For those who have these installed, what do you think about them? Now that some people should have them.

 

I've got one and I love it. The only concern I have is with 2.5" flange. If you get 2.5" all the way through, you won't have enough backpressure to suck the vaccuumed exhaust coming from the header. I have a 2.5" custom made high-flow cat that I use with it and the stock 2.25" exhaust. This is enough backpressure for what I need... although I haven't gotten it dynoed yet... but that's in the plans soon. However, I'm planning on eventually getting Toda cams so 2.5" all the way through will be a good thing

 

so anyone have a comment on using the jdm DC header for a 2.0L setup? i am going with a straight thru 2.5" exhaust header back. yup no cat. under the fuel tank one borla muffler. its a track setup. what am i dealing with in terms of backpressure and such on my setup? i have 12.6:1 compression. lets hope im making a **** load of power on the dyno!!!

 

I have no beef with my JDM DC, other than the fact it doesnt say "Mugen" on it. I dyno'ed my car with Mugen CAI, JDM DC, carsounds cat, and 2.5" B-pipe adaptor and hit 173.5WHP

 

Not to single you out, but this is why this board needs a Q/A & Tech archive. You don't want back pressure in your exhaust system for most cases. Fluid flow,in general, happens due to a difference in pressure from one area to another. Air from an air compressor exhausts from the tank because the pressure in the tank is greater than atomosphere. Back pressure will not suck exhaust. Excessive back pressure results in increased pumping losses.

An exhaust system for a street car is a compromise. You want something large enough to handle the flow in the upper rpm range but not too big so that you loose too much velocity (exhaust energy) in the lower rpm range to where it will have a negative effect on torque.

 

A guy posted a dyno curve over on Endyn of a DC JDM on a B20. Go to http://www.c-speedracing.com/cgi-bin...sed&sb=5&part= to view it.

You'll see that right after VTEC the torque curve starts droping off. For the money the header isn't bad for a B20 but the tubes are way too small to let a B20 really breath in the upper rpms. My guess is that it may work a little better than the ITR JDM on a B20, but you are choking a B20VTEC with it and the engine will come alive with a properly sized header.

 

My DC JDM header is on order. I went ahead and got the Carsound 94006 from Dave at SMS. Hopefully all to be installed this weekend along with B pipe adapter.

Regards

 

Thanks for the info

 

SMSP- I am considering going b20/vtec and was wondering about a header because my I knew my LS DC headers probably wouldn't do the job. I was probably going to get the DC JDM header because of the larger collector and I heard larger primary pipes than JDM OEM; It is also alot cheaper. You say the pipes are too small for the b20/vtec I was wondering if they would be big enough for me since the graph you showed was on a car with alot more aggresive cams. Here are my plans:

Vtec head
Stock Internals(maybe ITR cams)
7500rpm
Looking for 180-190hp

 

I have the DC JDM Header with Carsounds Cat and Mugen cat back and I love it. I agree with waynegro the only thing is it dosen't say mugen on it. I actually had a MUGEN USDM on my car and the DC is perfect replica of the MUGEN header.

 

Muglit- You are right your LS DC header won't handle it. The following is not meant to be a smart *** remark but I would hope you'd be over 200whp with a B20VTEC. 180+ isn't that hard to get with a B18VTEC.

Now in the graph above I don't know what kind of exhaust they were running or their full set up so I may be making some wrong assumptions here but if you look at the curve they loose about 30 lb-ft over 2500 rpms. That is significant. When Atomic tested one of my B18VTEC fully adjustable headers on a 208whp B20VTEC (200whp@7500), that engine lost about 20 lb-ft over 2500 rpms, still pretty significant. The B18VTEC header is a 4-2-1 but it has stepped primaries that are larger than the DC JDM. Now if the above engine could have kept a nearly flat torque curve to say 8000 rpm at 150 lb-ft they would have been at 228whp. To do that you need still bigger primaries and secondaries.

So to answer your question, no I don't feel that the DC JDM would be enough for your engine. Will it be better than a ITR JDM..yes, your LS DC...YES, a JDM Mugen...close but for the price it will be your best bet if you're on a tight budget.

BTW, I'll try to post some pictures in a couple of weeks of a B20VTEC header that I'm building for a local guy. If you're concerned about ground clearance you'll probably never even think about it after you see his set up. If he bottoms the car out it may just be the oil pan that hits first.