The truth about headers

[sj960]

In the case of exaust manifolds and headers, no. The a4 is an actual header, as its not cast iron.. I was able to obtain one cheap at a junkyard so thats what I put in place of my a1's cast manifold. The a6 is a cast manifold. I believe there is a thread here on the forum complete with pics.. If you wanted, search and you'd see the difference.

I know this is an old thread, just wanted to clarify.... The A6 has a 4-2-1 header stock, the A4 has a manifold... or at least my friends stock A4 has a mani.... mine had a header stock.

[owequitit]

Someone switched your manifold, or you got lucky. Perhaps it was an early F22A6, 91 SE perhaps?

The F22A4 had a 4-2-1 tubular header stock, whereas the the F22A6 was also 4-2-1, but it was a cast steel manifold, as opposed to the tubular welded steel design of the A4. It is probably not uncommon to find them on A6's though. A lot of people switch them over because they are better, and I imagine over the years some have been changed because the original manifold failed and the A4 mani was readily available.

[90AccordEXR]

just curious, why would Honda go from using the better a4 header to the a6 mani??

[d112crzy]

cuz the a4 is special?(se) ask honda.

[owequitit]

I am just making an educated guess here, but I imagine it was for cost targeting purposes.

They probably made the A6 with certain budgetary constraints, and they were easily able to meet their increased HP goal with the IM, camshaft, and ECU change (10 crank HP isn't very much after all), and either decided to save a little money (the cast manifold would certainly be cheaper) or they were trying to hold the HP down to keep it from out performing another Honda product. They could have also been trying to bolster low end torque (don't know why as the A6 is a pretty good improvement over the A4).

It was probably just for incremental cost savings.

[deckeda]

... the a4 header is as good as the DC header and any other header for around $400 ...

Yep, yet so many people think that "can't" be true of a lowly OEM part. Normal market competition ensures that boring old stock engines like the f22a4 will already be pretty well thought-out.

just curious, why would Honda go from using the better a4 header to the a6 mani??

It was probably just for incremental cost savings.

While it's true that cast iron would normally cost less than aluminum or probably even steel, cast iron will cost more per unit if you don't make very many of them.

With all of those EX models sold, any extra cost of the a4 mani would already have been amortized --- it would have been no big deal to slap that on the a6.

So that leaves the question, why use cast iron for the SE, especially since it weighs more and in this case probably costs more (again, per units sold)?

Cast iron retains heat longer than steel or aluminum, and that would help for low-end torque and response.

[owequitit]

As I stated, INCREMENTAL cost savings. While the A4 manifold was ammortized out because of the quantity produced, it still would have had a similar per unit cost as the A6 manifold because of the construction time and complexity of the manifold. Plus, the EX production run would have totaled out to probably 15-20% of all units sold.

One of the nice things about castings is that I only have to make a new die for the part and everything else can pretty much be reused. That basically means that with the exception of the die, the manifold could have conceivably come from the same plant and tooling as every cast B, D, and F series manifold (in total, that would be millions of units). That would have more than offset the increased cost of the low production volume, not to mention the fact that the casting process is probably about 1/2-1/3 shorter than the process used on the tubular headers, and I can build countless numbers at one time.

That is why OEM's generally tend to cast or press everything. It is quick and cheap and allows many different parts to be made on one machine, with no need for reprograming.

Personally, I think they were also trying to hold the power down, because it is bad for business (as far as the Prelude is concerned) to have a leather lined, fully loaded 4 door that can outrun your sports car. I also suspect that it was for NVH reasons as a casting is heavier, which makes it more resistant to vibration, but castings are also more resistant to noise transmission. One of my biggest criticisms about the original A4 was the valve clatter that was present as a result of the sound reverberation down the tubes of the manifold. It is easier to sell a car that costs $2,000 more if that isn't there.

[sj960]

I have a 92 ex coupe, the f22a6 has a STOCK 4-2-1 header, not a cast piece that only has one down pipe, there are two runners that combine after the oil pan. I dont know if you have seen a6's in person or not, not saying you haven't, but trust me, the reason they put out more power is because like you said, the IM, cam, and header!!!

[owequitit]

I have seen many A6s in person as well as A4s. I guess I should clarify here, as it is a little misleading what I said before.

Cast refers to a construction method not a design. The A6 is still 4-2-1, just like the A4.

The bottom half of the A6 manifold, which is the 2-1 section that you are talking about, is identical and interchangeable with the A4 peice. I don't know why they did this, but it is actually not cast. The cast peice is the upper 4-2 section that comes off of the head. It is significantly different in construction and appearance to the A4 peice. If you were to upgrade, you would actually only need the A4 upper peice.

[sj960]

Sorry if i dont understand, but my upper and lower parts were both tubular.... so am I to assume that even though its tubular it can still be cast? I have never seen this before, every cast manifold I've seen is just that, a manifold, not individual runners.

[TypeG]

OK, So all headers are made of stainless steel, right?

no. some are made from stainless, while others are made from mild steel. most that come stock issue are cast iron. there are even some made from aluminum.

and just so you know, it's header, when its just one in a set. later.

[starchland]

im looking at megan stainless steel header off ebay, anyone have any reputable sellers links...

[Jacob_Neal12]

im looking at megan stainless steel header off ebay, anyone have any reputable sellers links...

I got myself a Megan 4-2-1 Stainless from the seller "ezplus2003" on eBay. Search for item #7995539049 if you want details of see that seller's store. I paid $152.45 including S/H.

I installed them and they definately inproved throttle response and gave me smoother and slightly quicker acceleration, but my engine bay is warmer as a result.

When you install it you will have to make a steel bracket for the header to mount to the bottom of the engine block and you will have to bend it to like a 15 degree angle or something. Make sure its at right angle or it will break the support off the header and you will have to re-weld it (increas friction inside b/c its not smooth). That happened to me but it was because I had an eshaust that was like 3" too long for the car and put pressure on that support weld. Took it to minekee (sp?) and they rewelded it for free and I still haven't made a new bracket so its free. I haven't had any problems but I haven't bottomed out either .

Good luck man, overall my MR header is great. Plus I like the color the tempered stainless turns after some driving. First its gold then it turns a blueish hue, its pretty sweet looking IMO.