Cookee

Gents,

For the tuners builders with knowledge I would appreciate your thoughts.

I have a LS2 A4 with 421rwhp and 400rwtq and I drag race every other month. I am installing some new heads that should get over 450+ rwhp and was thinking it may be good to replace the OE 33lb injectors with the FAST 46lb injectors.

Do you need a minimum HP for the 46lb injector to work correctly?
Should I have concerns with idle quality?
Any other thoughts?

Thank you

Dano523

use the work sheet,
http://www.rceng.com/technical.aspx#WORKSHEET

schpenxel

Does proper injector data even exist for the FAST injectors? Last time I checked it didn't seem to

shawnaj7731

http://www.hptuners.com/forum/showth...jector-scaling i have them on my car i think this may help.

schpenxel

Are they actual LS2 injectors or are they drilled out LS2 injectors? Two very different things.

shawnaj7731

not really sure. I thought i read they were drilled out but dont take my word.

Cookee

"Uniquely designed for direct installation into LS2 engines"
http://www.fuelairspark.com/fas/8-ls...-injectorhtml/

Cookee

Great info thank you
The 46lb injector will be perfect for my 550 bhp motor...

schpenxel

Which answers precisely nothing.

Cookee

OK got it, a little slow.

Just assumed that FAST would be contracting with a mfg to build and they would be sized with a laser.

Drilling injectors out with a drill bit is amazing to me. Some quality hot rodding skills... lol

I sent FAST a message and asked the question will share the response.

Thanks again

schpenxel

Regardless of how they are sized, that doesn't make the injector data right. The thought process years ago was that since they started life as regular 'ol LS2 injectors, that all of the short pulse adder/offset tables would stay the same. However, in reality this is wrong. Change the size of injector and you change all characteristics. Fluid dynamics and such.

Does that mean they won't work? No.. you can make about anything work, it's just not ideal.

Having injectors that behave consistently and predictably is why I can run 1000cc injectors on a stock displacement, stock cam'd car and have it idle 100% as good as stock with zero drivability issues. I know a lot of people hate to pay what injector dynamics charges, but there is good reason that a lot of people still do. My car idles and drives much better on 1000cc ID injectors vs. ~600cc no name brand ones.

Joe_G

I have 475 rwhp and stock injectors and have had no problems for 8 years and plenty of racing. The duty cycle is 90+ at the top end but that's not been a problem. I am not a fan of over injecting a car, which it seems you would be doing with those big injectors because drivability and mileage in normal driving can suffer if the tune can't properly control the injectors. The spreadsheet method isn't as accurate as the stock calibration is.

Cookee

Good feedback Joe!
I have decided to keep the stock injectors and enjoy..
Thank you

dennis50nj

the injector duty cycle that high is alright for joe at the florida temps but wouldnt be good if it then turned to colder temps or he came to MIR in the colder temps and better DA

Cookee

More good news for OE 33lb injectors. Being in Orange County, CA our temps our similar to Joe. I have tried to time the few cold days we get 50-65 and no luck in 2 years always over 70 regardless if nights at Irwindale or mornings at Fontana.

Thanks Dennis

dennis50nj

I was around 460 when I did the cam and had the stock injectors it was done in the spring nearing summer, Julio advised me not to run full out once the fall racing season started until he got some resized injectors for me, so i had him do the heads also, now we are at 60% duty cycle with heads and resized injectors

Dano523

The only question I have with drilled out injectors, how well do they still atomize the fuel????

Hence the whole secret to an injector spray pattern is how well is will atomize the fuel to begin with or not, since the finer the fuel has been atomized, the more HP the motor will make.


Hence for Fast, I do come up with video on flow rates itself, but do not come up with anything on the size that the fuel is being atomized pre and post drilling the orifices instead.

dennis50nj

For my car to make the power on the dyno 492 and being a high stalled automatic, with its mph and et in the 1/4 proves resizing of injectors works and the spray pattern and atomization must be fine

schpenxel

No, not really

dennis50nj

I am always eager to learn so you are telling me that new injector over resized would make more power and go faster? because according to the AFR a very expensive one on Carteks dyno its tuned perfect, idles perfect no surging and shifts at 7200 rpm, with just the dyno tuning, no tuning at the track or street tuning, runs perfect runs cool and uses no oil between oil changes