D-series intake manifold differences

[habib_88]

Ok i dunno if anyone can even attempt to answer this but i'll ask here first. Lets say i was to put a SOHC vtec block & head (D16Z6) in my Si, but use my 4g intake manifold, some 4-2-1 headers or something, same Si ECU, and Si tranny.

Yea this all bolts together fine, here's my question. I've heard that there are differences between the D16Z6 intake manifold and the D16A6 manifold. I'm wondering if one makes more Hp or torque than the other.

My reason is when you auto-x, the D16A6 without the use of vtec has slighly better midrange torque than a D16Z6, thus allowing it to pull outta turns faster, etc. I'm trying to figure out the reason for this and i'm wondering it the intake manifold is one of them. So i could have the higher Hp of the Vtec motor but have better midrange torque. I'm also thinking this might have to deal with the D16A6 having to run on one cam all of the time, thus being better suited for midrange torque by nature. ANY input in this would be greatly apprecited. If anyone has dyno graphs of a stock D16A6 $ D16Z6 could you please hook me up so i could study this further.

Thanks Chris-

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"If Mercedes suddenly branched out into making food blenders, it wouldn't be long before Brabus came up with a tweaked version that chopped your carrots twice as quickly and made a louder noise"

[NC_Rex]

The differences between the D16A6 and D16Z6 manifolds are that the head is ported and made for the D16Z6 manifold. However, there's not an extreme difference between the manifolds one way or the other. The difference in diameter is 3/16 of an inch...with 3/32 of an inch taken off the si manifold all the way around to use the larger manifold.

I always tell the guys D16A6 turbo to use this manifold because it's already ported larger and there's less pneumatic lines to it.

You can easily port match the si manifold to the D16Z6 manifold. And then reuse the Si manifold. A lot of people I am finding do this to simplify the swap.

The only difference is that you change to use a different fuel rpessure regulator - one off the D16Z6 manifold, or buy an adjustable AEM or whatever unit to replace the Si one. They come anodized red or blue or plain silver slight polish to them...cool looking enough.


They made the D16Z6 for more economical reasons as a D-series replacement.....don't think this is a bad thing. They just made a more mild cam. However they kept the porting larger for the higher lobes. That is why the midrange is a little less.

I know this because I race a CRX Si with a D16Z6 and a bad VTEC solenoid or miswired...he had no VTEC...he was about one car's length behind me at the top of third. Fast still, but I still had some on him with the Si engine.

Now JG makes a VT-45 cam that I've been wanting to try sometime in the near future.

It's a better then stock cam supposedly its a good one too...far better then gude cams.

They do make some good aftermarket cams for the D16Z6 engine.

One other thing I suggest is milling off about 3 or 4 lbs off the stock flywheel or if you have the money get a lightened flywheel....it wil give you more torque (and take away a bit from top-end natural push of the engine at constant speeds - like highway, but not too much)...your acceleration will increase bigtime.

Also the D16Z6 exchuast manifold I believe is a pig too. The D16A6 is a 4-1, the D16Z6 is a 4-2-1. If you've ever driven a 92+ EX Civic, you'll notice they have good midrange and driveability. This is the reason why...but they have enitrely no top end - it just seems to seems to rev up, but no top-end pull even with the VTEC. I attribute this to that manifold. I would run a 4-2-1 manifold on this engine though as it gives it a hell of a lot of torque down low, coming in at about 3200 rpm. With the RSR 4-2-1 header (a basic typical header) I notice the economy, throttle response, and acceleration are greatest on the Stock D16A6 engine between 3200-3500 rpm with this header. I've also noticed hesitation around 2800 rpm with this same header on the D16A6 Si...but I think that was an ECU timing conflict, may have been too lean, not advanced enough.

...anyways I get too think talking into this stuff.....D16Z6, 4-2-1 header or ZC stock exhuast manifold, lightened flywheel, and possible came. Also keep the exhuast size at 2.25" and use the silencer to keep the backpressure up. (If you use the cam - get JG to tell you if it's for use with a lower restriction exhuast or not...as the valve overlap rates may change on the new billet or regrind...do homework).

And if you'd like...you can always try the two different intake manifolds....however it's jsut a difference in high-end, and I think you'll have more response on the midrange if you use the Si intake manifold.

Just my thoughts, don't take them to heart, but use them as a reference and somebody else's experiences.