WRONG INFO!!Injector Flow - Math/Info/Chart! - SRT Forums

duster360 · 11-05-2007, 05:34 PM

I went through the math in the Injector Sticky Speadsheet that equates the Mopar injectors to Aftermarket RC injectors and its WAY OFF!! Imo for a true comparison you need to equate the Mopar injectors so that the common CC/min to lb/hr conversion factor works as it does with the aftermarket injectors.

To get all the #s to out right and line up with the conversion factor, the actual density of the "RC test fluid" needs to be around 723Kg/m^3 not 760-770 as was reported. Now RC and others might use a bit heavier fluid to do in house flow test with, but if you take the mass flow rates listed by Bosch, Delphi, Siemens and Mopar, (which all btw use Heptane), and apply a new density to equal the common 10.5 conversion factor here is what you get:

"RC equivalent" cc/min 58psi
S0: 526
S1: 579
S2/3: 684
550: 637
650: 753
750: 868
850: 984

Here's how I came up with it.
Mopar using N-Heptane 685Kg/m^3
S0=527cc/min * 60min/hr * (1m/100cm)^3 * 685kg/m^3 *2.2lb/kg = 47.4lb/hr--Equates to Sticky's results
S1=577cc/min * 60min/hr * (1m/100cm)^3 * 685kg/m^3 *2.2lb/kg = 52.2lb/hr--Equates to Sticky's results
S2= 682cc/min * 60min/hr * (1m/100cm)^3 * 685kg/m^3 *2.2lb/kg = 61.7lb/hr
RC but with a different "fluid"
751cc/min(650cc@58psi) * 60min/hr * (1m/100cm)^3 * 723kg/m^3 *2.2lb/kg = 71.7lb

To make sure I had the equation right I divided 751cc/min by 10.5 to hopefully get a mass flow in lb/hr,,, and I got 71.5lb/hr Looks good

So now I recalced the Mopar S2 but swapped in the 723kg/m^3
682cc/min * 60min/hr * (1m/100cm)^3 * 723kg/m^3 *2.2lb/kg = 65.1lb/hr
This lb/hr mass flow divided by the same 10.5 aftermarket conversion gets you 684cc/min and NOT the 761cc/min as listed in the sticky! Quite a bit of difference

Turbocruiser13 · 11-05-2007, 07:25 PM

So now let me re ask my controversial question...what's bigger S2s or 650s?

Edit: NM, just saw you posted your change in the below thread. I knew I wasn't crazy...I go by real life numbers and as a last resort I look at paperwork

lyncoo · 11-05-2007, 07:31 PM

650s..

Turbocruiser13 · 11-05-2007, 08:26 PM

Quote: Originally Posted by lyncoo

650s..

See sig...that's what I got

me and duster were going back and forth over this in a couple different posts I thought 650s were bigger he thought S2s were bigger so it's good to see that controversy come to an end

Gmanigio · 11-05-2007, 08:59 PM

hahaha, i never got into that fight...just stated my opinion about the 650's.

Duster went off on a few threads i believe about that....

whatever......

I knew 650's were bigger, it took some math for him to get it right

DRASTIC. · 11-05-2007, 09:36 PM

Quote: Originally Posted by Gmanigio

hahaha, i never got into that fight...just stated my opinion about the 650's.

Duster went off on a few threads i believe about that....

whatever......

I knew 650's were bigger, it took some math for him to get it right

for a bright guy, how could duster not know the 650s were larger (regardless by "mopar fluid standards or not", its still by a good measure)?

duster360 · 11-05-2007, 10:33 PM

Hey cut me some slack. The info looked good. It suposedly came from a Chrysler engineer. I took the 760-770Kg/m^3 in good faith that it was correct.

Quote: Originally Posted by ???

I called RC and it sounds like they use 760 -770 kg/m^3 as the density of their test fluid. We use n-heptane which has a density of 685 kg/m^3. An injector's mass flow is dependent on the density of the fuel. If two different fuels are flowed through the same injector, the volumetric flow rate of each fuel should be the same. This said, both sets of numbers for the injectors that you have are wrong. The correct numbers are as follows:

For n-Heptane @ 58 psi,
2003 Injectors - 359.4 g/min = 47.4 lb/hr = 524.7 cc/min
2004 Injectors - 395.3 g/min = 52.2 lb/hr = 577.1 cc/min

RC Engineering and most aftermarket injector companies flow their injectors at 43 psi. Using Bernoulli's equation, the mass flow can be corrected to:

For n-Heptane @ 43 psi,
2003 Injectors - 309.5 g/min = 40.8 lb/hr = 451.8 cc/min
2004 Injectors - 340.4 g/min = 44.9 lb/hr = 496.9 cc/min

If RC Engineering flowed our injectors with their test fluid @ 43 psi, they would rate the injectors as follows:

2003 Injectors - 343.3 g/min = 45.3 lb/hr = 498.3 cc/min
2004 Injectors - 377.6 g/min = 49.8 lb/hr = 547.8 cc/min

Basically injectors are volumetric flow devices, so a more dense fuel will flow more mass flow than a less dense fuel at the same volumetric flow rate. This is a very confusing subject. As you can see, it is very easy for a company to skew their flow ratings in their favor. There will always be some error in ratings until all injectors in question are flowed on the same test bench with the same test fluid at the same test pressure.

I doubt any of you chuckle heads even know what the hell this guy is talking about, let alone be able to figure out its not right

It took me a couple hours of research and running to numbers to find out something didn't add up. It all hinges on what the ACTUAL density of RC's test fluid really is. I couldn't find any direct info on their site but found plenty of references to using 10.5 as the conversion factor. Since this conversion factor is use to go from a mass flow rate to a volumetric flow rate, it HAS to contain the proper density. I used this important fact to solved backwords to find the exact #.

Turbocruiser13 · 11-06-2007, 12:51 AM

Didn't need to know what the hell that guy was talking about. Common sense told me that 650cc @ 43psi was bigger than 682cc @ 58psi if they were both set to the same pressure

duster360 · 11-06-2007, 08:19 AM

Quote: Originally Posted by Turbocruiser13

Common sense told me that 650cc @ 43psi was bigger than 682cc @ 58psi if they were both set to the same pressure

Actually its more of an "Ignorance is bliss" sort of deal.

By not knowing the difference between mass flow rate and volumetric flow rate, it was out of pure luck, shear coincidence, that your guess,,,oh I mean "common sense", was closer to the correct answer.

If I were you, I'd hit the books or hope your luck doesn't run out ooorrrrr,,,,you could, like you have in the past, always just pm good ol' duster360 to help you figure out the hard stuff. I'm always willing to help you "common sense" guys out.

Turbocruiser13 · 11-06-2007, 04:14 PM

Quote: Originally Posted by duster360

Quote: Originally Posted by Turbocruiser13

Common sense told me that 650cc @ 43psi was bigger than 682cc @ 58psi if they were both set to the same pressure

Actually its more of an "Ignorance is bliss" sort of deal.

By not knowing the difference between mass flow rate and volumetric flow rate, it was out of pure luck, shear coincidence, that your guess,,,oh I mean "common sense", was closer to the correct answer.

If I were you, I'd hit the books or hope your luck doesn't run out ooorrrrr,,,,you could, like you have in the past, always just pm good ol' duster360 to help you figure out the hard stuff. I'm always willing to help you "common sense" guys out.

Eh...call it what you want, my luck er...common sense hasn't failed me in the past lol. You know I'd hit you up if I needed somethin man