DIY Honda B18 intake manifold-on-miata kit
 

Hey all. You may or may not have seen the thread in engine performance about adapting a honda b18 intake manifold to the miata. The long of the short is that the intake port spacing on the Honda B16 and B18 is very similar to the miata bp. The honda manifold allows you to run a intake manifold with nice straight and balanced runners as well as a nice large plenum. Also the manifold allows you to run honda throttle bodies. You can find a used 70mm honda throttle body with iac and tps for well under $100! The manifold used is an ebay skunk2 knockoff manifold which can be purchased for ~$130. I have bought 3 different manifolds from three different vendors and each has been identical. This is what Im talking about:

EG EK Da DC2 B16A B16B B17A1 B18C5 Aluminum Cast Intake Manifold Upgrade Bolt On | eBay

As of now, If you wanted to do such a thing you either had to design a custom flange or do some sort of drill and slot job on the honda flange. Ive designed and machined a weld on flange for myself and a few of my buddies and would like to throw it out there if anyone wants to buy one. The thread about the manifolds is:

https://www.miataturbo.net/engine-pe...d-43103/page1/

So what Im offering is a flange that is port matched between an ebay b18 manifold and a miata 1.8 head. As of right now I have the nb 1.8 flanged ready to cnc but I can easily do a na 1.8 head with a little cad work. The flange looks like this:
https://www.miataturbo.net/attachmen...old-ccnc01.jpg
https://www.miataturbo.net/attachmen...old-ccnc02.jpg
https://www.miataturbo.net/attachmen...old-ccnc03.jpg
https://www.miataturbo.net/attachmen...old-ccnc04.jpg
https://www.miataturbo.net/attachmen...old-ccnc05.jpg

To do the job you would cut off the honda flange off the manifold like so:

https://www.miataturbo.net/attachmen...old-ccnc09.jpg

and weld on like so:

https://www.miataturbo.net/attachmen...old-ccnc06.jpg
https://www.miataturbo.net/attachmen...old-ccnc07.jpg
https://www.miataturbo.net/attachmen...old-ccnc08.jpg

Then weld.

If you read through the original thread youll see that the biggest issue with this mod is the welds cracking. The fool proof way to prevent this is to use the stock miata manifold support. The honda manifold has the mass much further from the head then the miata manifold and puts a lot of stress on the welds. With the manifold I will include a weld on support bracket which will allow you to use the stock miata support. I have ran this setup for over a year (with poly engine mounts mind you) with out any issues. The support looks like this:
https://cimg0.ibsrv.net/gimg/www.mia...970ed9085e.jpg

https://cimg2.ibsrv.net/gimg/www.mia...8bb5ccd92d.jpg

Im offering to make both parts to order for $100 plus shipping.

Also, If you want to run a miata throttle body, I have made an adapter flange and throttle cable mount which allows you to do just that. I can make these 2 parts for an additional $50. They look like this:

https://cimg6.ibsrv.net/gimg/www.mia...4db5fe9a6c.jpg

https://cimg8.ibsrv.net/gimg/www.mia...b8917383a4.jpg

https://cimg9.ibsrv.net/gimg/www.mia...dc61e72132.jpg

https://cimg0.ibsrv.net/gimg/www.mia...e401f4d7a7.jpg
https://cimg3.ibsrv.net/gimg/www.mia...f03a253bd7.jpg

So if this is something you are interested in, let me know

Wow. That's incredibly slick how you machined the new flange so the Honda manifold slips in before welding. Pricing seems super reasonable too.

i likes this idea.

In!

Very cool indeed. Group buys will probably need vendor status tho.

Right now I'm just a guy who has a cnc machine. I haven't thought far enough ahead for group buys or what not. I tried to price the parts as fair as possibly could though, there is no point to this if it winds up costing more then a fancy fabed manifold. Let me know what I need to do to stay mt.net legal.

Oh I have no issues with this thread, carry on. Just pointing out something to keep in mind if this takes off.
Want to keep the vendors happy.

Thats excellent! If I dont follow threw with installing carbs....

Should we PM to buy, or are you just gauging interest?

I would be in for a flange kit!

Yes, pm me please.

Shipping to australia?


Dann

Here is mine by mike. He does a great job.

Attachment 231045
Attachment 231046
Attachment 231047
Attachment 231048

Can I ask one of yall for a approximate center to center measurement of the intake ports?

I'll shoot you a pm.

Subbed for future forfeiture of my paycheck.

Any possibility of selling a completed manifold?

miata side: 91mm - 91mm - 91mm
honda side: 88.7mm - 86.2mm - 88.7mm

I would do a fully finished manifold for $150 extra but you would have to supply the honda manifold. This number can go up depending on what kind of shape the honda manifold is in and if there is any customization.

This is the one i bought.

Mike does a great job and is well worth the money.


Honda Acura B Series DOHC vtec B16A B17A1 B18C5 Cast Aluminum Intake Manifold | eBay

any before and after DYNOs with just the intake change?

I personally do not since when I did mine al also stuck a turbo on the car. There is a lot of good information in the thread I linked to in my original post, it just might take a week and a day to read through the whole thing.

Has anyone done a back to back with a square top?

D


Poss in for a set

I plan to get a baseline dyno on mine whenever i get it swapped in. 03 VVT rods only with this intake manifold, ebay 4-1 header and ms3x.

Nicely done! If I were anywhere close to needing something like this I would be all over this deal. My build is very mild and low boost though.

https://cimg1.ibsrv.net/gimg/www.mia...57e55312d6.jpg
I had been searching the web for an intake solution for my mazda (its an 808 coupe same as rx3 coupe shape with space restrictions) which will be running an NA engine and came upon this thread, so i contacted Mike
and he made up an na flange, throttle body adaptor,cable bracket and support brace so i can run the honda manifold, then shipped over to me in Australia. He was really quick in getting this done,
if you are looking to go in this direction i would recommend Mike, absolutely no fuss.

Matt

Any updates on this? Keen for results.

Also interested. This would be a great setup to move to a skunk 2 throttle body correct? I'm curious on the dyno numbers as well if anyone can test it.

Received mine from mike today. Couldnt ask for better customer service. Looks great and is surprisingly light. Cant wait to weigh it against my stock 99 mani. Thanks mike!!
https://cimg0.ibsrv.net/gimg/www.mia...8df6283e5b.jpg

Thanks for the kind words Reed!

why not just buy a skunk manifold to fit a miata?

They are a little bit different things since some people are looking for a diy part that they can say they made themselves. It's also a bit cheaper if you do the welding yourself.

From the performance side (this is me speaking with no data to back me up) you do get a runner with no bends and a straight shot right into the port. You also get the ability to run a honda throttle body in any available size, 70mm or bigger for pretty cheap. Also no fittment issues (doeant hit the starter...).

An aside, the s2 miata manifold is bored to 64mm to work with their 64mm tb. I found that a 64mm bore exposes all of the iac passages on a stock mazda tb. Does that do wonky things to the idle?

Sign me up
 

Can I purchase a manifold still?

what do you do about injectors?

Why would injectors be affected? It looks like the flange clears the injectors. Btw, i've never seen anybody with an almost 1:2 post:neg cat ratio.

Oh i guess I did not know the head the has injector cast into them....