Independant Throttle Bodies (ITB's/IRTB's)

F

flat_black

Member
I just ordered a set of 50mm throttle bodies. I'll be building up a new manifold with the stock injector locations, and a custom fuel rail made of extrusion stock from here:

http://www.rossmachineracing.com/extrusion.html

Then have the throttle bodies off short runners, then the stacks off of that.

The ECU issue is still up in the air, and suggestions are welcome. I'd like to use the AEM, if I can ever save up enough cash, to eliminate some of the oddities of using ITB's by having it try and autotune to a degree using a WBO2 sensor. I'll probably use the same stock I'm making the rail out of to source vacuum from all four runners with a check valve, then have it output to a vac reservior to keep the brakes and cruise if I can.

Wish me luck!
 
Thanks, man. I'm doing a bunch of calculations, like fuel rail volume per the bore, and trying to add up how much all the lines, fittings, the pressure regulator, and whatnot are going to cost me, as well as the adapters and the stacks, as well as the TPS (Throttle Position Sensor) output... Didn't you get that memo?

Hehe. I'll try and keep things updated. I'll probably write a web page about it, too, like I did for the manifold porting and all that.

I'm going to need a Probe manifold to butcher, too, that being said. Or something of the sort that I can get the base from, then weld some aluminum runners in place, but that all remains to be seen as to how that's going to pan out. I'm going to have to be hitting up McMaster-Carr pretty soon. Hehe.
 
If I were to start a project like this I would buy a old set-up off of something that had it. I was at a swap meet yesterday and saw a couple of them pretty cheap (ranged from 120 to 390...) I have no idea what they were off of, but they had linkages and misc. items that will be really hard to make from scratch.

The tps will be the easiest of your problems to figure out, you only need one, and as long as you have the same throttle actuation for all throttlebodies you could put it anywhere on the linkage.

I'm not exactly sure why you want to make a fuel rail and pressure reg. Just use the stock one if your gonna use the port side of the stock manifold and make some brackets.
 
Keep notes on everything and maybe write up an instruction guide you can sell or even make a kit to sell and recoup your investment.
 
actuating the throttlebodies will be easy also.... just a couple of linkage bars and swivel portions are needed
 
I think your best bet is to install and tune a stand-alone first. There are guys running Haltechs, Tec II and HKS F-Con Pro in Miatas. Most important is sorting out the TPS for part throttle conditions. You're gonna need a co-pilot to play around with settings on the fly, so you're going to need a laptop too. WOT stuff can be tuned on the dyno of course.

What other mods do you have to take advantage of IRTBs? Although a stock Miata got 16whp(in a 1.6) with just installing RS Aizawa TBs. Some of that may have been from the PCM, but you'd see at least that with a Protege, since they run so rich to begin with.

I'm thinking 45-48mm TBs might be more appropriate, just because the FS doesn't rev very high. If you had Jamie's(Installshield2. Anyone seen Jamie in a while?) bottom end and could handle 8000RPM, I'd say go with the 50mm, but not for 6500-7000.
Here's the unit I'm getting. It has a plenum and venturis, and have been told is the ultimate in throttle response. I'm buying it from Randy Stocker(Miata Guru)

edit: That's a genuine FE3 it's attached to if you're wondering. I couldn't imagine how much that thing screamed.....
 

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Jamie is right here dude...not postin' much, but always watching...

and I fully agree with you Josh...50mm is absolutely huge if it is only feeding one cylinder each...Intake charge velocity will be unacceptable at low rpm most likely...hell our stock one is less than 60mm isn't it?

but its an awesome idea...I just think that those TB's are far too big for streetable lowend output...it will scream up high though...so hopefully that is what you are looking for...

Like Josh also mentioned...a number of decent standalones are more than capable of handling it...and come up with a linkage to deal with each butterfly and you are all set...let us know how it goes...
 
sounds like a fun project..50MM is pretty big per cylinder..I was contemplating this a while back..but only like 40's..Good luck on your project though!
 
I called up the place I'm buying them later this evening, and asked if he could find and spec some 42mm bodies for me. Looks to be a go, but I'll be waiting even longer for them.

No big deal though. I'm putting this together as a winter project, so there'll be no problem with time. I just need to save up the cash over the winter for the EMS.

The armatures and activators are going to be very little work. I've basically got it drawn up the way I'm going to need it. I'll scan said drawings pretty soon here, just so you can get an idea of where my brain is going (It's obviously gone, but you get the idea).
 
Me either! =) I've started saving a little cash for the ECU, but I still have yet to decide which I'm going to get; I think I'm going to end up getting the plug and play (ish) AEM EMS, but that requires I save up a good 2k, for the ECU, wideband O2 for it, and tuning.
 
Is Beau still working on that thing? I keep hearing rumors here and there that it is going to be released soon...but the threads always fizzle out...

I am in the same pond Flat Black...I need a controller yesterday....

Just out of curiosity...How much do you think your mod will cost? excluding engine management...
 
i'm totally lost with the ITB concept.
I saw the s2000 video with the kid, where it sounds like a busa ripping it up.
I've also read that a stroked ITB kit for the S2k produces around 60 more flywheel horses. (260 to the wheels on s2k).

Does this mean you want higher compression when employing these? Is something like the forged wagner block available in high compression?

Would you still want a 2.25" exhaust with this?

What #'s do you realistically expect....tuned

sorry for the newb attack
 
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