Exhaust system basics - Ranger-Forums - The Ultimate Ford Ranger Resource


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  #1  
Old 12-13-2006
optikal illushun's Avatar
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Exhaust system basics

Seen way to many people posting mis-informed information to people asking questions about exhaust systems, so ill take the time to explain.

First, an exhaust system is nothing more than a way to remove spent exhaust gases from the combustin chamber. anytime u can improve the flow through out the exhaust system, u increase its efficency.

id like to address the most common myth, back pressure.

what is back pressure? it is any restriction in an exhaust system and rescrictions is bad. peroid. u want the smoothest and quickest way to remove spent exhaust out of the engine. this in turn leads to mtyh #2...

removing a muffler(s)/cat(s) will result in less back pressure and less power. this is false. while it may not sound as good or be as good for the enviroment, removing the muffler (i do not recommend removing the cats) is a great idea...some opt to not replace it with an aftermarket one, others do. most of ur turbo or glass pack style mufflers (magnaflow, dynomax, borla, bassani, etc) are the best way to accomplish this. they are a straight through design so they will flow optimal but also keep the noise down. think about it like this, running a straight though muffler is just like running no muffler, just one has sound absorption material inside. also, chambered mufflers like flowmasters arent best to run for optimal performance due to the chambered design.

next myth is increasing exhaust size tubing. general u want to increase ur exhaust size one step over stock for most unmodified to mildly modified engines. anything larger and u begin to slow down the exhaust gas velocity and loose the scavanging effect. u do not loose power by removing back pressuse but by reducing the exhaust gas volocity by increasing its overall suface area. for a single exhaust on most rangers 2 1/2" is adaquate, for dual 2 1/4" is optimal (that is for a single in/dual out muffler).

Remember, an exhaust system needs to be tuned for peak scavanging, heat draw and efficency. so please, say no to back pressure.
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Old 12-14-2006
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Quote:
Originally Posted by optikal illushun
anything larger and u begin to slow down the exhaust gas velocity and loose the scavanging effect.



That is the most important and most overlooked portion of any exhaust system.

Good post man.
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Old 12-14-2006
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But if you decrease back pressure, wont you loose torque? Also, isn't it better to start off with a larger inlet size pipe and exit to smaller piping to keep velocity up?
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Old 12-14-2006
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Kind of like when the local ricer kids put 3" exhaust tubing and a 5" cantalope cannon on a 1.5L Civic and think that it's bad a$$. Too large of tubing definately hurts things and recuces torque. The largest I would go on a Ranger is 2.5 for single outlet exhaust. Dual exhaust looks good, but make sure to shrink down the size of the tubing to keep up the exhaust velocity.
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Old 12-14-2006
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Quote:
Originally Posted by klc317
Kind of like when the local ricer kids put 3" exhaust tubing and a 5" cantalope cannon on a 1.5L Civic and think that it's bad a$$. Too large of tubing definately hurts things and recuces torque. The largest I would go on a Ranger is 2.5 for single outlet exhaust. Dual exhaust looks good, but make sure to shrink down the size of the tubing to keep up the exhaust velocity.
So would 2.5 inch inlet to dual 2 inch outlet be good for me with 3 inch tips? I am looking to go to a dual exhaust setup and I tow allot, so I don't want to hurt my low end torque......
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Old 12-14-2006
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i prefer my 2.25 SI/SO exhaust for my 4.0, i have had alot of different setups and this is by far the best. IMO.

pretty good post for the most part.
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Old 12-14-2006
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Quote:
Originally Posted by zabeard
i prefer my 2.25 SI/SO exhaust for my 4.0, i have had alot of different setups and this is by far the best. IMO.

pretty good post for the most part.
same here with the 3.0 though. I gained noticeable torque and it sounds great too.
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Old 12-14-2006
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Quote:
Originally Posted by zabeard
i prefer my 2.25 SI/SO exhaust for my 4.0, i have had alot of different setups and this is by far the best. IMO.

pretty good post for the most part.
Yours is single in and out, just like I have now. I have the stock pipes with a flowmaster and the 3 inch tip. What size are the stock pipes? Are you saying that in order to maintain my low end torque, I should stay with SI/SO?

BTW, you are right, very good post.....
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  #9  
Old 12-17-2006
optikal illushun's Avatar
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Someone PLEASE stickey this!
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Old 12-17-2006
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nice info.
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  #11  
Old 01-06-2007
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STICKY PLEASE!!!
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