Bigger Exhaust Equals Loss Of Power?

[rexxdoggy]

Help me out here. I've heard it before from a friend who drives an MX 6 and was wondering about it. I've been looking around online but haven't found much. Is it true that sometimes with a bigger exhaust, you lose power?

Thanks
Mike

[Harrry]

Help me out here. I've heard it before from a friend who drives an MX 6 and was wondering about it. I've been looking around online but haven't found much. Is it true that sometimes with a bigger exhaust, you lose power?

Thanks
Mike

Of course. Different exhaust is needed with different applications for a reason. That s why you don't see every car with the same exhaust system :crazy: lol.

[gdub520]

something about too large a diameter and too little backpressure???

[bcubed]

A huge exhaust will almost always have more peak hp, but sometimes at the loss of mid-range power.

I saw this in a "Harley tuner" book I was reading one day. Straight pipes give more peak, but there's a big dip at 3000 rpm-just where the typical hog cruises.

My advice would be to decide what you want to improve more: peak power or power potential at cruise rpms and use a proven system (let someone else be the guinea pig!)

[yamaha racer 686]

same tuning is used in motocross. different bends in the expansion chamber of a 2 stroke give it power at different areas of the powerband

[95pgt-t]

it has to do w/velocity and scavanging. sure a 3" will flow more volume than a 2.5" catback,but at the cost of velocity.

[rexxdoggy]

Alright, thanks. It makes sense now.

[Teal4Banger]

it has to do w/velocity and scavanging. sure a 3" will flow more volume than a 2.5" catback,but at the cost of velocity.

yep, bigger isn't always better, usually only a small increase in size is benneficial for a close to stock system. It is actaully better to remove restrictions by replacing stock resonators and mufflers with high flow ones than it is to increase the diameter of the piping. You should only need to increase the diameter of the exhaust if you intend to put that much more air into the enging (forced induction).

[rexxdoggy]

Whats the diameter of the stock piping in the SVT?

[jolly8286]

the stock piping is 2 1/4. (I think)

[WiredMotorSports]

Im pretty sure the stock SVT pipe is about 2 1/2 and with most 4-6 cyl unless turbo/Supercharged with nos ive found that that is enough size that there are no restrictions as well with the diff race shops around the area say that anything bigger with out the actual need for it does start do drown your HP purely of the loss of backpressure...now as far as BP goes, i still dont have that down as to what and y it is... Good luck. the stock SVT with new mufflers is probly a great way to go as its already piped bent and nicely tucked. i kept mine just put diff pipes and tips on and it sounds great

[99Mystique ATX]

Stock svt piping is 2.25" all the way back till the split at which point it goes to dual 2" piping...

Replacing the stock resonator is the best place to start. That is the most restrictive part of the stock cat-back. The rear mufflers are pretty much empty so not really too much to gain there.

After replacing the stock resonator, next big gains are going to be either optimizing the stock y-pipe or replacing it with one from BAT or Trubendz. Either that or headers are going to be your biggest gains.

[Bradness]

The last statement is quasi-correct. The stock resonator inlet/outlet is actually 2" in diameter and is used in all Duratec applications. The rest of the piping fore of the Y split is indeed 2.25".

A 2.5" system is good for an increase in power when modifying a 2.5L or a necessity when utilizing a 3.0L. Even better is straightening out the various bends in the stock system (rr piping in the Y pipe) and replacing the stock res. Plus the short piece of pipe which runs from the flange to the res inlet is crush bent and s/b replaced.

[rexxdoggy]

Hmm, sweet. Thanks for all your advice and info. So would you say this would be a good step by step way to get things done:

1 Replace stock resonator
2 Optimize Y pipe or replace with aftermarket
3 Headers

Or really, those would be the most gains you would say?

[BigBEN]

Matching up Headers and Y pipe with aftermarket stuff is where you will get the most exhaust gains if i remember correctly.

[Bradness]

Hmm, sweet. Thanks for all your advice and info. So would you say this would be a good step by step way to get things done:

1 Replace stock resonator
2 Optimize Y pipe or replace with aftermarket
3 Headers

Or really, those would be the most gains you would say?

Seeing as your car is a non-SVT, your best bet is as follows (yes I've been there, done that).

Replace your stock 2" exhaust with an SVT 1. Remove the factory res and replace with something else the correct (2.25") size. A straight pipe will make it louder with annoying raspiness. To get the full benefits, you'll also need a SVT main cat assembly as the stock non SVT Duratec exhaust has a 2.0" exit on the main cat (entry is OK). Alternatively, you can simply cut the pipe where it exits the cat and replace with a length of 2.25" straight pipe. You'll have to re-use the flange because it's an oddball OR you can cut both flanges off and replace them with a matching set. As long as you've done some other complementary mods (intake, t-body, chip, etc.) this will provide a nice gain with a bit more bite sound-wise.

Stock Y pipes are difficult to optimize and require lots of labour and some specialized tools and equipment. Better to simply replace with something else. The old SHOShop Y was the best that I've seen. I believe BAT copied their design and may still sell them. I don't like the MSDS Y as it keeps the highly restrictive V bend on the rr pipe.

Of course, tubular headers are the best but there's lots of labour removing and installing them due to very limited access UNLESS you're pulling either the transaxle or the complete drivetrain.

[WHEELSPIN]

something about too large a diameter and too little backpressure???

Yup, cars need back pressure. That is unless you are boosting, in which case backpressure is your enemy!

[KennyT772]

Same goes for zetecs right?

My muffler is starting to rust out on mine so I was thinking about just using the resonator and going pipe after. Would cutting the muffler cause power loss or should resonator go first?

[striker2]

Same goes for zetecs right?

My muffler is starting to rust out on mine so I was thinking about just using the resonator and going pipe after. Would cutting the muffler cause power loss or should resonator go first?
For the Zetec you can open it up to either 2.25" or 2.5" (which ever is cheaper for you to get) and still gain power.

[KennyT772]

But should I cut out the resonator, muffler, or both?

[striker2]

But should I cut out the resonator, muffler, or both?
I dont want to hijack this thread but if you look around in the zetec performance section there are numerious threads talking about exhaust for the zetec. there is one fairly recently that pretty much answers your question.

[95pgt-t]

Yup, cars need back pressure.
WRONG!!!! back pressure is bad on any car:nonono:

[striker2]

WRONG!!!! back pressure is bad on any car:nonono:
your both right. too much back pressure is bad, however about 2-3lbs of back pressure is good

[Barge]

Back pressure is never good... I mean, unless you're a fan of having hot once burnt exhaust gas in your cylinder instead of cold fresh gas/air in your cylinders... but i dunno, maybe that's just me.

[Harrry]

your both right. too much back pressure is bad, however about 2-3lbs of back pressure is good

YOU ARE RIGHT!!

You need proper balance of pressure inside the cylinder heads. So some back pressure is needed.

End of story now lets all get together and put together my 3L.:shrug: :laugh: