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.