quick garrett turbo question... opinions

[Otterav]

Originally Posted by Dougal

You'll find the relevant equations in any good thermodynamics text book. Turbine (brayton) cycle.

The 3B may have 10% more capacity than a supra engine, but it has only 50% of the rev range.
Which gives you 55% of the airflow.

The Brayton cycle is a constant-pressure cycle that describes the workings of the gas turbine engine, basis of the jet engine and others. It is named after George Brayton (1830–1892), the American engineer who developed it, although it was originally proposed by Barber in 1791. It is also sometimes known as the Joule cycle. The Ericsson cycle is also similar but uses external heat and incorporates the use of a regenerator.

You were the one who brought up the Brayton cycle. I researched it and proved your VOODOO engineering is truly in your head.
eric

[gerg]

I disagree Otterav. If you look at a gas turbine (Compressor, combustion chamber, turbine), a turbocharged engine runs off of the same cycle. Granted that the engine (combustion chamber) is more complicated than in a turbine, the turbo's turbine does draw from the exhaust gases to run the compressor that in turn feeds the engine air.
Check this out. A turbocharger that looks strikingly similar to a jet engine. I don't think there is any vodoo, just a different application of the principal. TechNudge DIY Jet Engine

And on a side note... does anyone know what the combustion chamber volume is for a 3B?

G

[Dougal]

Originally Posted by Otterav

The Brayton cycle is a constant-pressure cycle that describes the workings of the gas turbine engine, basis of the jet engine and others. It is named after George Brayton (1830–1892), the American engineer who developed it, although it was originally proposed by Barber in 1791. It is also sometimes known as the Joule cycle. The Ericsson cycle is also similar but uses external heat and incorporates the use of a regenerator.

You were the one who brought up the Brayton cycle. I researched it and proved your VOODOO engineering is truly in your head.
eric

Wikipedia doesn't count as research.
The joule cycle is not the brayton cycle, but to a layman the similarities may cause confusion.

The ericsson cycle model is based on isothermal compression (no charge heating), the Brayton on adiabatic (air heats as it compresses).
I'd expect everyone here to know that turbo compressors cause air to heat and hence understand why the Brayton cycle is the applicable one.

[gerg]

OK OK OK... I want a jet powered canoe!
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So does 42cc sound about right for a 3B combustion chamber volume?

Thanks
G

[Dougal]

Originally Posted by gerg

And on a side note... does anyone know what the combustion chamber volume is for a 3B?

G

That's an easy one.

Bore = 102mm
Stroke = 105mm
So Displaced volume = 858cc
Comp ratio = 20:1
So clearance volume = 857/21 = 40.8cc.

Total volume = 899cc

[gerg]

Ahh thanks. I wasnt sure if I divided by 20, or 21.
G

[Otterav]

Originally Posted by Dougal

Wikipedia doesn't count as research.
The joule cycle is not the brayton cycle, but to a layman the similarities may cause confusion.

The ericsson cycle model is based on isothermal compression (no charge heating), the Brayton on adiabatic (air heats as it compresses).
I'd expect everyone here to know that turbo compressors cause air to heat and hence understand why the Brayton cycle is the applicable one.

Again discounting anything that goes not fit into VOODOO engineering principals.
Whatever
eric
What part of this basic theory don't you understand?
Ideal Brayton cycle:

* isentropic process - Ambient air is drawn into the compressor, where it is pressurized.
* isobaric process - The compressed air then runs through a combustion chamber, where fuel is burned, heating that air—a constant-pressure process, since the chamber is open to flow in and out.
* isentropic process - The heated, pressurized air then gives up its energy, expanding through a turbine (or series of turbines). Some of the work extracted by the turbine is used to drive the compressor.
* isobaric process - Heat Rejection (in the atmosphere).

Actual Brayton cycle:

* adiabatic process - Compression.
* isobaric process - Heat Addition.
* adiabatic process - Expansion.
* isobaric process - Heat Rejection.

[gerg]

Holy crap I think im deaf now!
I say victory goes to the guy who can use a word with the most syllables in a sentance correctly.

So if there is heat loss across a turbochargers turbine, I assume that some of this heat is soaked into the turbo itself, and some is transfered into mechanical energy, and the rest dumped out the exhaust.
Would it make sense in a compound turbo set up to have the larger turbo first with the smaller turbo second in the exhaust stream? That is assuming there is less potential energy (heat) available for the second turbo to work off?

Ohh and by the way, I just love all you guys. Big hugs for everyone
G

[Dougal]

Originally Posted by Otterav

* isobaric process - The compressed air then runs through a combustion chamber, where fuel is burned, heating that air—a constant-pressure process, since the chamber is open to flow in and out.

And the prize for the biggest letters goes to.......

You'd better tell us what problem you have with that description of isobaric?
See turbo operating conditions often result in backpressure and boost being equal pressure.

When they don't you simply change the pressure at that part of the cycle. It's not that difficult.

Time to update my sig too.

[joshoisasleep]

Wow I can't wait til I can get around to reading the last 2 or 3 pages of this thread later tonight. I had no idea it had exploded so much... my own thread!

Just to clarify, I haven't been arguing either side, know nothing about turbos, and am stupid enough to drive a newly installed one cross country loaded to the gills in high heat with no egt or boost gauge. I look forward to voicing my opinion!

[ozwallaby]

Originally Posted by joshoisasleep

I had no idea it had exploded so much... my own thread!

and to keep with the theme of the thread... It's ALL your fault...

[Tapage]

Originally Posted by ozwallaby

and to keep with the theme of the thread... It's ALL your fault...

Pull your turbo, back to your NA 3B and close this thread ..

On a serius note: Josh, time you get your pyro installed and let us know what happen there ..

[joshoisasleep]

Originally Posted by crushers

okay, bring me up to speed...
this is what i have gathered from reading this thread.
you installed a turbo
you reused most of your orignal exhaust system
you do not have a pyro installed yet
you have not cranked up your fuel yet
you are experiencing over heating on long hills

is this correct?

Yes except the exhaust is now something along the lines of a 2.5" straight short pipe. It's really wide and really short with only one real bend. It's also really loud... but not like engine loud... it's quite high pitched.

An aircraft EGT gauge is on its way to me that will have a dual reading, EGT on one side and intake air temp on the other. Only thing is they have clamp style probes... I asked him for screw in but I guess he's decided I'd be better off with clamp style. What's the disadvantage here?

Originally Posted by crushers

you are not experiencing any of what that setup can accomplish SAFELY.

I know I'm an idiot. Hopefully I won't be scrounging for a head and rebuild kit anytime soon...

Originally Posted by gerg

OK OK OK... I want a jet powered canoe!
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What are we all doing messing about with landcruisers?! With global warming these things are what will be ruling the streets in a few years time!

[brownbear]

Thread closed for evaluation. Seems like too much bad blood in here.