4-1 vs. 4-2-1 for D16A6

[Geezer]

Just got my H4 CRX back after a refresh and some tuning. The motor is pretty much full ITA spec, with an SMSP 4-1 header. The Dynapack chart (sorry, not hosted yet) shows I'm running 90% of max torque from 3000 rpm up, with the torque peak at 5700. The tuner commented on the strong midrange and hp numbers we were getting.

[exospeed*com]

Let me clarify something.
The Bisimoto header and the AN-R may look the same. but the Bisimoto is the only one that USES the Burns Collector. At this time, the Bisimoto has always been using the Burns collector in all its designs.

The Bisimoto header is available in B, D, and H series engines. and options are Street(with 2.5" exit pipe), Race(with a megaphone style exit pipe)and in Jet Hot Coated or Uncoated versions

any questions, feel free to contact us at [email protected]
thanks
Wil

[exospeed*com]

[This message has been edited by exospeed*com (edited February 18, 2004).]

[Danny M]

Has anyone dynoed the DC 4-1 on the D16? I know there is not a fitment listed but it is what I am using now in Solo II. I haven't had a chance to dyno yet but it sure does feel good above 4500.

[Jon Nelson]

A DC Sports 4-1 on a D16?

What fitment is listed? Ie, what do you have it on, and what is it supposed to be on?

J

[Jon Nelson]

Duh... found it. At Summitracing.

So, it's supoosed to fit 92-95 Civic. How well does it fit on the 88-91 Cars? Ground clearance OK?

Thanks (again),

Jon

[Danny M]

I found out the hard way BUT....

You need to take out the front cross member and front engine motor mount as well as the rad fan in order to have enough clearance to get it in. Stock manifold goes out through the top, 4-1 needs to go in from below. Then, the bracket on the header (on what would have been the secondary pipe on a 4-2-1) will bump into the oil pan before you can get the header up and around the head studs. So, you need to trim a bit of that bracket to slip the header onto the head studs then custom fabricate a bracket to make the factory hanger meet up to the hanger on the header because its in a different position.

Aside from that it bolts right in! I was told that the 4-2-1 does not have much of a power advantage over the stock Si manifold and that the 4-1 would be the way to go. I haven't tested it yet on a dyno, but that'll be soon. As for clearance, I'm running the car in Solo II in the STS category and the car is lowered with the tires (205/50-15) flush with the fenders, or 4-1/2" to the jacking points. I haven't had any clearance issues.

[Tyson]

danny, an aftermarket 4-2-1 certainly DOES have an improved gain over the stock exhaust manifold on a D16a6 which is 4-1 with very short primaries and a tiny and long collector pipe. on later d16 civics however, like the D16Z6, honda changed the stock design to 4-2-1 already, so for those engines, the gain is not so big since the design is already the same. but ive read some gains in just increasing the collector size on the stock Z6 manifold.