November 2014

Monday, November 03, 2014

DynoTech : More on RVP/ fuel volatility

I've done a couple more YouTube videos talking about what I feel is proper mixing of oil/ fuel, and transfilling from drum to jug, and jug to sled. They should be up by this coming weekend. And please forgive the Star-Wars-like intro and credits--that's the work of my 16 yr old son Marty's "Beast Productions" who helps me with video/ computer stuff, and he just can't help himself!

Our Koehler RVP test unit is helping educate us about fuel quality and the proper handling of race gas from refinery to end user. There are three major factors that contribute to the loss of fuel's front end components and reduction of RVP creating poor volatility:

*HEAT (refrigeration prevents the loss of front ends)

*AGITATION (it's just like shaking a can of beer)

*HEADSPACE (a place for evaporating front ends to escape to)

The RVP test is just like hauling a couple of gallons of fuel in a sealed five gallon jug in a black trailer 500 miles on a 100f degree day. If you start the trip with actual 5psi RVP, by the time you get to your destination there will be 5psi of pressure inside the jug. That 5 psi of pressure was created by the evaporation of about 1/2 of the fuel's front ends! So, when we open the jug, the sweet smelling whoosh means those important front ends are lost to the atmosphere. But what's left would still have an RVP of @2 1/2 psi. But any of the same fresh fuel that was in the tank of the bike or sled in the trailer would have an RVP of zero by the time you get to your destination--meaning it will be "dead" requiring lots of engine heat to vaporize and be able to burn. Remember--liquid gasoline doesn't burn--only gasoline vapor burns!

The educated racer goes to the track with no gasoline in the tank, and hauls his fuel in FULL jugs. With no headspace like we have in a partially full jug, only a small quantity of the front ends will be lost.

Last summer a pro race team came here for testing with a 5 gallon jug containing 3 gallons of 5 psi race gas (55 gallons kept under N2 pressure at their shop an hour away). By the time they got here, the actual RVP was down to 2 psi! Head Space! The next day, they came with a full jug of the same and it tested at 4 psi. And probably 1 psi was lost when they poured it from their DrumPreserve hose into the jug. Splashing is agitation! Watch that YouTube vid.

In the winter, natural refrigeration is your friend, because without heat of some sort it's difficult to get any front ends to escape. But summer is brutal on high RVP fuel--especially when there's agitation and, in the case of race vehicles, unlimited headspace with tanks and carbs vented to atmosphere!

Dyno testing solid mounted drag sled engines, we sometimes encounter foaming of fuel in the float bowls which for some reason makes fuel flow inconsistent. Heat and vibration causes the fuel's front ends to boil and turn the contents of the float bowls into something like a frothy milkshake. We often can cure that by racking and adding weight to the carbs, installing larger needles and seats, adding lots of fuel pressure (sometimes up to 15 psi will help), or perfectly balancing the crankshafts so they're smooth at the engine's operating RPM. But why does foaming fuel drastically reduce, or shut off the flow of fuel from a mechanical pump delivering 4-5 psi? One would think that lightweight foam would allow the floats to sink, thereby increasing flow. But today I was texting back and forth with Peter Duncanson about that (Peter sometimes runs low RVP C16 in his PS1000 asphalt sled) and I got thinking--are the vaporizing front ends creating enough pressure in the bowls to slow down or even stop the flow of fuel into the needle and seats? Could larger vent fittings/ hoses help? Or, could low RVP fuel help? I plan to keep some dead high octane fuel at the dyno to see if that helps the next foaming race engine.

A few years ago I watched then-NHRA Pro Stock bike racer Antron Brown complaining to a TV interviewer that his bike was surging, and laying down in high gear, causing him to lose a race in Brainard MN on a 95 degree day. Back then all the Pro Stock Suzukis ran Fast By Gast Lectron (Megatron) carbs, and I suspected that his solid mount 13,000 RPM Suzuki was buzzing the lightweight carbs, and turning his fuel into a milkshake. And, with the carbs being gravity fed, that could aggravate the problem. The next day I called Paul Gast and found out that many of the Lectron carbed Suzukis were suffering the same way at that hot Brainard race. I described what we do to overcome foaming on drag sleds here. So Paul had Kevin Gilham (who now owns Lectron in TX) get on a conference call with us, and the oversize, weight-adding billet Lectron floatbowls were born. I'm assuming that helped the ProStock bikes because I never heard any more complaining, and the Suzukis continued to run Lectron carbs for years until EFI was made legal.

Vibration is a great way to agitate anything. My Kubota lawn tractor (bought from Billy Howard) has a cup holder in the fender next to the seat. If I try to mow with any carbonated beverage in the holder, the CO2 is vibrated away in minutes! There's nothing worse than flat Molson Canadian!

Jimmy Cooper finally cured the Lectron fuel flow problems with his solid mounted PS1000 SkiDoo by having his crank rebalanced by an outfit in Canada. Now you can put a teacup on the head at 9200, and fuel flow is smooth and perfect. 


It depends on the source of the fuel, and where/ who/ how the pails are filled and sealed! Sealed 5 gallon pails are often coming with way lower-than expected RVP.

I dyno test and tune lots of flat track race bikes for RLJ race engines and his customers like AMA expert Kenny Coolbeth and other expert, pro and amateur racers. Recently AMA began requiring Sunoco Supreme as a spec fuel for the racers, and 5 gallon sealed pails of Supreme sold by a nearby retailer pal of mine seemed to change our tuning--requiring richer mixtures for max HP. I tested one of the pails of high RVP Supreme (said by Sunoco to be blended to 5ish psi in summertime), and it measured 2 psi! Not good, so I called my pal who buys bulk fuel shipped in small tank trucks from Insinger in Dushore, PA and repackages it into pails and seals them to explain the low volatility of the Supreme he was selling. So he ordered a pallet of sealed pails of Supreme from Insinger's and it tested excellent--4 to 4 1/2 psi.

What we now figure happens is Insinger gets bulk shipments of Supreme by either truck or rail from the Sunoco refinery in PA. It's stored in their bulk tanks. Then they fill smaller bulk tanks on their delivery trucks and deliver it to their retail dealers all over the northeast. The delivery guy goes city to city, retailer to retailer and in the case of my pal, he fills a bunch of empty 55 gallon drums for him. So if my pal is last on the delivery list, that part full tank on the delivery truck may have sloshed around for 100s of miles, leaving a trail of front end vapors from the tank's vents that have been agitated out of the Supreme. Then the delivery guy splashes it into my pals empty drums. Then my pal seals the drums with DrumPreserve nitrogen bungs, to fill and seal the 5 gallon pails later. But by then it's too late.

So now my pal insists on being on the first part of the delivery route, and has the delivery guy pour (not splash) the fuel carefully into his drums, and all is good. And, my pal now fills the pails from the bottom up with a long hose (see how we do that in the YouTube vid).

Insinger also supplies sealed pails of all grades of Sunoco to our local dragstrip in Leicester, NY and it always has tested good RVP.

So we have to figure that knowing the history of the fuel of any brand, in any pail is good. The same is true when buying bulk fuel, filling your own containers. A few months ago, dyno customer Jesse Hellwig filled and sealed his own 5 gal jug with Sunoco Maximal from Fat Nancy's in Pulaski NY. The next day we tested it, and it was 0 psi, so it was obviously old and stale. Fat Nancy's has since been acquired by Insinger and it is said that they disposed of all that fuel, and have refilled the bulk tanks with newly refined fuel.