Header Measurements - HP vs. Stock...

[JSIR]

I just took my HP header off the car to replace the manifold gasket (as I initially re-used the stock one and it was leaking) with a new one. Since I have the header off I thought I would take some measurments compared to the stock piece.

If anyone is interested I finally got a good look at the downpipe that leads to the converter. Our stock downpipe that leads to the catalytic converter is double walled, but it is not split into two pipes. It is one pipe only contrary to some earlier opinions. From the outside it looks like a 3inch pipe, but internally it is 2 inches or less as it is double walled. Makes me wonder why DC and Comptech use split collectors on their headers if the downpipe is not split ?. The HP header main collector is not split, it is one large open collector.

Here are some comparison specs: (stock) , HP

Primary pipes - (33-35 mm) , 40-42mm min. to max. - O.D.
Exhaust ports - (40 x 33 mm) , 44.8 x 38 mm - I.D.
Collector - ( 52mm, split into 2) , 60mm single - I.D.

Generally speaking the HP header is just larger all over with a single large collector, pipe lengths seem very similar between the two parts. I recommend that the exhaust manifold gasket be replaced when installing a new header, the stock one was leaking a good bit when it was re-used. These gaskets weren't really meant to be used more than once, so a new one would be a good idea. This is the thin metal gasket that sits between the manifold and the head at the exhaust ports.

Just some info for you.

[natesi]

Cool; thanks for the info. I was wondering how restrictive the stock header was.

how much horse power do you think I would get if I just did a CAI and a midpipe replacement? Is the stock header free flowing enough to see significant gains you think?

[JSIR]

Originally posted by natesi
Cool; thanks for the info. I was wondering how restrictive the stock header was.

how much horse power do you think I would get if I just did a CAI and a midpipe replacement? Is the stock header free flowing enough to see significant gains you think?

The stock header really doesn't look all that free flowing to me, the way the 4 primaries are squished and triangulated into the main collector looks real bad. And the primary openings that mate to the head are a good bit smaller than the actual exhaust ports.

In the end my estimte is the HP header is worth about 4-6 whp gains, not as much as I would have expected given the vast difference in size, but I guess it is still decent. I am still pretty baffled by the way this k20 engine responds to mods. I am convinced that you can't get the full potential of each mod until you have a full intake, header, and exhaust upgrade. Doing just one or two mods doesn't show much gains, until the third part is completed. I found that the three parts combined are worth at least 12whp, how that is broken up over the individual parts is a bit of a guess.

[2k2civicSi]

mine is leaking a bit to but the gasket from honda is 44bucks ill do it sooner or later

[JSIR]

Originally posted by 2k2civicSi
mine is leaking a bit to but the gasket from honda is 44bucks ill do it sooner or later

damn that is expensive, I paid less than $30 with all taxes up here in our crappy currency, I would expect in the US it would be around the $20 mark.

[PogoFX]

Great info JSIR. So, do you think there is any performance advantage for the DC header vs. the HP based on the differences in construction?

[JSIR]

Originally posted by PogoFX
Great info JSIR. So, do you think there is any performance advantage for the DC header vs. the HP based on the differences in construction?

The construction/design of the HP header lends it self best to top end power. The DC header should theoretically have better bottom end or lower midrange power due to the split collector and slightly smaller runners compared to the HP. But in the only comparison I have seen between my car (HP header) and myeverlovinsir's car (DC Header) there really wasn't much difference either way, I would say the results were pretty close. Perhaps my HP header might make 1-2 more hp on the very top end max. , hard to say. The DC header is nicer looking, the HP header is lower cost.

[myeverlovinsir]

I splurged a bit for the looks. But I would
agree that they are quite similar in performance. I had the chance to get
that baffle plate off and was contemplating how it would run. I
think a 4-1 setup without the baffle plate would have been even
more interesting. I am puzzled to know why DC decided to run
with this? HP for sake of economy may have done the right thing. tks

btw: joey, thanks for the numbers, will have to make a
comparison of each soon.


Primary pipes - (33-35 mm) , 40-42mm min. to max. - O.D.
Exhaust ports - (40 x 33 mm) , 44.8 x 38 mm - I.D.
Collector - ( 52mm, split into 2) , 60mm single - I.D.

Wonder how close the 40-42mm measurement is to the
exhaust on the head? just a thought. Is there room to have
even larger exhaust primaries?

[JSIR]

yeah Glen I was thinking about that when your collector plate came loose on that DC header , you should have tried running it without the plate to see if it made any difference. If it happens again I would try it. They claim that the plate improves mid-range power, but it seems that we are dealing with pretty small changes at any given rpm, probably hard to tell.

[B18CXr]

see below post for pics


http://www.ephatch.com/forum/showthread.php?s=&threadid=5013