What makes a turbo spool?

[All Show]

I was talking to a couple diesel mechanics today and they were telling me that it is not the exhaust thrust that makes the turbo spin but the heat. Is this true? I can kinda see how this may work but then again it seems a bit odd. Their argument was that a turbo usually spins 75000 rmps and that the exhaust would not move fast enough to cause it to spin that fast. And that is also the reason why a turbo is usually mounted so close to the engine. If anyone knows how it works I would like to know.

Thanks

[beerbongskickass]

So if I get a blow torch and put it to my turbo with the car off, my car will start boosting? Lol I don't see how just heating a turbo up can make it spin. Oh and what about those cars I have seen with the turbo way back near the end of the exhaust? That's pretty far away from all the heat. This question looks like it involves lots of thinking though so I will let the smart guys answer.

[ryan89crx]

I was talking to a couple diesel mechanics today and they were telling me that it is not the exhaust thrust that makes the turbo spin but the heat. Is this true? I can kinda see how this may work but then again it seems a bit odd. Their argument was that a turbo usually spins 75000 rmps and that the exhaust would not move fast enough to cause it to spin that fast. And that is also the reason why a turbo is usually mounted so close to the engine. If anyone knows how it works I would like to know.

Thankstalk to those mechanics again and ask them if you can get a can of compression because you want more in your car. or maybe ask if they'll check your muffler bearings or blinker fluid. sounds like they were jerkin your chain a bit.

[bigwig]

Hes half right. The heat will increase spool times which is why a log manifold actually will spool sooner than a EL.

Its a combination of heat, exhaust gas being pushed, size of turbo, type of turbo, and im sure a hand full of other things.

Posts like this really make me wish i had Corky bell's Maximum Boost because im sure this is more than covered in there

[All Show]

I would like to hear from DseriesScience and hear what he has to say.

[redteg87]

They are right - but omitted information.

Exhaust gas velocity itself is too slow.

A gas in an enclosed space will apply pressure to the surroundings when heated. The incredibly hot exhaust gas expansion causes the turbine to spin.

[rotory20]

talk to those mechanics again and ask them if you can get a can of compression because you want more in your car. or maybe ask if they'll check your muffler bearings or blinker fluid. sounds like they were jerkin your chain a bit.

I dont care who you are thats funny right there...
ok yeah your getting yanked around, but you have the most versitile tool any one could ask for...
the INTERNET...
heres a little help..

http://www.turbocalculator.com/turbocharger-works.html

[gftgrill]

ok, since hot air moves quicker than cold air, wouldn't the heat that's built up in the exhaust gasses actually be moving quiker. thus the faster moving exhaust gasses would spin the turbine faster, actually creating more boost?

another thing to take into consideration is that the turbine is fairly small in diameter and 75000 rpms isn't that hard to get.

for example if your engine is running at say 7,000 rpms, at the turbo is spinning at 75,000 rpms. then for every 1 rpm your engine is spinning, then the turbo is spinning about 10.7 rpms. so on each exhaust stroke, each cylinder is spinning the turbo about 2.7 rpms. 75000/7000=10.7/4=2.7(rounded)

if you think about it, that's very easy for gas to do. if you had a little windmill type thing that kids get. it's not very hard to blow on it to make it spin fast.

now this would only work to a point, that's where the heat comes into play. the heat speeds up velocity of the exhaust gasses thus giving the gas more umph to spin the turbine.

I think I have that right, anyone please feel free to correct me if I'm wrong