Help with fuel injectors
Thread Starter
Pro
Joined: Nov 2007
Posts: 555
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From: Celina TX
Help with fuel injectors
I slowly gathering the parts to do a head and cam swap and need some advice on which fuel injectors to get. My MN6 LS2 will have PRC 2.5 LS6 heads and a medium size cam. I can get a set of Bosch 47lb injectors for $250, or a set of Fast 46lb injectors for $340. Can anyone tell me if the Fast are worth the extra money or are they pretty much the same?
Regards, Eric
Regards, Eric
Race Director
Joined: Mar 2007
Posts: 11,331
Likes: 18
From: Missouri City Texas
I have a set of FAST 57# injectors unopened that I can sell you for less than the cost of the FAST 46#. I was going to do a big cam setup but opted into forced induction instead.
They're direct swaps for the LS2 if you're interested.
They're direct swaps for the LS2 if you're interested.
Tolero Apto Victum
Joined: Jul 2007
Posts: 9,669
Likes: 37
From: Woodlands TX
OP: If you have an LS2, I would recommend adding the FAST intake to your build. Take a look at my FAST tread. I have Fast 33# injectors on my build. http://forums.corvetteforum.com/c6-t...st-intake.html
Le Mans Master
Joined: Mar 2010
Posts: 7,050
Likes: 945
From: DFW TX
. Great price to. I run the fast 46s and they work great.
Thread Starter
Pro
Joined: Nov 2007
Posts: 555
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From: Celina TX
OP: If you have an LS2, I would recommend adding the FAST intake to your build. Take a look at my FAST tread. I have Fast 33# injectors on my build. http://forums.corvetteforum.com/c6-t...st-intake.html
What if any are the disadvantages of running too large an injector?
Le Mans Master
Joined: Mar 2010
Posts: 7,050
Likes: 945
From: DFW TX
I can't think of any really, If you're talking about just going up to a 57# injector. Tuning would probably be a nightmare on say an 80# injector or something crazy like that on a NA car.
If you ever want to go FI then the 57 would be a good choice. You might even need bigger for FI. I think the A&A kit comes with 60#.
Just a NA H/C/I car you can get away with 37s or 42s or 46s.
If you ever want to go FI then the 57 would be a good choice. You might even need bigger for FI. I think the A&A kit comes with 60#.
Just a NA H/C/I car you can get away with 37s or 42s or 46s.
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Thread Starter
Pro
Joined: Nov 2007
Posts: 555
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From: Celina TX
I can't think of any really, If you're talking about just going up to a 57# injector. Tuning would probably be a nightmare on say an 80# injector or something crazy like that on a NA car.
If you ever want to go FI then the 57 would be a good choice. You might even need bigger for FI. I think the A&A kit comes with 60#.
Just a NA H/C/I car you can get away with 37s or 42s or 46s.
If you ever want to go FI then the 57 would be a good choice. You might even need bigger for FI. I think the A&A kit comes with 60#.
Just a NA H/C/I car you can get away with 37s or 42s or 46s.
This is where I'm confused, some tell me I'll need to upgrade them and some tell me I'm fine with stock. I'm only looking at 440-450rwhp with my set-up. How is duty cycle measured?
Drifting
Joined: Oct 2004
Posts: 1,790
Likes: 29
From: STL MO
St. Jude Donor '09-'10
I am installing some Trick Flow "as cast 220 heads" and will try to retain the stock injectors, we will see just how much the LS2 injectors can handle in the next 2-3 weeks.
Le Mans Master
Joined: Mar 2010
Posts: 7,050
Likes: 945
From: DFW TX
It is good practice to stay below 80% duty cycle on a fuel injector. Most heads and cam 475-500 rwhp cars should change injectors. In my experience everyone sticks with stock injectors on cam only <450 rwhp, but when they do heads the injectors are changed. It is pretty good insurance IMO. You don't want to get on the dyno and run out of injector.
Track Junky
Joined: Jun 2007
Posts: 4,074
Likes: 36
From: Orlando Area
Tech Contributor
I was at 89% duty cycle on my LS2 injectors at 384 rwhp (12.7 AFR). Stock LS2 injectors will max out around 425-450 rwhp. On the other hand, LS3/LS7 injectors (42#) are good to 550 rwhp or so. I currently have 485 rwhp with LS7 injectors and am at 76% duty cycle at 12.6 AFR.
You can pick up used LS3/LS7 injectors around $200. If you decide to go that route, you will need spacers but make sure to get top spacers (as opposed to bottom spacers).
You can pick up used LS3/LS7 injectors around $200. If you decide to go that route, you will need spacers but make sure to get top spacers (as opposed to bottom spacers).
Last edited by taken19; Nov 20, 2011 at 05:28 PM.
Track Junky
Joined: Jun 2007
Posts: 4,074
Likes: 36
From: Orlando Area
Tech Contributor
John, don't know why we are/were so different on duty cycle. I have heard from several dependable sources that the stock LS2 injectors are only good to 450 rwhp at best and that is pushing close to 100% duty cycle.
You sure you are still running the 33# injectors? Maybe Dave hooked you up during a recent tune? I thnk it would be a tough sell to believe your 460 rwhp is THAT much more efficient than mine at 384 rwhp, but I guess stranger things have happened in the world of cars...
You sure you are still running the 33# injectors? Maybe Dave hooked you up during a recent tune? I thnk it would be a tough sell to believe your 460 rwhp is THAT much more efficient than mine at 384 rwhp, but I guess stranger things have happened in the world of cars...
Race Director
Joined: Mar 2007
Posts: 11,331
Likes: 18
From: Missouri City Texas
If you change your mind, just let me know.
Drifting
Joined: Oct 2004
Posts: 1,790
Likes: 29
From: STL MO
St. Jude Donor '09-'10
John, don't know why we are/were so different on duty cycle. I have heard from several dependable sources that the stock LS2 injectors are only good to 450 rwhp at best and that is pushing close to 100% duty cycle.
You sure you are still running the 33# injectors? Maybe Dave hooked you up during a recent tune? I thnk it would be a tough sell to believe your 460 rwhp is THAT much more efficient than mine at 384 rwhp, but I guess stranger things have happened in the world of cars...
You sure you are still running the 33# injectors? Maybe Dave hooked you up during a recent tune? I thnk it would be a tough sell to believe your 460 rwhp is THAT much more efficient than mine at 384 rwhp, but I guess stranger things have happened in the world of cars...
(my apologies) I was at 83% when I was putting out 399/403. I am at 90% according to our last tuning session but I don't have a rwhp number from that, I can say the car was making more power than when I dynoed the car at 452 rwhp with a base tune. The other change I made besides the tune was going to an LS7 MAF installed in a Vararam MAF coupling/tube.
