rodent

iTrader: (1)

Still trying to decide on my injectors. Is 42lb injectors too small for my setup?

ATI D1SC @ 8lbs
MMS stage II heads
MMS blower cam (specs at home)
Walbro 340
stock shortblock
(may go with forged 6.0 block with stock crank, depends on funds)

BIGBOS

I have a stock short block, with stage 2 heads, and a large reverse split cam, I'm going to be running 42lb injectors on my new setup...

parish8

iTrader: (6)

go here http://www.rceng.com/technical.htm

those 42 are closer to 48's at our fuel presure

48's at 90%duty cycle and .6BSFC are good for 576FWHP.

i would go bigger.

rodent

iTrader: (1)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by parish8:
<strong> go here http://www.rceng.com/technical.htm

those 42 are closer to 48's at our fuel presure

48's at 90%duty cycle and .6BSFC are good for 576FWHP.

i would go bigger. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">According to that calculator, maybe I should go with 50's.

650fwhp (550rwhp) *guessing here*
.55 BSFC
80% DC
55psi at rail

49.68 lb/hr injector

1dirtyZ

iTrader: (1)

just go with the 50's , that way WHEN you expand , you won't have to worry about that.

qqwqeqwrqwqtq

Lucas 42's running at 58psi base pressure have supported 634rwhp on my LT1.

MelloYellow

I feel comfortable with the 42# up to 600rwhp. The larger injectors are much harder to tune.

parish8

iTrader: (6)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MelloYellow:
<strong> I feel comfortable with the 42# up to 600rwhp. The larger injectors are much harder to tune. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">with a blower and the higher BSFC? why would you risk it if you haven't even bought the injectors yet?

i am no expert on injectors but so far i have ran the stock 23lb units, then some 41's@58psi, and now some 50's@43.5psi, the truck idles exactly the same and my ltrims were easy to tune in, still very responsive.

MelloYellow

I had 50# Delphi's, but returned them for tuning reasons. More reliable 42# programs out there. I definitely feel comfortable running the motor with 42#'s and that they will be plenty to 575rwhp. My setup will most likely run 550rwhp. I've seen them support up to 639rwhp.

How much injector will a 225lph pump support in any case? Or the fuel rails?

parish8

iTrader: (6)

a single walbro flows around 60gph. multiply that by 6 and you have 360lb/hr or 45lb/hr(actual flow) per injector. so yea if you dont plan on going with any more fuel pump than a single 340, the 42's would more than cover it.

but with a heads and cam blower motor i would sure go with more than a single 340 for fuel the fuel system.

rodent

iTrader: (1)

Thanks guys. Maybe 42's will be enough. Just in case, I might run two Walbro's. It's a pain with the new style pump housings soo I might run an inline Walbro 255lph to help.


</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MIGHTYMOUSE:
<strong> and at least a new pressure line and rails. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">*sigh*.... Something else I'll have to add to the list to get. Does it ever end? Is this the whole line going from the pump to the fuel rails?

chasgiv3

iTrader: (1)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by INTMD8:
<strong> Lucas 42's running at 58psi base pressure have supported 634rwhp on my LT1. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Does Lucas make 42? I thought it was 42.5lb/hr? At least those are the ones currently on my car.

I assume the ATI kit utilizes an FMU as does INTMD8's. What is the MAX pressure the FMU on the ATI kit produce? I guess assuming the full 8PSI that was described above.

Let's assume a max of 68PSI. And 42.5 Lucas injectors. And also assume a 6-speed with 10% losses.
42.5lb/hr Lucas would equal 52.51lb/hr at 68PSI
52.51lb/hr can support (at 90% dutycycle)756FWHP. Assuming a BSFC of .50 of course. This would equate to 680.4RWHP.

I feel comfortable bringing the Lucas injectors into the 90% dutycycle range. Everything I've read tells me that they are stress tested to that level and have no significant failures at that range. Above that I wouldn't want to risk my motor. On an expensive motor I would also have them flowed and matched. Other injectors I would seriously look into the manufacturers claims on failure rate at duty cycle. Typically you do NOT invade the 80% duty cycle for safety reasons.

I've seen INTMD8 tune 50lb/hr injectors on the dyno and the car runs like a top. So I know it can be done.

Anyway my 10cents on the subject...lol

chasgiv3

iTrader: (1)

Here's some interesting reading that I found. It really outlines some interesting testing that was performed.

http://www.supras.com/~riemer/sonict...rs/RCtech.html

OCMike

I have the SVO 42# injectors. With the ATI P1 and a 220 cam, Stage II heads, etc., I have no issues and I am over 600 rwhp. LS1-Edit and a wide-band dyno will give you the answer to your question.

MIGHTYMOUSE

iTrader: (59)

and at least a new pressure line and rails.

parish8

iTrader: (6)

wow! now that is some interesting stuff. wish i would have seen that sooner since i have some of those old style pintle injectors now. acording to that article you difinately never want to go over 85% duty cycle. i always thought you could go higher but it just wasn't good for the injector but thats not the case, once you go ever 85% the fuel delivery rate becomes unstable and may actualy drop before going static(100% open)

here is that part

Most pintle type injectors fail at 86%/88% and the Disc will usually go to 92% +, depending on system pressure. All must cycle smoothly up to 85% to Pass. Bad injectors will sometimes go "static" at 70% or so and are discarded. NOTE: Most pintle injectors will increase flow rates up to 88%, 92% with Disc injectors, and then go "semi-static", half open-half closed, just before going full static. This time-out event occurs at different time/pulse width durations, in different injectors, but always produces a 50% or so Duty Cycle flow rate. This extremely dangerous situation will usually occur at the worst of times, full throttle-max boost-high RPM- just when you need 100% fuel delivery you get 50% and go dead lean. BANG!!! This problem seems to amplify a bit at higher pressures.

qqwqeqwrqwqtq

Actually yes, they are 42.5's. And my car doesn't have an FMU.

chasgiv3

iTrader: (1)

INTMD8, do you have a boost referenced fuel pressure regulator?

The Lucas 42.5lb/hr injectors using a 58PSI fuel pressure can suppport a maximum of 785FWHP. That's the calculated absolute maximum that the injectors can support. That's 100% duty cycle, .50BSFC to bring you the absolute number.

Recommended calculation would be 42.5's can support 571FWHP. That's with .55BSFC and 80%duty cycle.

Now with the Lucas we know we can invade the 90% range. With that being known. We can pretty safely support 643FWHP with a .55 BSFC.

Now I argue that both the LT1 and LS1 engines seem to be pretty efficient. I would argue that we should use the .50BSFC rating even in a forced unduction application. This allows the 43.5lb Lucas injectors to support 707FWHP with a safety margin since the Lucas injectors can support 90% duty cycle with no significant failures.

Perhaps the formulas need to be updated but this is the current calculations used by most injector places for sizing.

Formulation'98

Don't froget those 55#@42.5psi they are ready to go, much easier to tune at higher fuel pressure than 50# MSD's and will be enough for sure. The price is right too about $475 a set, let me know if you need a set Thanks Dave indacalinc@attbi.com

SStolen

iTrader: (22)

Whats Harlen running??