Bigger injectors?

**Supersport0126** · 03-14-2012, 12:50 PM

Need to know if I need bigger injectors or not? Got a 98 ss a4 (28lbs/hrstock inj.) Typhoon intake85mm and tb, frost tune,bellow,lid,160stat,alum. Rad,cool bypass, kooks headers and t/d's with cats on the way,and 3.73motives that need to be installed! It runs pretty good, I just dont want to be to lean! Installing a wide band when I get my exhaust, but I was on witch***** website.(i forgot the name), and if the calculations are correct,it says I need around 31lbs if im at 400 horse. Dont know where ill bee hp wise once I install exhaust,etc. What do you guys think? Considerimg mods.how much Hp roughly? Bigger injectors needed? Thanks!

**Supersport0126** · 03-14-2012, 12:55 PM

Oh and air/egr deleted also!

**35th-ANV-SS** · 03-14-2012, 01:09 PM

These are all very common mods that you are doing that a lot of people on here also do with stock injectors. You will be fine with the 28's. Now, if you go adding a cam and heads later on, then I would suggest you upgrade your injectors to a larger size.

If you did end up being over 400 at the crank with your mods, that just means you will be more than 80% duty cycle on your injectors. Typically you don't want to do that, but I can't really see it being an issue with your current mods.

**Supersport0126** · 03-14-2012, 01:25 PM

yeah was hopin I didnt have to. Injectors would be a little much for me right now considering what I just paid for that exhaust! Just wanted to ne sure the car wont be running lean or anything! that wouldnt be good!

**gashkerwin** · 03-27-2012, 03:01 PM

I have 400rwhp on the stock injectors, but up at the top of the RPMs they're @ about 100% capacity.

**Firebirdjones** · 03-27-2012, 04:22 PM

Like 35th mentioned, you would have to log your duty cycle under load. Only way to know would be a dyno session with a laptop and Hptuner, or some other software to log things.

**TA98** · 03-28-2012, 12:06 PM

^^^ agree. Datalogging will tell you for sure. However on the dyno you get less air across the vehicle so on the road you see more air and with more air you will need more fuel.

**Supersport0126** · 03-31-2012, 04:21 AM

I have a really nice genesis scan tool that does just about anything. Your saying I should monitor duty cycle?

**Firebirdjones** · 03-31-2012, 08:50 AM

Yes, log it and watch injector duty cycle. Usually something in the 80 percentile is acceptable. Over that and you might want to consider an upgrade.

**Mike0202** · 03-31-2012, 04:36 PM

Originally Posted by Firebirdjones

Yes, log it and watch injector duty cycle. Usually something in the 80 percentile is acceptable. Over that and you might want to consider an upgrade.

I see alot of people over at ls1tech running cammed cars with around 390rwh still using the stock injectors. I thought it was okay until the heads are upgraded.

**Firebirdjones** · 03-31-2012, 07:27 PM

Could be fine. Each car is going to be slightly different in it's requirements depending on alot of factors. It also helps to confuse things that GM used different sized injectors throughout the LS1 4th gen production. It's always best to log and be sure, only takes a few minutes.

For instance, my wifes 2000 SS (which I believe runs the smaller injectors from the factory) 26 pounders?? is well above 80% duty cycle last time I checked at sea level. It's just a small Crane cam (near LS6 specs), an LS6 intake and headers with an off road Y. I'd have to log it again to get the exact figure as I don't remember.

**2002ssslp** · 03-31-2012, 07:27 PM

I have about 400hp at the crank because I dyno'ed at 345rwhp and I am running stock 28's without any problem. A cam and heads will change your needs but stock injectors should be ok for now.