D15Z1 Intake Manifold

[StorminMatt]

I finally got my D15Z1 yesterday. At $125 with ECU and EGR control box, it was certainly not a bad deal. BUT, it came with the larger DX/LX intake manifold rather than the VX manifold. I know that this manifold will probably not work optimally, given that the runners are SO much larger than the intake ports. Notice the size difference between port size here and the mark from the intake manifold gasket.



So I was wondering whether there might be an alternative available to the VX manifold. I know that both the 1988-1991 HF manifold and the 1992-1995 CX manifold are similar in size to the VX manifold. Will either of these work? And do the ports properly line up? Or am I going to be stuck having to find a VX manifold?

[Brian D.]

If it turns out that a CX or HF manifold would work, I've got both. Either way, let me know; I'm curious also.

[GasSavers_TomO]

CX manifold will work, plus you should be able to grab one from some kid that is swapping it out for a larger manifold for free. I'm not 100% certain that the HF manifold will work properly, but since you have the manifold off of the Z1 already, it wouldn't hurt to try if you can get one easily.

[Danronian]

I don't think finding the VX manifold would be too hard. I've seen a few for sale on ebay before.

The CX probably has a similar size to the VX, but I would look for the VX since it's the only OBD1 intake for a D series with an EGR.

The HF intake manifold might work fine since it does have the EGR and is MPFI, but I think that one will be just as hard to find, and I don't know if it has the tiny intake ports of the VX.

The HX manifold would probably work, but it will lack the IAT sensor, but you could add one pretty easily. The issue wth the HX would be that the intake ports are large since it's basically an EX intake with an EGR on it instead of vtec-e specific as the VX intake is.

If you want to give the HX manifold a try there is one at my local junkyard and I might have seen the HF manfold there too, but I'm not so sure about the HF.

[StorminMatt]

At my local junkyards, I have seen a good number of HFs and CXs. But NO VXs. I guess these are ALOT less common. Also, doesn't the CX manifold have a place for the EGR with a blind hole for the valve and untapped holes for the screws? I almost want to say that this is what I saw at the junkyard. Anyone have pics? If this is the case, then it seemslike it wouldn't be too hard to get the CX manifold set up for EGR. Then again, I would have to find an EGR valve. But maybe one from an HF would fit.

[Brian D.]

Well, if it turns out to be an HF manifold that you need, I have one in my shed that I was hoping to one day have polished. As it currently sits, it is stock, as removed from the car. If you need the EGR valve with it, I have that on it as well. It is currently complete, with all sensors in it...but I hoped to keep those. Just let me know if you need the manifold & EGR...or whatever else; I wouldn't be looking to rob you.

[StorminMatt]

Originally Posted by Brian D.

Well, if it turns out to be an HF manifold that you need, I have one in my shed that I was hoping to one day have polished. As it currently sits, it is stock, as removed from the car. If you need the EGR valve with it, I have that on it as well. It is currently complete, with all sensors in it...but I hoped to keep those. Just let me know if you need the manifold & EGR...or whatever else; I wouldn't be looking to rob you.

How much would you want for it? I need to take a look first to see what I can get locally, as I know that shipping could very well kill the deal.

[Matt Timion]

I'm willing to bet that the CX manifold is identical to the VX manifold. The HF Manifold MIGHT work, but since it's obd0 the MAP sensor is in a different place (obd0 is mounted on the firewall, not the IM itself).

then again, is the EGR on the intake manifold, or is it mounted to the block? Either way, check ebay first, or put a "for trade" ad on honda-tech or craigslist. Trade your big one for a small one.

[Danronian]

Originally Posted by StorminMatt

At my local junkyards, I have seen a good number of HFs and CXs. But NO VXs. I guess these are ALOT less common. Also, doesn't the CX manifold have a place for the EGR with a blind hole for the valve and untapped holes for the screws? I almost want to say that this is what I saw at the junkyard. Anyone have pics? If this is the case, then it seemslike it wouldn't be too hard to get the CX manifold set up for EGR. Then again, I would have to find an EGR valve. But maybe one from an HF would fit.

You could probably drill out the mounting "boss" for the EGR on the CX manifold, but it might be hard to get it right. I would just hold out till you find the VX manifold since I don't know if lean-burn will work right w/o the EGR.

[StorminMatt]

Originally Posted by Danronian

You could probably drill out the mounting "boss" for the EGR on the CX manifold, but it might be hard to get it right. I would just hold out till you find the VX manifold since I don't know if lean-burn will work right w/o the EGR.

I actually had a look at a CX intake manifold today. And it is not even 'roughed in' for the EGR valve. This is quite interesting, as it almost certainly costed Honda more to do things this way vs either 'roughing in' the CX manifold for EGR or having a block-off plate. So I guess I will have to look for a VX manifold.

As for lean burn without EGR, I don't see why this wouldn't be possible. But it certainly wouldn't happen. Having no EGR would cause a check engine light (code 12), which would certainly cause the ECU to not run in lean burn (the previous owner probably ran it with a P28 to avoid a check engine light). It would also cause the ECU to run in open loop mode, which would be GREATLY detrimental to FE. Not to mention that it would fail smog visually, at the very least.