Back to Horsepower Chart
Engine brochures speak of horsepower. Why horsepower? What is it anyway?
Horsepower is a time factor. Torque is the muscle factor. An engine with a maximum torque of 100 ft/lbs will develop an output at 1000 rpm of approximately 19 horsepower. If that same torque is applied at 2000 rpm the horsepower will double. It's that simple.
Modern engines that turn much faster than traditional engines need to develop less torque but at a higher speed to produce the same output. Camshaft design plays a major role in determining at what speed the maximum torque occurs. The more the design is tweaked to obtain maximum torque the sharper the peak in the horsepower curve. That boils down to a rapid drop off in torque at speeds above and below that peak.
A milder cam profile will lessen the peak and broaden it. This improves performance generally - particularly easy starting and smooth idle. This also reduces the maximum horsepower, decreases overall efficiency and increase fuel consumption.
For years the question of what to do about it was answered with total silence. The solution did not exist so we lived with what we had. We have lived with it for over a century and done reasonably well, at least as well as could be expected.
Happily the century is over and so is the silence. Variable valve timing has been developed, tested and put into production.
What that really means to the response curve produced on the test dynomometer is quite remarkable to say the least. It is now possible to tune an engine for maximum torque for the speed at which most of its running is done. In an aircraft application maximum torque can be applied at take-off speed and be maintained as the speed is reduced for cruise. This results in better fuel economy, and quicker response time when sudden application of power is required. At the same time docile handling qualities are retained for starting and slow running.
Firewall Forward Aero Engines Inc. has produced a variable camshaft timing engine, the CAM 125, based on a Honda 1600 cc 16 valve VTEC engine. This engine produces 134 hp at 2700 propeller rpm. The performance curve obtained from the dynomometer print out has been superimposed on Lycoming's published curve for the O-320 150/160 engine. Figure 1 shows the comparison with the CAM 125 outperforming the O-320 up to 2500 rpm. This could never have been accomplished with a 1600 cc engine during the century of silence.
Firewall Forward has been producing dual electronic ignition for 10 years with an excellent record of dependability, but they believe that there has never been a piece of equipment designed and built that couldn't be improved upon. The new version for the CAMPUTERTM ignition module is a perfect example of the progress that comes from constant research and development. In the new CAMPUTERTM the principle feature is the introduction of capacitor discharge (CD) with the latest control circuitry. CD ignition provides high energy spark at cranking speeds for cold weather starts. It also provides the same undiminished spark at take-off speed which distributor ignition with points or reluctors are incapable of.
An electronic fuel injection system has been developed in concert with the ignition. This system is designed to meter fuel to the best possible power/consumption ratio.
Perhaps the biggest advance is the diagnostic feature provided. A problem in equipment such as this is that it can never be isolated with a short circuiting screw driver. A diagnostic module will be supplied which will interface with both the ignition and fuel injection micro processors.
This module can feed its data into a lap top computer and then be forwarded in real time via internet or direct modem connection to the factory. In that way virtually anyone anywhere in the world can have access to the diagnostic data analyzer at the factory.
What does the R&D philosophy at Firewall Forward mean for the customer? It means continued support, new products designed for retro fit where appropriate, and above all the security that we will be there to help - wherever you are.
Copyright © 1999