33lb/hr to 36lb/hour???????
07-19-2018, 11:31 AM
#1
33lb/hr to 36lb/hour??????? OK just off the dyno last month, my sig at the bottom shows what I got LS2 injectors are 33lb/hr. I've been playing with the formula for injector size and with my mods and crank HP somewhere around 490? I'm right at the ragged edge of my stock injectors, I got a really good deal on a matched set of 36lb/hr injectors, WILL I have to change the tune or can the computer compensate for this small of an upgrade?
07-20-2018, 08:13 AM
#3
why? why didn't chevy just put the same ones in almost everything they make? would be easier for them wouldn't it? less stock on the shelves, right? there is a reason, you do know that there are engines out there that use a smaller one then one would think, you are not only trying to get enuff fuel to the motor but your trying to get it across the RPM band, why would a small motor use bigger ones, then a bigger motor? too get more fuel in a shorter amount of time because the rpm's are higher and your trying to keep the injector in around a 80% duty cycle, that's why they do it, it most be some kind of "sweetspot" for a modern injector. if you were an engineer you'd probably put in Top fuel injectors the flow 13.5 gallons in about five seconds. why don't I just put those in?
07-20-2018, 10:26 AM
#4
why? why didn't chevy just put the same ones in almost everything they make? would be easier for them wouldn't it? less stock on the shelves, right? there is a reason, you do know that there are engines out there that use a smaller one then one would think, you are not only trying to get enuff fuel to the motor but your trying to get it across the RPM band, why would a small motor use bigger ones, then a bigger motor? too get more fuel in a shorter amount of time because the rpm's are higher and your trying to keep the injector in around a 80% duty cycle, that's why they do it, it most be some kind of "sweetspot" for a modern injector. if you were an engineer you'd probably put in Top fuel injectors the flow 13.5 gallons in about five seconds. why don't I just put those in?
There's multiple solutions to your question. If you're running a return style setup with a bigger pump you can increase the base pressure. You can swap or the injectors. His point is that for the work required to swap out and then tune the injectors a 10% increase in flow isn't worth it considering the next time you mod the engine you'll have to swap them out again.
Also, don't be a dick. If you think you know everything already then why post the question?
Last edited by eaglegoat; 08-05-2018 at 05:30 AM.
07-20-2018, 10:29 AM
#5
Restricted User
why? why didn't chevy just put the same ones in almost everything they make? would be easier for them wouldn't it? less stock on the shelves, right? there is a reason, you do know that there are engines out there that use a smaller one then one would think, you are not only trying to get enuff fuel to the motor but your trying to get it across the RPM band, why would a small motor use bigger ones, then a bigger motor? too get more fuel in a shorter amount of time because the rpm's are higher and your trying to keep the injector in around a 80% duty cycle, that's why they do it, it most be some kind of "sweetspot" for a modern injector. if you were an engineer you'd probably put in Top fuel injectors the flow 13.5 gallons in about five seconds. why don't I just put those in?
07-20-2018, 10:50 AM
#6
Actually Chevy did do that. They LS3 and LS7 use the same injectors as do the LSA and the LS9.
There's multiple solutions to your question. If your running a return style setup with a bigger pump you can increase the base pressure. You can swap or the injectors. His point is that for the work required to swap out and then tune the injectors a 10% increase in for isn't worth it considering the next time you mod the engine you'll have to swap them out again.
Also, don't be a dick. If you think you know everything already then why post the question?
There's multiple solutions to your question. If your running a return style setup with a bigger pump you can increase the base pressure. You can swap or the injectors. His point is that for the work required to swap out and then tune the injectors a 10% increase in for isn't worth it considering the next time you mod the engine you'll have to swap them out again.
Also, don't be a dick. If you think you know everything already then why post the question?
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07-31-2018, 12:51 PM
#10
TECH Senior Member
Cmysix- You DID get an answer, it just wasn't what you wanted, as was said above. I read the whole thread (a few minutes reading...) and Joe Nova's answer is quite clear. So let's knock off the profanity and stick to the subject.
08-02-2018, 08:10 AM
#11
I DID NOT START IT BILLY, OL EAGLEGOATstarted with the insults, Billy IF you read this you would see that. telling me to put in Oversized injectors is not in ANY way answering the Q. BTW the answer I found on many injector MFG's websites, They have calculators or you can do the math yourself, my estimated crank HP is 490 and a 80% duty cycle IS RECOMENDED. when you do the math you come out with a calculation right at 34 LBS/HR and they ALL{including GM} said to go UP TO THE NEXT SIZE, THEY DID NOT SAY TO GO UP 10 OR 20 LBS/HR because "YOU MIGHT MOD IN THE FUTURE". Now GM has people who know what their doing{unlike most of the forum engineers here} so they have their reasons for doing what they do. BUT for me my best choice for my motor to run right was 36 LB/HR AND IN ANSWER TO MY OP. You have to change the injector tables in your tune when you swap injectors. AND JoeNova, I did go with what WILL give me the BEST performance
08-02-2018, 09:04 AM
#12
Restricted User
Seeing as how your knowledge is extremely limited, I would take a guess that this isn't the case.
Not only did you probably not understand the reason for that 80% duty cycle recommendation, I'm also guessing you didn't bother to check understand the flow ratings on aftermarket injectors in relation to pressure ratings.
Having an injector that flows closer to the amount of power you're making doesn't mean that you bought a better injector, higher quality injector, smoother idling injector, or an injector that works better for your setup.
It means you just spent X amount of money for a 9% increase in injector flow, nothing more, nothing less.
Not only did you probably not understand the reason for that 80% duty cycle recommendation, I'm also guessing you didn't bother to check understand the flow ratings on aftermarket injectors in relation to pressure ratings.
Having an injector that flows closer to the amount of power you're making doesn't mean that you bought a better injector, higher quality injector, smoother idling injector, or an injector that works better for your setup.
It means you just spent X amount of money for a 9% increase in injector flow, nothing more, nothing less.
08-02-2018, 09:56 AM
#13
TECH Senior Member
Joe, I think at this point, ANY advice given might as well be spoken to the wall....
Cmysix, yeah, there are plenty of internet engineers around here, but all you need to know right here and now is Joe Nova knows MORE THAN YOU! I would listen more and spout off less...
Cmysix, yeah, there are plenty of internet engineers around here, but all you need to know right here and now is Joe Nova knows MORE THAN YOU! I would listen more and spout off less...
08-02-2018, 06:31 PM
#14
OK JOE YOUR right I do know nothing BUT I did take the advice of 3 major injector MFG Co's. so since they don't know what their doing, how do your chose an injector for a certain HP/engine level? all we have got from you so far is words , Please lets have your math and science behind choosing an injector, WE are waiting..... BTW installed the 36 LB/HR today and the car, runs ,idle's and pulls better but what do I know.
08-02-2018, 09:15 PM
#17
TECH Senior Member
He advised to go to 42# injectors, as 36# over 33# was not worth the trouble. Post #2, and then Post #5, recommending to choose injectors for performance, unlike the OEM's. Then there were others advising you to not be such a dick, but I would not say that...
08-03-2018, 10:44 AM
#18
Restricted User
Stock LS2 injectors are rated at 33 lb/hr at 58 PSI (stock LS fuel pressure).
If you bought injectors that are rated 36 lb/hr @ 43.5 PSI (as most aftermarket injectors are rated at 43.5 PSI), then you basically bought 42 lb/hr injectors @ 58 PSI. You took my advice and didn't even know it.
I'd explain why I made that recommendation, but you wouldn't likely understand when I started talking about (duty cycle vs pulse width + dead time) vs (maximum fuel trims on a stock PCM and scenarios when you'll need that headroom).
If you bought injectors that are rated 36 lb/hr @ 43.5 PSI (as most aftermarket injectors are rated at 43.5 PSI), then you basically bought 42 lb/hr injectors @ 58 PSI. You took my advice and didn't even know it.
I'd explain why I made that recommendation, but you wouldn't likely understand when I started talking about (duty cycle vs pulse width + dead time) vs (maximum fuel trims on a stock PCM and scenarios when you'll need that headroom).
08-04-2018, 02:17 AM
#20
It seems like we always have to do some digging to answer your question. You are already completely aware of this, so I am guessing your post was just a "time out" for the idiot who started this thread. There is a lot of ambiguity when you get to 42# injectors, however. There are a lot of 30something # injectors marketed to the GM crowd as 42's because of the 58# rail pressure. I was unaware that 28s are marketed in a similar manner.