I read alot of post with people using all kinds of injectors. Delphi,Bosch,Lucas,Siemens,Motrons what are the better brands out there that won't lock up under the high fuel pressure? I am looking to build a forged 355 with 12# of intercooled boost and looking to stay high Z injected. Will 42# cut it? Some say yes and some say no. Also what about the Motrons 60# any one like those? How is there idle and streetablity? Really looking for some answers here!..Thanks, John.

 

I think depending on the camshaft and headwork FMS 42's will do it.

 

Thanks for the reply! I am having the stock heads done, with a 218/230-114 cam. What will the duty cycles be on that setup and what rail pressure should I run?Thanks again...John.

 

Since my company has an injector flow bench I've been able to check out of lot of different brands and sizes. Here's a thread that explains why I don't like the big (bigger than 42 lb/hr) high impedance injectors:
http://web.camaross.com/forums/showt...0&page=2&pp=15

42s won't take you very far up the hp ladder. I tried to get MSD 50s and an FMU to work with my s-trim 351 (best run was 10.74 at 135.6), but it was a nightmare to tune, and I was logging commanded pulsewidths with over 100% duty cycle. I had the static fuel pressure up in the 50 psi naighborhood, and the injectors would sometimes lock up. That's when I decided to build the first VersaFueler and switch to low impedance injectors. I ran Delphi 75s with the s-trim and switched to Delphi 95s for the ys-trim.

I've flowed Delphis, Siemens, and the 160 lb/hr Boschs. The Delphis have more of a fan pattern while the Siemens have a narrower pattern. The big Bosches are like a fire hose! The Siemens are more consistent, meaning that a batch of injectors will be well flow-matched from the factory. I have to sort the Delphis to get sets of 8 to be matched within 1%. But I've run the big Delphis on the street for years now with zero problems. The car idles at 900 in gear, has crisp throttle response, and the plugs always come out clean and tan.

The only PCM adjustment I had to make for the Delphi 75s was to set the injector constant to 75. I used the stock 'injector offset vs voltage' table. No need to mess with that table the way you do with high impedance injectors!

I know it's easy to think that I'm just trying to make a buck, but the simple truth is that your car will run better, both in town and at the track, with properly sized low impedance injectors than it will with high impedance injectors with an FMU, or just high fuel pressure. Everybody that has gotten back to me is happy with their VersaFueler.

 

I've had the 42's on my car for quite some time. They have been excellent, very streetable. They will support 600+ horsepower. I ran them with 12 psi procharger and now with the vortech blower. You can get a set of them for around $300 a set. A few years ago they were $400, so the price has gone down. I would try these first and go from there. From what I've heard, Bosch makes the best injectors

 

For 42s to support 600 crank hp, assuming 90% duty cycle, 12 psi boost, and a reasonable BSFC of 0.55, your fuel pressure must be in the upper 60s in the rail. You could get to 650 with a rail pressure of 75 psi, but IMHO that's pushing your luck. I like having a safety margin.

 

I have ran a few sets of siemans over the past 3 years with no problems at all. A have heard a few horror stories about msd injecters and FI apps. The only problem is sieman only goes up to 83#'s before 160.

 

Sorry, don't have the answer to good large high-Z injectors. Don't recommend them though.

If you want to do it right and buy injectors once only, I would recommend doing the low impedance injectors, somewhere around 72#/hr, and the impedance box. This will allow you to safely and easily run 400-700rwhp.

I have been running the seimens 72 #/hr with the www.acceleronics.com box using stock fuel lines, stock fuel rails, and one in-tank 340M fuel pump for two years. This also worked great when I pull the supercharger belt and run with just all motor. The car drives through Bay Area commute and once had a cop followed me for a mile coming home without any problem.

cheers

 

Hey LJ, any comment on Lucas injectors?

 

LJ your advice is always welcome and is never taken as advertisement.

 

No, I've never tested Lucas injectors.

 

Thanks guys on all the insite. I will have to do alittle shopping around to see what is out there. I still have afew months before the car comes out anyways. Thanks again....John

 

I'm running Siemens 72s on my car. When I had them tested, they were all very close to each other as far as spray pattern and flow.

Not sure if anyone answered your question completely, but I use this to figure all my fuel calcs.

Duty cycle between 80-90%
Rail pressure for LT1 cars is about 42#. Most injectors are rated @ 43.5 so it works out great. LS1s have a higher F.P. too...keep that in mind.
BSFC #s:
N/A-0.40-0.45
S/C-0.50-0.55
Turbo-0.60-0.65
You can get a rough idea on hp supported w/ this formula:
(Injector size X Duty cycle) X (Number of injectors X BSFC)= Approx. HP supported.

To figure how much an injector changes by going w/ higher rail pressure...
(new fuel pressure/old fuel pressure)sqrt)*injector rating= new injector rating

I've got all the approx. HP #s wrote down based on a .80 duty cycle and a .65 BSFC, but it's @ the shop.