atomic_fungus (atomic_fungus) wrote,

#5258: Compensating?

On my way to work yesterday I saw a guy with a large pickup truck towing a trailer. I don't remember what (if anything) was on the trailer because my attention was captured entirely by the truck itself.

Huge dually pickup, bigger than normal tires...and four huge pipes sticking out of the bed near the cab, where some people like to put vertical stacks.

These pipes were monstrous. I mean, for a heavily-modified diesel truck a single four-inch exhaust pipe is generally enough to prevent back pressure; you can go to six if you want overkill. This guy had four eight-inch pipes sticking up, each ceramic-coated black, with well-executed bends and beveled ends. A professional installation of far too much exhaust plumbing for the engine he has.

Looking at that, I thought about what his intake had to look like. I made the assumption that he had some kind of aftermarket cold-air intake on the thing, which in all probability is a four-inch pipe with a K&N filter in a cold air box. The engine only needs a four-inch pipe to pull air in; and furthermore I can guarantee that the exhaust headers on his engine aren't bigger than four inches even if he went with an entirely custom exhaust system. There just isn't room on the cylinder head of a light truck engine for an outlet pipe bigger than an inch and a half at the outside; and that's stretching it.

So, assume a massively built Powerstroke V10 costing $20,000 with a Dale Banks turbocharging system. Further assume that it was shoehorned into a daily driver which is in really good shape but not a show truck. Assume monster turbochargers--maybe two for each side--and an epic torque figure. Even with all that, you still wouldn't need an eight-inch exhaust pipe (not even one) to prevent there from being any back pressure at all.

Look: the engine inhales through a four-inch tube. That cross-section is 12.6 square inches. Even accounting for expansion due to combustion it doesn't need to exhale through sixteen times the cross-section. (Four pipes of about 50 square inches' cross section each.)

Well, it's his truck and he can do with it as he likes. I don't have to agree that it's cool, though.

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