why no blowers in daily drivers?

[flatheadmurre]

Its the pressure in the exhaust that powers the turbocharger, so it will always be a restriction compared to an open exhaust.
For the turbo to start vacuuming out the exhaust it has to be driven by the intake air flow.

[scooder]

Tim,
The turbo doesn't create a vacuum behind it once it's started spinning. It does a bit when you come off the loud pedal after stomping it, due to some inertia. But not when your under boost conditions. The inlet side of the turbo, the compressor under boost, of say 8lb has that same 8lb pushing against it (pressure being equal all over the area being pressurised) inturn, the exhaust side also "sees" this, due to the common shaft. So the exhaust gas has to overcome this 8lb pressure to spin the turbo.
You see, no vacuum behind to pull the exhaust gas out. A turbo works like a centrifugal supercharger (Frenzle and McCullouc (sp?) and the Paxton, to name a few) only the drive is by exhaust gas rather than belts from the crankshaft.
Under cruise conditions the turbo does turn freely, as there's no boost pressure in the inlet manifold pushing back.
And yes, the common shaft and the fact that both sides of the turbo are touching, a bunch of this heat gets sucked up by the inlet charge as it passes through the inlet manifold side of the turbo. Hence the need for intercooling.
In a blow through setup, using a (hat) on top of the carb piped to the turbo, so the whole carb is seeing boost pressure, the carb does somewhat cool the charge due to the latent heat evaporation of the fuel through the carb. This does remove a surprising amount of heat.
Hope that helps your questions.

P.S. There was an aftermarket turbo setup in the early 50's, for the flathead, it was developed by Bessia (sp? Again) not very successful, though not due to it being a turbo, it made 7lb pressure if I recall, more like money was the killer here, along with it being "new" untried and untested. I've only seen 1 pic of this, vary poor pic you can't really see what's going on under the hood.
Martin.

[Tim Ayers]

Originally Posted by scooder

Tim,
The turbo doesn't create a vacuum behind it once it's started spinning. It does a bit when you come off the loud pedal after stomping it, due to some inertia. But not when your under boost conditions. The inlet side of the turbo, the compressor under boost, of say 8lb has that same 8lb pushing against it (pressure being equal all over the area being pressurised) inturn, the exhaust side also "sees" this, due to the common shaft. So the exhaust gas has to overcome this 8lb pressure to spin the turbo.
You see, no vacuum behind to pull the exhaust gas out. A turbo works like a centrifugal supercharger (Frenzle and McCullouc (sp?) and the Paxton, to name a few) only the drive is by exhaust gas rather than belts from the crankshaft.
Under cruise conditions the turbo does turn freely, as there's no boost pressure in the inlet manifold pushing back.
And yes, the common shaft and the fact that both sides of the turbo are touching, a bunch of this heat gets sucked up by the inlet charge as it passes through the inlet manifold side of the turbo. Hence the need for intercooling.
In a blow through setup, using a (hat) on top of the carb piped to the turbo, so the whole carb is seeing boost pressure, the carb does somewhat cool the charge due to the latent heat evaporation of the fuel through the carb. This does remove a surprising amount of heat.
Hope that helps your questions.

P.S. There was an aftermarket turbo setup in the early 50's, for the flathead, it was developed by Bessia (sp? Again) not very successful, though not due to it being a turbo, it made 7lb pressure if I recall, more like money was the killer here, along with it being "new" untried and untested. I've only seen 1 pic of this, vary poor pic you can't really see what's going on under the hood.
Martin.

Martin:

Thank you. Learn something new every day. I guess I was wrong about how a turbo set up works. Makes sense how you explained it.

Tim

[flatheadmurre]

The need for an intercooler comes from that compressing air gives heat.
Doesn´t depend on what type of compressor root/piston.
And when you start turning up the boost you come to a point where you cant really benefit from it without a intercooler.
The heat transfer between hot/cold side of the turbo isnt the big problem.

[Ol' Ron]

This summer a 35 PU will be roaming the streets of CT. With a Blown 294 flat motor.

[scooder]

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Originally Posted by flatheadmurre

The need for an intercooler comes from that compressing air gives heat.
Doesn´t depend on what type of compressor root/piston.
And when you start turning up the boost you come to a point where you cant really benefit from it without a intercooler.
The heat transfer between hot/cold side of the turbo isnt the big problem.

We'll have to agree to disagree on the heat transfer, yes compressing the inlet charge will create heat no matter how your compressing it, and yes an intercooler will always help in cooling this charge. However, the turbo system does add more heat to the charge due to the heat transfer in the turbo. The temperature the turbo gets at high rpm boost is substantial and a good deal hotter than a proper supercharger, this fact can't be ignored surely.
A turbo setup most all the time needs an intercooler at the same boost pressure a supercharged setup is happy without the intercooler. An intake temperature sensor at the inlet manifold will tell you how much hotter the turbo setup gets without an intercooler. With a normal sized intercooler on the turbo setup, the intake charge temps are mostly equal to a supercharged setup with no intercooler with the same boost pressure.
Martin.

[flatheadmurre]

I agree you got heat transfer but its not the main reason for an intercooler.
Plenty of turbochargers around running happily without intercoolers.
Modern turbochargers are often also watercooled to deal with heat problems.
Are you compairing the same type and size with the only difference being direct driven ?
Or are we talking different types of superchargers ?

[scooder]

Different types bud, just using the 8lb number for comparison, turbo and a roots type gmc or Magnusson or Scot or whatever.
Martin.