redfire2002 wrote:
I have an egt gage and I assure you temps from stock to a 4" is a 200 degree difference. A muffler is all he needs. You don't want to go from a 4" down pipe to a 3" half way back. It's like an hour class, sand will flow fast at first then slow down as the opening gets smaller.
BBURD wrote:
Purchased (new to me) Ford 250, 7.3 ltr turbo, 126000 miles. Exhaust has been modified and has big tip. Wife says too loud. (I have to agree) Saw 4.5 inch tip silencer that attaches to tip of exhaust to supposedly quiet it down. Has anyone used? Will it restrict exhaust too much and inhibit performance? Etc Thanks
It is very true that it wouldn't make sense for the OP to install a 3 inch tailpipe. I agree, all he needs is a muffler. But I "reasoned" the muffler will have negligible effect on "restriction and inhibiting performance".
If an original installation only used a 4 inch header pipe, it might make a lot of sense. The exhaust would still dump into a large 4 inch pipe, likely retaining the coveted 200 degree drop. My line of thinking is that the forward part of the improved 4 inch pipe ahead of the muffler
may be all that is needed to enhance power. Incidentally, exhaust gas rapidly diminishes in total volume as it cools and contracts during it's trip, whereas sand never takes up less total volume, if that makes sense to you.
In other words, as the burned gas continuously cools and contracts in volume as it exits, the exhaust pipe diameter could logically continue to get tapered smaller and smaller like a gradual funnel. Of course a funnel shape wouldn't make practical sense, but my point is, the possible option to have a full 4 inch section up to the muffler, and then purposely drop down to a more economical size 3 inch pipe after a stock muffler, might allow money to be spent better elsewhere. Such a semi-improved exhaust system could sell for half price for instance, and possibly suffer no measurable performance loss. Food for thought.
TRIVIA:
On the exhaust leading to the turbo, my buddy used to wrap his Corvair "feed" exhaust to prevent pre-turbo heat loss (therefore pressure loss) in turbo performance. But right after the turbo, heat loss is ok, and free expansion into a low-restriction cavernous 4 inch pipe is a good way to do it. His factory Corvair only used stock diameter pipes and then free-flowing OEM turbo mufflers, but with a rear engine, there wasn't a lot of header length ahead of them for much pipe cooling and volume reduction.
Almost all two stroke dirt-bike type engines benefit from an expansion chamber and then taper to a
narrow "stinger" pipe that maintains the velocity of cooled gas for scavenging. This "tuned pipe" and the hourglass shape have one thing in common; the matter (gas, sand) moves slowly in the large "bell" part and actually faster in the tapered part. The key here is to note how unusually small the final stinger diameter may be and still be sufficient.
Wes
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