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JBurer JBurer is offline
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Join Date: Nov 2008
Location: Austin, TX
Posts: 205
No black magic - just found some ways to reduce backpressure in the very limited rpm/boost band he was racing in.

At the time he was very quick - high 7's in the quarter in a 1.3L tube chassis car.

Both size and length of the exhaust manifold tubes have an impact on response and power. For a car with a narrow operating range, (ie. a drag car operating only from 7k to 9k rpms and with 36psi of boost) those things can be optimized.

Quote:
Originally Posted by Raceboy View Post
It is no black magic, it is common knowledge of 4stroke engine and turbochargers.

Since spinning the turbine is all about energy, the less energy you waste before it reaches turbine, the best spool and power you get as it is not the speed of the gases that turns the turbine, it is the heat energy of the exhaust. The faster you get the gas onto turbine blades, the less energy is wasted by cooling (=heating the exhaust manifold). This is the reason for opting for smaller headers.
The reason behind the most power with long headers was because the turbine was single inlet type and the primaries were just separated longer thus not letting the pulses to work against each other. Twin turbo (one bank of cylinders feeding each turbo) or twin-scroll turbine housing do the same with very short headers.
And when searching for the point where most energy is expanded (though I cannot see any reason why one needs to find it) can be found easier: using EGT sensor and moving it in the exhaust.
Old 06-10-2012, 07:12 AM
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