Exhaust work

First the quote of 450.00 was a lot steeper than before, but since he was local I gave him the job. Upon pickup of the vehicle a quick inspection I instantly noticed the mufflers were interfering parking brake cables. I was told this was "normal". It is not as the movement will either wear out the cables or cut a hole into the mufflers. I was then told it was my fault as I wanted "quiet mufflers". After a bit they finally fixed the problem. On to round two, once I had left the shop I notice there was now a large flat spot in the throttle from tip-in to 1/4 throttle. Looking closely to my other truck I notice that the new exhaust was much larger in size from front to rear. This does have an affect upon the operation of an engine. My case with a stock engine used in daily driving the large exhaust was a determinant to driveability. I was told he was not going to do anything & that I was an "idiot". So why is a too large exhaust system a problem you ask. It has to with velocity of exhaust gases in the system. The smaller the pipe the higher the velocity. This in turn with the pluses from the firing order create a vacuum effect behind the exhaust pulse that helps remove exhaust gases from the cylinder. With the vacuum effect the cylinder is ready for a fresh & FULL charge of air & fuel mixture. When a too large exhaust pipe is installed the velocity is effected & reduces the vacuum effect on the cylinder. This too large of an exhaust system installed into my ride is effectually leaving exhaust gases in the cylinder past the exhaust phase. This in end robs power & torque on the low end of the rpm scale due to a NOT complete charge of & air and fuel due to spent gases taking up the volume. There are many engineers who work hard at this at the factory to get the size correct. Mine was 1 & 7/8 inch internal diameter and not the 2 & 1/8 inch that Jim's installed. I would say with the attitude I got from Jim he fancies himself to be better than the trained engineers.