Turbos, A What If Question

On are trucks We just run nitrous if we have one that's slow to light. Hit the switch and instant boost.

how about two small turbos. they call it a compound turbo set up. they spool up faster and having the two you will still put out the same amount.

vGT turbos are not practical on a tractor less the electronics are there as in the newer tractors with emission controls. Ford used them in 03+ along with dosge and there cummins power plant, Chevy in 04.5. Uses electroics to control vains in turbo to make the exhaust housing area bigger or smaller for quicker response and over all performance. But with tractors the manufacture already did the work for you by calling your nearest dealer. Pulling tractors With the right set up as in changing housings and wheel diameters for your needs.

MATPA47 wrote: Heat drives a turbo not air pressure. If you need more air and can't get more heat, put a bigger turbo under the small one.. Aka compound turbos.

I respectfully disagree.

A turbo is driven by the pressure of the exhaust turning a turbine in the turbo, which is connected to another turbine on the intake side. The turbine on the inside blows air into the intake, which results in boost (pressurized intake air) verses the engine needing to suck the air in on a naturally aspirated engine.

Heat has nothing to do with how a turbo makes boost, except the turbo gets hot (because it is driven by hot exhaust) The exhaust heat tends to heat the intake air, which makes it less dense. Some engines push the "boost" through an innercooler, which lowers the density and makes it burn better.

Ok if air pressure drives a turbo, then explain this. I'm driving up a hill with my trailer on my semi, I mat it and it's smoking like crazy, it's makimg 50psi of boost, then I get to the top of the hill and don't let off the throttle, I start going down the hill with my foot to the floor, boost falls to 5 psi, it's not making boost because there is no heat coming out of the engine! if air drives turbos then you would make the same amount of boost by revving your engine in neutral as you would fully loaded. Air pressure does not drive a turbo, heat does.

It's a combination of air volume thru the engine AND very hot expanding exhaust gases escaping the engine. Connect an A-C 185 non-turbo tractor to a PTO dyno and run the engine at full throttle, no load. Get yourself up on a step ladder and hold your bare hand directly above the muffler outlet and into the exhaust gas stream. I don't know how close you'll be, but probably 2 or 3 feet above the exhaust pipe I'd guess. Now, while your bare hand is comfortable at that location and with the exhaust temperature, I'm going to suddenly load that engine. Remember, a diesel engines air volume will be nearly the same from no load to full load (2400 RPM down to 2200 RPM) because there is no throttle butterfly like a gasoline engine. I wonder how many seconds it will take you to move your hand up much higher, or more likely move it clear away from the exhaust gas stream...???? The total air volume is almost exactly the same, less 200 RPM, but your flesh is now burned.......hot expanding exhaust gases drive the turbo. That is why the same tractor with a turbocharger has very little turbo boost at no load, but as soon as it is loaded may have 10 to 20 psi of boost.....the same thing that caused you to pull your hand away is driving and creating that turbo boost. Let's schedule a dyno date and set this demonstration up. I'll bring the ladder.

We must all be crazy.. I guess il go make boost with my special turbo that uses heat and air..

A turbo is like a jet engine. What makes the turbin turn in a jet engine? HEAT from the fuel being burned. There are no pistons or fan to push air HEAT from fire.  MACK

Mack, yep, heat, there is a temperature drop across a turbine as heat flows from hot to cold. There is also a pressure drop across a turbine as the flowing media moves from high pressure to low pressure (it has too!) Also, the density of the media has a role. Enthalpy is a term that basically means the total of a all forms of energy