How to make 30+hp for $500 or less... (DX/LX F22A1 only)

[CB7Man]

Interesting, In all my days junkyarding I have yet to come across one A6 with this "Cast" 4-2-1 exaust
I do recall some Canadian Accords using a seperate manifold, but the picture showed the same thing

I don`t know if i read this wrong, but i thought f22a4's were only in 90-91 ex's?

both of my 92 lx's have/had f22a1's in them.

You are correct A4 ended in Dec 1991
A1 was standard in 90-93 LX/DX
A1 Was in base model Prelude 91-93
A4 was in 90-91 EX
A6 was in 91 SE 92-93 EX/SE

Now some variations do exist in Canadian Markets
Ex in canada is like an A4 in 92
EXR however is an A6

[CB7Man]

WOW mine is cracked in the same exact spot

That is a major casting flaw, I noticed 3/4 accords in the JY have the same crack, just poor metal
Pushing stock HP it only makes noise when ice cold, once warm it "seals"

[owequitit]

Because NOBODY reads the stickies. Ever. Trust me on this one...





And Scott, I'll have to disagree with your claim that the F22A4 was in the 92-93 LX/DX... the F22A4 designation ended in 91. I've worked on quite a few 92-93 LX/DX models, and even owned 2 myself... all had F22A1s.

I'll have to check out the manifold on a 91 SE... I never even considered that it would be tubular... that has me curious!

That is probably true. I was trying to it from memory late at night. I remembered there was a designation overlap, but I can never remember what it was.

And yes, I have seen a number of 1991 SE upper halfs, and they were tubular, just like the EX. Cheaper to use one manifold design.

[deevergote]

Yeah, that definitely makes sense.

I wonder if that means the 91 F22A6 makes more power than the 92-93 F22A6... or if the A6 cast manifold flows as well as the tubular manifold...

[js593]

That is a major casting flaw, I noticed 3/4 accords in the JY have the same crack, just poor metal
Pushing stock HP it only makes noise when ice cold, once warm it "seals"

I have yet to see a 4-1 manifold crack here int he junkyards. I have seen the 4-2-1 cracked, but i think that may have been due to the accident... i

[Cdn Wolf]

great thread, if i dont go with a h22 swap i'll be doin this for the time being

[owequitit]

Yeah, that definitely makes sense.

I wonder if that means the 91 F22A6 makes more power than the 92-93 F22A6... or if the A6 cast manifold flows as well as the tubular manifold...

If I had to venture a guess, I would probably say that it flows equally. If it does flow slightly worse, I bet it isn't enough to make a difference overall.

[Camurai]

The tubular header will flow better because of the smoother design. A cast iron manifold will have a rough surface unless it's been extrude honed, which would be a monumental waste when you can pick up an A4 header for a few dollars at your local JY. At most, however, you're probably talking about 2-3hp difference. For comparison...

Cast iron 4-2-1 header from an F22A6:



Tubular steel 4-2-1 header from an F22A4:

[areannecl]

thanks deever- quick question though with the ecu what other steps should be done before installation? or is it just plug and play???

* Curious

[deevergote]

You'd need to wire up the IABs on the A6 manifold. I don't have a diagram handy, but there must be one around here somewhere... Other than that, it's plug and play.


Also, for the cast manifold... a little roughness helps to a point. That's probably more than what is useful, but a slightly abrasive interior wall will actually cause the slower moving air to act almost as a lubricant for the majority of the airmass. An overly smooth interior wall (which I'm SURE the tubular manifold doesn't have) will actually cause more turbulence, and less efficient airflow.

Still, I'm sure the tubular manifold flows better. However, it's also probably not THAT big of a difference that it would matter all that much. The A4 header most likely will NOT add 5hp to the F22A6.

[F20A CB7]

HMMMMMm, u have no idea wat hp mt f20a sohc is. i think its like 130


The only think i can acutally use and it worth wild is the ecu
I dont think an a6 cam would do much but a 272 yes, wat u think bossman

[owequitit]

The tubular header will flow better because of the smoother design. A cast iron manifold will have a rough surface unless it's been extrude honed, which would be a monumental waste when you can pick up an A4 header for a few dollars at your local JY. At most, however, you're probably talking about 2-3hp difference. For comparison...

Cast iron 4-2-1 header from an F22A6:



Tubular steel 4-2-1 header from an F22A4:

I can guarantee you there is a lot more to the total flow of an exhaust system than just the internal surface of 1/2 of the manifold. The odds are likely that there isn't a total flow difference between the A4 manifold complete and the A6 manifold complete. You have the inner diameters, the shapes and the curves of the bends etc. You would need a flowbench at the very least to verify it, and CFD on the top end to figure out why the results are the way they are.

For instance. Since the A4 manifold is double walled with a space between both walls, that means the ID is quite a bit smaller than the OD that you see on the outside. The cool thing about cast vs tubular manifolds is that the cast metal is thicker and thus retains heat better, negating the need for the double wall construction on the A4, which was there solely to improve cat light off. I would be willing to bet that they could enlarge the inner diameter a fraction of an inch and offset the additional surface friction inside the primaries. Not to mention the fact that the steel used to make the A4 manifold in the first place was not the greatest for surface friction because it had to be cheap and mass produced.

If you look at your posted pics of the A4 vs the A6 manifold, you will also see how abrupt the collectors on the A4 manifold are vs the more gradual merges on the A6. That alone could potentially offset the difference. If you look at a high end collector such as Burns Stainless, you will notice that they will try to merge the exhaust gases over the longest possible distance, and will try to do so as smoothly as possible. Why? Because the more abruptly or severly we force gases to change direction and velocity, the more resistance to flow we get.

There are a lot of less than ideal variables in a stock manifold, and the A4 is no exception. Just because it has tubular construction, doesn't mean it is automatically better. There are about 1,000 different variables in play, and that is only accounts for a couple.

I bet if you flow tested them, they would be almost identical. If the A4 was better, I bet it would amount to less than 2 CRANK HP.

[owequitit]

HMMMMMm, u have no idea wat hp mt f20a sohc is. i think its like 130


The only think i can acutally use and it worth wild is the ecu
I dont think an a6 cam would do much but a 272 yes, wat u think bossman

The A6 cam makes a VERY noticable difference on an F22A1/A4.

[CB7Man]

If there is any flaws in the cast header, carbon seems to make things smooth

[PakaloloHonda]

Ok, then what I have here is from an A6?
Is that correct?
So this would be more beneficial then the stock a1 that I have?
And is it really, really necessary to re-istall the heat sheild? Because I dont have it.
Unless of course the a1 heat sheild fits back over the a6?
And I've read every post in these 12 pages .. very, very awesome info,
specialy the ecu stuff .. I have intake, (a6 header) and exhaust ..
Maybe look into a re-chipped ecu ..



A Hui Hou !!!
Tomi