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Discussion Starter #1
Do I have this thought out right?

I installed a moderate turbo upgrade, and it gave me increased boost. The boost comes from the heat exiting exhaust. If I now turn up the fuel some I will get more power, but the added heat will actually INCREASE the boost levels. This keeps escalating until I finally reach a point that more fuel will not add more boost, because I'm at the limits of turbo capacity. At that point more fuel just adds more engine heat and a rich mixture.

Is that correct all the way thru?
 

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Yes that's correct.
The more fuel - more boost cycle feeds on itself until limited either by the fuel supply (i.e. your right foot) or the strength of your engine (expensive).

Kind of on this topic, I figure that at max torque I'm currently running an air/fuel ratio of about 28:1 as a result of using boost to keep EGT's down with no intercooler.
I figure a good intercooler will bring me down closer to 20:1.
 

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Interesting! I was first confused, thinking more fuel only creates the need for more boost. Then realizing boost can be a product of more fuel it gives a clearer pitcure.

I originally thought that exhaust gas simply blew on the turbo impeller, like the wind or your breath on a pinwheel. Then to hear about the exponential power being actually gotten from HEAT, NOT air/gas motions, well a real head scratcher there! Almost more similar to a steam engine.

It's a shame we haven't developed more of our techno-cleverness: add a heat pump engine at exhaust, post turbo, to drive all accessories of any type with no horsepower loss? Why not?

I'm still wondering on diesel Air/Fuel ratios. So used to gasser numbers and stochiometric perfection! Diesel throws it all out the window!
 

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Interesting! I was first confused, thinking more fuel only creates the need for more boost. Then realizing boost can be a product of more fuel it gives a clearer pitcure.

I originally thought that exhaust gas simply blew on the turbo impeller, like the wind or your breath on a pinwheel. Then to hear about the exponential power being actually gotten from HEAT, NOT air/gas motions, well a real head scratcher there! Almost more similar to a steam engine.

It's a shame we haven't developed more of our techno-cleverness: add a heat pump engine at exhaust, post turbo, to drive all accessories of any type with no horsepower loss? Why not?

I'm still wondering on diesel Air/Fuel ratios. So used to gasser numbers and stochiometric perfection! Diesel throws it all out the window!
There's an easy way to picture the turbine feeding off heat, it's not 100% accurate but it works quite well.
The hotter the exhaust gas gets, the more volume you've got flowing out the exhaust. Since the turbo scroll is a fixed size bigger volume means it has to travel faster and travelling faster spins the turbine better.

I believe there's a lot of research going on with waste heat recovery. A whole array of little thermoelectric devices (which turn heat into energy) has been tried, but they're still quite new and efficiency quite poor.
BMW is working on something along the lines of steam generation using the waste heat.
Such things are easy to fit into stationary applications like power generators, but are quite a challenge for a car.
 

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Discussion Starter #5
Good info Dougal, thanks!

I once installed a waste heat generator into a canning plant. They had to heat the canned goods to quite a high temperature, can't remember exactly what, and were using a steam plant to do it. I installed turbofan gensets after ducting the waste steams and the electricity generated was more than enough to light and operate the whole plant year round!!
 

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The boost/fuel relationship is a codependent relationship as you guys have discussed. One point to understand is that the turbine on your turbo is not simply driven off of exhaust volume but heat transfer. The greater the heat differential across the turbine the harder it is driven. This is the main reason higher EGT drive the turbine harder.
 
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