Any sense to upgrade 19lb injectors on NA?

doctorj357

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Trying to identify if I have fuel issues. Suspect I have a week fuel pump (stock) and looking to replace it. But while I am at it, the injectors are stock 19lb. Wondering if there is any value in upgrading those on a NA motor.

I have a Edelbrock Performer intake and heads, E303 cam. Car should be near 300hp at crank still have to Dyno it. But just wondering if the 19s are border line on Max cycle duty since they supposedly rated to 270hp, with a 15% buffer.

And if the cycle duty is 100%, what does that mean exactly? I'm just wondering if upgrading to 21lb would be a better fit. 24lb seems overkill for my setup as I have no plans to change the power.

Just looking for input
 
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96pushrod

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I’ve heard the newer 4 hold 19lb injectors flow like a set of 21lb ones.

I’d say you’re right on the brink of needing 24lb injectors. Just make sure you either get a maf which will work, or tune for the bigger injector.
 

doctorj357

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There's a local guy selling a set of brand new oem, never used 19lb 4-hole injectors, with harness/rail/FPR for $40. Not sure what its from exactly, not a SN95 for sure, but its the newer EV6 jetronic style. I don't care about the rail or any of that stuff, just want the injectors. From what I read it should be a direct swap with my older EV1 injectors. Its cheap enough, I just might try that.

But if I went bigger injectors, lets say 21lb, or even 24lbs will it work on a stock MAF? So long as its properly tuned? I still plan to replace the pump here soon and will probably choose between a stock pump (95lph?) up to 190lph.
 

96pushrod

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If it’s tunes with an actual laptop then you can use whichever injector size you want. The maf won’t make a difference.

I’d just get the 190. Shoot even a 255 won’t hurt.

Imo if you’re going to put injectors in you might as well go bigger than a 21lb
 

RioRed95Cobra

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24's, a cheap maf, and an intank 255 are under 200 these days.

Just do it if you think it's on edge. Fwiw, I just burned through THREE sets of 42's.. I mis calculated what kinda power I was making and pegged 3 sets before my tuner said :leghump: this and go 60... zero issues since.

Hell i've got a set of fms 24's and maf if you want lol.
 
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RioRed95Cobra

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If it’s tunes with an actual laptop then you can use whichever injector size you want. The maf won’t make a difference.

I’d just get the 190. Shoot even a 255 won’t hurt.

Imo if you’re going to put injectors in you might as well go bigger than a 21lb
Well.. it sorta will. If the MAF isn't big enough to meter enough air.. like.. if it's forced induction... it still won't work. Also.. lots of people mistake, and get confused, a blow through, and draw-thru MAF. It matters. A lot.
 

Blucifer99

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19lb injectors only flow like 21s if you up the fuel pressure.. and thats at max duty cycle.. if your gonna swap pumps and get injectors.. with your setup the 24s will be good.. and give you room to grow for future upgrades.. Im running 30s and its just what i needed for my setup plus it gives me decent room to grow. or atleast until i install my turbo ill be goin 60s.. go with the 24s..
 

FastDriver

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Skip the 24s, and go straight to whatever size you think you may need eventually. People have always idled fine with the old FMS 42 lbs injectors. Now, I've read that some people are using the stock EEC with 80s. If they can idle and put around, so can you.

Another band-aid solution is to bump fuel pressure up, assuming you can. You'll still need a calibrated MAF, or some adjustments in the computer, but if you bump it up to 55 psi, 19 lbs injectors are roughly equivalent to 24s. Without a calibrated MAF, it'll be extremely rich at idle. The pressure makes it harder on the fuel pump, though. So, you don't want to do that on a stocker, but any bigger aftermarket pump would handle it fine.
 

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Blucifer99

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People are only able to idle with 80lbs injectors using the stock computer is when the computer is superchipped.. or heavily tuned.. the stock ecu doesnt have the adaptive stratgey to idle at that low of a pulse width.. so you would need a dyno tune with 60s or 80s... the stock ecu can handle up to 48lb injectors and idle fine with the matching maf.... after 48lbs your gonna need a tune.. also bumping the fuel pressure sure you can run 19s like 21s.. but like i said thats at a max duty cycle of 100%.. barely any closing time for the 19s... just go 30s and be done with it... room to grow,, and you will idle fine
 

FastDriver

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Is a quarterhorse a "superchip"? That's what the guy was referring to that led me to believe you can run big injectors now.

From "the other" site
I would go with 80s as they are almost the same price as 60s and you could easily go to e85 and have the head room (assuming you have a 340lph). Why buy injectors twice? Unless you go with a dart block, its doubtful youll ever outgrow 80s. Get them at PowerAdderSolutions if you do. There are so many companies selling fakes. I know they sell genuine. Fakes are impossible to tune
Me(skeptical):
Dwain, with your 80s, what do your AFRs look like at idle and cruise? Is the Moates QH still an EEC-IV based tuner? It was when I looked at it, if I recall correctly.

I run 120s without issue, and I self-tune like you, but I'm running a stand-alone with awesome injector drivers (BS3). I was under the impression that the EEC-IV could not actuate the injectors quickly enough to keep AFRs at idle and very low loads reasonable. What has your experience on gasoline been?
Another guy (ragtop50):
Genuine Siemens-Deka 80s are no issue with an EEC-IV and Moates QH. You could run them on a bone stock 302 and idle and driveability would be fine. I run them on a very mild H/C/I setup and you would think I had 24s. The Deka 80s break the old logic of issues of running large injectors since they have such great low pw control.
Me:
External driver box?
ragtop50:
No, just my A9P with the Quarterhorse. I use Decipha's A9L2 as a base for my tune, and he even recommends going straight to the Deka 80s to avoid injector changes later (unless you outgrow those).
me
Well, I guess even old technology improves over time. Good deal. Good to know. If the EEC IV's are doing that well, I'll probably just use them on my next fox build.
 

96pushrod

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Well.. it sorta will. If the MAF isn't big enough to meter enough air.. like.. if it's forced induction... it still won't work. Also.. lots of people mistake, and get confused, a blow through, and draw-thru MAF. It matters. A lot.
The OP isn't running forced induction and likely won't max out the factory MAF.

So anyways; buy a bigger injector, skip the MAF and invest in a program (quarterhorse and binary editor are great) to tune your factory computer. The factory 70MM will do just fine for what you're trying to accomplish.
 

RioRed95Cobra

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The OP isn't running forced induction and likely won't max out the factory MAF.

So anyways; buy a bigger injector, skip the MAF and invest in a program (quarterhorse and binary editor are great) to tune your factory computer. The factory 70MM will do just fine for what you're trying to accomplish.
The More air you can tell the computer you're getting, the more fuel you can deliver and make more power. A stock maf with an upgraded set of heads/c/intake etc. is dumb.. I got my 90mm for $90 on amazon, and it's a real FRPP part. Don't be cheap. Lol. If he decides to go forced later, guess what? It'll still work.

As for the Quarterhorse.. it's a plug in piece, that goes over the j9 port on the computer. It allows you to plug in your laptop and monitor/tune on the fly.. I have my guy out in Virginia (i'm on west coast) tuning the damn thing while i'm driving it.. he can adjust it down to injector pulse timing on the fly, as i'm driving.. air fuel.. timing, you name it.. it's awesome. Worth the money, imo, esp. if you have no dyno anywhere near you, which I do not.

The car absolutely hauls ass and is super safe on my wideband. All done remotely.
 

96pushrod

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The More air you can tell the computer you're getting, the more fuel you can deliver and make
more power. A stock maf with an upgraded set of heads/c/intake etc. is dumb..
How do you figure? A stock, 70mm maf will allow around 700cfm if air to move through it. You really think a hci combo will be moving more air than this? Because I can promise you it won’t.