Is back pressure important with four cylinders? I ask that because I am looking at getting a custom header back 3" exhaust and I am a little worried that 3 inches is too much.

What do you all think I should do?

I appreciate your comments

 

You'll be fine with the 3". It is more future proof anyhow as you get more and more power. With your current setup you might a small loss in lowend, but once you get the stage kit or something with a smaller pulley, it will start to come back.

 

If it flows to freely i guess you loose back pressure and it effects your boost pressure. Im not an expert so dont quote me.

 

And thats what im worried about. I wanted to get the ZZP Header and downpipe, and just go 3" all the way back, but i dont wanna do that if it messes with my Boost Pressure.

 

I had a custom 3" exhaust put on while I only had the K&N cai on and I noticed an improvement in go. I would do it. As was mentioned, it will benifit every other power mod you do. And for the ones who say 3" will hurt your car, I predict they are all non 3" exhaust owners.

 

if you have an engine thats breathing well enough for the 3 inch exhaust, by all means opt for it.

 

They should ship my header downpipe combo monday... Hopefully, so ill give you a heads up when i get it installed.

 

less boost in this case is NOT a bad thing......i see so many people confusing loss of boost due to an increase in flow as a bad thing......wake up people

 

another thing.....guess what will happen if you ever get your heads ported and get bigger valves.....thats right you will loose boost OMFG better not do it then cause that must mean u will loose power /sarcasm off remember a engine is a big air pump the the easier it is to get the air in and out the better

 

Yea, definately let me know how installation goes, and how much of a difference it makes.

 

Makes sense, but a friend told me that 4 cylinders need some back pressure, so is that not true?

 

I love my 3" exhausts.

 

RANT ON

OK think...back pressure...pressure that is holding stuff back...what is it holding back...air...from where...the engine...what else does that...a clogged cat...what does that do...kill engine performance...from this we can conclude that:

backpressure kills performance

in turbo cars they operate on pressure differential so the less backpressure the better

in na cars they operate on exhaust velocity. backpressure is bad in either situation but the thing is ppl confuse backpressure and exhaust velocity...dumping air from a small pipe into a large one will kill velocity and may cause flow reversion and lack of pulling air from cylinders. This happens at low rpm and is why u lose some tq with a 3" because u cant pull spent exhaust out as well as a smaller setup...but the flow advantages of a larger setup make up for it high in teh revs where exhaust velocity doesnt matter that much and outright flow does. That is why the bigger pipes make more hp up top cause there is LESS BACKPRESSURE

Dan

RANT OFF

 

looks like im going with a 3" exhaust.

Thank you everybody for your help.

-Jordan-

 

no prob glad u didnt take it the wrong way

 

also another thing to keep in mind at least for the 2.0 guys is that last time i checked we werent lacking in the torque department

 

thats for sure, were probably better off losing some of that low end torque
I plan on going with the JBP 3" Full back sistem myself.(Header, Downpipe, Exhaust)

 

With future mods, and if your heavily moded, a 3" will compliment your set-up greatly, Works really well with my curent setup, and i plan on getting thr header dp combo soon.

 

Well if your planning on having more than 300whp then go for the 3" exhaust. As previously mentioned going to a bigger exhaust will hurt your bottom end. Especially at part throttle. Though the top end will benifit from it more. Also be aware about the extra noise from a bigger main pipe. As well as ground clearance loss. I dunno how well teh cobalts can tuck a big pipe but my T/A certainly has issues with my dual 3s I've put a few small dents in them and honestly if I knew I would have done this I woulda staywd with stock size exhaust pipes and installed dumps.

 

well, I've seen the JBP 3" and it's tucked pretty good, but I haven't seen any other 3" for myself. except for a custom one that was still being modified.

 

the 3in did cost me some low end grunt BUT the mid/high rpm power is worth the trade off...

in a race your winding out the whole gear and with us being rev-friendly the car makes up the low end differance and then some!

dam is rite about the "backpressure" VS" velocity" tho...good point!