Yes,atdsupra said:I think the cuestion should be , why a turbo is driven by exhaust . . .and a supercharger by a belt . . is it the only difference between . . . the way they're driven ???
The power required to compress the intake air comes from nowhere?Turbos are effectively "free" power, in the sense that they create no physical drag on the engine. The exhaust gases are what drive the turbo.
DannyG said:I like to think of the the Supercharger as a great street weapon :evil: Fast response and less lag than a turbo. Might beat the turbo opponent in the streets do to faster response 8)
But a turbo is so much easier to manage and I think more potential in everything except the turbo lag :twisted:
But I have seen like a year ago in SuperStreet and SCC an Integra thats both Super & Turbo charged. As well as an MR2 w/4AGZTE :shock: Imagine that, both fast response and topend power 8) :twisted:
of course the power comes from somewhere, but the bulk of it does not come from "backpressure" that the engine has to overcome. engine exhaust gases for a naturally aspirated motor as well exit combustion at high temperature and high pressure (and high enthalpy). as the gases goes out the exhaust piping, they will expand and give off heat and end up at a low enthalpy state, whether there's a turbine in its way or not. the turbine is just something that creates power from the expansion of the hot exhaust gases to lower pressure. without a turbine, there would just be a drop in enthalpy of a lot of gas with no useful work done. so it really is "free" power.The power required to compress the intake air comes from nowhere?
If only it were true. How about additional exhaust back pressure that the engine has to overcome
The turbo takes energy (enthalpy ~ heat + pressure, for anyone not familier with the term) from the exhaust stream which leaves less energythe presence of a diffuser, exhaust housing and turbine wheel are not parasitic in nature. your point of the backpressure is valid in that they can reduce engine power by creating more pumping losses and lower VE cause of reversion and stuff but that change in engine power due to the restriction in the exhaust is definitely not where the power to compress intake air comes from.
stan are you sure about this? going from high enthalpy (post combustion, right out of the cyl) to low enthalpy (lower temp and atmo out the tailpipe) doesn't require work...The turbo takes energy (enthalpy ~ heat + pressure, for anyone not familier with the term) from the exhaust stream which leaves less energy
to blow the exhaust into the atmospheric pressure, thus back pressure.
that would be interesting to see. but whatever the difference may be, it still doesn't mean that the backpressure is what is responsible for spinning the turbine, though the inverse of that statement is true.It would be nice if someone knew of BSFC comparative curves for the same mechanical engine (and a/f ratio) with a supercharger and then with a turbo intake. Then we could see the difference.
Peeps wrap na headers and catback to get more power. don't they?going from high enthalpy (post combustion, right out of the cyl) to low enthalpy (lower temp and atmo out the tailpipe) doesn't require work...