Forced Air? TURBO? Options

[bob91403]

Could someone tell me why a scoop can't increase air pressure, as you go faster, and create the same kind of HP "boost" you get from turbo or superchargers? Excuse me for being ignorant. But, isn't it just a matter of increasing air pressure to the intake, and pumping in the right amount of gas for mixture? What about a pressurized tank of air, or both air and propane tanks? Couldn't you use a small compressor for boost, or as a source to refill a "boost" tank? I really don't understand this obcession with tubocharging. Nitrous systems have been around for a long time, and are much simpler. I was told, by my top rated Porsche mechanic, that, "Yeah, higher compression heads, turbocharging, supercharging, nitrous oxide, will all increase horsepower. But, anything you do to increase the horsepower will seriously lower the longevity of the engine." He doesn't even recomend european compression heads for a rebuild. I do understand, tubocharging a smaller engine gives you increased horsepower, plus the weight advantage of not having to put in a 3.2L six. But, if you have to rebuild it every 50K, instead of 150K miles, doesn't conversion cost less? Curious to hear your replies.

[soloracer]

For increased power you need to increase both the oxygen and fuel that are going into an engine. Getting more fuel in is easy - just upsize your fuel system. Getting more oxygen in is more difficult.

One atmosphere is 14.7 psi. Turbo's can generate over 100 psi if you want them too. However, most stay between the 10 psi to 30 psi range. Turbo's have an efficiency range where they work best that you can determine by looking at their compressor maps. If they are forced to work outside their efficiency range they tend to heat the air which can lead to detonation. Turbo sizing is very important when matching a turbo to the motor and the desired performance characteristics.

Like Redshift said the "Ram Air" style of getting more air into an engine will only give you a slight increase in airflow to the motor and be no where near the same as the turbo is capable of doing. Nitrous systems or systems that use a compressed gas also get more oxygen into the engine. However, the supply of oxygen is limited by the volume in the bottle. You run out of gas in the bottle and you have to go buy more. Works great for short distances but you would run out of gas in about 5 miles if you were on it steady.

The nice thing about a turbo is that once installed the extra power is there all the time and IS basically free. It's also easily adjustable. Want more power? Just turn up the boost. Or if you find the turbo you have is not giving you the power you were looking for you just bolt on a new turbo and change your mixtures. No pulling the engine, no cracking open the block to change the internals. An additional advantage is turbocharged applications also make good torque gains. Plus for many of us the feel of a turbo car is more of a rush. I rode in a Viper that has more power than my 944 turbo and it did not feel as quick. I know the Viper is faster but because the power is so linear it doesn't have the same "power rush" that I get with my 944 turbo.

P.S. I would like to know where you are getting a rebuilt engine for only $1500. I spent over $7000 rebuilding my 944 turbo engine and know a Porsche 6 costs more to do. I can't even buy a core engine for $1500.