posted October 01, 2000 11:27 PM
For those of you who may have missed a part of the "Turbo Fundamentals" series, or for those who may not have wanted to sit through all my rambling, here's a summary of the last few posts, plus the old important point that may have slipped through the cracks.(1) Turbos reclaim energy that would otherwise been dumped overboard in the form of heat, by using exhaust gasses to spin a turbine, which in turn spins a compressor, which compresses the intake air.
(2) Compresses intake air makes more power, because it allows you to burn more fuel per power stroke of the engine, and because it helps scavenge the engine.
Side Note: The new, compressed, intake charge "blows out" the remaining exhaust gases.
(3) The amount of work done by a turbo's turbine depends on the amount of gas flow through it, and the pressure differential across it.
(4) You can improve the turbine pressure differential by installing an exhaust system with a higher flow capacity than stock. It's impossible to have "too much" exhaust flow downstream of the turbo.
(5) The intake compressor works best when it has been specifically sized for an engine's flow requirments and boost levels.
(6) The best way to choose a compressor wheel and housing is to call the manufacturer of the turbo, and answer all their questions.
(7) Intercoolers are our friends. They reduce the temperature of the compressed intake charge after the compressor has heated it.
(8) An intercooler is only good as the air flow into it and out of it!
(9) Wastegates limit boost levels by acting as a "rev limiter" for the turbo.
(10) "Boost creep" indicates a wastegate that is too small.
(11) High boost motors require good ignition systems. Most top end stumbles and misses are ignition problems.
(12) There's no substitute for a day on the engine dyno.
There, that should about do it.
Keep in mind that I've just summerised about eighty years of turbocharger development and theory into a couple of posts over the past few hours. I haven't covered everything, and I've simplified a number of concepts where I could without losing the important stuff.
Side Note: The physics of what goes on between the cylinder head and the turbine alone could make a book all on their own!
While my posts should help you get by, if you're really interested in this stuff, there's a lot of good books that cover this material better than I do.
Again, thanks for taking time to read all this information, and I hope you find it very helpful! Best of luck in your future tasks.
------------------
Chris
-2000 Civic Si
-1998 Eclipse GSX
-1991 Talon TSi AWD
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posted October 01, 2000 11:27 PM 
Administrator 
very informative. i knew basically all of that, but there were a few points in there that were new to me... thanks 
