Quote from Ball Bearing Turbo :

Yes, he IS serious, and he's technically quite correct I'm afraid.

Judas Priest...

The turbine side of a turbocharger is not driven like a pinwheel you find at the fair, although I can understand why people think that. Of course, there is some component of plain kinetic transfer but in fact it's quite small (I forget the typical numbers but it's not much).

Exhaust gases are very hot, and with that comes pressure (heat/pressure is the key). It is in fact the expansion of gasses inside the turbine that causes the vast bulk of energy transfer, and without heat that does not happen. In essence, it's working off of a pressure differential between the inlet side and the outlet side of the turbine housing. This is why you want large diameter plumbing on the outlet side, so that the pressure differential is greater and spool times are quicker (as opposed to an NA engine where you'd want proper diameter/length tuning for pulses etc). Just think of it as a compressed gas exerting pressure on a closed container - except that the container isn't closed, one side of it happens to move and one side is open.

If you think that the heat is not the dominant factor, simply play with a turbocharger on a bench - you can blow ambient temp air through it, and yes, it will move somewhat... However you can use a blowtorch to put much LESS air through it, and spin the thing up like crazy using far less "flow".

Predominantly, you're converting thermal energy (not heat if you want to be freakin anal) in to kinetic energy. No thermal energy, no happy fun times with your turbo. Burn more gas=make more thermal energy in the same little space = more pressure differential = more boost = more gas etc etc, a positive feedback device - unlike in LFS where boost is delivered linearly and then the increase tapers off.

...I don't get it. Can someone simplify?

Is there something specific that does not compute?

Quote from Mithras :

...I don't get it. Can someone simplify?

Exhaust gases are hot -> hot gases expand -> expansion of gases add to flow -> spin turbine more than the flow of (ambient temperated) gases would -> more POOOOWWWAAAH!!!

Quote from bbman :

Exhaust gases are hot -> hot gases expand -> expansion of gases add to flow -> spin turbine more than the flow of (ambient temperated) gases would -> more POOOOWWWAAAH!!!

It's not the flow per se, but rather the energy released during the expansion that is dumped into the blades on the turbine - so the velocity of the gas flow isn't the big factor.

This is also why the turbine housings are shaped the way they are.

edit:
http://images.google.ca/imgres ... m%3D10%26hl%3Den%26sa%3DG

Check out the turbine housing (turbine on the left, impeller on the right...) You can see that the gas is forced through a small opening (creater high pressure) and the the blades are shaped so that as gas expands between the blades, it causes torque on the turbine.

edit: another way to think about it: it doesn't matter as much what the velocity of the exhaust gasses are on the way IN to the turbine as it does on the way OUT of the turbine.

What a beautiful machine.

Quote from dougie-lampkin :

That doesn't matter, I didn't adjust ANY settings, so therefore the turbo is more efficient than the non-turbo, regardless of gearing, as it would be that way on a real turbo car.

Your "experiment" shows that the XRT has better fuel economy then the XRG. However, it DOES NOT show that turbocharged cars are more economical then non-turbocharged cars. Try your so called experiment with the same gearing in the XRT and XRG. It will be even closer!

Quote from wheel4hummer :

Your "experiment" shows that the XRT has better fuel economy then the XRG.

Which shows that turbo cars have a better fuel economy than standard cars....duh!!! If the XRT has different gearing, then that's the way turbo cars come. So turbo cars are more economical.

The Turbo also has different compression ratios afaik...

Either way LFS is _NOT_ accurate enough to work out which is better, although i'd geuss the Non-Turbo would be, but i really have no clue!

Quote from Jakg :

The Turbo also has different compression ratios afaik...

Either way LFS is _NOT_ accurate enough to work out which is better, although i'd geuss the Non-Turbo would be, but i really have no clue!

Well, from what I can gather (don't quote me on this - no really, don't) this experiment was originaly put together by theycallmebrian as an LFS experiment, and as such, I have been treating it as an LFS experiment. That's why I did the turbo vs non-turbo experiment in LFS, and not real life (which could have been organised!) to find out which was more economical.

BTW, as far as boost in neutral goes... It totally, completely depends on the engine at hand. I've seen cars that can generate 10+ lbs just by revving. Of course a small ceramic blade ball bearing turbo (teehee) helps that sort of thing, but it can be done. There isn't a "normal" because there are a lot of factors involved. Most driveable street cars can at least generate some positive manifold pressure without a lot of effort.

Very simply my understanding of why turbocharged cars are more economical (when running with negligible forced induction) for there power outputs (with significant forced induction) is that when they are cruising a modern turbo engine is very similar to a non-turbocharged version of the same capacity, obviously when you put your foot down you get a huge comparative rise in performance and the fuel economy goes out the window. I don't really see where this debate is coming from because without being terribly scientific about it the turbocharger isn't doing very much in the situations being discussed

...and W4H have you taken into account the proximity of local forests, makes a difference to the oxygen content in the air...

Quote from ajp71 :

...and W4H have you taken into account the proximity of local forests, makes a difference to the oxygen content in the air...

lol he's causing global warming!!! (in a race sim somehow) and also in summer oxygen content rises, and in winter oxygen falls, so you get better performance in summer (in cars with carbs, as discussed before!)!

Quote from ajp71 :

...and W4H have you taken into account the proximity of local forests, makes a difference to the oxygen content in the air...

But that is the exact opposite of what I was trying to imply. How many times do I have to tell you that that is not what I meant? I don't see how you get that insult out of my post, I just don't! STFU you f*cking c*nt.

Quote from dougie-lampkin :

lol he's causing global warming!!! (in a race sim somehow) and also in summer oxygen content rises, and in winter oxygen falls, so you get better performance in summer (in cars with carbs, as discussed before!)!

Density :doh:

Quote from wheel4hummer :

STFU you f*cking c*nt.

So much for the pretense of intelligence.

Nice work!

Quote from wheel4hummer :

STFU you f*cking c*nt.

Joe: last warning here, once more like that and you can have another, longer break. I don't care what anyone says to you, responses like that aren't welcomed. Also Scawen asked you to change your sig, perhaps you didn't see the post. Do it now.

Quote from Ball Bearing Turbo :

edit: another way to think about it: it doesn't matter as much what the velocity of the exhaust gasses are on the way IN to the turbine as it does on the way OUT of the turbine.

Just to complete this thought so nobody gets the wrong idea, it could more accurately be said this way: it doesn't matter as much what the velocity of the exhaust gasses are on the way IN to the turbine compared to what they would be on the way OUT of the turbine if it was held still. The whole point is that that's the energy that's dumped into the turbine.

Quote from Bob Smith :

Also Scawen asked you to change your sig, perhaps you didn't see the post. Do it now.

I'm not changing my signature until Shotglass changes his.

EDIT: It was erased anyway, and I'm too lazy to re-type it.

God this thread should really be closed right about......now!

Vast majority of cars are seriously underpowered, so when you accelerate you really have to ask lot from engine and still it takes long time to accelerate, lot of revs etc. When you add turbo you need to accelerate shorter time and you don't need to rev so much etc. that gives better fuel consumption. Well just one example that fits to some cases.