Ok, I've been hearing rumors to contradict what I thought was true...

DC JDM and JDM 4-1 collector's ARE 2.5 inches.

I've heard now that, JDM 4-1 is doubled walled and not a true 2.5 inches, while the DC JDM is....now I thought that altho the JDM is double walled, it was still 2.5....

true/false/maybe?

 

The JDM 4-1 collector's inner diameter is <U>not</U> 2.5" (just a bit smaller). HTH.

-Shawn

 

I don't know the measurements, but I can tell you that the DC JDM Stainless collector is DAMN close to the Mugen JDM 4-1. I compared mine to my friend's Mugen. Really. Anyone who spends that much money on a Spoon or a Mugen header at this point is stupid. For $500.00 less, even if it makes 2hp less(which I doubt), the DC is 100% worth it.
It's even a better deal and a better performer than a JDM 4-1 and the ceramic DC can be had for less than what JDM 4-1 goes for USED!

 

I dunno, I got my JDM 4-1 brand new with heat shields (upper and lower) for $350 (hookup). I think the DC SS JDM header is about the same price, more or less. Plus with the DC you don't have any facility to attach a heat shield to it, and it will void your warranty whereas the JDM one will not. True, the DC JDM header might be a good choice for those people who are out of their warranty range, but for those who are still covered, I'd splurge and get the JDM instead.

 

Hmm. What about those of you with the bigger setups (cams, etc)....I can't justify dropping almost a grand on mugen/spoon/toda....the JDM seems to be more than adaquate for the basic bolt on setup and maybe a toda B setup later down the road...?

 

I will agree with Mike the DC JDM is a replica of the MUGEN 4-1.

 

J, I'll make ya a deal,

You get the DC or JDM header and just for fun, next summer when you have The time "on break" Lets go and dyno together. Hell lets get a bunch of guys together and dyno. And post the results. between all of us we have a bunch of mods that Everyone questions about EVERY Day!

And BTW if with your DC or JDM header "just for fun again," if you win with more HP or TQ, I'll buy you lunch, Heh Heh Heh...

All in fun now but I'd love to see a dyno to set this straight too,

A.

PS Turkey-day holiday is sooner if you are free and will have the header? We had a dyno day set but had to cancel about a month ago.

PPS we also should Dyno my "icebox" against your AEM/CAI.

 

aftermarket headers will void your warranty?! Tell me it aint so...

 

Why doesn't this board have a tech archive?

The DC JDM has a 2.50" OD x 2.37" ID collector. The JDM ITR has a 65mm (2.56" OD) x 55mm (2.16") ID collector. The ID on the ITR JDM is smaller due to the anti reversion chamber in the collector and is actually a little smaller a couple inches in from the end of the collector. The JDM ITR has 43mm (1.69") OD primaries (I don't know what the wall thickness is) and the DC JDM has 1.75" OD x 1.62" ID primaries however the DC JDM primaries are a little longer than the JDM ITRs.

 

Hey SMSP,

Heres my question: Why aren't you a Tech somewhere? You obviously are intelligent and know your stuff with regards to Bolt-on performance and H & E, and Tuan holds you in High regards, So why aren't you a Tech either her or on SHO?

That way you could start A Tech archive related to this and many other similar topics.

You know as well as I that this Topic and all it;s variants have been covered here and elsewhere to DEATH! I mean I learned and am still learning but, "Hell, I've held off getting a catback ever since I saw your system a bunch of months back." But you're right and most new guys get turned off by Snide remarks from people who Think they know alot, "trying not to include myself."

I know I don't know half as much as you technically in relation to some things Auto related, "I just have some personal exeriences to draw upon." But most here and on SHO learn by many others mistakes. Thank God others make these mistakes and post results so others "Me included," may prosper.

IMHO,

A.

 

Actually technically there is not such thing as 2.5 inch collector it just we US people like to round up. The JDM collectors on OEM and some aftermarket headers are 60mm which is actually 2.36 inches. The Mugen and Spoon header is 60.5mm which is 2.38 inches. If the JDM DC sports header is based off the JDM OEM header it's smaller then the Mugen by slight bit and even if it's a copy Mugen it's still not even 2 and half inches. Also I do not believe there is 64mm piping..as the normal next size up is 70mm piping which is 2.75inches in dia. From what I've seen of DC sports headers they tend to rust..I have one on my CRX and it's rusting in the welds and corners and they don't use salt down here in the south plus it's not even driven all that much just few times a week. Friend of mine bought one for his GSR and it's rusting as well..got it replaced and that ones now starting to rust. For me on my ITR I have spoon header and it's not rusted even in the metal scratches. For me seeing that rust header makes me wish I kept oem header on it because in yr they will look the same with the rust look. But for me I just rather spend the money on something that someone put quality into and not put it on some NCR machine and do it for you...DC Sports had few recalls in the past on there headers for parts not working right or actually pieces falling off. I believe it was a TL that came into Acura shop that they found piece of metal in the header. If you want US header get a Comptech in my opinion that or JDM header. I believe the pricing I got one JDM header with front and back sheilds and all shield screws and gaskets flange and dounut..for around $415-425 shipped I was planning on selling them for. Just waiting on my JDM catolog..already got pricing on JDM DC5 Parts already.. Sorry to rant but DC sports just hasn't impressed me. The reason DC Sports even has JDM header now is because company bought rights to dist DC Sports in Japan and they need JDM headers to fit..Integras and such. Its funny they sell for 77,000 yen in Japan..which is $673 with tax in Japan...just under the price of most Japanese manufactures exhaust manifolds. But whats bad the AD for DC SPORTS in Options claims 14hp with there header!? It also says add colour with DC sports parts and the word cheapest parts. I've seen this in few ad's for them. But the Cheap word is right..most my friends that bought them said they bought them either for looks or because they where cheap. It still makes me laugh when one my friends told me I should sell DC Sports..and I said hell no I won't sell parts I don't even want to put on my car cheap or not...with all there recalls..I don't want alot people calling me because something clinging around in there header or its rusting.. I rather sell Speed racing header or RSR headers if you need something not as high as Spoon or Mugen and perform just like them. The new Speed racing headers on the S2K out performed Spoon header recently on the same car.

 

So why aren't you a Tech either her or on SHO?
-------------------------------------------------------

Because my user rating is 98% I guess. No real urge to be one really and more importantly I don't know enough about the Rs. Hell I drive a 2001 Ford Truck with a measly 505 ft-lbs of torque (can't wait to put a 4" Magnaflow exhaust on it) and my race car is a 86 Civic with only 12 valves, one camshaft and 4 doors. Maybe I'll build a shop drag car if I can get some good sponsors and have Steve Sakai or Jamie Dunn drive it.

 

Anton - Sounds good about next summer.....I'll be home thanksgiving but I wont have any new mods done...altho I'd like to dyno the car to see how it is in stock form...well stock + aem anyway...i'd also like to see the diff between the aem/icebox

So basically what we're getting at here is, yes, the JDM's collector is not a true 2.5 inches, and neither is the DC, but they are both not 2.5 and the differences between the DC and JDM are small..probably even negligible?

 

David,

I have to respectfully disagree with you. Technically headers and exhaust systems are built from tubing not pipe. We really should call it a B tube and not pipe and for that matter race in the all engine class versus all motor. Last time I checked I didn't see electrical chords hanging out the rear of the all motor class cars.

Tubing is specified by outside diameter (OD) and wall thickness. So all 1-3/4" tubing measures 1.75" OD but the ID will vary based on the wall thickness or gage (20g, 18g 16g). The smaller the gage number the thicker the wall. Where as pipe is spec'd by the ID and the wall thickness or schedule (10, 40, 80, etc.) but in this case the higher the schedule the thicker (OD) the pipe.

On to headers, I believe all the DC JDM 4-1 headers are built in the US and so will use US spec tubing. They use 1-3/4" 16g for the primaries and 2-1/2" 16g for the collector outlet, there may be a slight taper opening to 2-1/2" but I'm not sure since I've never had one in hand. 16g is .065" so the ID should be 2.50 - 2(.065)=2.37". Now the JDM ITR header is made from metric spec tubing, 43mm primaries and a 65mm OD collector (outer part of the anti reversion chamber) but since the exhaust gases go through the inner tube of the anti reversion chamber its effective inner diameter is 2.16". So the difference between the DC JDM (2.37" ID) and the ITR JDM (2.16") is .21" but an increase of 20% in area. That's why I recommend removal of the anti reversion chamber but you'll still have the internal taper which will help the mid range.

The same goes for cat back exhaust systems the 60mm (2.36") systems are the OD measurement and are about 2.25" ID, where for instance my 2-1/2" system is made from 16g sst tubing and measures 2.37" ID. For a gain of 12.8% in area.

BTW, I sell 2-1/2" ID and 65mm (2-9/16") ID donuts. The 2-1/2" ID donuts are for my B18VTEC headers, the HyTech header and the DC JDM header. The 65mm donut is for the ITR JDM, Spoon, Mugen and Toda headers. I've had some customers have problems installing the 2-1/2" ID donut on the DC JDM headers while others haven't and I believe this is probably due to some ovaling of the DC collector during fabrication. So, I've been sending out the 65mm donut for the DC JDM headers lately.

So, I'll assume the dimensions you state above are the inside diameters. We just all need to be talking on the same terms to reduce the confusion.

 

First, I am referring to the IS Dia. not OD. Also I mostly work in metrics so when anyone ask sizing I tell them the metrics as it's more exact in my opinion then inches. As for me saying pipe, which is just another word overseas for tubing. I've talked to exhaust comapany overseas that does custom works on rally cars and when asked about my car. He told me which piping you like to use and then then we can get pipping those works out for you just give us sometime make a few prototypes. Piping just another word for tube. I'm sure if I talked like I talked to my friends and contacts overseas about my cars nearside and farside wings..people think I'm talkin about near or far sided car with wings. But I'm actually talking about right and left fenders. Sorry for the confusion my Jargon creeps over from time to time. Probably because the Japanese refer to many of that same parts with same names as the Europeans do. Also for the most part most JDM exhaust manifolds tend to be measured on the inside dia. If anyone doesn't believe on the pipe is used instead of tube..just goto the japanese spoon site and click on english portion for products and you will see where it say Pipe Dia. and not Tube Dia. I almost think tubing is only used here so people don't confuse exhaust works with plumbing works. Kinda like people say side markers here and there actually called side repeaters in Europe and Japan..and side steps are known here as side skirts.

 

Remember just because a Japan company uses the term pipe on their web site doesn't make it the proper term. What I wrote about above is pretty standard across the world. You can also buy metric tubing here in the states and it also goes by OD.

 

SMSP - Racer-X talks to retailers pretty much every day in Europe and Japan, and they ALL use the term pipe, so are all of them wrong and you are correct?

 

We are spliting hairs here, I'm not trying to **** anyone off either and I have nothing against Racer-X. What I'm saying is that technically speaking your exhaust and header are made from tubing not pipe. Now I know the hog riders will say they have pipes and not tubes, so what. Does it matter what you call it? No. Maybe the exhaust manufacturers liked the sound of B pipe better than B tube, I don't know. Hell, I say and write B pipe too. It easier for me to use the term in an email since the person knows what I'm talking about.

Does my text book from college say Internal Combustion Engines or Internal Combustion Motors?

Please go to http://burnsstainless.com/index.html, I don't see the term pipe used on that web site and Burns is probably the largest supplier of specialty exhaust components in the country.

What this thread is about is what are the collector sizes of these 2 headers. I also added how primary tubes were specified for those who may not have known. One last thing, if you buy a 2-1/2" cat back system from me or HyTech, you'll get 2-1/2" OD tubing, if you buy a 60mm APEXi, Mugen or Tanabe cat back system you'll get 60mm OD tubing, if you buy a 2-1/4" CompTech or Magnaflow cat back system you'll get 2-1/4" OD tubing. These systems are not specified by the ID, the only way you'll know that is if you have the tubing gage or wall thickness.


[Modified by SMSP, 6:28 AM 10/11/2001]