Bought the car with headers all the way back to a giant catback

[RandomFact314]

I was wondering if you guys thought it would help my city fuel economy to change the aftermarket pipes that come of my headers back to stock pipes (look at picture)

I would usually think stock would be better for MPG but since these aftermarket pipes are probably more light weight and probably easier to push the exhaust out since its all straight pipe I wasn't sure... Also, with these new pipes, there is no o2 sensor hooked up so that concerned me too.

I was also wondering if the aftermarket headers I have would be more fuel efficient that the stock ones were.

Thanks!

[mcrews]

I have seen charts that based on the displacement (cubic inches or cubic mm) and the possible air flow in can show what size pipe you should have to avoid scavanging.

Bit I just don't remeber where!!!

What I took away from it was that 90% of factory systems are pretty close to correct but tend to error on being slightly undersized.

The other varialbe is the rpm range that your are going to operate at the majority of the time.
For me w/ a 4.5liter V8 that range is 1700 - 2200. with the 2200 being accelerating and the low being what is 60-65mph on the freeway.

[oil pan 4]

I would say keep the headers.
My engineer friend put a set of pacesetters on his 4cylinder 2000 tacoma and picked up a little under 1mpg.
It was a very economical thing to do. He had a cracked manifold and couldn't get his truck to pass inspection. He could not find a used one that wasn't cracked. The dealer wanted $440 for a new one. Pacesetter sells a bolt in header for his truck and its under $200. Also if they crack, you can repair them very easy.

[CigaR007]

An aftermarket header, depending on the type (4-2-1, 4-1) can help with low-end to mid-range torque allowing for more efficient acceleration and cruising.

[jakobnev]

I doubt that the improvements of even the bestest exhaust would be worth the effort and cost - keep the fart cannon.

[graydonengineering]

Originally Posted by CigaR007

An aftermarket header, depending on the type (4-2-1, 4-1) can help with low-end to mid-range torque allowing for more efficient acceleration and cruising.

I agree. Headers are more efficient by design. They are not installed from the facory because they take up more space and they generally don't last as long as cast iron manafolds. They can rust though quickly if not cared for. If they are showing any signes of rust, wire brush them and spray with header paint.

The only reason I would mess with it is if the aftermarket pipe is significantly larger (more than one size) the stock. Some people want go way too big on aftermaket pipe, reducing back pressure too much. Usually a reputable installation shop will talk sense into people before they make this mistake though.

[brucepick]

I understand how + why headers and fat pipes would help on a car that runs at or near WOT and between say, 4000-6000 rpm (assuming red line somewhere between 6-7K).

But if you're going for max mpg you likely run at half that rpm range or less, and nowhere near WOT. So where's the benefit of the huge capacity exhaust system? I've always read/heard that you do need SOME back pressure. Running at low throttle and low rpm's I'd think there's precious little back pressure even with a stock exhaust.

[RandomFact314]

What about the air sensor? there is none hooked up to the rice cannon and I figured that would make it worse MPG than the stock one...

[mcrews]

For starters you don't have what you say you have.
"headers all the way back......"

Headers are pipes that extend individually from each exhaust port. they typically form into 1 pipe.
IF you REALLY had "headers all the way back" there would be 4 pipes going ALLLLLL the way back. There is only one pipe.
So you have headers. period. stop
you do not have a "cat back'. UNLESS there is/are CATalitic converter that we cant see right after the header that we can't see.
A "CAT BACK" exhaust is an aftermarket system that is designed to keep the catalitic converter in place.

From the various posts it SEEMS like you have a header, attached to a staight (no mufflers along the way) pipe and then some type of ricer muffler/glasspack on the end.

If infact that is what you have

and your goal is to get good gas mileage

what you have is crap.

If that pipe is bigger than 1.5 - 1.175 dia. there is NO backpressure. THat may be fine at wide open throttle but will do NOTHING for mpg

And the poster that said 'my buddy installed headers.......' well...........
Shortys, what? and what size pipe?
My Q45 has factory headers.......so whaT? I also have 4 cats.
You cant make blanket staements about the addition of one part that requries other parts to make it work.
And you REALLY van't post a 'poll' to decide what will work.
1. go do a test run. you have a scangauge right? run 10 miles at 45, 10 at 55 10 at 65. write down the #s. rpm, temp, mpg, load, hp
2. pull the plugs. the tips can show if there is scavanging
3. find the website that has the air intake air exhaust calculator
4. then post up

[RandomFact314]

Originally Posted by mcrews

For starters you don't have what you say you have.
"headers all the way back......"

Headers are pipes that extend individually from each exhaust port. they typically form into 1 pipe.
IF you REALLY had "headers all the way back" there would be 4 pipes going ALLLLLL the way back. There is only one pipe.
So you have headers. period. stop
you do not have a "cat back'. UNLESS there is/are CATalitic converter that we cant see right after the header that we can't see.
A "CAT BACK" exhaust is an aftermarket system that is designed to keep the catalitic converter in place.

From the various posts it SEEMS like you have a header, attached to a staight (no mufflers along the way) pipe and then some type of ricer muffler/glasspack on the end.

If infact that is what you have

and your goal is to get good gas mileage

what you have is crap.

If that pipe is bigger than 1.5 - 1.175 dia. there is NO backpressure. THat may be fine at wide open throttle but will do NOTHING for mpg

And the poster that said 'my buddy installed headers.......' well...........
Shortys, what? and what size pipe?
My Q45 has factory headers.......so whaT? I also have 4 cats.
You cant make blanket staements about the addition of one part that requries other parts to make it work.
And you REALLY van't post a 'poll' to decide what will work.
1. go do a test run. you have a scangauge right? run 10 miles at 45, 10 at 55 10 at 65. write down the #s. rpm, temp, mpg, load, hp
2. pull the plugs. the tips can show if there is scavanging
3. find the website that has the air intake air exhaust calculator
4. then post up

1) Obviously I didnt mean that there was headers that lead all the way to the back of the car -_-

2) Cant test with scan gauge right now because the speed sensor in the car is broken, fixing it soon

3) Chill out, its not that big of a deal