Sinister-one

I'm planning on building a stoker motor just haven't decided what size yet.

At this point I still have the stock LS1 in the car and will be adding the following mods:

FAST 92 with LS2 90mm TB
Headers with high flow cats
TSP Stage 2.5 heads
EG Whiplash cam

With the above as mentioned, what size injectors should I buy that will work properly and still have room to grow ?



Thanks for your input and help !

neutron82

I think a 42lb injector would be fine and give you some wiggle room if you plan to stay n/a... fwiw, my motor made 420rwhp n/a and I'm running a 127lb injector and driveability is fine when just cruising around out of boost

enoniam

I'm running the following with 42# injectors:

Comp Cams' 54-428-11 (228/230 on a 112 with 2 advance using the XFI RPM High Lift lobes)
Weiand / Lingenfelter Intake Manifold
Ported stock heads
Long-tube headers
No cats
Corsa Indy Exhaust

Seeing max injector duty cycles around 75%.

Motor made 383 rwhp (A4) with different cam before failed lifter, rebuild and slightly undersized injectors (over 100% duty cycle). MAF readings indicate about 10% more airflow now so I'm conservatively projecting now about 420 rwhp.

neutron82

were you using the 42lb injectors at 75% idc when you made 383rwhp?... that seems a little high on the duty cycle for that power level in my opinion... when I was running stock injectors (either 26 or 28lb for the ls6, I can't remember) they were in the low 90's duty cycle at redline and I ran them that way for a year or so before swapping out to 60's when the blower went on and then 127's when the fuel system was built

Last C5

I switched to 42# flow matched when I built my LS6 to 440 rwhp and I'm using the same injectors on my LS7 built to 580 rwhp, so you'll have plenty of room to grow.

Sinister-one

Looks like 42# injectors seem the popular vote.

Sinister-one

Now I just need to find someone selling some 42# injectors for my FAST 92 intake and make sure they connect to my LS1 harness.

enoniam

No - not sure what size the injectors were, they were on the car when I bought it about 16 months ago, could have been stock. I was seeing up to about 106% duty cycles on HPTuners' scanner then.

Keep in mind behind an auto the rule of thumb is you're loosing 20% of the power when measured on a chassis dyno. Therefore 383 rwhp should be close to 480 at the crank.

I'm also running 42# injectors in a crate 6.0 truck LS engine that was supposed to be good for 460 crank hp in my truck. Seeing about 60% max duty cycles with that setup.

tblu92

Just remember when buying injectors---Most all injectors are rated at 3 bar (43 psi) while a LS injector is rated at 4 bar (54 psi) As an example if you buy a 3 bar 30 lb injector it is really on a LS engine rated at about 34 lb
A 40 lb injector rated at 4 bar is very large --suited more for a SC application or heavily modded---
If you get an injector that is too large your P/T and idle will suffer as well as your drivability----
Depending on the year of your car a 97-98 xar came with 28lb injectors stock and 1999 and newer ls1's came with 24lb injectors--
My 98 car with similar mods as yours I sued the stock 28 lb injectors--the duty cycles did go up to like 92% but as long as you don't run it like in road racing it should be fine as long as you let the injectors cool off sometimes in beween drag rounds--If your car had 24ls injectors stock YES you would need larger injectors even a stock set of 28's would be ok---but if you like to lower the duty cycles a set of 30 lb'ers would be fine
If it were me----I would start out with your stock injectors--data log your duty cycles to see exactly where you are at then make a decision----My car made approx. 400 RWHP
a set of 30 lb 3 bar injectors would be the best choice--rated at 34 lbs at 4 bar and plenty enough for your car and you won't have to deal with all the issues too large of an injector creates---dying--surging--stalling--etc----

feeder82

My car makes 430rwhp on stock injectors bigger isnt always better

Sinister-one

Okay then... my Vette is a 2000 FRC... so I have 26lb OR 28lb stock injectors ???

neutron82

as I stated my motor makes 420rwhp n/a and with 127lb injectors it runs fine at idle or cruising while out of boost with no driveability issues... these are overkill for his setup I'm just making a point that with a good tuner they can work around these issues and the car drive close to what a stock car would drive like... 42lb injectors would not be overkill for his setup, keep his duty cycle lower for the power he will be making right now, and still give him room to grow with less of a chance of the injector working too hard when he does add more power... 30 or 32lb would probably work just fine for his current setup but will not allow as much room for future power upgrades

neutron82

if you want to find out for sure grab the part # on your current injectors

Sinister-one

will do !

enoniam

Bigger surely isn't always better, but too small can certainly be much worse.

I've got 42# injectors in my car and in my truck. I've tuned it myself (only 1 day of tuning school) and don't have any dying, surging or stalling in either vehicle. If these are too hard to tune you must not be doing it right.

c5z06.O

What injectors did you go with after all?

Sinister-one

Still looking.... I found someone selling a set of 44lb injectors and am waiting the hear back form the seller.

Sinister-one

In looking through my stuff in the garage I found a set of LS2 injectors. If I'm not mistaken, the LS2's are 32-34lb. I may not have to buy any injectors.

I'm thinking these will do for now.