Why Aren't Headers Standard Equipment?

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Apparently, some low-po cars also come with headers from the factory.
My 318i has headers, although I guess it's fairly hi-po for its displacement, and it does make a lovely snarl when wound through the gears.
The rest of what was said above explains why most engines come with cast iron exhaust manifolds.
 
A lot of the reasons OEM's do not use headers is due to noise. Traditional exhaust manifolds are quieter and cheaper to make. Also a lot of late model manifolds look almost like headers anyhow. I just looked under the hood of a new 2015 Tahoe as it went down the line.
 
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Originally Posted By: supton
How many cars "need" headers? A few hp gain at an rpm that few use.


How many cars "need" more than four cylinders and two liters of displacement?
It isn't always or even usually about need, it's about want.
 
Originally Posted By: circuitsmith

Modern cast manifolds are far better than the "log" manifolds of yesteryear.

True but the old SBC iron Ram Horns are hard to beat and perform as well as or better than many tube headers.
Header performance without the drawbacks.
 
The primary reason OEM's don't do stuff like this, except in their high end offerings, is production cost, pure and simple. OEM's, like most any business right down to a mom and pop hotdog stand, will try to trim every dollar from production cost they can. To that end, they will only use what they need to get the results they need. Even a $1 part, if it is not necessary, will be trimmed off of production. When you factor the number of vehicles produced, that $1 saving runs into the millions of dollars. Sure, this is all about profits, but they have to compete in the marketplace with everyone else making vehicles. And the majority of potential customers don't think in terms of headers, superchargers, etc. They want a vehicle that does what they want, and the cheapest price they can get it for.

Hey! That is exactly what the OEM's are doing themselves!
 
Originally Posted By: OVERKILL
Stock M5 exhaust (foreground):

ssheadee39comp2.jpg


You'll note the cats are a fair ways back from the headers, which I would categorize as "mid length", as they aren't shorties and they aren't long-tubes either.


Does Bimmer play with the timing/firing order/etc. in order to get the catcons to light off, like Mazda does with the high compression skyactivs??

Yes, those are about mid lengths, but it perplexes me that they did not put the catcon right at the flange of the header (already quite far away from the exhaust port) for faster/more efficient light off, and instead put it way back in the connecting/intermediate pipe.
confused2.gif


I am guessing that unibody/subframe clearance and interference problems are the reason?
 
Originally Posted By: dailydriver
Originally Posted By: OVERKILL
Stock M5 exhaust (foreground):

ssheadee39comp2.jpg


You'll note the cats are a fair ways back from the headers, which I would categorize as "mid length", as they aren't shorties and they aren't long-tubes either.


Does Bimmer play with the timing/firing order/etc. in order to get the catcons to light off, like Mazda does with the high compression skyactivs??

Yes, those are about mid lengths, but it perplexes me that they did not put the catcon right at the flange of the header (already quite far away from the exhaust port) for faster/more efficient light off, and instead put it way back in the connecting/intermediate pipe.
confused2.gif


I am guessing that unibody/subframe clearance and interference problems are the reason?


Subframe and transmission.

The engine has a big electric air pump that runs for a bit on cold start, I assume to aide in lighting off the cats.
 
Originally Posted By: fdcg27
Originally Posted By: supton
How many cars "need" headers? A few hp gain at an rpm that few use.


How many cars "need" more than four cylinders and two liters of displacement?
It isn't always or even usually about need, it's about want.


I won't disagree with you, my contention is with the OP. I don't need 2-3 more hp at the cost of reliability/durability/initial purchase price. I don't want much less "need" headers.
 
Originally Posted By: artificialist
Some cars left the factory with pipes that are similar to headers. The 2.2 and 2.3 engine found in Honda Accords are built that way.


My 1995 Ford Escort looks like this as well.
 
Originally Posted By: circuitsmith
Tube headers make more noise under the hood as well as at the tailpipe end.

Tube headers extract and cool the exhaust gases from the cylinder more quickly.
That increases HC emissions and makes the cat converter take more time to warm up.


Headers aren't necessarily louder. On my Jeep, the under-hood noise is about the same as it was with the stock cast iron manifolds. Tailpipe noise actually dropped a hair when I put the headers on.

It does throw a little more heat into the engine bay, however. In my case, the headers allow the piping to be routed a bit differently than how the factory handled things, terminating the y-pipe further forward and allowing the cat to be moved closer (which led to it lighting off faster than stock and taking less drive time to become non-smelly) as well as making space to add a resonator where the cat originally sat to quiet it down further.
 
I worked for Dinan Engineering when the E39 M5 was new. Our headers increased power almost 40 HP. The stock manifolds are extremely restrictive and are designed for emissions only.
 
Originally Posted By: OVERKILL
Originally Posted By: dailydriver
Originally Posted By: OVERKILL
Stock M5 exhaust (foreground):

ssheadee39comp2.jpg


You'll note the cats are a fair ways back from the headers, which I would categorize as "mid length", as they aren't shorties and they aren't long-tubes either.


Does Bimmer play with the timing/firing order/etc. in order to get the catcons to light off, like Mazda does with the high compression skyactivs??

Yes, those are about mid lengths, but it perplexes me that they did not put the catcon right at the flange of the header (already quite far away from the exhaust port) for faster/more efficient light off, and instead put it way back in the connecting/intermediate pipe.
confused2.gif


I am guessing that unibody/subframe clearance and interference problems are the reason?


Subframe and transmission.

The engine has a big electric air pump that runs for a bit on cold start, I assume to aide in lighting off the cats.


Yes, it would HAVE TO BE a VERY 'high flow' air pump in order to help light off catcons that far away from the exhaust ports.
wink.gif
 
Originally Posted By: Scott_Tucker
I worked for Dinan Engineering when the E39 M5 was new. Our headers increased power almost 40 HP. The stock manifolds are extremely restrictive and are designed for emissions only.


I don't recall the gains, from many posts on m5board, being that high for the headers alone
21.gif


Maybe for the entire exhaust system? They have that squished crossover pipe, the resonator, and the massive quad mufflers. I'm sure that stuff is restrictive. But I don't find the stock headers look that bad quite frankly. Not compared to the rest of the exhaust system anyways.
 
Originally Posted By: OVERKILL
Originally Posted By: Scott_Tucker
I worked for Dinan Engineering when the E39 M5 was new. Our headers increased power almost 40 HP. The stock manifolds are extremely restrictive and are designed for emissions only.


I don't recall the gains, from many posts on m5board, being that high for the headers alone
21.gif


Maybe for the entire exhaust system? They have that squished crossover pipe, the resonator, and the massive quad mufflers. I'm sure that stuff is restrictive. But I don't find the stock headers look that bad quite frankly. Not compared to the rest of the exhaust system anyways.


It is close to that figure (40 rwhp) on LSxes for long tubes (at least the best ones) alone, as long as it is TUNED as well.
wink.gif
 
Originally Posted By: OVERKILL
Originally Posted By: Scott_Tucker
I worked for Dinan Engineering when the E39 M5 was new. Our headers increased power almost 40 HP. The stock manifolds are extremely restrictive and are designed for emissions only.


I don't recall the gains, from many posts on m5board, being that high for the headers alone
21.gif


Maybe for the entire exhaust system? They have that squished crossover pipe, the resonator, and the massive quad mufflers. I'm sure that stuff is restrictive. But I don't find the stock headers look that bad quite frankly. Not compared to the rest of the exhaust system anyways.


Since Dinan only produces their parts in 'stages' you generally wouldn't buy just the headers. The whole 5 stage package produce an additional 70 HP. I can tell you that the headers were the single biggest improvement and they added about 40 HP just by themselves.

We kept the squished pipe because it was there for a reason and eliminating it didn't add any usable power. It was their to smooth out exhaust flow in the pipe and eliminating would result in check engine lights due to turbulence near the O2 sensor.

The stock manifolds were incredibly restrictive with unequal tubes of improper length. The Dinan headers are equal length tubes of the proper diameter made of extremely high quality stainless steel and jet coated. It is built up from weld els which means the diameter of the pipes is consistent throughout the header.

The muffler weren't all that restrictive.
 
Originally Posted By: Scott_Tucker
Originally Posted By: OVERKILL
Originally Posted By: Scott_Tucker
I worked for Dinan Engineering when the E39 M5 was new. Our headers increased power almost 40 HP. The stock manifolds are extremely restrictive and are designed for emissions only.


I don't recall the gains, from many posts on m5board, being that high for the headers alone
21.gif


Maybe for the entire exhaust system? They have that squished crossover pipe, the resonator, and the massive quad mufflers. I'm sure that stuff is restrictive. But I don't find the stock headers look that bad quite frankly. Not compared to the rest of the exhaust system anyways.


Since Dinan only produces their parts in 'stages' you generally wouldn't buy just the headers. The whole 5 stage package produce an additional 70 HP. I can tell you that the headers were the single biggest improvement and they added about 40 HP just by themselves.

We kept the squished pipe because it was there for a reason and eliminating it didn't add any usable power. It was their to smooth out exhaust flow in the pipe and eliminating would result in check engine lights due to turbulence near the O2 sensor.

The stock manifolds were incredibly restrictive with unequal tubes of improper length. The Dinan headers are equal length tubes of the proper diameter made of extremely high quality stainless steel and jet coated. It is built up from weld els which means the diameter of the pipes is consistent throughout the header.

The muffler weren't all that restrictive.


good to know!
 
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