Yup, a really simple, basic question that reveals my automotive ignorance. But I've done a ClubLexus search, a Google search, heck I even asked Jeeves! There are lots of places that sell headers, but nobody seems to want to explain what they are and how they enhance performance. Anyone here want to give me the idiot's description?

 

think of it as the first part of a car's exhaust system. From the end there is the muffler that everyone knows about. Then there are mid-pipes, then catalyc convertors, then the front pipe and then headers. It's the thing that looks like many pipes going into 1. It is the first part the exhaust gas gets to after the combustion cycle.

it enhances performance like how a muffler or any other exhaust parts do. It helps the exhaust gas flow.

turbo cars don't have headers, they have turbo manifolds. Instead of directing gas all the way out of the car, it takes the exhaust gas back to the turbine.

 

Go to Hollywood Blvd. and vine Street in Hollywood and look for them standing on the corner. Those kind of headers go for about $20 bucks.....hahahaha.. Just kinding, i am joking. It was explained well already..

 

hey bro check this link out...this site is great for nearly any technical question you have...

http://www.howstuffworks.com/question172.htm

good luck

Bryan

 

Sounds like the same as exhaust manifold which is what I'm used to.

 

Another way of describing a "headers" is it is a "stretched" exhaust manifold. It helps increase power as the exhaust gas "bottleneck" - that area where the exhaust from individual cylinders join together before exiting into one pipe -- is further along the manifold. However, torque is decreased a bit as the back-pressure is decreased.

Naturally aspirated rally cars don't use headers as its speed depend much on mid-band power. Putting on a header actually kills performance when leaving a corner. Most other type of races will benefit from headers as it involves a lot of high rpm application.

 

So headers help you at high RPM (there's a lot of exhuast to push out and the back pressure is highest) but actually reduce power at lower RPM?

 

Headers usually refer to individual tubes or pipes That connect each cylinder to an exhaust system. The tubes are normally refered to as the "primary pipes." The primaries are connected via a collector. Performance race headers are usually of equal length design. The length of a header determines the particular rpm band that it is tuned for. This is due to the propagation of pressure waves in an exhaust that can help empty the cylinder during the exhaust stroke, and even assist in pulling in fresh intake charge during valve overlap. Merge collectors ( see http://www.burnsstainless.com/MergeC...ollectors.html for more info) can be used to "broaden" the power band of a header.

There is much mystique surrounding headers and the processes occurring in the exhaust system are not very well understood. Therefore there is alot of misinformation about exhaust headers.

As with any other performance device, headers must be designed to work with an engine system. The idea that rally cars do not use headers because it kills the bottom-end is false. The wrong header on any engine will kill the power/torque. The reason that rally cars may not use headers is that the conditions are grueling and the only exhaust manifold that will hold-up in those conditions is the stock cast iron manifold.

Turbo cars also benefit from running tuned length . Ever looked at the engine bay of a CART car?

Unfortunately, the problem with equal length headers is that a well designed and built header is typically very expensive. Any engine (well maybe I should stick with saying "most engines") can be optimized with a properly designed equal length header. I suggest looking at the Burns Stainless site for additional information on exhaust headers and collectors.

Vince

 

Sorry but "any" long-run header will kill the bottom-end. The shortest run header is still longer than any stock exhaust manifold and therefore still hurts the bottom-end.

It is far more inaccurate to advance the idea that headers are not used in rallies because it will not hold-up in those conditions. Headers will hold up as it should be properly braced when installed and is protected by the car's suspension (ideally not too stiff nor too soft ).

I should qualify my statement about rally cars. The truth is, and this is from personal experience, ( I drove in the ASEAN circuit in the 80s and SCCA Pro-Rally in the 90s), most special stages in a rally require a lot of low-end power due to the need to power out of tight hairpins.

As a newbie then, I actually used headers in my initial entry but killed my time during the first few special stages. Out went the headers and in came the stock manifold. Oh what a difference. Ever since, other drivers and mechanics, even the rally driving school, confirmed that such is the case with headers. But there is an exception - and this is on rallies that involve a lot of high speed tarmacs. That's where you want to have a properly designed headers. But you still have to really be careful here in that the probability of creating a mistake is more than the risk of using the stock manifold.

 

Whitels, a PROPERLY designed header will generate MORE torque than a stock manifold... PERIOD. Now, I am not denying that your experience was true, rather the header you used was not designed for the needs of the engine. The most critical component of a header is its collector. A large collector area will create a turbulent area that does not promote scavenging. At high rpms this is overcome and the primary tubes will flow MUCH better than stock "log" type runners and show a high rpm boost. As vroman suggested, read through www.burnsstainless.com for some very good insight on this situation.

Now, many stock manifolds are actually "headers". Honda and BMW (and most others now) have been building Tri-Y style "header" manifolds for years. The tri-Y design has 3 small 2-into-1 collectors (hence the designation) and this design is proven to produce more torque than a 4-into-1 large volume collector "header". This is the type of "header" BMW used on their 4 cylinder M3s of the 90s. Here is a link (BTW, this whole site has good info and data) http://e30m3performance.com/installs...haust/exh5.htm
I GUARANTEE that Rally teams would not replace this exhaust "header" with a cast iron manifold to gain "torque".

In the case of the Lexus V8... the stock manifolds are FAR from optimized. However, as already stated, the cost and effort involved in building a BETTER part would be prohibitive. Here is a picture of the passenger manifold http://www.users.bigpond.com/pgscott...s/standard.jpg
3 of the 4 ports enter the stream at 90 degree angles. The collector area is small and restrictive complete with the O2 sensors jutting into the very small runner. see here http://www.users.bigpond.com/pgscott...d_endsmall.jpg
LOTS of room for improvement. Just gonna be expensive to do so!

 

Could not have said it better myself. Thanks.

The other issue I would like to address is that long primaries promote low-end performance and short primaries improve top end performance. Therefore the stock OEM manifold does not promote torque because it is short. It is because it does not flow well, but then this kills top-end. The e30mrperformance site has some good information.

Vroman

 

Don't forget that the diameter of the pipes will play a large part in determining where your powerband will be. Obviously the smaller ( within reason ) pipes will generate more torque at the expense of top end power & vice versa. I never did much autocrossing ( I'm a dragger at heart ) so can't vouch for the durability of a header system for that sport but they certainly hold up in NASCAR. I tried the old trick of going slightly larger with the pipe diameter but adding a crossover tube just downstream of the collectors. This seemed to restore SOME of the lost torque ( about 40%, based on some dyno tests ).
Hey JB - So BMW "stole" the tri-Y header design from GM, huh?! I remember that those headers were originally on the old 389 cid "Goats" of the early 70's. That's a GTO for all U young whipper snappers!!
FWIW - RMM & some others feel that the stock GS400 exhaust system is fairly efficient as it comes from the factory. After all, they are true dual exhausts. Might be the reason why no one has developed a header system for the model just yet. I'm with the rest of the guyz - I DOUBT that U'd gain enough power with a custom designed header system for it to be economical enough to do. Now maybe with SRT's Stage 4 S/C or TT setups - HMM??!!

 

Gene, I certainly didn't mean to imply that BMW "invented" the Tri-Y header design... just thought that would lend more credibility to a modern Rally enthusiast than some 50's or 60's model American V8

So, you have modified your Y pipe? Have you posted pics of it here? If not, would you?

Do you have before and after dyno tests? What data do you base the 40% restoration of lost torque on? Do you have a before and after dyno for stock, modified, modified with cross over? Is it an "H" crossover or a "Y" or an "X".

Thanks

 

John - Guess it's my turn to clear up a statement!:eek: I was referring to the H style crossover tube I had on my '69 Z-28 WAY back when rocks were soft!! Haven't done any exhaust mods to the GS4 other than the Borlas. However, maybe I should look into trying one on the Lexus. Not sure how it'll work with the dual O2 sensors though. Might also have ground clearance problems as well but I'll jack her up & look anyway.