Pump Gas Blues - Water Injection
Gary Palmer; Byron, IL: With today's turbo and blower production cars requiring 91-octane or better, I need some guidance on gasoline. My past experience buying premium fuel has not been good. Several years ago, I was told that regular automotive gasoline has about a 30- to 60-day life expectancy before its properties deteriorate to the point of being noticeable. How true is this? I know the adage of buying your gas at the busiest gas station, but how many people are buying premium? Do current cars adjust boost and timing to correct for the fuel in the tank? What about water/ethanol injection? How do you set up a water/ethanol system and what are the limitations?
Jeff Smith: I spoke with my pal Tim Wusz at Rockett Brand Racing Fuel, and he confirmed that pump gasoline is designed to be stable for about that 30- to 60-day time period. The deterioration of the fuel begins with a gradual evaporation of what are called the aromatics or the light ends of the fuel. Gasoline is a complex blend of several different hydrocarbon chains mixed with a multitude of additives; among them are aromatics that are often associated with higher-octane fuels. These light ends also make up the portion of the fuel that evaporates before the heavier-end components. Losing the lighter ends reduces a fuel's ability to light easily. Keep in mind that most fuels across the country now use 10 percent ethanol as an octane booster instead of ethers like MTBE, which have been removed from gasoline because they have been determined to be carcinogenic.
Unfortunately, it's difficult to generalize because there are dozens of different gasoline formulations used throughout this country. Nevertheless, alcohol-based aromatics are generally considered less stable under long-term storage situations, so it would be best to try and use the fuel as quickly as possible, because allowing the fuel to remain in the tank over the winter, for example, could cause problems. Alcohol has an affinity for water, which means that alcohol attracts water out of the air and pulls it into suspension. The water then mixes with the alcohol and causes the mixture to create what is called phase separation, which separates the water/alcohol from the gasoline. None of this is good, and this process occurs when gasoline is allowed to sit in a vented tank. In this situation, a fuel-stabilizing additive like Sta-bil is a good idea because it prevents phase separation. It's also a good idea to keep the tank either as full or as low as possible if you plan to store the car for a long period of time, as this will reduce the formation of water.
According to Wusz, olefins in gasoline are the real troublemakers when it comes to long-term storage. Olefins represent a larger percentage of pump gasoline and serve an important function, but they are also the least stable additives and tend to oxidize, eventually converting to gum and varnish. Wusz says the amount of olefins is one of the main differences between high-quality race gas and pump gas, with the better race fuels having a lower percentage of olefins. This is one reason race gas can be stored in a sealed container in a cool, indoor location for as long as two years with no fear of degradation. Wusz also mentioned that even when pump gas degrades and loses some of its aromatics, that generally has a very minor effect on its octane rating. It's also important to note that octane rating on gas pumps is a combination of research and motor-octane ratings, and Wusz emphasizes that of the two, the motor-octane rating is the more important to a street engine under load. To further emphasize this point, most octane boosters you buy in a can add only minor numbers to the research octane number. When octane boosters claim an increase of four points, that means a 91-octane fuel improves to 91.4, not 95.
As for your question about whether late-model cars correct air/fuel ratio and timing to compensate for fuel quality, the answer is yes. All late-model engines use feedback air/fuel ratio sensors, and many now use wide-band sensors that are what most performance enthusiasts use to monitor engine performance. This feedback maintains the engine's optimal part- and sometimes full-throttle air/fuel ratio for best fuel mileage and driveability. Detonation sensors are used to help protect engines from harmful knocking if low-quality fuel is used. These sensors detect knock and automatically reduce ignition timing until the knock stops. This allows the engine designer to push the limits of timing, knowing that he has the ability to pull timing back should knock occur. There are also aftermarket knock sensors. We've used a J&S sensor on some dyno testing, which worked very well. The company even has a unit designed for late-model engines with distributorless ignition systems that uses smart coils and includes a boost and nitrous-retard feature.
Water injection might be a reasonable solution for mild detonation problems for users currently mixing race and pump gas to raise the octane. Mixing fuel works directly along octane lines (half 91 plus half 100 will produce 95.5- octane fuel), but this tends to be expensive. Race gasoline on the West Coast is around $8 per gallon, and even mixing it at 25 percent with pump gas will increase the cost of fuel to roughly $6.50 per gallon. Water injection is most commonly associated with supercharged and turbocharged engines as a way to combat detonation, but water can also be employed on high- compression, normally aspirated engines as well. Many enthusiasts believe water (and water/alcohol) injection is equivalent to pouring water on a flame. While in one sense this is true, the more accurate evaluation is that small quantities of water work to reduce the extreme peak cylinder pressures associated with detonation. So in a general sense, the water does not put the fire out but instead reduces those harmful peak cylinder pressures that contribute to the "rattle."
Jeff Paulin; Laguna Niguel, CA: Thanks for the info on our new drag car in the Ask Anything series in the Oct. '11 issue. I have just installed the factory front sway bar with Genuine Suspension bushings and added a BMR Pro-Series rear drag sway bar. Our best run last time out at the May PSCA meet was 10.20 at 131 mph with a 60-foot time of 1.47. That's from a 3,900-pound car with driver. With the changes, the car ran a best of a 1.37 60-foot time and 10.18 the first time out.
Jeff Smith: Jeff sent us the above photo of his new launch technique with the bars installed, and it's clear that the Chevelle launches much better now with the front end even and hooked! When you can run low 10s with a normally aspirated big-block at 3,900 pounds and pull the front tires like that, the suspension is definitely working.
BMR Suspension; Thonotosassa, FL; 813/986-9302; BMRSuspension.com
This is Jeff's '72 Chevelle at California Speedway with both wheels in the air. Compare th
Here is how the Chevelle launched before the conversion to the rear sway bar.
The trick to making water injection work is to use the least amount of water possible to minimize the detonation. The most common approach is to inject a measured amount of water into the inlet airstream at a point just before the engine would normally experience detonation. On a normally aspirated engine, this most often occurs near peak torque, when the engine is producing maximum cylinder pressure. For boosted engines, the water can be injected once positive manifold pressure is achieved. The more sophisticated systems, such as those from Snow Performance or The Supercharger Store, are tunable, and the amount of water injected is adjustable based on variables such as rpm, engine load, and boost. Both systems use a high-pressure pump (which helps explain their cost) to help vaporize the water and ensure proper delivery. These systems are not difficult to install, but they can be expensive, so you have to weigh the costs versus the advantages.
J&S Electronics; Garden Grove, CA; 714/534-6975; JandSSafeguard.com
Rockett Brand Racing Fuel; Yorba Linda, CA; 714/694-1286; RockettBrand.com
Snow Performance; Woodland Park, CO; 719/271-5644; SnowPerformance.com
The Supercharger Store; Huachuca City, AZ; 520/456-9706; TheSuperchargerStore.com
TV Cable Update
We were at Art Carr's California Performance Transmission shop the other day when Art mentioned that the classic carburetor TV cable adapter for the 700-R4 and 200-4R transmissions had recently changed. This adapter is used to attach the throttle valve (TV) cable for either the 700-R4 or the 200-4R nonelectronic, four-speed automatic overdrive transmissions. Previously, there were two different brackets used depending on whether the carburetor was a Holley or an Edelbrock. Recently, Art noticed that a new single part number replaced the two separate numbers, and he ran down the basic change. If you look closely at the accompanying photo, there is a small tic mark near the top bolthole for the bracket (arrow 1). If you are using a Holley carburetor, the proper approach is to elongate this mounting hole down to the mark. If you notice, the bottom bolthole (arrow 2) is already elongated. Lowering the upper hole approximately 0.070 inch repositions the bracket and the TV cable pivot point, creating proper cable travel for the Holley carburetor. The bracket is a Holley PN 20-95 that, according to the Holley catalog, is intended for 4160- and 4150-style carburetors. Unfortunately, the instructions currently in the field do not indicate that this modification is necessary. Holley has told us they are aware of the issue and later kits will reflect this change on the instructions. This same bracket can be used without modification on Edelbrock carburetors. This kit is also available through California Performance Transmissions; the PN for Holley carbs is 15599 ($39.99), and the PN for Edelbrock carburetors is 15601, at the same price. If you are considering running one of these TV- cable–style transmissions, these are the correct brackets to use. From Holley, the PN is 20-121 ($25.95 Summit Racing). The bracket that attaches the TV cable mount to the carburetor is Holley PN 20-95 ($20.95, Summit Racing).
California Performance Transmission; 800/278-2277; CPTTransmission.com
Here is our entire TV cable assembly bolted to the carburetor on our budget small-block Ch
Donald Muchemwa; via CarCraft.com: I am an industrial and manufacturing engineering undergraduate student in my final year. I’m designing a three-cylinder, 1.2L engine for my final-year project, which is going to be hydrogen fueled. What crucial info do I need to consider concerning the design process. Your advice is greatly appreciated.
Jeff Smith: While this is not a typical tech question for Car Craft, I thought it was interesting and also felt this information could be useful at the next cocktail party, when some tree-hugger begins to spew about hydrogen as an alternative fuel. Besides what I dredged up on the web, I called Kurt Urban, owner of Kurt Urban Performance in Clayton, North Carolina, who has first-hand experience with hydrogen-fueled horsepower. With gaseous hydrogen (as opposed to liquid hydrogen), the gas displaces roughly 30 percent of the volume in the cylinder, which means it displaces that much air, which makes it difficult for the engine to make as much power as with gasoline (which displaces around 2 percent of the volume in the chamber). With the large volume that hydrogen displaces, the engine must be roughly twice as large to make the same power as it does with gasoline. Kurt discovered this when working with a 404ci LS engine that made 570 hp on gasoline but only 230 hp on hydrogen. The engine then required a turbocharger with 19 psi of boost to raise the power to 530 hp. Later, Kurt built a 572ci big-block Chevy for a Jesse James’ dry-lakes, top-speed television stunt. The octane rating for hydrogen is roughly 100 ([120 research + 80 motor] / 2 = 100), and it requires very low ignition power to ignite. As hydrogen ignites easily, it causes several problems. Hydrogen enjoys a very fast flame speed, but when Kurt tried to spin the engine above 5,000 rpm, he said the exhaust gas temperatures (EGT) spiked to unacceptably high levels. These temperatures would eventually migrate into the inlet manifold during valve overlap, causing pre-ignition of the fuel and air and creating what Kurt called a back flash. On a test done on the engine before Kurt inherited it, the back flash had been so violent that it blew the entire intake off the engine. He mitigated this possibility by using a much longer intake runner, so if the back flash were to occur, it would remain within the runner and not migrate to the greater volume of the plenum. Plus, the longer runners would benefit power below 5,000 rpm where the engine was forced to run. He also widened the camshaft-overlap numbers to minimize the backfire potential.
As we mentioned, the engine speed was limited to around 5,000 rpm, because anything higher spiked the EGT. One way to deal with that was to lean the air/fuel ratio, but this also reduced power. He was finally able to make 740 hp with a pair of turbochargers, moving as much air as a gasoline engine would ingest to make more than 2,000 hp. He was finally able to make 740 hp only by injecting water into the inlet stream to reduce the inlet air temperature and prevent back flashing. Also, because hydrogen has a reduced specific heat output versus volume, Kurt had to use three 370-lb/hr injectors per cylinder to move enough volume of hydrogen to make this power. This isn’t very efficient. Unfortunately, the limitations of hydrogen are many and daunting, especially if you intend to make power with this fuel. Hydrogen is not only difficult to work with because of the high working pressures and the limited volume you can store in the large storage bottles, but it also suffers from serious limitations in terms of range for the vehicle. Since you can’t spin the engine very high because of the EGT problem, you can’t take advantage of the rpm to make power.
In my opinion, the main reason hydrogen garners attention as an alternative fuel is because it offers reduced emissions. By eliminating carbon (gasoline is a hydrocarbon fuel), the main emission components resulting from the combustion of hydrogen is water and oxides of nitrogen. Since hydrogen does not occur naturally, it must be created artificially by applying energy to disassociate water into its two major components of hydrogen and oxygen. As a performance fuel, hydrogen is just not a good idea. Add to the fact that it is easily flammable and there are no inexpensive ways to transfer the fuel, and you can see why hydrogen has never really caught on. Conversely, E85 is a far better alternative fuel, as it enjoys a 105-octane rating, is a liquid fuel and a renewable resource (although it too requires energy to create), and it works extraordinarily well in performance applications, especially in super- or turbocharged engines. But that's just my somewhat prejudiced opinion. The price of E85 has also risen lately, mainly due to the loss of government incentive programs. We priced E85 with a 105-octane rating locally at about 75 cents a gallon cheaper than regular 87-octane pump gas.
Kurt Urban Performance; Clayton, NC; 919/938-1771; KurtUrbanPerformance.com
Relays are simple devices that allow a low-amperage switch to control a high-amperage circ
Glen Hiller; via CarCraft.com: I have an ignition question for you. I have a '69 Chevelle big-block and all the go fast goodies, such as a 750-cfm Demon, a dual-plane intake, 11:1 compression (with a 50/50 mix of 93-octane and VP C12), a 3-inch exhaust, and a blueprinted HEI. Years ago, I replaced the resistor wire that feeds the distributor because I was getting a popcorn-popping backfire when I would open it up on the highway. I replaced the wire with a nice, big 10-gauge copper wire that went directly into the distributor. Problem solved. However, after a few years, the popping started again, but only on long, uphill stretches. What is this new PerTronix relay kit that replaces the resistor wire? Will it do anything different than I have already done?
Jeff Smith: That's a great question, Glen. My guess is that the relay may not really change much, but there's a simple way to check if your wiring modification was completely successful. The test is to start the engine and use a multimeter to read the voltage at idle on the output terminal of the alternator. Let's use 14 volts as that number. Now use the voltmeter to read the voltage at the distributor. If the reading is within half a volt of the power coming from the alternator, then this is not your problem. However, if the reading is 13.5 volts or lower, then there is resistance somewhere in the long, circuitous route that the current must travel to reach the distributor. It's possible that it reads 12.5 volts or less, depending on how much resistance is in the circuit. As the voltage drops, the potential power output of your HEI ignition reduces, and that could be the source of your misfire under load. It's important to mention that higher- compression engines and any super-or turbocharged engine create high cylinder pressures. This additional pressure requires more initial voltage at the spark plug to ionize the air path between the spark plug's center electrode and the ground strap. Lower-feed voltage to the distributor will drastically reduce the maximum voltage at the spark plugs.
This simple drawing illustrates how to wire the Pertronix relay to feed full-system voltag
Back in the day, all three major car companies used some kind of resistance circuit (GM and Ford used a resistor wire; Chrysler employed a ballast resistor) to reduce the voltage to the points. This was done because 12 to 14 volts would quickly burn up a set of ignition points. The reason the HEI was such a major improvement was because it used all the 14-volt input. Often what happens is the installer will cut that resistor wire off and use a switched 12-volt wire from the fuse box to the HEI. It's a safe bet you are still using the original wiring harness in your Chevelle, which is probably a bit crusty at age 43. These old circuits can build resistance, so it's possible there is some resistance in that circuit. That's where the PerTronix relay (PN 2001, $29.95 Summit Racing) can be beneficial. Relays pull voltage from a clean power source such as from the horn relay or near the alternator-output terminal, so you can use that original, switched, 12-volt wire from the fuse box to trigger the relay. This does not have to be full-system voltage, since you are only using it as a trigger for the relay. There are only four wires to connect, and we've included a small drawing to show how simple it is. We like the Bosch 30-amp relays, but any quality relay and wiring harness will do the same job. The PerTronix unit was originally intended to be used with the PerTronix point conversion, which works better when fed full-system voltage, much like the HEI.
Relays such as this can be used for all kinds of electrical applications in older muscle cars. A classic example is using a pair of 30-amp relays to eliminate the major voltage drop that occurs in the headlight circuit. By using the headlight switch to trigger the relay, full-system voltage is fed to the headlights. In the stock situation, it's common to measure barely 11 volts that actually reaches the headlights.
PerTronix; San Dimas, CA; 909/599-5955; Pertronix.com
Summit Racing; Akron, OH; 800/ 230-3030; SummitRacing.com
Believe it or not, we don't receive a ton of technical questions, so if you have a problem that's been bugging you or you need to settle a bet with your gearhead buddies, fire off a question to Ask Anything at the address below. And while your high school teacher may have told you there are no stupid questions, we thrive on queries that raise everyone's knowledge level. So fire away!