418 ls3 injector sizing
418 ls3 injector sizing i currently have a 418 ls3 block
w/ 1 3/4 header
ud pulley
tsunami cam
ported stg 2.5 ls6 heads
3 inch dual exhaust
currently have 36lb ford injectors but dont know if those are good enough.
will most likely run what i have to break in the motor w/ the oem ls6 intake
however i will swap it out to a fast 102 once its broken in.. anyone recommend injector size? 50lb?
Thanks
w/ 1 3/4 header
ud pulley
tsunami cam
ported stg 2.5 ls6 heads
3 inch dual exhaust
currently have 36lb ford injectors but dont know if those are good enough.
will most likely run what i have to break in the motor w/ the oem ls6 intake
however i will swap it out to a fast 102 once its broken in.. anyone recommend injector size? 50lb?
Thanks
Those 36 lb injectors will support 650+ HP at 58 psi fuel pressure. Verify the wot fuel pressure by taping a fuel pressure gauge to the windshield.
I also have a TSP 418, TFS 215 heads (valve pockets opened up to match the bore), YT rocker arms, LG G5X3 114 cam installed at 114 ICL, LG long tube pro headers & HF cats, LG big 3 mufflers and a Mamofied 90 mm Fast intake. I'm going with the Fast 36 lb injectors.
Russ Kemp
I also have a TSP 418, TFS 215 heads (valve pockets opened up to match the bore), YT rocker arms, LG G5X3 114 cam installed at 114 ICL, LG long tube pro headers & HF cats, LG big 3 mufflers and a Mamofied 90 mm Fast intake. I'm going with the Fast 36 lb injectors.
Russ Kemp
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TECH Addict
iTrader: (41)
Joined: Feb 2007
Posts: 2,005
Likes: 2
From: Battlecreek, MI / Mansfield, OH
im over 100% duty cycle with 42# injectors on my 416 LS3, mods are in my sig. I'm going to have to pick up some bigger injectors soon. I'd say 36# is going to be way to small for you.
One thing to keep in mind you need to have a stable fuel delivery.
I see 3 psi drop from idle during a pass but it stays right at 39 all the way down.
The injector may not be to small if the volume is not there.
If you can find a way to monitor fuel pressure during a pass to make sure it is rock solid it would be worth the time
Tim
I see 3 psi drop from idle during a pass but it stays right at 39 all the way down.
The injector may not be to small if the volume is not there.
If you can find a way to monitor fuel pressure during a pass to make sure it is rock solid it would be worth the time
Tim
i have an aeromotive fpr and a decent walbro pump. i havent seen any fuel pressure drop at wot on the dyno however i have not seen it in real life conditions...
the 36's are rated at the lower fuel pressure so realistic pressure of those 36's are close to 40 ish... at this point i am unsure if i should go try and get it tuned or should i wait and pick up some 50's
but at the same time.. i don't want to oversize my injectors either.
the 36's are rated at the lower fuel pressure so realistic pressure of those 36's are close to 40 ish... at this point i am unsure if i should go try and get it tuned or should i wait and pick up some 50's
but at the same time.. i don't want to oversize my injectors either.
TECH Addict
iTrader: (41)
Joined: Feb 2007
Posts: 2,005
Likes: 2
From: Battlecreek, MI / Mansfield, OH
hmmmm maybe i need to monitor my fuel pressure..... I have the racetronix pump with the hot wire kit, ran to the alternator..... and my 42# injectors are definitely over 100% duty cycle. I have the FAST fuel pressure gauge on my fuel rail, but that don't help much... lol.
Here is a formula, you must remember that the injectors max out at 80% duty cycle.
http://www.rceng.com/technical.aspx
http://www.rceng.com/technical.aspx
TECH Apprentice
Joined: Jan 2008
Posts: 366
Likes: 0
From: Gladstone, Queensland, Australia
I have tuned LS7s that rev up to 8000 rpms with solid rollers with factory 42 pounders and still have room to move. 42 is more then enough, 36 is plenty in a 6500 rpm hydro roller engine. Hydro roller engines with plastic intakes are pushing **** up hill to keep making power past 7000rpm no need for it.
Last engine I built/tuned 4.010 x 4 large heads very large hydro roller plastic intake 82% duty cycle, remember poor efficiency means higher BSFC requiring larger injectors. 63s would be needed on a gasoline engine that is making power still at 7800 rpm plus.
80's all you require for e85 4XX cube setup.
36s will just scrape in by I would go 42lb bosch.
Last engine I built/tuned 4.010 x 4 large heads very large hydro roller plastic intake 82% duty cycle, remember poor efficiency means higher BSFC requiring larger injectors. 63s would be needed on a gasoline engine that is making power still at 7800 rpm plus.
80's all you require for e85 4XX cube setup.
36s will just scrape in by I would go 42lb bosch.
TECH Apprentice
Joined: Jan 2008
Posts: 366
Likes: 0
From: Gladstone, Queensland, Australia
Those 36 lb injectors will support 650+ HP at 58 psi fuel pressure. Verify the wot fuel pressure by taping a fuel pressure gauge to the windshield.
I also have a TSP 418, TFS 215 heads (valve pockets opened up to match the bore), YT rocker arms, LG G5X3 114 cam installed at 114 ICL, LG long tube pro headers & HF cats, LG big 3 mufflers and a Mamofied 90 mm Fast intake. I'm going with the Fast 36 lb injectors.
Russ Kemp
I also have a TSP 418, TFS 215 heads (valve pockets opened up to match the bore), YT rocker arms, LG G5X3 114 cam installed at 114 ICL, LG long tube pro headers & HF cats, LG big 3 mufflers and a Mamofied 90 mm Fast intake. I'm going with the Fast 36 lb injectors.
Russ Kemp
