LQ9 Injector Limits?
Oct 6, 2005 | 07:49 PM
#1
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LQ9 Injector Limits?
OK...I have searched until I can't search anymore. 
Or maybe I don't know how to use it properly. Anyway, for a LQ9 NA application, what is the limit of the stock injectors. I found a thread from BigTex that suggested 350 rwhp, but that is the closest I came. I am looking at about 450 @ the fly, maybe 460, and want to make sure I am doing it right. Thanks guys.
Or maybe I don't know how to use it properly. Anyway, for a LQ9 NA application, what is the limit of the stock injectors. I found a thread from BigTex that suggested 350 rwhp, but that is the closest I came. I am looking at about 450 @ the fly, maybe 460, and want to make sure I am doing it right. Thanks guys.
Oct 6, 2005 | 09:58 PM
#2
Staging Lane
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From: Annapolis, MD
You'll need more than the LQ9 injectors. My LQ9 is stock besides some computer tuning by me and a comp 212/218 cam. My injectors were trying for 130% duty cycle. Switched to 8.1 truck injectors and all is fine.
Oct 7, 2005 | 01:28 PM
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Originally Posted by PSWired
You'll need more than the LQ9 injectors. My LQ9 is stock besides some computer tuning by me and a comp 212/218 cam. My injectors were trying for 130% duty cycle. Switched to 8.1 truck injectors and all is fine.
Right now I have mid-length headers, t-stat, k&n intake, efans & Nelson 93 tune. I could be maxing them out now??
So I guess with a TR 224/224 I am really in trouble? Where can I get 8.1 truck injectors, and are they a direct swap (no cutting or splicing)? I didn't expect this. 
Anyone else have this problem??
Oct 7, 2005 | 10:56 PM
#4
Staging Lane
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From: Annapolis, MD
You should really get a scanner on it to see what the injector duty cycle is now. I got my 8.1 injectors new on ebay for $90. Quite a deal. They are a direct replacement for the stockers. My stockers are 24.95 lb/hr and the 8.1 truck ones are 35 lb/hr if I remember correctly. The 8.1 marine injectors are also a bolt in and flow 41 or 42 lb/hr but you will have to shell out quite a few more bucks for them.
Oct 8, 2005 | 12:50 AM
#5
Originally Posted by PSWired
You should really get a scanner on it to see what the injector duty cycle is now. I got my 8.1 injectors new on ebay for $90. Quite a deal. They are a direct replacement for the stockers. My stockers are 24.95 lb/hr and the 8.1 truck ones are 35 lb/hr if I remember correctly. The 8.1 marine injectors are also a bolt in and flow 41 or 42 lb/hr but you will have to shell out quite a few more bucks for them.
set ifr table across the board to 31 good to go i could see them being used safely with up too 500hp at the crank NA mine read around 16 ms max Im around 400 hp
Oct 8, 2005 | 11:15 AM
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Originally Posted by PSWired
You should really get a scanner on it to see what the injector duty cycle is now. I got my 8.1 injectors new on ebay for $90. Quite a deal. They are a direct replacement for the stockers. My stockers are 24.95 lb/hr and the 8.1 truck ones are 35 lb/hr if I remember correctly. The 8.1 marine injectors are also a bolt in and flow 41 or 42 lb/hr but you will have to shell out quite a few more bucks for them.
Originally Posted by 02sierraz71 5.3
the 8.1 L truck inj. are 31lb/hr
set ifr table across the board to 31 good to go i could see them being used safely with up too 500hp at the crank NA mine read around 16 ms max Im around 400 hp.
set ifr table across the board to 31 good to go i could see them being used safely with up too 500hp at the crank NA mine read around 16 ms max Im around 400 hp.
Thanks guys. 
Oct 8, 2005 | 02:46 PM
#7
Staging Lane
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Just did some data logging today. Now that it's colder my injectors are running at 93% DC at WOT at 5500 RPM. This is in an LQ9 with a comp 212/218 .558/.563 cam, dual 3" exhaust, and open element air filter. VE tables are corrected with wideband tuning.
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Oct 8, 2005 | 05:38 PM
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Originally Posted by PSWired
Just did some data logging today. Now that it's colder my injectors are running at 93% DC at WOT at 5500 RPM. This is in an LQ9 with a comp 212/218 .558/.563 cam, dual 3" exhaust, and open element air filter. VE tables are corrected with wideband tuning.
That is very interesting. I would have to say with a TR224/224 I will definitely be running into a problem...
Weird this topic doesn't come up more with all the cam swaps going on. Maybe I just never noticed. PSWired, where did you get your injectors?
Oct 10, 2005 | 12:27 PM
#9
An LQ9 with headers, tuning and some bolt ons will probably push the 100% limit of the stock injector. Adding a camshaft will definitely push the injectors past their limits.
As far as saying stock injectors are good for XXX amount of power, thats going to change with each situation. The injector limit is directly affected by the rpm the engine is turning. Higher rpms mean less time for the injector to spray fuel between each cycle. If your mods are adding power and increasing rpms (i.e. camshaft), then be prepared to upgrade the stock injector.
As far as saying stock injectors are good for XXX amount of power, thats going to change with each situation. The injector limit is directly affected by the rpm the engine is turning. Higher rpms mean less time for the injector to spray fuel between each cycle. If your mods are adding power and increasing rpms (i.e. camshaft), then be prepared to upgrade the stock injector.
Oct 10, 2005 | 01:03 PM
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Originally Posted by BigTex
An LQ9 with headers, tuning and some bolt ons will probably push the 100% limit of the stock injector. Adding a camshaft will definitely push the injectors past their limits.
As far as saying stock injectors are good for XXX amount of power, thats going to change with each situation. The injector limit is directly affected by the rpm the engine is turning. Higher rpms mean less time for the injector to spray fuel between each cycle. If your mods are adding power and increasing rpms (i.e. camshaft), then be prepared to upgrade the stock injector.
As far as saying stock injectors are good for XXX amount of power, thats going to change with each situation. The injector limit is directly affected by the rpm the engine is turning. Higher rpms mean less time for the injector to spray fuel between each cycle. If your mods are adding power and increasing rpms (i.e. camshaft), then be prepared to upgrade the stock injector.
Thanks BigTex. Now I just need to figure out where to get 'em. I am looking for a direct replacement, so I am leaning towards 8.1L truck injectors if i can find them. Or any other direct swaps if you have a recommendation.
