SRT-4 Common Injector Flow - Math/Info/Chart!

[chuck's_srt-4]

Quote: Originally Posted by ROCKY_7_11

might be a dumb question but why do stage 2 and stage 3 have different flow rates if there are using the same injectors??? i dont think the new fuel rail could have changed the flow.

Bump this.... I also found this strange since we are measuring strictly the injector flow at the given fuel pressure in the table. If both S2 and S3 are using 682cc mopar injectors, how are we coming up with different flow rates?

[funks]

S3 is boost referenced while S2 is not (static).

So as boost goes up on S2, the effective fuel pressure drops while it's maintained on S3 (hence the later has more fuel).

[chuck's_srt-4]

Quote: Originally Posted by funks

S3 is boost referenced while S2 is not (static).

So as boost goes up on S2, the effective fuel pressure drops while it's maintained on S3 (hence the later has more fuel).

I understand how S3 uses a boost referenced regulator to keep the pressure constant, but if you look at the chart on the first page you will notice that the injectors in question were measured with a consnant pressure. This is strictly flow related with 2 given constant fuel pressures. They are 43.5 psi and 58 psi. Or in other words, the only thing in question here is, HOW DO S3 INJECTORS FLOW MORE THAN S2 INJECTORS WITH IDENTICAL FUEL PRESSURES WHEN THEY ARE BOTH 682CC INJECTORS? They are the same injector. And once more, just to make sure you understand the nature of the question, I am not asking how S3 delivers more fuel than S2. That's obvious. I'm asking how S2 & S3 injectors (mind you they are the same injectors) would have a different flow rate when converted to RC Engineering standards. I would prefer that the person who made the chart (SY04SRT4) answer this question since he knows what calculations he based his conclusions off of.

[funks]

I believe chad setup that chart a long time ago when it was speculated that S3R would be getting different injectors - not the same injectors as S2.

[FOFO]

Hey guys great forum! I need help with a part# of SRT4 inectors I have that I don't know if they are 2003 or 2004. The part# 04891574AB and below is 4073W10015. I don't have a SRT4 but I'm using this injectors in my project car which is a 1987 Mitsubishi Mirage 1.6L turbo with lots of engine mods. I made my own Port EFI and I'm using this injectors because they are high resistance and work well with Megasquirt. Right now I'm working on tuning the car but I found out that this injectors work at 58psi and not 43.5 that I'm using, beause it will hurt atomization. Now I have to raise the pressure to 58 and see what happens. The thing is that I don't know what year they are and what flow rate. When I bought them, they told me 440cc. Can you please help?
Thanks...

[DeatschWerks]

Any chance of getting our DeatschWerks injectors added to the charts? PM me with any info needed to update them. Thanks

[hercfe]

Just a FYI for all who don't want to do the math...The PTP FPR 80psi mod+S1 577cc injectors=677.65cc @ 80psi. S2 injectors @80psi are 800.968cc

[TNT]

Do the following numbers/info seem correct?

"RC Engineering uses 760 -770 kg/m^3 as the density of their test fluid.
Mopar uses n-heptane which has a density of 685 kg/m^3."
_________________________________________________

Using the equation from the sticky:
(sqrt(new pressure/old pressure))(old flow rate) = new flow rate

Stage 2 injectors: (using n-Heptane liquid)
@58psi = 682cc/min
@43.5psi = 590cc/min



Are the following conversions correct?

if stage 2 injectors were rated using RC engineering liquid (assuming their liquid is 765 kg/m^3):
@58psi = 762cc/min
@43.5psi = 659cc/min

to get those numbers, use the following (@43.5psi): 590/765 = x/685 and solved for x

I'm just checking my options for fueling a higher flowing turbo set-up.

I already have stage 1 and 2 injectors and want to find a rating system that is equal....

Using different testing fluids seems like comparing apples to oranges.

[tgspeedracer]

is there a rule of thumb for what size injector will suport so much hp?

[chuck's_srt-4]

Quote: Originally Posted by tgspeedracer

is there a rule of thumb for what size injector will suport so much hp?

Yes. There is a formula for it. It is as follows:



Injector Flow Rate (cc/min) =

Engine HP x BSFC x 10.5
Number of Injectors x Injector duty cycle

BSFC (Brake Specific Fuel Consumption) varies depending on the type of induction. Here's a breakdown:

* For naturally aspirated engines, estimate BSFC to be 0.4 to 0.5
* For nitrous engines, estimate BSFC to be 0.5 to 0.6
* For forced induction, estimate BSFC to be 0.6 to 0.7
* For rotary engines, estimate BSFC to be 0.6 to 0.7
* For engines running methanol, double the appropriate gasoline BSFC (e.g. a forced induction methanol engine has a BSFC between 1.2 and 1.4)


Injector duty cycle should be around 80%, so where the equation asks for duty cycle, use .8 for the value.

example: 400 Hp Turbocharged 4 cylinder

400(HP)*.6(BSFC)*10.5=2520
4(injectors)*.8(duty cycle)=3.2

2520
3.2 =787 cc injectors

(note: The equation bases calculations off of an assumed fuel pressure of 43.5 psi. Different fuel pressures will result in different needs in injector size.)

Now you must remember that all this is theoretic, so it has margin of error. It's absolutely possible to achieve 400 HP+ on 750cc injectors, and has been proven time and time again. In fact, I believe it's been done with 650 cc injectors, but usually requiring higher duty cycle, and higher fuel pressure. So take all this theory with a grain of salt.

[fixit]

I was curious what the injectors would do at different fuel pressure, soooo... Using chuck's_srt-4 HP formula & modifying SY04SRT's xls...
( good link boost injector flow http://autospeed.drive.com.au/cms/A_107986/article.html )
here's the link http://i155.photobucket.com/albums/s...math-fixit.jpg




here is the raw numbers..
Injector cc/min cc/min cc/min cc/min HP (max) HP (max) HP (max) HP (max)
Fuel Pressure (lbs) 43.5 58 80 100 43.5 58 80 100
Mopar Stage 0 456.4 527.0 618.9 692.0 231.8 267.7 314.4 351.5
Mopar Stage 1/ 2004 SRT-4 Stock 499.7 577.0 677.7 757.6 253.8 293.1 344.2 384.8
Mopar Stage 2 590.6 682.0 801.0 895.5 300.0 346.4 406.8 454.9
Mopar Stage 3R 590.6 682.0 801.0 895.5 300.0 346.4 406.8 454.9
RC Engineering 550 550.0 635.1 745.9 833.9 279.4 322.6 378.9 423.6
RC Engineering 650 650.0 750.6 881.5 985.5 330.2 381.2 447.7 500.6
RC Engineering 750 750.0 866.0 1017.1 1137.1 381.0 439.9 516.6 577.6
RC Engineering 850 850.0 981.5 1152.7 1288.8 431.7 498.5 585.5 654.6

[TNT]

Quote: Originally Posted by fixit

I was curious what the injectors would do at different fuel pressure, soooo... Using chuck's_srt-4 HP formula & modifying SY04SRT's xls...
( good link boost injector flow http://autospeed.drive.com.au/cms/A_107986/article.html )
here's the link http://i155.photobucket.com/albums/s...math-fixit.jpg




here is the raw numbers..
Injector cc/min cc/min cc/min cc/min HP (max) HP (max) HP (max) HP (max)
Fuel Pressure (lbs) 43.5 58 80 100 43.5 58 80 100
Mopar Stage 0 456.4 527.0 618.9 692.0 231.8 267.7 314.4 351.5
Mopar Stage 1/ 2004 SRT-4 Stock 499.7 577.0 677.7 757.6 253.8 293.1 344.2 384.8
Mopar Stage 2 590.6 682.0 801.0 895.5 300.0 346.4 406.8 454.9
Mopar Stage 3R 590.6 682.0 801.0 895.5 300.0 346.4 406.8 454.9
RC Engineering 550 550.0 635.1 745.9 833.9 279.4 322.6 378.9 423.6
RC Engineering 650 650.0 750.6 881.5 985.5 330.2 381.2 447.7 500.6
RC Engineering 750 750.0 866.0 1017.1 1137.1 381.0 439.9 516.6 577.6
RC Engineering 850 850.0 981.5 1152.7 1288.8 431.7 498.5 585.5 654.6

Too bad the #'s are off... The injectors must be tested with the same fluid or you are comparing apples to oranges... Which you are...

RC Engineering uses 760 -770 kg/m^3 as the density of their test fluid.

Mopar uses n-heptane which has a density of 685 kg/m^3.

Which means if stage 2 injectors were rated using RC engineering fluid thier flow would be quite higher.

Stage 2 Injector flow with RC engineering test fluid.
@58psi = 762cc/min
@43.5psi = 659cc/min

[fixit]

TNT, good catch.. thx!!!
i updated the XLS, here is the new link http://i155.photobucket.com/albums/s...th-fixit-1.jpg

<version 2, has 2 notes -- cut and paste of TNT's comments>

[dodgez]

Making the RC750's flow like stage1 injectors. From what I have figured out is that the rc750's would have to running 25psi to flow 55lbs/hr or 577cc. I don't think the injectors will work right at that low of PSI.

[ImportLabSRT4]

Maybe Im reading this way wrong but... If stage 2 injectors are considered to flow 769cc at 58psi (RC fluid) and RC 750's flow 866ccs at 58psi, then I should start by pulling 11% fuel globaly? Or for that matter if static pressure is 43.5psi ([659/750]-1) then pull 12% of fuel globaly??

~~After looking more closely (once again I may be retarded here), but If I have a stage 2 PCM (stg 2 injectors = 761.6 cc's @58psi) and run my RC 750's at 43psi.... shouldnt I be adding 1.5% of fuel as a baseline?(761.6/750-1= .015xxx)