NOS / liquid propane jetting

[treynor]

All,
I'm doing my final calculations before tomorrow's wet/wet run of the BTR Viper NOS/Propane system. I have a few assumptions I'm making, and would appreciate the benefit of any fluid dynamics experts out there. To date, I've been running NOS (liquid) and Propane (gaseous), and have a nice safe 12.0:1 A/F using a #40 NOS jet @ 900PSI and a #46 PRO jet @ 160PSI. I'm switching to a Liquid NOS / Liquid Propane setup, which will avoid the pressure drop and flow limits I've encountered using large jets with a gas propane system. So...

From what I can determine, flow rate through a jet & fogger nozzle setup varies with the square of the jet size and the square root of the pressure. What I don't know is how the flow rate (lb/min) will change when I switch from a pressurized gas to a pressurized liquid.

Assumptions:
Liquid propane contains ~91,700 BTUs / gal
Liquid gasoline contains ~115,000 BTUs / gal
Liquid propane and liquid gasoline flow the same volume at the same pressure.

Calculations:
NOS specifies a #44 liquid gasoline jet @ 5-6PSI to work with a #40 liquid NOS jet at 900-950 PSI. This combination should produce 50 HP.

Going from 6 PSI to 150 PSI implies a (sqrt(150) / sqrt(6)) = 5.0-fold increase in flow. Adjusting for the lower energy content per volume of propane, this means a 4.0-fold increase in BTU/s. Thus, the jet size should shrink by a factor of sqrt (4), or 2, so the correct jet size would be #22

Stepping up to a #46 NOS nozzle would increase HP by a factor of 1.32, and would require a 25.3 Propane jet (22 * sqrt(1.32))

A #52 NOS nozzle (the largest supplied) would increase HP by a factor of 1.69 (to 170HP for the pair!), and would require a #28.6 Propane jet.

(note -- I have edited this post from an earlier version in which I was comparing energy content *per pound* vs energy content *per gallon*. Flow rates deal with volume, not mass...)

Does this math make sense? Can anyone out there correct / improve these calculations?

 

[treynor]

As a followup to today's successful test, I have developed a spreadsheet to calculate jetting based on various NOS jet sizes and NOS & Propane pressures. Here's a set to get all you other liquid propane types started; feel free to email me if you want the excel sheet so you can "roll your own"

Assume NOS at 900PSI, Propane at 160 PSI

#42 NOS + #24 NOS = 120 HP
#46 NOS + #26 PRO = 150 HP
#52 NOS + #30 PRO = 190 HP
#56 NOS + #32 PRO = 220 HP
#60 NOS + #34 PRO = 250 HP
#64 NOS + #36 PRO = 290 HP
#68 NOS + #38 PRO = 330 HP
#72 NOS + #40 PRO = 365 HP (you animal!)

Also, for those cold days when you don't want to fire up the bottle heaters, here's a few with NOS at 700 PSI and Propane at 120PSI:
#42 NOS + #24 PRO = 110 HP
#46 NOS + #26 PRO = 130 HP
#52 NOS + #30 PRO = 165 HP
#56 NOS + #32 PRO = 200 HP

 

[Tom Welch]

Ben,

Thanks for sharing the "secret" numbers!!LOL......You forgot to mention though that your calibrations are based upon the fact that your cars system does not incorporate the fuel enrichment controller which is 60% of the total enrichment when nitrous is in use.

The typical kit that we ship will use jet combinations that are leaner on the propane jet due to the above statement.

Stay tuned for those acutal dyno numbers with hopefully 200+ rwhp n20/liquid propane pulls on my car within the next few weeks.

I will have an upgrade available to all current users of our system once testing is complete.

Thanks again Ben, and great numbers!

Tom
Http://btrviper.com

 

[MW]

I thought the big advantage to the n2o/pro was it's gas form when injected into the Viper manifold. What do you mean by "liquid" system, as they are both liq. in the bottle?

 

[9 seconds]

The normal setup for the propane bottle is to take gas off of the top of the cylinder (small propane cylinder). To get liquid you need a dip tube (like the NOS cylinder) or just turn it upside down.

 

[MW]

<FONT COLOR="Yellow">So, when referring to a "liq" or "gas" system, it's just a matter of WHEN the liquid turns into the gas...
The standard 5 lb propane bottle has no pickup tube I suppose...?</FONT c>



<FONT COLOR="#ff0000" SIZE="1" FACE="Verdana, Arial">This message has been edited by MW on 03-25-2002 at 05:15 AM</font>