Quad ITBs
 

Hi all,

I've recently been planning on what to do with my next project, which will be a NA FC3S.

So far, I have been focusing on engine mods which at the moment im leaning towards; full bridge port, as well as ITBs - this post is focused on the latter.

iirc, someone had recently posted a thread which is very similar to what I'll be asking however with multiple questions being asked it seems there was no reply to one question I was also wondering about.

*please bare with me as I've been interested in ITBs for a few years now but this is the first time of which I'm seriously considering using them - so I have a lot to learn.

So, my question... obviously with the 13b only have 2 rotors, this means most people (with an exception of a few examples i've seen online) naturally run twin ITBs. I was hoping to turn this project into a mix between a show car, yet still having the power to back the looks.

I was wondering if theres any way to run quad ITBs as IMHO, I believe these look alot more aesthetically pleasing than twin ITBs, and if not - would it be possible to essentially run quad horns into twin ITBs (so 2 horns per ITB).

I have been searching forums for a while with some good info on ITBs but little info on quad setups. I have also seen someone has a few youtube videos on their DIY quad setup which I intend on watching through ASAP, but I've decided to ask here in the meantime.

Thanks all,

Ben

i'm not sure it matters of you have 2 vs 4 ITBS, as long as you get the sizing right.

there aren't any off the shelf manifolds for a 4 ITB setup, as far as i know

easy enough to make, the question is do you stage the secondaries either with a second DBW controller or vacuum/solenoid Renesis-style :suspect:
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Here ya go
buyer beware though. I've never heard of these guys and their only other online presence seems to be on facebook and wordpress.

That's a good point! Since your reply I've been gradually learning and understanding more information regarding how to stage the secondaries. I found quite a few people didn't seem to like using a DBW (it seems some people say it doesn't feel so good when driving - however I believe this could be down to improper installation/tuning), and the vacuum/solenoid method is giving me a hard time to wrap my head around how I could make that work & I'm struggling to find much information about how to implement it in the ITBs system!

However, since researching through the rx7club forum again for more posts on ITBs (it seems every time I go through the posts again I'm really starting to understand them as I keep picking up more knowledge upon the topic), I found someone who actually made an intake manifold for the FC, which is 3D Printed out of nylon and paired with Honda CBR600RR Bike ITBs interestingly. On top of this, included in the kit is a 'Throttle cable with firewall adapter' and a 'Throttle correction adapter'... so now I'm wondering if me having to sort out how to stage the secondaries is still an issue.

I'll read up more about the kit however I may end up emailing him and ask if I need to worry about staging the secondaries.

(Link to the kit if anyone is interested: 1989-91 NA Mazda RX-7 ITB Adapter Kit) :)

Thanks for your reply!

Coincidentally, I just came back onto the forum to share that I had found a quad ITB kit made by JAFA Engineering (The same manufacturer of the kit which you had just shared). Very interesting design as I believe I read it is 3D Printed out of nylon - This is the kit I found which is similar to the one you linked JAFA Engineering FC Quad ITB Kit.

As for credibility however, I have only just come across them too, but their website, ebay shop and so on seems quite legitimate.:icon_tup:

Thanks again!

To stage motorcycle ITB's, you have to alter the linkage. It's not one continuous shaft, but four that are connected by a linkage, they can be removed individually. They tie the throttle bodies together to get vacuum, port on each one connecting to a single, with check valves. You can buy vacuum pots from Summit, find a way to separate the two outside ones from the centers, and put them on a common, vacuum operated shaft. As I said, you have to modify the throttle shaft end linkage that engages the next ITB.

I bought set considering this same thing and, it's still sits on the shelf in the garage.

DBW isn’t cheap, but can be done. Jenvy and others offer the motor drive for that purpose. The difference is you can control a secondary pair via DBW-PWM relative to rpm and load. You can phase the vacuum pots in a similar way, but only open vs. closed.

AT Power offers one on their bladeless TBs, but those might be better suited for vacuum pots like on the Renesis SSV secondaries; no restriction in the flow path.

What I failed to think of though, for vacuum pots it requires a single TB at the front feeding the intake runners in a plenum. Otherwise having your secondaries suddenly snap WOT without any control might get exciting … :suspect:
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I was going down the road of like a Holley vacuum secondary. Lock out cam, restrictor pill to slow the opening.

that tends to be different because I haven’t seen a 13B 4Bbl intake manifold that dedicates the 4 intake runners individually to to each carb barrel opening. You could build one though, yet some people on here think it won’t work regardless based on their experience. The big difference between these 13B engines and the Renesis is the impact of overlap port timing vs. none at all on the Renesis. Yet even the factory intake manifolds managed to configure the secondary pulses to compliment each other. It might require a lot of effort to find out, and then maybe not be successful in the end either.
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the RB holley intakes are IR and the holley, and its EFI throttle bodies are all setup to do primary/secondary.
so you can have a bolt on 4 ITB setup that is progressive, it just won't look like it.

yeah I came back to say my memory was bad on that point, they mostly all have dedicated runners

I think I need to clarify this. My idea was the inline four ITB with the secondary's divorced from the primaries, and using a second shaft, operated by a vacuum pot, that operated like a Holley vacuum secondary carburetor.

The secondary's on those don't snap open (tiny vacuum orifice) and don't open in part throttle high vacuum like cruise (lock out cam).

I never pursued it but, had pretty much figured and sketched it out.