Supercharger or turbo charger - which one ?

muller1

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I think this is an American quote where they are bought as kits to add to any engine.
They are only the most cost effective as they simply bolt on and are run from a drive belt.

A turbo requires a new exhaust system to be fabricated if fitted as an add on and therefore is more difficult.

This thread has nothing to do with loving or hating them, the question was asked, "what are the differences between the two", that is all.

Russ
"
WHAT IS THE DIFFERENCE BETWEEN THE TWO" ??

The best place to find all the answer is to get the book by Allan Allard, Supercharging and Turbocharging.
Allard is a British company and have been involved in supercharging engines since the 1940s and still are involved to this day.

1982 saw Alan publish his knowledge in a book titled 'Turbocharging and Supercharging', re-issued in 1986 in paperback form it has since been accepted as the leading technical handbook to the keen enthusiast. Alan continues with turbocharging and intercooling to this day in Monmouth, South Wales.
This book is a great read honest.

Mike
 
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HERBIEMERCMAN

HERBIEMERCMAN

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come on alex, then how would you blow a tyre up ? my volume is the mass flowing not the volume of the container or system,this is the inverseley proportional bit, the system, or container.

the more air you blow into the inlet manifold the higher the pressure goes, up to the pressure setting on the release dump valve. it's benuilie's law not mine. herbiemercman.
 
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Seeker_UK

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come on alex, then how would you blow a tyre up ? my volume is the mass flowing not the volume of the container or system.

the more air you blow into the inlet manifold the higher the pressure goes, up to the pressure setting on the release dump valve. it's benuilie's law not mine. herbiemercman.

Bernoulli's principle says that the pressure of a gas (air), reduces when velocity increases.

Pressure and volume is Boyles law.

:)
 

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Bernoulli's principle says that the pressure of a gas (air), reduces when velocity increases.

Pressure and volume is Boyles law.

:)

Is that similar to a venturi?
Takes me back to college but my memory is not what it was.

Russ
 

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Pressure and temperature is Pascals law. (Closed system, pressure will rise proportionally to the temperature).

Don't forget that with a supercharger the compressed induction gasses are cooler than from a turbo charger, hence the reason for intercoolers on turbocharged engines.

On the whole a supercharger is a simpler way of boosting engine power than use of a turbo charger. Hence increased reliability.

The whole system runs cooler and you don't have the need for cool down periods to stop the bearings from seizing in the compressor or ceramic impellor vanes that can fracture due to thermal stresses.

That said if looked after even the delicate turbos should last a long time. Personally I'd prefer a supercharger on a petrol engine just becuase of its more relaxed power delivery.
 

Seeker_UK

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Is that similar to a venturi?
Takes me back to college but my memory is not what it was.

Russ

The Venturi Effect is when you constrict the pipe which a fluid (or gas) travels along, it speeds up and when it widens out, the gas slows down causing an associated pressurfe change in accordance with Bernoulli's law.

Some recolless guns used a flaring tube at the breech end to reduce the velocity of exhaust gases and reduce the 'kick'.

A venturi meter was often used to demonstrate the Bernoulli effect when I did my O-levels.
 

Number_Cruncher

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>>Don't forget that with a supercharger the compressed induction gasses are cooler than from a turbo charger,

I don't think that's actually true if you compare like with like.

For example, the superchargers fitted in the heavy engines like the ship engines and the GM EMD engines mentioned previously are fitted because these engine are 2 strokes, and they need the function of a blower to blow out the exhaust gas from the previous firing.

With a turbo instead of a supercharger, these engines would barely start or tick over, because the turbo isn't a positive displacement device when referred to the crankshaft motion. So, superchargers aren't fitted to these engines because they are inherently more efficient or capable of providing more boost, they're fitted simply because they can work as blowers at low engine speeds. The pressure provided by these blowers is low, and despite the inefficiency of a supercharger, the temperature of the air they supply is also low.
 

brandwooddixon

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>>Don't forget that with a supercharger the compressed induction gasses are cooler than from a turbo charger,

I don't think that's actually true if you compare like with like.

I'm afraid it is. From Wikepedia

The exhaust gases passing through the turbine section of the turbocharger are usually around 450 °C (840 °F), but can be as high as 1000 °C (1830 °F) under extreme conditions. This heat passes through the turbocharger unit and contributes to the heating of the air being compressed in the compressor section of the turbo. If left uncooled this hot air enters the engine, further increasing internal temperatures. This leads to a build up of heat that will eventually stabilise, but this may be at temperatures in excess of the engine's design limits- 'hot spots' at the piston crown or exhaust valve can cause warping or cracking of these components. This effect is especially found in modified or tuned engines running at very high specific power outputs. An efficient intercooler removes heat from the air in the induction system, preventing the cyclic heat build-up via the turbocharger, allowing higher power outputs to be achieved without damage.
 

Number_Cruncher

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>>I'm afraid it is.

Sorry Chris, I didn't see anything on that page which backs up your assertion. The paragraph you quote is talking about the hot exhaust gas side of the turbo - the intake side is much cooler.

In fact, the very next paragraph after the one you quoted goes on to say

"Compression by the turbocharger causes the intake air to heat up, rather than the air being heated by contact with the hot turbocharger itself, the vast majority is through the act of compression"

The supercharger, being inefficient in proiducing this compression will actually leave the gas it compresses hotter than an equivalent turbo.
 
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hi seeker, boyle's law and charle's law are based on the expansion of gasses with temperature.

benuilli's law is as i stated, volume /mass is proportional to the pressure providing the SG and system volume remain constant.

i have an HND in mechanical & electrical engineering and was design director at baxi uk for 30 years. part of our development work involved the gas and pressure laws. the simple example is a car tyre, if you increase the air mass/volume you increase the pressure.

boyles law which you have quoted means that as the temperature of a tyre increases then so does the pressure.P1. T1 etc.

let's get back to turbos and superchargers. best wishes. herbiemercman.
 

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hi seeker, boyle's law and charle's law are based on the expansion of gasses with temperature.

Sorry, can't let this one lie ;)

Boyles law:

"For a fixed amount of an ideal gas kept at a fixed temperature, P [pressure] and V [volume] are inversely proportional (while one increases, the other decreases)."

Or to put it another way: pV = k

Which has nothing to do with temperature.

Charle's law is the one to do with the temperature / volume relationship. :)
 

muller1

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>>I'm afraid it is.

Sorry Chris,
The supercharger, being inefficient in proiducing this compression will actually leave the gas it compresses hotter than an equivalent turbo.

Where on earth did you get this from ?.
I am afraid you have this the wrong way round.
It is not usual to fit an after or inter cooler to a supercharged engine (although you can) but most turbo engines have aftercoolers or intercoolers.
The supercharger has closer limits than a turbo and has a swept volume which is constant even at LOW speeds.
Lastly if the supercharger was inneffecient at probucing this compression as you say the air will be cooler as most of the heat is due to the compression of the air.
Just think how a diesel engine works.
Higher compression = hotter air.
This is a fact.

Mike
 

Number_Cruncher

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>>I am afraid you have this the wrong way round.

I don't think so.

>>It is not usual to fit an after or inter cooler to a supercharged engine (although you can) but most turbo engines have aftercoolers or intercoolers.

Yes, because it's more usual to use a supercharger as a low boost pressure blower, as I have already written.

If superchargers are so useful and efficient, why are they not fitted to truck engines, which are almost universally turbocharged? You have to think back to Foden 2 strokes and TS3 engines, where the scavenging function of a blower was needed to find examples.

>>has a swept volume which is constant even at LOW speeds.

Yes, that's my point about a supercharger being used as a scavenging blower to enable a 2 stroke diesel to start and idle - a turbo couldn't do this.

>>Higher compression = hotter air.

Broadly speaking, that's quite true, and can't be argued with. However, there are many thermodynamic processes which can be used to change the properties of the air, and the pressure versus temperature relationships are different for each process - as an example, compare an adiabatic process with an isothermal one.

In short, the process does matter, and, superchargers are significantly less efficient when compared with turbos. In niche applications, there are good reasons to use superchargers, but normal road going cars really isn'y one of them IMO.

EDIT: The P-V diagram towards the lower end of this page shows the difference between processes - http://en.wikipedia.org/wiki/Adiabatic_process
 
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HERBIEMERCMAN

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hi seeker, we are at cross purposes,your volume is the container's size, benullie's volume is the mass of air or gas flowing cubic feet / minute.

i know that if you have a fixed volume of gas in a certain size of container and you increase the size of the container the pressure will drop. your volume is the container, completely different situation, just the word volume being used in two different contexts. best wishes, herbiemercman.
 
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hi myros, the potterton suprima was one of several products with design problems which baxi inherrited when we bought potterton myson for £450M in 1999.

baxi was the biggest partnership in europe at the time and we bought potts/myson to make us the biggest heating company in europe.

as an analogy we had bought a ship that had been well painted, it looked good, but in time we discovered there was a big hole in the ships side and it nearly took us down.

we got into trouble with the repayment on the loan finance, which was the first and only loan baxi had ever taken on. the lovely caring bank pulled the plug on us, we lost the partnership and we were taken over by "newmond", a salvage slush fund company, at the time baxi was worth £480m.and we had just paid £450M. for potts myson, newmond got the lot for £400M.

this was eight years ago when i took my shares and took early retirement. i can liaise with engineers but don't mix well with short termists from the great british banking world.

prior to buying potts/myson baxi had superb products and customer support, which is how we were able to make our purchase.the more recent products like the barcelona condensing boiler,uk designed in preston, my lot, and the baxi 105E combi made in a factory we purchased in bassano italy, these combis go all over the world and are best in class. the products last year acheived "corgi" first prize and "which" top reccomendation.

buy the baxi 105e instant you will not regret it. several of my family have these products. herbiemercman.
 
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Myros

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Thanks herbie

I just wondered why my Mum's baxi bermuda gave no trouble for 25 years, and her gas fire for 35 years, but our Pottie is on pcb no3 after just 8 years, and now on for a gas injector as well.

With you on short-termism there. There is more to life than pure profit.
 

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hi seeker, we are at cross purposes,your volume is the container's size, benullie's volume is the mass of air or gas flowing cubic feet / minute.

I think there is some confusion occuring between the principles of static versus dynamic systems.
 
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HERBIEMERCMAN

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hi myros, the first design i worked on at baxi was the baxi bermuda plus i was still at college doing my HND. i guy called trevor dore from british gas watson house HQ, came to work for us, he had just graduated as a gas engineer, he designed the boiler and i designed the fire front, we started in 1964 and launched the product, the first of its kind in 1966. we sold nearly 4 million, they were bomb proof just like the old mercs. herbiemercman.
 

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Herbie

I know we are now well well off topic but I used to maintain the PC and printer kit in Baxi Preston (ooh, must be 12-15 years ago)! We may have walked past each other at some stage.

What I remember best is the subsidised canteen - great food, dirt cheap. Guess when I used to make the most calls into Baxi? :D:D:D

Dave
 

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