Because it had too much high
 

Because it had too much high end bias?

What is your opinion on me using that cx/vx exhaust on my d15b2 in terms of mileage?

first thing i would do is
 

first thing i would do is measure with a micrometer the port width openings and MAKE ABSOLUTELY SURE that cx exhaust manifold is not a step-down in size...

that would be really bad...probably too much reversion...lack of escape...higher temps...etc...

i dont think it is...but i have never measured...
other than that...the cat is great for the environment...
and it seems to be a good design that has stuck with the economy civics thru 2000...

Did the hx have the same
 

Did the hx have the same design? Yeah, I figured that cat alone would be a good thing about it, also the o2 sensor would warm up a lot more quickly.

Right now I'm wondering about some cat insulation I saw a while back that keeps it warm for 24 hours to reduce start up emissions.

the dc 4-1 header on the z1
 

the dc 4-1 header on the z1 has too much highend/wot bias. remember, the section of the rpm band controls the frequency the gas is pushed ,which indirectly effects the amount of gas. while throttle position decides the amount of gas pushed. the z1 has super small ports and the header is just too large for while in the primary cam. do you follow?

GENERALLY the shorter the primaries and secondaries the lower the intended use in the rpm band. which is why your super expensive headers have adjustable primaries, so that you can tune it for the power band your aiming for and harmonize the lengths of all the primaries so the exhaust flows through the collector sequentially. also the thinner the pipes, the less gas is intended to flow.

google 'anti-reversion' for a little help in understanding some of the tricks with stepped primaries and things of that nature.

I just have trouble
 

I just have trouble following the differences in the frequency **** for intake and exhaust, *shrug*

When I get the superMID we'll see some good exhaust ****.

intake
 

With FI the smoother the better as it minimizes the surface area and keeps the air cooler - my xB has plastic intake manifolds that are extreemly smooth and thermally insulating from the engine block temps all adding to more power and MPG. Raising the compression is going to help the most.

The plasticness of the
 

The plasticness of the intake manifold could only hurt FE as I see it, since a warmer intake charge is generally better.

Hence the reason honda people cut off their coolant to the IM and use insulating IM gaskets in order to squeeze more HP.

weird
 

Not with this engine - seems a lot of people are adding cold air intakes and the engine doesn't run right. I get pretty poor mileage when very cold but too hot is bad too - this engine has high compression ratio. Better not to second guess the people that created the motor.

I'm not second guessing
 

I'm not second guessing them, but the fact nowadays is that most engines are designed for power.

I think they knew what they were doing, just that they were doing it not for MPG but for power.

ok
 

OK then I guess I should play with a warm air intake - as it is, it takes the air from the left fender under the hood next to the battery to the side of the radiator. I can monitor the intake air temp with the ScanGauge so adding a little ductwork to get some air from the rear of the engine near the header should give some different results. Might be cool to increase the MPG even more ha ha ha!