wuz up, need to know if i can install headers and still have it sound like stock and still get the benifit of having the better flow? any help would be cool. ive got my intake on (sr) and am having a blast. thanks

 

Some members say headers make your exhaust sound more throaty, others say they notice no difference. The bottom line is headers change the sound minimally, if at all. Your SRI will pretty much drown out any sound they would add anyway.

 

could you put on headers w/ stock pipe and mufflers?

 

yes you can. from what people say you dont gain a whole lot from mufflers maybe a few HP. not much.

 

yeah this is correct. mufflers are really for sound. personally i didn't notice a major sound change when i put my headers on but i did notice *something*.

headers are completely worth it. i gained nearly 20ft-lbs of torque at redline from this relatively cheap mod!

SSTS

 

is that a butt dyno or an actual dyno with the 20ft-lbs

 

actual. you can check out my posts, just search under my name, although i don't have the whole sheet posted for viewing. now that i have a scanner i should actually post my stock and header dynos.

SSTS

 

I don't think it make much of a noise difference if you've got stock exhausts, headers reduce backpressure= more power apparently header wraps would help too, by keeping the heat in the headers and out of your engine bay.

 

Headers reduce head pressure not back pressure

 

you're both correct in a way if you think about it. it's all related since the pressure originates in the cylinder head and travels to the manifold. but it's not usually referred to as "head pressure".

the real measure with exhaust is back pressure since you're really measuring how much pressure is getting placed back against your exhaust valves when they open. most of you probably allready know but i'll say it anyway, the idea is more back pressure against the cylinder impedes the ability of the exhaust gasses to quickly escape the combustion chamber. bigger exhaust alleviates the back pressure, allowing the chambers to empty quicker and more completely, hence allowing the engine to breathe better and operate more efficiently.

somebody correct me if i messed up anywhere here, i'm a bit hungover this morning and i've been up since 5am.

importvizion - yes header wrap is good because it keeps your exhaust at a more uniform temperature which allows the engine to scavenge the exhaust gasses quicker and more efficiently, (the idea being that as your exhaust gas gets cold it doesn't flow as quickly) but for engines like our i don't think it would help much. big V8s and muscle engines benefit more from header wrap. for the price though it doesn't hurt. i wrapped my megans in some spots but only because of the resonance. whether i got any performance benefit from it i couldn't exactly say but i don't think i did. although like you said it does help keep heat out of the engine bay and depending on what kind of intake you have that could help too.

SSTS

 

I always thought "head pressure" was exhaust gas build up/pressure in the exhuast manifold and "back pressure" was the exhaust pressure at the mufflers?

 

well what you're saying is technically correct, and that's probably the term used to describe the pressure inside the chamber before the exhaust valves open (i honestly don't know) but when i looked it up on several automotive sites i got the following:

head pressure:
[1] Pressure which exists in condensing side of refrigerating system.
[2] Force caused by the weight of a column or body of fluids. Expressed in feet, inches, or psi.
[3] Refrigerant pressure in the lines and condenser between the discharge reed valve and the expansion valve orifice

and:

exhaust back pressure:
any pressure holding back the flow of the gases in an exhaust system. Pressure exerted in exhaust system in reverse direction. Also called back pressure.

also:

Definition: Restrictions in the exhaust system that slow the exit of exhaust gases from the combustion chamber. (i like this definition slightly better)



so i would be more inclined to say headers lower back pressure due to less flow restrictions through the exhaust system. pressure within the cylinder heads should remain exactly the same until the time the exhaust valves cycle open in which case it's subject to whatever the pressure of the exhaust system is - hence like you said: lowering head pressure to equalize it with the exhaust pressure. so you're right that it lowers head pressure during the exhaust cycle, but it only does that due to lower back pressure in the exhaust system.

i would also agree with you that your back pressure is probably measured at the mufflers (someone jump in and correct me if i'm wrong). i'm pretty sure you're right about that one but i don't completely know. i imagine it's slightly different at the manifold, but if your exhaust is all uniform piping it shouldn't be terribly different. the stock exhaust manifolds are overly restrictive and i imagine they create alot of extra back pressure as well.

SSTS

 

Nice write up.