Wnts2Go10O

iTrader: (12)

http://mccabism.blogspot.com/2014/12...-enthalpy.html

"So, all other things being equal, increasing exhaust gas temperature with insulation or a log-type exhaust geometry will increase the loss of total enthalpy between the inlet and outlet of the turbine, increasing the power generated by the turbine.

However, there is another side to this coin: the required pressure drop between the turbine inlet and outlet for a desired enthalpy-reduction, decreases as the inlet temperature increases. Hence, if there is a required turbine power-level, it can be achieved with a lower pressure drop if the exhaust gases are hotter. This could be important, because the lower the pressure at the inlet side of the turbine, the lower the back-pressure which otherwise potentially inhibits the power generated by the internal combustion engine upstream. So increasing exhaust gas temperatures might be about getting the same turbine power with less detrimental back-pressure on the engine."

Ran across this and thought it could lead to some interesting discussion

Wnts2Go10O

iTrader: (12)

no one?

Meth Sled

iTrader: (1)

Makes sense to me.. As the turbine wheel itself is most efficient with no back-pressure from the outlet side of the exhaust housing.

iliveonnitro

This has been known for awhile and it's a big reason insulation for the exhaust system came about in the first place (other than protecting nearby components). In fact, the same principle works for wrapping headers.

I wonder how much, mathematically, the turbo and engine efficiency actually increases with exhaust temperature. The next step beyond this article is that the turbo is only part of an entire system. Eg, a turbo loses enthalpy when engine timing is increased. Does anyone, other than F1, actually pay attention to this? It's really only something that can be modeled and not measured.

Meth Sled

iTrader: (1)

Too much math for my head

Wnts2Go10O

iTrader: (12)

concerning headers... found this: http://www.mie.uth.gr/labs/ltte/grk/pubs/exhsysht.pdf

from the blog:
"As the exhaust gases pass through the turbine, they lose both kinetic energy and static pressure, but gain some internal energy due to friction. As a consequence, the entropy of the exhaust gas increases, and the enthalpy reduction is not quite as large as it would otherwise be.



However, (and here is the crux of the matter), for a given pressure difference between the turbine inlet and outlet, the reduction in total enthalpy increases with increasing temperature at the inlet. In other words, this is another expression of the fact that the thermal efficiency of a turbine is greater at higher temperatures (a fact which also dominates the design of nuclear reactors)."

So.. the higher the heat.. the better. It sounds like that as long as you dont melt the damn thing, make it as hot as you can.

I did find the equations covering this but well.. yea..
Scroll to 'Open Systems'
http://en.wikipedia.org/wiki/Enthalpy

iliveonnitro

Without getting into too much detail, I'm actually an engineer for diesel aftertreatment systems and run a lab that tries to optimize reactions in catalysts, so I'm pretty familiar with the back-end of these system and the heat they require. It's the fuel vs. EGR vs. turbo pressure vs. timing that is upstream where I'm not quite as knowledgeable as the true engine designers.

So, basically, yes. Keep it as hot as possible without damaging components.

Wnts2Go10O

iTrader: (12)

I think the most extreme version would be an anti-lag system which dumps timing to throw a lot of heat into the turbine.

Concerning the lack of experience of the 'front end,' I found this:
http://rescomp.stanford.edu/~efroeh/...erformance.pdf

Seems to show the relationship with the front end and what you have most experience with.

Guard dog

I think this is a good argument for a babysoft tune with a turbo. Keep timing low and exhaust temp high and let the turbo do the work.