Originally posted by: Yucky
For a turbocharger to be effective you want cold air
Efficient is the word. A turbo is effective regardless of environment.
To an extent, new larger turbos still give turbo lag. Quite a lot, actually, depending on size.
I personally like a turbocharger because they offer better performance.
Top-end, you mean.
No actually, he meant everywhere. Sure you can get a massive turbo and you won't get performance until the top end and you will have horrible lag, but that isn't true with a properly setup system. Drag racers typically use this large single turbo approach to supply massive top end but purposefully soften the bottom end so they dont spin out on the line.
Properly designed systems have lag that competes with a eaton or lysholm type supercharger and completely put to shame a centrifugal supercharger. My car has full boost at 2700 RPM. Anytime after that if I nail the throttle the response is instantly full boost with the turbo lag consisting of the time it takes me to floor the pedal. As far as power is concerned, two engines that are equivalent, one with a s/c and one with a properly sized twin turbo setup, the TT will slaughter the s/c throughout the range, low end and high. In fact, if one is comparing a centrifugal to a TT setup the results are very lopsided. The torque of the TT setup will be much higher due to its full boost on the low end while the centrifugal won't hit full boost till redline. People talk about turbo lag, but in all reality centrifugals have the worst lag of anything out there seeing as you have to wait till redline before max boost.
The previously mentioned thread is not worth your time reading IMHO, its so full of BS it would be hard to wade through it all. Mainly its people speaking of which they do not have on a subject they hardly know and have heard someone else tell them. (Quite incorectly I might add)
Turbocharging makes more sense from a performance stand point on any size engine, and anyone who tells you otherwise is a fool. Why in the hell would turbos all of a sudden stop working for a larger displacement engine? Turbos are actually quite limited in pro drag racing (read: Big displacement V8's) due to their tremendous advantage when tuned properly. They are becoming more popular and rules are allowing them to be run more and more lately with weight or other restrictions. And as far as the persons statements regarding lysholm screw s/c's being 99% efficient.... please, you can't design a toaster oven that is 99% efficient. In fact, turbos generally have more efficient compressors than any s/c's because of their opperational speed. Seeing as how they can be designed to have little rotating mass with no heavy gears and induced vibrations allows them to operate ~100K RPM. This is a more efficient range than the operational speed of say 45K RPM for a s/c centrifugal. Granted lysholms are much more efficient than centrifugals, but still no where near 99%.
Turbocharging is essentially "free" because of the fact that turbos get the greater majority of their energy from the heat of the exhaust, heat that ordinarily would be wasted out the exhaust. This is power that a supercharged combo must provide from the crank hence lower torque levels. However, equal engines, equal boost, the turbo will have more output, even at lower levels. Only roots and lysholm's can even compete with a turbo at lower output levels due to the fact that a turbo will have boost while a centrifugal will not. Typical centrifugals only have about 1 PSI at 3K if they redline at 6K with say 8PSI. Its a exponential type curve, not linear as many on here tout but a good approximation is it is linear between 50-100% of redline. Screw and roots type usaully have full boost down low like a properly setup up turbo and then hold full boost till redline. However, the top end potential of a roots or screw s/c cannot compete with an equivalent turbo setup. The two s/c's both become less efficient at higher RPMS and start to slack off and heat the incoming air charge more.
Turbos are generally considered easier on the engine as they do not place side loading on the crank. They do add more underhood heat, however a properly designed setup should not come near melting all of the plastic under the hood. That is just a poorly thought out design, either in turbo placement, cooling design, or material selection. Modern Ceramic ball bearing turbos not only have no turbo lag, but are also usaully water cooled and oil lubricated. This means the whole "let your engine idle before turning it off" problem is gone as the center section of the turbo never gets that hot and the oil will not coke in the turbo. This all adds up to a awesome experience on the street or on the track. The general reason for turbos not being more popular is past designs generally had reliability and other issues and engine tuning is much more complex with a turbo than a supercharger because turbos operate on engine load, not engine RPM. This however is easily overcome with custom tuning, newer technology, and some skill. However that adds more complexity that alot of people dont want, hence, they slap on a s/c and forget about the additional tuning/installation hassles. So either way, the decision is up to the individual based on what he/she wants.
Bryon
"Been turbocharged for many years"
P.s. You think that the 2003 Cobra decision to use a Eaton s/c over a turbo was based in any way on performance potential? Pllllllleeeeeeeeeeeeeaaaaaaaaasssssssseeee Gimmie a break. Try cost and availability. As if going back to a iron block was based on ultimate performance and the fact Ford could have anything they wanted in the car yet choose to use iron because it was the best they had.
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