good point! torque rules.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

DaBenz,

Actully, in both NA and Turbo engines the air is pushed into the cylinders. NA engines by atmospheric pressure and Turbo engines by atmospheric pressure enhanced by the turbo increasing manifold pressure above atmospheric pressure.

There is really no such thing as "suck". A flow of air is caused by atmospheric pressure filling a void that has lower atmospheric pressure such as a cylinder that has a receding piston causing a lower pressure inside that cylinder.

P E H

Now that really sucks!!!!

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1977 300D Lost coolant while someone else was driving
1983 300D Can't run without oil
1985 300SD (gone but not forgotten)
1990 300TE 4matic Sold
1991 Yamaha Venture
1975 Kawsaki 250 triple
1974 Honda 200CL
1951 8N Ford
2008 Wildfire 650C

P.E.H.: you're right. There is no such thing as suck or suction or suction devices. They don't exist in the automotive, medical, or vacuum cleaner worlds, to mention just a few industries that I'm sure you can expand upon. Those words don't exist in the dictionary, either. Jeepers, I'm starting to sound like....

I could have used differential equations and the 2nd law of entropy to give a basic explanation of why a turbocharger is used, which was the original question. However, this forum is read by people (who I consider to be very intelligent) from many different backgrounds. Differential equations just aren't used by most people who read this forum, so I choose to use a common language that I think will be understood by most people, regardless of their background. Most people who put their hand in front of the air inlet will say that the engine is sucking air into the engine (or that rag they were hanging on to). Most people won't say that air is being let into the engine due to the differential pressure difference between the cylinder volume and the local atmosphere (which, from a rigorously technical point of view, isn't correct). Hopefully the sky really is blue in both of our worlds, P.E.H.

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daBenz - 1970 220D

i think it was the noted physicist, w c fields who said, "suck....blow is just an expression."

that is good enough for me.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I wouldn't have started the whole thermodynamics discussion if I knew it was going to turn into a geek-a-thon

Dabenz
Never read about differential equation in any real applications.
I took the introduction many yrs ago. Only thing i can still remember is X= cekt, a half life decaying time. Or simplest application is to time how long it needs for your hot coffe to cool down.
Since the prof is real nice guy I did 1 st year calc course with him, easy to get good marks as long as u do all the exercise in the back of chapter.

Turbo and super charge works the same, Turbo uses the exhaust to drive the compressor, Super charge uses a fan belt to run. Both applications' parasitic loss s much lower than the net gain. Or else we have to call it something else.

For some reason Diesel Turbo seem to last much longer than Gas turbo. IE Volvo Turbo, i heard many of them need new ones. Seems most turbos are supplied by a handful of manufacturers.

I have seen twin turbo in logging trucks, but in series, gives off almost 40 lbs boost!


If we can install an intercooler , it should add a few more HP too.

First, I need to apologize for the temper tantrum.

SD300: I've made a few $$ translating differential equations to the real world so that stuff can get built. Truely usefull tools as long as the engineer understands that the person with the checkbook usually doesn't do that level of mathematics.

I hope my answer to the original question can be understood by most people. From a historical perspective, superchargers came first. Then somebody asked a dumb question: why can't we use some of the engine's waste energy to power that fan, instead of stealing engine power with a mechanically driven supercharger?

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daBenz - 1970 220D

IMHO you did a good job of explaining this in lay terms. I'm not an expert on IC engine design, but it appears that a turbocharger also imposes a power penalty on the engine in the form of increased backpressure. While I agree that obtaining the energy from exhaust gasses has less impact than using shaft power from the engine, it's still not a totally free lunch. From a historical perspective, I suspect the primary reason that practical superchargers were developed first was the material limitations associated with turbochargers. While supercharges have been in service for a while now (maybe 70 years) I don't believe the were reliable turbochargers on auto engines until the 60's (and I'm not sure how reliable they were). I find it impressive that my 23 year old turbo is still operating reliably under fairly extreme service conditions.

to remember the miller indy cars running superchargers in the twenties. the duesenberg road cars had them in the thirties for sure, and bugattis and mercedes. there was some level of reliability but the road cars were not noted for supercharger reliability until quite recently. back in the sixties people ran paxtons and some studebakers did also. they were noted for bearing failure. it seems to me as if turbos became reliable in street run autos before supers did.
the mercedes in the thirties had a clutch setup which did not engage the supercharger til you floored the gas. then you were only supposed to run the supercharger for maybe 30 seconds, kind of like nitrous today.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Interesting,

I was also thinking of those early autos with superchargers. I'm not sure how reliable they really were, but some were good enough to put into production. I also believe that IC aircraft engines from the same era used superchargers to allow reasonable power at high altitude. I agree that the bearings would be the limitation of early superchargers. My thinking was that the design of high temperature turbochargers was more limiting than ambient temperature superchargers operating at similar speeds. I seem to remember stories of 60's vintage turbos (euro BMW 2002s, I think) melting down on a regular basis. Interesting stuff.

yes. in the beginning they tried different things to make them last. the corvairs and f85s were the first that i was aware of. they had a system that injected water from the windshield washer into the intake when you really mashed them. still there was a lot of pinging. it seems that maybe saab was one of the first to get it right. in about 1978. porsche was about the same time with the 930.

in ww2 airplanes of war they used superchargers and superchargers on some engines at the same time. sounds complicated, but when running at a constant speed a lot of things are simpler.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

The current C-xx Series ACERT Cats put out 50+psi boost! The down sides? 14 bends in the intake tubing after the first turbo. Air-to-coolant AND air-to-air intercoolers. Sheesh, it almost makes an EGR worth it.

I'm sure the aircraft engines also got more PM than the average auto.

It still amazes me that my 23 year old turbo, with 290K, is still just chugging along. I'm don't even want to calculate how many revolutions of the turbo that corresponds to .

The biggest problem was maintaining a propper air/fuel mixture under all conditions....

Pinging was obviouly a lean condition...but alternately under boost it can mean too much spark advance....its typical to retard timing under full boost in the honda world to prevent this...even using Racing fuel.

In the early days engine controls were well, primative if not non-existant.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche