Picking injector flow

Many of you know I'm building an LS chevy engine. 6.0L block, CNC ported heads, 234/240 cam.

Dyno simulation software (with which I consider myself to be very experienced) shows 510 hp. I wouldn't be surprised if it makes a little more, but no more than 550 I'm sure. If I calculate 525 hp, it spits out 41.01 lb/hr injectors. 42 lb/hr is a common size, but so is 39, 45, and 50.

I know that oversizing injectors can lead to idle fuel control issues (short pulsewidth reasons), and I know I can compensate a little for undersized injectors with more fuel pressure, but what is the "right" way? Or am I being too picky and I should just get some 42s and shut up?

Right way - I halve expected horsepower to get rough fuel requirements in pounds per hour, divide by .8 to get a safety factor, divide by number of injectors, and then choose the common size injector around that size erring towards larger.

So 550hp = 275lb/hr fuel or 43lb-hr with a 80% duty cycle at peak power.

Mind you, injectors are rated at 42.5psi. If you are running 58psi base pressure, then the 42lb injectors will make more sense.

I have a set of "60lb/hr" injectors at 58psi in a red/blue computer 6.0 and it idles just fine. Well, it idles fine considering the cam that is in it IIRC the correction factor for pressure means they flow 68-69lb/hr actual.

"Oversizing" to 42lb won't give you any measurable difference in idle challenges over 41lb injectors.

With modern injectors, this isn't a problem anyways. If you want 210lb injectors to idle like stock, you can have it.

http://www.rceng.com/technical.aspx

I'd go with 42 to 50 lb/hr myself. The warning about oversized injectors generally applies to something ridiculously huge, like running this motor on 95 lb/hr units.

Ok, good to know. I didn't know how far I had to go before being "oversized." I think I'll go with 50 or so in case I decide to swap a cam later.

And... where does one find good prices on injectors these days?

The junkyard. Find an OE app that has injectors about the size you want, if you don't go too large.

That, or maybe Summit.

There really aren't any OE applications for injectors this large.

You have to be careful WHICH engine you are dealing with. There are three different injector sizes that Chevy used on that architecture engine, so which intake manifold/fuel rail you're using will be critical.

Be careful about choosing injectors, low and high impedance, you need compatibility with your electronics.

Yeah, I'm kinda stuck with 2.5" tall injectors with EV1 connectors and high impedance. This is an LS6 intake. I could adapt, fabricate fuel rail brackets to compensate a bit, or find some way of making others work, but so far it doesn't seem like that would offer any specific benefits. (financially or otherwise). Physically, LT1, LS1, LS6 and TPI injectors would fit and connect. There are some Ford injectors that might fit as well, but unsure of high/low impedance.

Technically, the current wiring harness I have has EV6 connectors so I could adapt, but I can't find EV6 injectors taller than 1.9". That would mean some serious fuel rail adapting.

Summit has one offering. Its a name I don't know (DeatschWerks) and its $500/set. http://www.summitracing.com/parts/dwk-18u0100608/overview/make/chevrolet . That link is for the 60 lb/hr set, but its the same basic price from 39 lb up to 60 lb.

I didn't know if maybe there was something like an injectorwholesalewarehouse dot com or something.

DW makes really good fueling stuff. $500 for a set of 8 injectors doesn't sound awful to me.

Delphi 25176061 43.77# high impedance for LS1

There are a few Bosch some Fords, I quit looking at this point.

bentwrench wrote: Delphi 25176061 43.77# high impedance for LS1

Again, good idea, but 5/8" too short. Adaptation is a maybe. I can't use brackets to drop the fuel rails that far because it would hit the runners, and I'm not a big fan of extension tubes. I've never had them that they didn't leak eventually.

Swank Force One wrote: DW makes really good fueling stuff. $500 for a set of 8 injectors doesn't sound awful to me.

Good to know. My idea of a good fueling system is a $25 junkyard Qjet with an $18 rebuild kit and jets/rods that I drill and file until I get them right. :)

The injectors in my miata were $170ish, but the set I actually want is almost $400. That's for 4.

These any good? http://www.southbayfuelinjectors.com/siemen-deka-ev1-60lb-630cc-saturated-fuel-injectors/

Or maybe what of these might you recognize as good ones? http://www.ebay.com/sch/Fuel-Injectors-/33554/i.html?mvsub=1&_mcatda=true&selfil=1%2C2%2C3%2C4%2C5&selvel=2002~Chevrolet~Camaro~Z28%2520SS%2520Coupe%25202-Door~5.7L%2520350Cu.%2520In.%2520V8%2520GAS%2520OHV%2520Naturally%2520Aspirated&_nkw=2002%20Chevrolet%20Camaro%20Z28%20SS%205.7L

There's not much reason to buy EV1s these days. EV6s at least, EV14s are nice.

I'd spring the extra $100 for the DWs over the first link.

Swank Force One wrote: DW makes really good fueling stuff. $500 for a set of 8 injectors doesn't sound awful to me.

Agreed. Have used DeatchWorks injectors with good success. (The injectors I need for my RX-7 are around $250... for two.... urgh)

Spend some time with this chart:

injectors

Start off sorting with for flow similarities (everyone runs different base pressures), then look at impedance, then look at feed (ev1, ev6 etc)(although can be adapted), then I would grab part numbers of injectors you think can be close and look up dimensions to see if they would fit.

If you find something factory, look for used injectors from take offs or junkyards.

I used this chart to swap failure prone (GM) injectors to reliable bosch ones from a ford 4.6. They were almost identical but rated different as the ford ran a higher base pressure, run the bosch at the lower gm pressure and they were the same (useless for you, like 22lb /hr). The reason I mention this is I got the injectors from a crashed ford for $5 a piece at a junkyard, and put new filters/seals for far less than the average $100/injector price.

I didn't dig too deep for newer links, perhaps check out the megasquirt forums for better links on injector references.

I've been running RC injectors for over 10 years now.... no problems

Ls3 injectors are 42 lbs iirc.

Also I think the gt500 used a bigger injector in an EV14 that you can get pretty reasonable and the early mod motor injectors fit ls motors so maybe the later ones do to.

Another vote for using an oem injector

Gt500s are cheap, so if you find they fit or can be made to fit easily/cheaply, probably a good way to go. Under $250 for a set of 8.

In reply to daytonaer: Great chart, thanks.