Ideal coolant temperature for fuel economy? 2

[dicer]

Any new discoverys on this topic?
Years past adiabatic was the buzz word for diesel economy improvement, what about SI engines?
Also induction temperatures? Ideal for power is cool induction, what about for economy?

 

[patprimmer]

Yes

Lower air density means wider throttle for same power. It also means lower power and performance and fuel consumption at WOT.

Regards
Pat
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[evelrod]

Ahhhhh. Finally we have segued into the "dirty air filter" scenario fuel consumption argument. Sorry, I couldn't help myself...;-)

Rod

 

[patprimmer]

But Rod

A dirty air filter is still a restriction on the intake side so it creates pumping losses exactly the same as the same restriction generated by a throttle, but yes I see the funny side.

Regards
Pat
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[LionelHutz]

Pat, that theory goes very much against the 48% gain in power also claimed.

Lets see, the claim was 30% economy improvement and 48% power improvement. If the engine remained at the same efficiency then a 48% gain in power would require a 48% increase in fuel consumption. Now, there is also a 30% fuel economy improvement, which is implied to be 30% of the origional fuel usage and also implied to occur at the same operating conditions which produce this 48% power increase. So, the motor starts at 100% fuel usage. Add 48% fuel usage for the new power to put the fuel usage to 148%. But, the engine needs to end up at 70% fuel usage, which means cutting the fuel usage by 53%. Are the numbers still believable?

 

[SMOKEY44211]

A large percentage of the power gains observed is directly attributed to the oil control techniques. In this case there was 35 hp @ 5900 rpm gained. This engine produced 110 hp in un modified form. Final form with all the modifications noted on earlier post was 155 hp. There is a lot of power lost by the crank churning in the oil. There is no additional fuel needed by reducing a parasitic loss. The pecentages in this case are fairly large because it's such a low power # to begin with. Over the road at cruise speed (2200 rpm) its only adds about 3% to the power and economy.-------Phil

 

[patprimmer]

Lionel

You have seriously misinterpreted my posts if you think I support SMOKEY44211s point of view.

I was in fact saying very little of it could be explained and was questioning where the rest came from. 30% power gains from crank counterweight design. Give me a break unless about 2000 grade oil is being used.

Gains by loss of friction should yield the same %age increase to both power and economy I would think.

My comment about smoke and mirrors was both a pun and a cheap shot at Smokey Yunick and his tendency to use bullshit to divert attention from his cheating, just like magicians use smoke and mirrors.

I was trying not to be to confrontational to SMOKEY44211, but I guess that horse has now well and truly bolted.

Regards
Pat
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[LionelHutz]

Pat, I didn't misinterprete your posts.

 

[patprimmer]

OK

Now I see what you are saying and I completely agree.

Regards
Pat
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[tbuelna]

Lets make it a bit easier, what induction temp would be ideal?
A simple hot or cold.

dicer,

Once again, that's not a simple question.

In very general terms, combustion cycle efficiency is dependent on pressure ratio and heat release. SI engines are detonation limited, so having a lower T1 allows the use of higher CR's (up to about 14:1), which in turn gives greater cycle efficiency. With GDI, injecting later in the compression phase gives a greater charge temperature reduction due to the fuel latent heat effect, thus reducing the knock tendency.

CI engines are not detonation limited, and a low T1 is not so critical. T1 needs to be high enough such that the T2 is sufficient to ignite the injected fuel, but the lower air density of hot intake air can be compensated for with increased turbocharger work. Indeed, the best efficiency in CI engines is obtained with a CR around 14:1 and very high levels of boost. Current production turbo CI engines all use charge air cooling, but it's for NOx reduction, and the intercooler's flow and thermal losses hurt BSFC.

Finally, there is the extreme example of turbine engines. Turbine engine efficiency is greatly improved with the use of thermal recuperators, which are heat exchangers that transfer heat from the exhaust flow to the compressed intake flow. In this case, it's the hotter the better. To improve thermal efficiency even more, turbine engines also use fuel/oil heat exchangers that cool the engine oil and recover waste heat in the fuel prior to injection into the engine.

 

[Lou Scannon]

tbuelna, nice analysis.
Remind me, what is the difference between a regenerator and a recuperator?