combination that is working well, I JUST CAN'T GET IT TO IDLE so I wanted to just tinker with these decapped truck injectors to see if they were better AT ALL for idling on a tiny 5.3 stock engine since it's so easy to swap injectors/tune back and forth as needed. I heard they were bad at idle tuning too, but since their overall flow is a little lower I hoped they'd just be a LITTLE more tolerant for idle tuning. I don't need much, with good weather I can get the Deka's to occasionally idle in CL mode, it's on the hairy edge.

This is all just playing around at this point. My car is running well in OL mode leaving my Deka 80's in there, but I have to keep the AFR like 12's at idle (injectors fat) to keep them smooth now that the weather has warmed up. Any leaner and it starts a tiny misfire, and if in CL mode that misfire drives the O2 artificially lean where it tries to open the injectors even MORE somehow causing a worse misfire and throws trims into a panic and makes it idle like total poop. Whatever the cause, I've just exhausted every attempt at getting Deka 80's to idle in a small 5.3 so I'm done farting with that. It's only 12AFR at idle not when running down the highway but that still can't be good for the car/turbo/wallet/whatever.

I have a hard time justifying $500 for injectors on a junkyard engine that it itself only cost $500 (well, $530 with tax). Aaaand, it's a lot of fun telling people about how cheap I've been able to do things and still beat a (I think) 2018 Corvette at the track (true story) with a 1999 trans am that looks like it should be in a demolition derby.

Also, thanks for the kind words, I promise I'm not a troll. I do have strange ideas and priorities but it's all fun. Makes me feel old to realize I'm a 17-year member here. This site has helped me through 6 fbody cars and I'm sure over 1/2 million driven miles over the years on the various DD fbodys.

I figured if I can get them to idle OK and just be safe at WOT those are the only 2 parameters I really care about, since I was able to get the Deka 80's working OK everywhere but idle. But you may be right, I might start getting hiccups at part throttle or whatever. I'll give it a shot and see what happens. I just don't wanna blow up the engine, hell that'd be $500 down the drain!! (Actually more now, it seems everyone's learning the L33's real value).

 

Post up your tune, plenty of things that can be wrong that can cause those issues even with Deka 80s but they are in general not nice at idle and lower pulsewidths.

Don't forget you can also hurt a lot more than just the engine in the process of blowing something up, imagine making a pull and having coolant blow out all underneath your rear tires and then what happens... Also don't forget time is money unless your spare time isn't worth anything, but I think for most people it's worth something and for some it's worth a lot more than a junkyard motor.

 

It's all fun and games until your el cheapo pile of parts grenades itself as depicted above, causing OTHERS as much or more damage than anything you have in yours.
Cheap is only amusing to a point.

 

NicD, thank you for the input. You are absoltutely right, all valid points. I will keep all that in mind as I proceed. I think getting the decaps to balance around 5% and arrange them fattest in the rear that it'd be pretty safe with my sub-15 degrees of timing and rich AFR in the boost tables. I didn't mention this in the other threads, but I am now working with 93 octane until I get it leveled off again, and then I'll try some 87 and see if I can get a zero-knock recipe in the summer heat with my build. Time will tell.

G Atsma, if you are implying that I shouldn't be tinkering with Decapped injectors because I'm risking the lives of others, I think you need to look around you more when you race.

You think my decaps are any more risk than the guy with the L33 pushing 20psi, or the kid slapping nitrous on a ricer?

I guarantee those high horsepower hyper weight reduced airbagless 800HP monsters fighting between lifting a wheel and slipping all over the track are more risk than my decapped injectors in a 10psi L33 running a 1.8 sixty.

I typically appreciate your input and participation here, and I'm normally a pretty calm dude, but I sorta resent your accusation that I'm way more of a risk than these other tincan hondas/whatnot out here.

Yea, I know there's risk with this, there's risk with about EVERYTHING going fast. Just don't try to single me out that I'm some menace to society.

 

This reinforces the point I made that so offends you. NicD is one of the most knowledgeable people here. Some of your thinking just sounds frivolous and naive, comparitively.

 

Considering literally 100% of my knowledge comes from the Internet (mostly this site), I actually agree that I am naive. That's why I am asking the questions I ask.

NicD didn't imply testing things shouldn't happen because I'm risking the lives of others as you did. He made a point, and he's absolutely right. There's risk with this, and I need to be mindful and careful. You make it sound like I'm strapping gas cans to my roof or running with 2 lug nuts.

Look, you just hit a button with me. I just resent being accused of being the menace to society you imply by tinkering with decapped injectors.

You shouldn't have posted that, because you're wrong.

 

I never implied anything like that. What drama!
And you are entitled to your opinion, misguided as it is....
To add... you mention yourself 100% of your knowledge comes from the internet. Much but not all of mine does too, BUT you need to know who to pay attention to. What I learn from here, I back up with book knowledge by authors with huge cred. David Vizard is but one example. And NONE of said authors mess with decapped injectors. They are loose cannons.

 

I'm not a fan of decapped injectors but for 10psi on a 5.3L you can get away with almost anything.

I think some people forgot how to hot rod. You don't need to spend a bajillion doll hairs to have fun. OP said he makes 530hp, there's almost no point spending a bunch of money at that power level.

Anything can blowup, seen guys blowup multiple billet blocks in the same event, money doesn't always solve the issue. Guys with $500 engines are typically reserved in the power they make and they last a long time, a 5.3L at 530hp is certainly in that category.

 

Why do you think that you need 80 when a 60 or even a 42 injector will get you 80 percent duty cycle?

On my Procharged 1998 Z28 with stock block at about 7 lbs of boost on 42 lb injector it made 500 RWHP at about 80 percent duty cycle. I went down a pulley size to make more boost and installed 60's easily supporting 550 rwhp on a Mustang dyno. Just recently added 2 lb of boost upping rwhp to 600 on DynoJet eddy current dyno with duty cycle still around 80 running dual 550 lph pumps.
Am now running a 3.7 pulley with boost around 12 psi with flow matched Signature 80 Dekas with duty cycle less than 80. It idles almost as smooth as my C7 Z06. But it idled smooth with 60's as well. Cam is a 227/234 with a 115 LSA. Engine is now is a TSP lq9 iron block.

IMO bench the 80's and install a smaller injector.

 

Honestly, it was all about the money. I got a killer deal on REAL Deka 80's that were flow matched last year, can't remember the price but they were cheaper than other 500-600hp options and I made sure they were real and had pretty balanced flow. I knew Deka 80's were troublesome to tune at idle but took the chance, what I didn't realize is that my tiny stock low-volume airflow 5.3 engine was going to make it even HARDER to tune idle than the 5.7's or 6.0's out there LOL.

So I figured I'd give this decapped solution a shot. Again, I have a working solution with the 80's in OL but it idles at 12afr and I really want something that'll run in CL because that's just what I want.

Very good chance I missed some other economical injector solution that doesn't involve no-name or chinesium injectors, I'd be curious to hear any options, will review what you mentioned. Thanks for that.

EDIT: If I had the money I'd buy the flowed Deka 60's on Huron Speed for $400ish.