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Frequently Asked Questions
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| Q: Will attaching a scoop to my injector improve my performance? |
A: To get the answer, you need to look at the engine inlets on modern aircraft. Aerospace engineers know that air doesn’t respond to being "scooped" like some people think it does.
At the starting line, there is no ram air, and air coming into the injector comes from all around it, including behind. A scoop restricts this, so clearly it’s no help there.
At 250 mph, scoops do not recover more air: they spill more air. The reason is that typical dragster scoops do not resemble jet engine inlets at all, even though it seems pretty obvious that they need to be optimized to capture ram air by all available knowledge about air flow
The downsides of a scoop are cost, weight, and drag, and the benefit just isn’t there. For a simpler, more effective solution, see the part in the Injector section about PSI injector inlets, which we call "lips." They’re designed to be a similar as possible to the jet engine design, and they are effective. |
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| Q: What difference does it make whether I use eight or sixteen nozzles? Doesn’t it all end up in the same place? |
| A: The point of your tune-up should always be to have all eight cylinders in the proper state of tune everywhere in the run. At the finish line, you must not have any lean cylinders. At idle or staging, a too-rich cylinder stumbles and slows the 60-foot. It’s a fact that the fuel/air distribution is different at staging than it is at the finish line. So, a cylinder might be cold at staging, which is bad, or lean at the finish line, which is worse. So what do you do? The answer is not to cut out your manifold plate (see above). Instead, set up a separate tuneable system for staging, which can be done with a second set of eight nozzles. |
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| Q: What is the story about crank-hub galling? |
| A: We hear this question frequently, and it’s an odd one, because it occurs with all superchargers, both in Top Fuel and Funny Cars with their 14-71s, and with other screw blowers. Frankly, our titanium crank hub and magneto drive have solved the problem. The natural incompatibility between titanium and steel prevents galling. And, keeping the magneto accurately in phase with the crank shaft prevents firing early, which slows the engine down, and voids working the joint between the crank hub and crank shaft. |
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| Q: What should I do if I think my boost is down? |
A: The first thing you should check is your fuel tune-up. If you’re burning the right amount of fuel for the conditions, your air delivery isn’t really down. You could be having an instrumentation problem. You need to check your boost pressure calibration and look for instrumentation leaks . If you really are burning less fuel than you should, you need to look further.
One frequent cause for low boost is a defective ignition system. Cool gas is easier to push than hot gas. If the ignition system isn’t firing properly, the air inside the cylinders will be cooler when it exhausts, lowering the system pressure: i.e. lower boost. We’ve seen this plague several of our customers; the problem always went away when they replaced their magnetos.
Another thing that can make it seem like your boost is down is too great a spark plug gap. Contrary to "old wives’ tales." Increasing spark plug gap does not release more energy and ignite the charge better It actually makes it harder for the magneto to fire the spark plug, and you get what seems like low boost.
A third problem can be leaks between the blower and the manifold or manifold and engine. |
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