[QUOTE=ConnClark;218634]Big rigs have them to aid in starting and engine warm up. In figure 14 of this report
http://aerade.cranfield.ac.uk/ara/1937/naca-tn-619.pdf you can see that fuel economy and power increase as intake air temperature go down. All the way down to 26 Degrees F. At -3 Degrees F there is some power loss at lighter fuel settings. The engine in this test was only 14.5 to one compression ratio so with higher compression ratios the peak power for the intake air might be at a lower temperature.
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Try unhooking your exhaut after the down pipe and let me know how the free running exhaust works for you. Everything has limits. That said, it won't be an issue if he stays with practial pipe size. I have seen trucks that run like dogs with dual 8" straight stacks.
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Actually I know people with engines just like mine who have run a straight pipe right out the side after the down pipe. It works great other than the fact its loud and against the law in most states.
I can't speak for the pickup trucks. They probably went with a turbo that is tuned for towing and max power that takes longer to spool.
Yes, and you stayed with a reasonable size pipe I assume. Had you gone too large it would slow down the gasses and create a buildup on the back side of the turbo.
Actually the whole idea behind the Diesel cycle is to keep the combustion stroke at a constant pressure. The closer you approximate this the more power you get per unit of fuel. Trying to get all the fuel to burn near TDC is like the Otto cycle which is less efficient.
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It is still not an Otto cycle engine. The HP/FE gains are well documented. It is the same principles used in VWs 150hp race version and in Mercedees new Bluemotion (well they upped the injector PSI, but same result)