Exhaust flow - wtf ???

[MYBAD79]

A dual exhaust setup 2.5" pipes seems to be the most common setup on a 350 or 383. Some use a custom made dual 3" setup...
Now for years there is all this discussion about what muffler is the least restrictive.

I have a 2" single pipe on my 140ci (2.3L) Mustang. The engine is about as powerful as my lawnmower but that's beside the point: I removed the exhaust to fix a cracked pipe... I ended up replacing the rusted stock muffler with a stainless 2.5" Magnaflow muffler that I had laying around. Guess what I found.... the ceramic honeycomb inside the catalytic converter broke into several pieces and one big chunk was plugging the pipe, reducing flow signifficantly, I'd say 3/4 of the pipe diameter was blocked.

I removed the chunk of ceramic honeycomb and got all of the crap out of the converter. I expected this and the "performance" muffler to make somewhat of a difference... well... it did not...

It's quieter because I welded the fractured pipe and it's not leaking anymore.

It did not significantly improve performance, maybe a little but not much.... gas mileage seems to be better though....:1st:

 

[Twin_Turbo]

2.3L <- the problem right there :1st:

 

[MYBAD79]

I know.... 2.3L 4cyl, 105HP

but I'm getting 27mpg on the highway :yahoo:

 

[knodty]

I know.... 2.3L 4cyl, 105HP

but I'm getting 27mpg on the highway :yahoo:

Doesn't make sense !!! i get 19 mpg on my bb vette on the motorway with a engine that has over three times the cc as yours :confused2:

 

[bobs77vet]

I know.... 2.3L 4cyl, 105HP

but I'm getting 27mpg on the highway :yahoo:

Doesn't make sense !!! i get 19 mpg on my bb vette on the motorway with a engine that has over three times the cc as yours :confused2:

is that with the imperial gallons or us gallons? damn its good in any event

but getting back to Karstens ?.....i think many times people miss the whole picture of free flowing exhaust vs the proper back pressure.....i beleive you cant simply make more flow and increase power unless you tweak things up front so i am not surprised there are no big gains.....i also think the newer engines that were designed with computers dont necessaruly respond to simple changes as the older engines did

 

[MYBAD79]

I just put 1200 highway miles on this thing, 70-80mph and 24-27mpg (numerous fill-ups, small tank)... it runs fine on 87 octane gas so I can't complain

About the exhaust: I really did not expect a 20HP gain from the new Magnaflow muffler but unplugging the exhaust from the ceramic converter chunk really did not make a big difference, it was running fine with approximately 75% of the exhaust pipe plugged and if it wasn't for the cracked weld and the rusted muffler I would have left it alone and I would have never noticed the plugged exhaust....

 

[69427]

I know.... 2.3L 4cyl, 105HP

but I'm getting 27mpg on the highway :yahoo:

Doesn't make sense !!! i get 19 mpg on my bb vette on the motorway with a engine that has over three times the cc as yours :confused2:

is that with the imperial gallons or us gallons? damn its good in any event

but getting back to Karstens ?.....i think many times people miss the whole picture of free flowing exhaust vs the proper back pressure.....i beleive you cant simply make more flow and increase power unless you tweak things up front so i am not surprised there are no big gains.....i also think the newer engines that were designed with computers dont necessaruly respond to simple changes as the older engines did

Proper backpressure?

 

[Twin_Turbo]

backpressure, it's not a 2 stroke where you need a properly tuned exhaust for proper scavenging and eliminate overscavenging.

I hear that backpressure BS all the time, like ramming a baseball up the tailpipe is going to improve performance LOL

 

[MYBAD79]

I believe it's just a wrong term. Proper exhaust pipe size, especially the primaries is important on high performance engines - obviously NOT on my 140ci 4 cyl.... one example is the Hooker 1 7/8" primary tubes that seem to perform not as good as 1 5/8 tubes on a 350... or how great a LS1 responds to headers and the removal of the stock Y-pipe (F-body).

I've heard the term backpressure many times and for 2 stroke engines it's very important, not for a 4-stroke.

ramming a baseball up the tailpipe might not improve performance but blocking the exhaust flow with a chunk of ceramic honeycomb didn't hurt performance either.. :crutches::rofl: