fuel injectors

[mooseknuckles]

Ok so I made a few mods to my lq4 6.0l over the winter, and I'm trying to have it ready for when my guy comes to tune it. now I did a cam swap to a comp thumper 275/295 .553 .536 lift. I upgraded the valve train with new trick flow push rods 7.400", 1.7 roller rockers, and ls6 valve springs. I also added a holley sniper intake with a nick Williams 92mm throttle body. still running the longtubes as well. the part that worries me is that I'm still running the stock truck injectors and I'm thinking that I'll be pushing the limit with them, so should I go ahead and upgrade the injectors while I'm at it...? and if so how much bigger will I need to go.?

[Robznob11]

Yes you should. 36# will probably be fine but you could go with 42# and grow into them. Im near certain that you will eventually want a larger cam and a stall. These engines crave them and they are very streetable. If i were you I would call fuel injector connection in Georgia. They are cheap reliable and will spec exactly what you need. Not to mention they will give you your data files for your tuner in either hp tuners or efi live. Which ever you prefer. Plus they will also buy your old injectors for $90 bucks. I have there 42# and love them.

[Robznob11]

Just fyi if you take a stock lq4 and put a hot tune in it you will be running your stock injectors at @ 80% duty cycle now add all the cam and goodies and you get the picture. If you haven't already you need to step up the fuel pump as well.

[mooseknuckles]

Originally Posted by Robznob11

Just fyi if you take a stock lq4 and put a hot tune in it you will be running your stock injectors at @ 80% duty cycle now add all the cam and goodies and you get the picture. If you haven't already you need to step up the fuel pump as well.

Thanks! yeah..I got a custom Boyd tank with the Aeromotive 340 stealth inside.

[BR3W CITY]

If you get injectors off a donor vehicle, keep in mind that factory flow ratings are done at "rail pressure" which is different from brand to brand, and sometimes model to model.

All GM injectors for the GenIII-IV are rated at the 58psi rail pressure, with the exception of a few flex fuel and alt-fuel vehicles which run 48-52psi.

If you were to pick up a very common donor injector, the Ford SVO Blue's, you'll be given an advertised flow rate 39lb/hr. The problem is that Ford uses a rail pressure around 10psi LOWER than GM does. This means that @ "GM" rail pressure, the actual flow goes to over 45lb/hr.

Its also worth noting that there are a few different types of tips/nozzles on injectors. While you do have some freedom to interchange, its worth being cautious. Depending on power levels, pressure its being run at, an duty cycle, these tip changes can create spray patterns that cold spot or risk fuel pooling...and thats just no fun.

For what your running; if you want to keep a MultecII plug on the harness then either some Marine 8.1 shorty's or an aftermarket/reflowed injector on the Delphi injector body. If you don't mind swapping the plugs (or if you were setup for the EV1 of Ev6 plugs) then I'd consider looking at the Ford SVO/SVT injectors, LS3 injectors #12576341, or any of the aftermarket options.

[Robznob11]

Originally Posted by BR3W CITY

If you get injectors off a donor vehicle, keep in mind that factory flow ratings are done at "rail pressure" which is different from brand to brand, and sometimes model to model.

All GM injectors for the GenIII-IV are rated at the 58psi rail pressure, with the exception of a few flex fuel and alt-fuel vehicles which run 48-52psi.

If you were to pick up a very common donor injector, the Ford SVO Blue's, you'll be given an advertised flow rate 39lb/hr. The problem is that Ford uses a rail pressure around 10psi LOWER than GM does. This means that @ "GM" rail pressure, the actual flow goes to over 45lb/hr.

Its also worth noting that there are a few different types of tips/nozzles on injectors. While you do have some freedom to interchange, its worth being cautious. Depending on power levels, pressure its being run at, an duty cycle, these tip changes can create spray patterns that cold spot or risk fuel pooling...and thats just no fun.

For what your running; if you want to keep a MultecII plug on the harness then either some Marine 8.1 shorty's or an aftermarket/reflowed injector on the Delphi injector body. If you don't mind swapping the plugs (or if you were setup for the EV1 of Ev6 plugs) then I'd consider looking at the Ford SVO/SVT injectors, LS3 injectors #12576341, or any of the aftermarket options.

Br3w, not to argue but some of the gm injectors are rated at 43 psi. Like i said your best bet is fuel injector connection....they have adaptor plugs as well if you want to swap styles. But the fuel maps that you will get with it injectors is way better than trying to cobble together a tune with doner injectors. You should really visit the ls1 tech forum and read up there. Lots of info on injector swaps. And for what its worth I paid like 300$ for new injectors with swap plugs shipped to my door and then got $90 back for my stockers. You cant beat that and you will get unmolested, no varnish build up, ready to run injectors that are spec'd for your build!

[BR3W CITY]

Originally Posted by Robznob11

Br3w, not to argue but some of the gm injectors are rated at 43 psi.

Which?


Injector scaling shouldn't be hard for most tuners. Don't get me wrong, FIC's stuff is great, and getting the injector tables from them makes life easy, but it shouldn't be a dealbreaker. The only reason I lobby for SVO injectors is the fact that some guys literally have them laying around. Under 60lb/hr, its hard for me to justify the cost differential. We've had a few sets of them float around through probably 9 vehicles now as customers scaled up from stock, then into needing aftermarket-only flow rates. The LS3 injectors also fit the cheap n available, and injector tables are readily available.

[Robznob11]

[QUOTE=BR3W CITY;7971729]Which?


Injector scaling shouldn't be hard for most tuners. Don't get me wrong, FIC's stuff is great, and getting the injector tables from them makes life easy, but it shouldn't be a dealbreaker. The only reason I lobby for SVO injectors is the fact that some guys literally have them laying around. Under 60lb/hr, its hard for me to justify the cost differential. We've had a few sets of them float around through probably 9 vehicles now as customers scaled up from stock, then into needing aftermarket-only flow rates. The LS3 injectors also fit the cheap n available, and injector
I guess i need to retract that statement. LOL!
I wad thinking of the fact that most companies use 43.5 (3bar) as their standard for therir flow ratings. Its important that the OP makes sure he gets injectors at the 4 bar rating (58 psi)

[Hart_Rod]

BEFORE you buy injectors, just make sure you can get good data on them. Flow rate, Offset voltage, short pulse limit, short pulse adder, min injector pulse. If whatever company can't provide you with that data, look somewhere else. This will save your tuner (and you) a lot of time and aggravation.

Brew - the injectors in my factory 2002 LS1 were flow rated at 43 psi.

[Robznob11]

Originally Posted by Hart_Rod

BEFORE you buy injectors, just make sure you can get good data on them. Flow rate, Offset voltage, short pulse limit, short pulse adder, min injector pulse. If whatever company can't provide you with that data, look somewhere else. This will save your tuner (and you) a lot of time and aggravation.

Brew - the injectors in my factory 2002 LS1 were flow rated at 43 psi.

Lol, didn't think I made up the 43# but could not remember why I thought that!

[boostedc10]

Just to clear up a few things about injectors and sizing;

The PSI the injector was flow tested at only gives you a reference of where the injector puts out the advertised lb/hr, nothing else. An example is the deka 60's which are flowed @ 39.15 psid. Put them in an application like a boosted LS with a rail pressure of 58psi they flow more lbs/hr (about 73#s).

Hart is right, having the data is good and most reputable injector companies will have it. Any good tuner should have most of this data though so its not a deal breaker in my opinion.

Almost every LS based engine out there runs a base line pressure of 58psi, including the LS1. When you see an injector lb/hr for them they will be at this PSI not the 43.5 (unless noted).

Not saying Rob is wrong because many of the LS injectors used are also used in other applications and more than likely flowed at 43.5 by the manufacture.

In the end you need to figure out what lb/hr your engine requires at 58 psi and buy the ones that match the closest. If you are between 2 normal sizes go up not down. 40's for your combination will work just fine.

[Hart_Rod]

Originally Posted by boostedc10

Just to clear up a few things about injectors and sizing;

The PSI the injector was flow tested at only gives you a reference of where the injector puts out the advertised lb/hr, nothing else. An example is the deka 60's which are flowed @ 39.15 psid. Put them in an application like a boosted LS with a rail pressure of 58psi they flow more lbs/hr (about 73#s).

Hart is right, having the data is good and most reputable injector companies will have it. Any good tuner should have most of this data though so its not a deal breaker in my opinion.

Almost every LS based engine out there runs a base line pressure of 58psi, including the LS1. When you see an injector lb/hr for them they will be at this PSI not the 43.5 (unless noted).

Not saying Rob is wrong because many of the LS injectors used are also used in other applications and more than likely flowed at 43.5 by the manufacture.

In the end you need to figure out what lb/hr your engine requires at 58 psi and buy the ones that match the closest. If you are between 2 normal sizes go up not down. 40's for your combination will work just fine.

I just did a quick search and it looks like 58 psi is the correct number. I could have sworn my LS1 was at 43 psi, I stand corrected! I should have searched before I opened my mouth......

[boostedc10]

Hart you may have seen the data on a LS1 28lb'er from the manufacturer which was done at 43.5

[Robznob11]

Originally Posted by Hart_Rod

I just did a quick search and it looks like 58 psi is the correct number. I could have sworn my LS1 was at 43 psi, I stand corrected! I should have searched before I opened my mouth......

Lol! I kinda felt in the same boat. When I originally was searching back when everyone was recommendeling 8.1 truck injectors. I could have sworn someone posted a gm injector chart with some rated at 43# but they may not have been ls, just usable. The main point is like I originally said get some with all the data. I know i probably sound like a fic sales man but my research led me to believe they were the bes bang for the buck! Im sure some others are good but call and ask why some say theirs are bettet than others and then look at what others run and make decisions. From my experience you are better off with new warranty parts ....you usually spend just as much to get where you want with used just to have unknowns and 0 warranty. And that goes for all hotrod stuff!

[boostedc10]

The 8.1 injectors are Delphis and at Delphi they are tested at 43.5 flowing @ 30lbs/hr. This is the data everyome is sharing on the net. At 58 they are 35s.