PaiN

Okay say you are looking at a laying down 500rwhp N/A...what size injectors would you go with...why?

what if you were gonna shoot for say 600-650rwhp on the bottle with the same setup...what injector would you go with, and why?

PaiN

ttt

Colonel

I'd go with Lucas 42.5 lbrs just because I like lots of overkill (never know when you might want to slap on an easy 150 dry shot) BUT, even SVO 30s will work fine at 500 RWHP. Did for me.

I like to figure that each LB is good for a MAX of about 17 RWHP with an automatic. Now this doesn't leave much extra room and WOULD NOT be at only %80 duty cycle....more like %100 (I DON'T recommend running them like this!.) So, SVO 30s (actually 36 lb at our FP) would be good for a MAX of about 610 RWHP. %80 of that would be 485 RWHP. %90 would be about 550 RWHP.

SpeedDemon

I would go with the 42# SVO injectors on this. They might be a little big, but the 42# SVO's behave very well at low RPM and idle so you are not going to run into issues with that. These will also give you the room to grow into 600 RWHP. <img src="images/icons/smile.gif" border="0">
Good Luck,

Pro Stock John

iTrader: (34)

I have GTP (supercharge Grand Prix) injectors.

Supposedly 37lbs at 58psi.

And ARE intank single pump.

Big Mike

iTrader: (4)

If you are running a wet shot of N2O, it doesn't matter what size injector you have because the fuel is supplied by the fuel nozzle in the wet kit. It's N/A rwhp that would demand the larger injector. What size you say, I don't know, but I'm interested in finding out to.

PaiN

well going by the formula on RC engineerings website

1) guestimating that 500rwhp is equivilant to about 600hp
2) BSFC is .50
3) 8 injectors (duh)
4) duty cycle of .80 (80%)

you come up with a injector size of approx 46.875 #/hr for those criteria.


I currently have some SVO dark blue top injectors which I've been told are 36#/hr; which in our fuel system with its higher pressure equates to approximately 42#/hr

Larry

Godspeed

Yes the SVO 36# injectors would be a good choice for 500RWHP. As mentioned, spraying it to the 600-650RWHP mark would require fuel pump upgrades. I would look at ARE's dual Walbro in-tank setup.

-Jeremy

pedaltothemetal

[quote]Originally posted by Pro Stock John:
<strong>I have GTP (supercharge Grand Prix) injectors.

Supposedly 37lbs at 58psi.

And ARE intank single pump.</strong><hr></blockquote>

Hi John,
Are those the white injectors? I have a set of those too.

Hi PAin,
I do remember this formula from my days at the FI forum waiting for my TT's, now sold.
(X * 8) / .47 = FWHP
X is the rate of the injector times 8 cylinders divided 47 BSFC to give the FWHP at 100% duty cycle. You want 80% duty cycle cause your injectors could burn up at 100% duty cycle. So you should get them 20% larger than the formula reads. This is all flywheel and you have to deduct 12% driveline loss to get the RWHP figures.
Use this formula RWHP * 1.12 = FWHP. If you know one you can get the other.
On a side note please note our LS1 injectors are flow rated at 58psi, and the industry standard is 42psi. So standard injectors will flow more in our cars. So multiply the injector size you are using times 1.38 to get the correct flow for our engines.

Leo

[ November 27, 2001: Message edited by: pedaltothemetal ]</p>

383LQ4SS

iTrader: (33)

I have SVO 42 lbders and Walbro intank that sees around 60 psi. 140 dry shot. Nice and fat on the dyno! See sig. <img src="images/icons/cool.gif" border="0">

383LQ4SS

iTrader: (33)

BTW guys...using the above formulas..whats the max I can go through these injectors? Math is not my Forte'

Godspeed

I had a Walbro intank, SVO 42's, and a boost referenced fuel regulator (60psi) that supported over 600RWHP with 12.20 AF's on the dyno and pump 93 octane gas.

SVO 42's = 49#'s at 58psi.
With a BSFC of 0.50 and 80% injector cycle they can support 620 flywheel horsepower or 575RWHP manual dynojet.

So running past 575RWHP with SVO 42's at 58 psi is running past 80% injector duty cycle. 100% injector duty cycle would be 775 flywheel horsepower or 730RWHP manual dynojet.

-Jeremy

y2khawk

iTrader: (5)

[quote]Originally posted by Pro Stock John:
<strong>I have GTP (supercharge Grand Prix) injectors.

Supposedly 37lbs at 58psi.

And ARE intank single pump.</strong><hr></blockquote>

actually closer to 40 at 58 psi, they are 37 lb at 3.5 BAR. Why they rated them there i'll never know <img src="images/icons/smile.gif" border="0">

Nine Ball

iTrader: (38)

Excellent thread guys! I've never done any research on my fuel system. What are the current stock injectors values? If I am not mistaken, they are:

1998 = 28 lb
1999-2000 = 26 lb
2001-2001 = 28 lb

I currently have '01 injectors in my car. By looking at these formulas and doing calculations, I should have a minimum of 33.4 lb injectors. But, that is for the current power. If I am realistically looking for 460 rwhp, I need some 36 lb injectors.

NOW, the question is, will larger injectors improve my performance at the drag strip, or just make my injectors work easier? If there is no gains to be found, then why bother? FYI, I pulled over 500 rwhp with a completely stock fuel system (98 injectors) on a dry nitrous shot in the past:



So, how come I could make so much power on stock injectors on nitrous? If I could make that power back then, then why can't my stock injectors handle "only" 450-460 rwhp on motor now?

Tony

Colonel

"So multiply the injector size you are using times 1.38 to get the correct flow for our engines."

58/42=1.38

It doesn't work like that. Like Godspeed said, the 42 lb injectors would flow about 49 lbs at 58 psi, not 58 lbs. 1.167 x 42 = 49

Also, I was told that Ford rates their injectors at 44.5 psi.

383LQ4SS

iTrader: (33)

So what about the 80% duty cycle mark. Is that just a standard reference, or a mark that should not be surpassed. If it can what would be considered safe? 90%...95%? I know on my stock setup it was a 99 fuel system pushing close to 500 rwhp and was probably 100%.

PaiN

[quote]Originally posted by 383LQ4SS:
<strong>So what about the 80% duty cycle mark. Is that just a standard reference, or a mark that should not be surpassed. If it can what would be considered safe? 90%...95%? I know on my stock setup it was a 99 fuel system pushing close to 500 rwhp and was probably 100%.</strong><hr></blockquote>

On the tech note's on RC's website ( see link in my original post ) they say the that most injectors actually max out at a 80% duty cycle. Thats where I got the number from.

Godspeed

[quote]So, how come I could make so much power on stock injectors on nitrous? If I could make that power back then, then why can't my stock injectors handle "only" 450-460 rwhp on motor now?<hr></blockquote>

The stock GM fuel pieces are all that is needed to get the job done in stock trim and be safe. A stock manual LS1 is rated at 345HP (300RWHP.) Using a BSFC of 0.50, and 80% injector duty, your 28# injectors will support ~360HP (315RWHP)flywheel. These are safe duty cycle numbers that you could sustain WOT with a little room to spare - that's why GM dropped down to 26# injectors.

Running these 28# injectors at 100% duty cycle will support ~450 (405RWHP.) The injectors will be maxed out, but they will still be delivering the fuel. Running injectors at the 100% duty is running "on the edge." Once you pass the 450HP mark with the injectors you will be running lean and the motor will detonate. As mentioned before you can surpass this mark on a dynojet (with lower loads) and for very short periods of time on the drag strip. For these brief periods of time you are running very lean as a wideband o2 would indicate. If you were to stay WOT in 5th gear and continue to make that power level your motor will break. You will start to detect audible detonation, notice the coolant temperature rising, and then enjoy the sound of a piston/rod shattering. <img src="images/icons/smile.gif" border="0">

For your 460RWHP NA goal the minimum injectors I would consider running are the SVO 30# (which are 36# at LS1 58psi.) Since I know you primarily drag race and won't run any Silver State Challenges they will support ~575HP (530RWHP) at 100% duty cycle and ~460HP (415RWHP) with 80% duty cycle. This would keep you running happily at 460RWHP NA without quite maxing out the injectors and give you room to spray another small 50-60 shot at 100% injector duty cycle. You will me maxing out the injectors at that point, but at least won't be running lean.

Of course the next issue to start worrying about is running out of fuel pump, which you do before those SVO 30#'s injectors are maxed out. I can't find the all my data from last year when I did the calculations, but if I recall the 1998 style pump is 114lph and maxes out close to 500RWHP and the 1999 style 112lph and will support 475RWHP. Again in short bursts on the dyno the fuel pump can keep up a little longer because of fuel in the line, but sustained at WOT it will fall behind. The minimum upgrade I would consider is a single Walbro 340 intank pump, but preferably I would do a dual intank setup such as in this pic:

http://www.frontiernet.net/~cendres/...fuel_pumps.jpg

-Jeremy

Godspeed

Also it was not mentioned but when you were spraying did you do it on pump 93/94 octane gas or were you running any higher octane 100+ race gas?

Obviously with higher octane gas your engine can make more power and keep safe AFR's with those smaller injectors.

ChrisB

[quote]On a side note please note our LS1 injectors are flow rated at 58psi, and the industry standard is 42psi. So standard injectors will flow more in our cars. So multiply the injector size you are using times 1.38 to get the correct flow for our engines.<hr></blockquote>

Since we are talking about an essenstially incompressible fluid, the flow rate at a different pressure drop will be proprotional to the square of the pressure ratios -

e.g.

Effective size = rated size *sqrt (actual pressure / rated pressure).

or in your example, the square root of 1.38

also as a point ford injectors tend to be rated at 39/39.5 psi (depending on who you talk to).


Pain: I would suggest either the 36's or 42's (in the SVO series). Since you already have the 36's I would stay with them - but if you were buying new injectors my suggestion would be 42's.

Chris

[ November 27, 2001: Message edited by: ChrisB ]</p>