How Turbos work ,the math and tech behind it.

SBSP · Post by **SBSP** » 14 May 2008, 12:15

Sorry had to start a new thread.

We all know how it works
http://auto.howstuffworks.com/turbo.htm

What i want to know is.

It generates Pressure from the force of the exhaust fumes spinning a 'fan' right. that spins another fan in a separated compartment. sucking in air and blowing it out again into the air intake of your car. at a rate measured in PSI/BAR

1 BAR = 14.5038 PSI
How many Kpa's = 1 BAR a 1000kpa ?

more combustion in the cylinders, needs more Air, and more Fuel ?
So if you push in more air, does the fuel injection system of you car some how measure AIR ?
Cus obviously if you add more air you need more fuel otherwise the ratio will be out, so you then might either running the engine to hot
and lean or mess up fuel consumption ?

a Citti Golf 1.4i as far as i know is the same as 1.6i except the Head is bigger. and delivers 11Kw more.
So in theory a 1.4i Citi should handle 11kw without harming anything. ? without needing to replace pistons and all that.

Anyone knows of someone that has a 1.4i with a turbo and how much kw its it deliveries ? and how much bars the turbo pressures.

To get the turbo pressure into picture here how much pressure are we talking about 10Bar ? 20Bar's
A polo GTI 5 bars ?

Post by **KillerByte** » 14 May 2008, 12:34

1 Bar is normal air pressure, as you said 14 pounds per square inch.

1 Bar = 100KPa as far as I remember.

SBSP · Post by **SBSP** » 14 May 2008, 12:39

KillerByte wrote:1 Bar is normal air pressure, as you said 14 pounds per square inch.

1 Bar = 100KPa as far as I remember.

Thanks Man.

Does a standard Fuel injected cars sense the amount of air and adjust fuel accordingly ?

I also wanted to ask how quick does a turbo spin RPM wise ?

Post by **KillerByte** » 14 May 2008, 12:42

i am no expert but I would suspect that a vehicle with an ECU would have to have it updated.

Where are the guys who know this stuff?

Skidd · Post by **Skidd** » 14 May 2008, 12:55

10 bar, 20 bar bwahahahahaha

You going to break something. Factory turbo cars like the Polo GTI only push at most 0.6bar with a 0.8bar over-boost. Anymore than that and fueling becomes a problem and not just the amount of fuel but the octane of fuel as well.

what a turbo is essentially is a compressor, it creates a positive pressure at the intake of the motor so when the valve opens more air/fuel gets pushed into the engine. It is one of the reasons why a turbo car does not suffer from a loss of power due to altitude.

The power production of a turbo motor is down due to the ability to sustain a "boost level". Certain factors come into play with this like turbo size, compressor and exhaust wheel trims, flow design of the turbo etc.

Now to answer your question. Turboing say you 1.4 motor there is a possibility, but you anything over 0.5 bar boost and you going to start getting detonation and if its severe enough you could break the pistons.

And here is why, say you have a 2lt motor, that motor in all its piston chambers can hold 2lt of air(at normal atmospheric pressure). Now say we start to boost that motor at 1bar(thats double atmospheric pressure). It is now taking that very same motor and pushing in double the amount of air into the motor, essentially making it a 4lt motor theoretically speaking.

PS: Maybe you should read this http://auto.howstuffworks.com/fuel-injection.htm to get an idea of how a fuel injection system works.

Skidd · Post by **Skidd** » 14 May 2008, 12:56

PSS: A turbo spins from anything of 15000rpm to 50000rpm depending again on design. A turbo is also designed to produce its best pressure at certian RPM ranges.

SBSP · Post by **SBSP** » 14 May 2008, 13:39

Great Thanks.

Next Question

The air from a trubo becomes very hot, When it compresses, does it cool down ?

Compressed Air is just compressed air , heat plays no role.

Can you have lets say 60oC heat at lets say 1 bar or have 40oC at 1 Bar

Cus when air is hot it expands, So you cant have different heats at the same pressure ?

So my conclusion is i can add .2 to .3 bar into my 1.4 i

Joburg pressure = .8bar + .3 bar = 1.1Bar in total

Hex_Rated · Post by **Hex_Rated** » 14 May 2008, 15:05

The air from a trubo becomes very hot, When it compresses, does it cool down ?

No, you need an intercooler for that.

SBSP · Post by **SBSP** » 14 May 2008, 15:10

Hex_Rated wrote:
The air from a trubo becomes very hot, When it compresses, does it cool down ?
No, you need an intercooler for that.

No, The inter cooler would be there to have more pressure. if you want to pressure probly like 1 bar and up

I think

Hex_Rated · Post by **Hex_Rated** » 14 May 2008, 15:13

It works on the principle that the cooler the air, the more air can fit in a give volume under a given pressure. I think they only put them on big turbos though, not sure.

SBSP · Post by **SBSP** » 14 May 2008, 15:17

Hex_Rated wrote:It works on the principle that the cooler the air, the more air can fit in a give volume under a given pressure. I think they only put them on big turbos though, not sure.

Thats what i think too.

But it might also be when the air leaves the turbo you loose pressure because of all the friction.

Take a bicycle pump and put you finger where it pumps air and partially close it, then pump it you will notice it would actually burn your finger

Lol yes i have done it before

Hman · Post by **Hman** » 14 May 2008, 15:20

Like Hex mentioned you need a intercooler to cool the compressed air down.

Why you ask, because blowing compressed air over your hand feels cool? The problem here is that with a compressor the air escapes from the compressed system and has room to expand, thus cooling down.

In a closed system like your car's induction system there is no room to expand, thus the air stays warm.

Why don't you want warm air, because it increases risk of detonation, and because warm air wants to expand it is at a higher pressure than cooler air, thus you have to lower boost, and you get less air and fuel into your cylinders.

Skidd · Post by **Skidd** » 14 May 2008, 15:29

Intercooler is purely there to cool the air down, it has no effect on boost levels. It yields more power due to the cooler air that has been said.

We even go more in depth and use a little nozzle to inject a mist of methanol / water mixture into the intake to cool down the charge temp's. It doesn't yield anymore power on its own but it increases the octane of the fuel and decreases the chance of detonation which allows for a higher boost level and so the end result is more power.

If you going to turbo your car with a "bolt on" kit, then i suggest you get an inter cooler installed for a more safe and reliable running car. With south African weather as it is things get pretty hot under the bonnet especially when the exhaust housing is glowing

SBSP · Post by **SBSP** » 14 May 2008, 15:32

Hman wrote:Like Hex mentioned you need a intercooler to cool the compressed air down.

Why you ask, because blowing compressed air over your hand feels cool? The problem here is that with a compressor the air escapes from the compressed system and has room to expand, thus cooling down.

In a closed system like your car's induction system there is no room to expand, thus the air stays warm.

Why don't you want warm air, because it increases risk of detonation, and because warm air wants to expand it is at a higher pressure than cooler air, thus you have to lower boost, and you get less air and fuel into your cylinders.

I disagree Mr Hman.

You cannot have 'a' GAS at 1BAR at 60degrees and have the same gas at 1BAR 40 degrees. in the same size compartment.

all kinds of gas cools down under pressure and have a specific temp at a specific pa. Thats how the fridge was invented.

so 1 bar of air is 1bar of air and 1 bar of air, and would be a x amount of degrees

Skidd · Post by **Skidd** » 14 May 2008, 15:39

NoSBSP you are wrong, you can cool down pressurized gas's

How do you think you get dry ice?

Post by **maxxis** » 14 May 2008, 15:53

So if you push in more air, does the fuel injection system of you car some how measure AIR ? The intake or throttle body is usually equipped with some form of air mass or airflow sensor.

Cus obviously if you add more air you need more fuel otherwise the ratio will be out, so you then might either running the engine to hot
and lean or mess up fuel consumption ? On some turbo applications an extra injector is added to inject more fuel or bigger injectors are fitted . The combination of throttle position, airflow etc will have the ECU adjust the amount of fuel needed.

a Citti Golf 1.4i as far as i know is the same as 1.6i except the Head is bigger. and delivers 11Kw more.
So in theory a 1.4i Citi should handle 11kw without harming anything. ? without needing to replace pistons and all that. Yes but why would you upgrade something for 11kw extra?

I34z1k · Post by **I34z1k** » 14 May 2008, 15:56

Ok first off

The bore of the 1600i and 1400i differ, the stroke is the same. Headwork, it's mainly the larger valves that allow more petrol in, which you will need if going turbo.

As pressure increases, so does temperature, so you want to keep pressure as high as possible while cooling it down.

WRT to your 1 bar <> 1 bar statement, rather work in mols or equiv.

Pv = nrt, the ideal gas formula.

Pressure x volume = moles x ideal gas constant x temperature.

So air @ 1bar x 1 litres worth = 1 mole (Ignoring the constant as it'll just complicate things) x lets use y for temperature...

Now @ 2bar, x 0,5 litre = 1mole x 2y (So twice as hot).

Take note, different pressures, different volumes, same amount of air.

Now basically, you want something like 1.5bar (In total so 0.5 bar boost), and say now 1litre, at as low temperature as possible to get as much air as possible in.

About the pressurized gas, how do you think dry ice is formed? Or how fridges work

SBSP · Post by **SBSP** » 14 May 2008, 16:15

maxxis wrote: Yes but why would you upgrade something for 11kw extra?

I like my citi, and like the sound of trrrrubo charger

sounds sweet!

to have the extra bit of power is just there to make it almost worth the money

I34z1k · Post by **I34z1k** » 14 May 2008, 16:17

Get the 1.6i head, it'll lower the compression enough to turbo it, and it'll handle the larger air + fuel intake too.

Skidd · Post by **Skidd** » 14 May 2008, 16:20

Bleh still a golf...

Maplassie_GTR · Post by **Maplassie_GTR** » 14 May 2008, 16:25

LOL@ skidd.

I have so many unhappy Golf R32's and Gti's in my area it aint even funny.

oh what's that mr G5 GTi did my dumpvalve sound in your window hurt your pride?

I wouldn't Even bother Turbo'ing the 8V 1.4i or going to a 1.6i Head.

Go 16V . Expensive, but worth it.

I34z1k · Post by **I34z1k** » 14 May 2008, 16:27

Dude, I've seen some 8vs make just as good power as 16v. Really...

I think Spongey wants to not go the whole shabang?

SBSP · Post by **SBSP** » 14 May 2008, 16:29

I34z1k wrote:Get the 1.6i head, it'll lower the compression enough to turbo it, and it'll handle the larger air + fuel intake too.

Ye but then i get back to the crapy brakes on a golf argument again

Bigger head = $$$ turbo = $$$ labour = $$$

In the end i can then just let SAC do a 2L conversation which they claim delivers 90Kw the the wheel in JHB. for 10K

I figure installing a turbo cant be that bad. all i will need is a few pipes a trurbo and a spanner or 2

Does any one know if the engine has to be taken out to get to the outlet manifold ?

Cheap turbo from Autostyle = 2K and the rest cant be more than 1K.

Maplassie_GTR · Post by **Maplassie_GTR** » 14 May 2008, 16:33

I34z1k wrote:Dude, I've seen some 8vs make just as good power as 16v. Really...

I think Spongey wants to not go the whole shabang?

I know dude, but 16V is better, cause I said so

Yeah going 16V is expensivo. My 16V head was 6K alone! It's rediculous seeing as a brand new 2.0 16V ecotec motor goes for between 12-16K and the Legendary C20XE (Superboss and calibra) goes for between 8 and 12K

I34z1k · Post by **I34z1k** » 14 May 2008, 16:38

Golly dude... Be very careful...

The lower CR means that you can boost more btw

Cause with a 0.5bar boost, you're car will be knocking like ANYTHING. You can pick a head up for about R650, find a cheap local backyard mechanic and whammo like R1200 for a car that'll run well then add the turbo and it'll fly

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How Turbos work ,the math and tech behind it.

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