ZL1Killa

iTrader: (17)

Did I say something wrong? Where did you get that I stated you would not change injector size for a forced induction car versus a naturally aspirated car? We are all talking about the OPs car, which is NA.


You stated that "A fast NA engine is a different deal". I don't understand this, are you on my *** because I have a forced induction car and I'm making injector recommendations for an NA car?

You stated that if you have a blown or turbo engine they are close ? what is close, injector calcs? and you are stating a fast NA engine is different? So are you saying injector calculations for a "Fast" NA car are different? I don't think so...I'll say it again:
your IDC and my calculation of your IDC and of the OPs IDC all show a duty cycle of >80% so why the hell are we arguing?

You misinterpreted what I was saying when it comes to calculating injector size per application. your BSFC changes per NA, turbo, or supercharged

ZL1Killa

iTrader: (17)

Notice if you put in 8 cylinders, 58psi (rail pressure), naturally aspirated, 600HP CRANK, 80% DC, it comes up with a 41# injector. Well you are at that due to you running those 36# @43.5psi rated injectors AT a FUEL RAIL pressure of 58psi; which gives you a 41.5# injector (previously mentioned in your posts)

this agrees with what Ed has found by real world experience & you and I have calculated within a few percent. You are on the high limit.

If you notice at http://rceng.com/technical.aspx *SCROLL all the way down.
They tell you "X" injector rated at 43.5psi; well the thing is you are running at 58psi; so on that website, with that calculator, it states a 40.59 @ 43.5psi. This can be very misleading as the point is, you need an injector that flows 40.59# at your fuel pressure.

Have you looked at or read the fuel & injector sticky on the fuel and injector sub-forum? Fuel Sticky

Ed Wright

iTrader: (1)

Hey kid, put down the crack pipe.

Rick Speed

iTrader: (55)

If you decide to put an aftermarket regulator on give me a call and I'll show you how to do it. It does appear that based on that calculator finding you have what you need to get the job done.

S10LSa

Zl1killaaa, Suggest maybe letting the adults talk. You may learn a thing or two. Yes a na engine is a bit different than a FI engine in its fuel requirements. Stop with the injector calculator stuff as the end all. Especially when you are not using it correctly. HMMM how bout the BSFC ?

BlackDuk98

iTrader: (34)

I am still here, still researching and trying to take all of this info in. No descisions yet, want to learn every option.

I was looking at the BSFC equation that 03EBZ06 posted and when you plug in your hp number, is that rwhp or at the crank? I apologize for all the dumb questions, slow learner here.

-I actually sent you an e-mail Rick, before I saw that you posted here.

thanks

-mark jr.

LT1RAY

iTrader: (21)

It's crankshaft hp.

42lb/hr injectors x 8 injectors = 336lb/hr
336lb/hr / .50bsfc (N/A gas) = 672 crankshaft hp

BlackDuk98

iTrader: (34)

Thank you. That clears that up for me and is right in line with the duty cycle being on the high end.

jp260z

iTrader: (5)

News Flash1) Running injectors beyond 80% duty cycle will not cause the world to stop turning or contribute to global warming. (2) In many cases it's better to run closer to the high end as opposed to low to avoid loss of precision fuel metering on the low end. (3) When you put out the call for input from a "Tuner God" (if there is such a being) pay attention to the credentials of the responder!!! If a Heavyweight such as Ed Wright says you are OK with 36# injectors then you are done researching. He has been building, racing and tuning longer than most if not all of the smarty pants, snot-nosed responders have been alive!

ZL1Killa

iTrader: (17)

no **** an NA engine is different in fuel requirements, we are ALL saying that. yall are killing me. I'm not saying its the end all but it is funny how Eds ~80% duty cycle and the calculations & what I'm saying state the same damn thing.

BlackDuk, yes the calculation is based on crank HP, but also be careful, as some websites/calculators have the option or only calculate based on rear wheel.

Ed Wright

iTrader: (1)

Only on the internet do dumb asses tell you 80% duty cycle is high.

Out in the real world, where most knowelagble racers run fast with 80% to 90% duty cycles.

Russ K

iTrader: (1)

Here is another stock 6L 2007 Silverado scan. 83% IDC @ 5500 RPM, and this is at ~2000 ft elv. Also on a stock 2004 Silverado SS, the IDC hit 84% @5500 RPM.

As said before, there is nothing wrong with >80% IDC.

Russ Kemp

03EBZ06

Yeah, gotta agree. I have seen people program their engines rich, on accident of course, then claim the IDC is too high. Most people don't know that IDC is directly tied to a good or poor tune or shall we say commanded fuel. If the tune is overly rich or lean, the IDC may = False data.

I have never been one to depend on IDC as I already know the fuel requirements and provide them for the engine, then use the plugs for fine tune and WB for raw data. To each his own.

However, that said, I agree, that it is probably better to lay that injector on the line, and I mean way out there. It doesn't take a rocket scientist to see when the engine starts to go lean. That said, you tell some noob on the net that and they will go exercise that option and then come back and complain of melt down.

This is not directed at you Ed, but there are varied levels of experience on this board. I think we should all learn to respect others opinions. I started tuning in 1972 on my dirt bike, then first car in 1975, so I've seen a few cars in my time. Even so, there are always interesting things to read, from both new and old. We are all car enthusiasts. There is no credential test on this site that endows some to spew data and others not. I think most of the post were meant to help the OP.

Now, where are all you experts and noobs racing at? edit: I meant RACERS.

I'll be at Top Gun Raceway, Fallon, NV on 3/29/14 testing a new cam and probably Sacramento Raceway (my home track) weeks before.

ZL1Killa

iTrader: (17)

Very well said. and this is my PM that I sent to him regarding where the OP is at: Sorry if I came off as the worlds going to end if he hits high duty cycles.

soundengineer

iTrader: (16)

theres nothing wrong with running 80% or more IDC...
but there are benefits to having a bigger injector and running less...

gotta remember where that fuel is spraying...
the less time the injector is open, the better atomization you are going to get
less time to hit other solid objects and collect into a puddle

end of injection timing is something that is important...
stock, most of our cars shoot for an ideal place for emissions reasons...on a stock unmodified setup.

once you start modding, all that goes out the window because their choice of EOIT was carefully planned for the exact stock setup...
Ideal EOIT changes if you change anything.

so if you can find the EOIT that makes the most power...and not spray too early to let the fuel puddle up, then you can get better fuel atomizing and a more complete burn...

the only way to get that, is with bigger injectors that spend less time open..
smaller injectors open 80% of the time will spray some of the fuel on the back of the valve....and leave it not atomized....leading to a less efficient burn and making a little less power.

Ed Wright

iTrader: (1)

Those statements about shorter duty cycles making less power is exactly backwards to what most engine builder and EFI racers have found. Longer duty cycles have proven over and over to make slightly more power, and make the car more consistent on the track. Many of the fastest Stock eliminator racers run their injectors right at 100% duty cycle. It's not like those of us with 30K to 50K in our engines can't afford larger injectors. Smaller injectors have shown to atomize the fuel better than larger injectors, which results in a more complete burn. Many of us have tested that over and over.

You are absolutely correct about timing the end of injector pulses. For sure you do not want it after BDC.

I agree with most of your posts, but too many of us have found the above statements about duty cycle to not agree with the extensive testing we have done. Many of us have spent a lot of time and money on engine dyno time, and race track rental for on track testing, chasing down all the small things we can come up with. This has been tested many times. I don't know of anybody, at least with an LS or LT, or TPI engine to find differently. Might sound good in therory, but has not proved to be the case.

soundengineer

iTrader: (16)

made more power on my car going from a smaller injector to a larger injector...


perhaps my smaller injectors were just not as good at atomizing as my larger injectors were...
I dont know... I just know it made more power when I changed injectors
we went from a known injector offset table, to tuning on a new injector to find a new injector offset table for it. changed injectors while on the dyno.
we knew VE was correct already with known good data...
spent a while working on new injector data...
ended up making a bit more power with the new larger injector

Ed Wright

iTrader: (1)

I've never seen that, but old as I am I have not seen everything yet. :-)

soundengineer

iTrader: (16)

I did go from something reasonably cheap to a much better injector all together...
so nothing is impossible...

jp260z

iTrader: (5)

Wow, I've become completely enthralled with how this thread has played out.Seems that the OP had 36# injectors and a matching tune and no cash for larger injectors and a retune. I think that issue was completely and quickly resolved. Now the thread has evolved into "splitting and already split hair". In short I suspect that the last two posters are both correct, given their own circumstances. IE different cars, engines, fuel, weather and so on.( just too many different variables so adequately measure the double split hair) I think you guys have "checkmated" each other. In conclusion I would like to do what the OP should have done, THANK YOU both for taking the time and effort to share what is very obviously very good input to this thread and forum for the benefit of us less experienced users!!!