Today I had a sled racer from Utica with a sealed pail of C12 and it tested dandily–6-7psi. But last month Tripod Dan’s sealed pail of Q16 was nearly dead at 2psi. Then Jesse Helwig bought 5 gallons of Sunoco Maximal from a bulk tank at a retailer–0 psi, totally dead.
It’s great that we lucked into this RVP testing equipment so we can test fuel for our dyno tuners and local racers who bring their fuel samples to be tested ($40 charge). But what about the rest of the country? Is your race gas dead, or half dead, or dandily fresh and volatile? Mailing fuel samples here seems expensive and in some cases like USPS illegal. So why can’t a person do their own RVP test in the kitchen sink?
OFFICIAL RVP TEST PROCEDURE:
The RVP test “bomb” (yes, that’s what they call them!) is a two piece stainless steel chamber with an accurate bourdon tube 0-15psi pressure gauge at the top. The bottom chamber is where the fuel sample goes–then its attached to the top air chamber by a threaded Oring sealed connection. The top air chamber is 4x the volume of the fuel sample chamber.
The water bath that heats the bomb and the air and fuel inside to 100.0 F constantly circulates to provide turbulence that helps heat the bomb chambers and their contents quickly. The procedure is to immerse the top chamber–open at the bottom–and bring that up to 100.0 F. That expands the air inside, causing the excess air to bubble out the open bottom. Meanwhile, the fuel chamber is in the refrigerator being cooled to 32 F before the gas sample is poured into it. This prevents the loss of front ends that would occur if poured into a warm chamber. So with the top chamber at 100.0 F, the fuel sample is poured into the chilled fuel chamber and immediately attached and sealed to the top air chamber. Then the assembled bomb in inverted–allowing the chilled fuel to drizzle into the preheated air chamber, and front ends begin to boil off and pressure rises (as seen in the Jim Czekala DrumPreserve.com RVP YouTube video) some. Then the bomb is immersed in the water bath to bring the whole bomb and sample up to 100.0 F. While it’s warming up, the bomb is removed and agitated and immersed again every five minutes or so until the pressure in the bomb quits rising.
If we didn’t preheat the top air chamber, and assembled it with a filled fuel sample chamber, the cool air in the top chamber will expand and add to the pressure exerted by the boiling off of the front ends!
RVP TESTING AT HOME:
My idea is if we understand what the RVP test is all about, why cant we take a sealable aluminum bottle of some sort and make a homemade bomb and test your fuel in your kitchen sink? If we have, say, a 16 oz beer or Monster Energy drink can we can punch two holes into the cap (or even the body of the can) and JB weld (1) a 0-200 F meat thermometer with a probe long enough to reach within 1/2″ or so of the bottom of the can and (2) a 1/8″ hose barb. Then a short piece of 1/8″ ID hose can be attached to a 0-15psi boost gauge.
UNOFFICIAL APPROXIMATE RVP TEST:
Let’s call this a HVP test (home vapor pressure). Chill the aluminum home-made bomb in the refrigerator until the thermometer says 35 or 40F. Then to determine the effect of expanding air, remove the bomb and immediately pour in 3.2 oz of tap water and seal the bomb (or 20% or 1/5th of the volume). Now hold it totally submerged in a sink full of running hot water until the thermometer registers 100 F, and note the pressure buildup on the gauge. Empty and dry the bomb, and chill it in the refrigerator again. Now, pour in 3.2 oz of your fuel, reseal the bomb and bring it up to 100 F in your sink of hot water, and then shake it to agitate the fuel. I surmise (I’ll need to do this same test for real, to be sure) that you should subtract the WVP from the unofficial RVP that you just got.
It might not be a perfect test–the grade 3A precision gauge on our bomb is accurate to .25% or with fuel that tests at 5 psi, it would be + or – .0125 psi. A boost gauge is surely more than that, but close enough to get and idea of the relative volatility of your fuel. And a thermometer for checking roast beef is probably not spot-on, but once again close enough!
And what if your $100 pail of 6psi fuel is really low on HVP? We are experimenting with Isopentane that is available from chemical supply companies. It has a RVP of 20.5psi and you can do the math to figure out how much isopentane is required to bring your dead fuel up to a reasonable level. Some people are currently running isopentane in their fuel and it is working as expected.
I plan to do a HVP test here, and then a real RVP test on the same fuel to see if my math is correct.