I presume you mean direct bolt up to the manifold you're using Madjak, but I see S90 do have a 55mm TB for the Honda Fit/Jazz on their website, is that a possible option for an MX5 inlet mani?
S90 Performance

Being a bit new to owning a built motor (not the same as researching and trying to understand them... owning is the operative word here!) I've begun to worry about the shaft and screw problem. Its a BP05 inlet manifold in my case.

I'm know the motor in my car isn't so hawt and my driving on track so good that 70mm S90 would see any gains, but I would certainly swap for reliability on any level if a stock TB could kill my bits.

 

Thats stock size, might work.

The issue is the throttle plate screw, or shaft. Not the idle screw.

 

Just had a look and s90racing yeah they do make a 55mm... and 68mm also. Whether or not this is a good choice is dependent on your own skills and if you like being a pioneer or not as you'd be moving into new territory. I don't think it's hard to fit any throttle body up to any manifold, it's other issues like throttle cable length, idle control, throttle position sensor that can make it tricky or not depending on how the stars align. Really someone just needs to go and try it and see how hard it is. Or one of the vendors could approach s90 and get them to make an actual solution specific for a miata thats not a compromise either way. If the S2 can be made reliable with the knowledge of what to correct it's still a good option, just out of the box it's not so great.

Personally I think the stock throttle body is fine, but then it would suck to be the one where it's not and you destroy a motor. I ran one for over a year, reving the engine over 8500. I'd be lying to say it's one thing I'm happy not to worry about... but then I have other issues to compensate. Also it's the shaft that fails not the idle adjustment.

 

I did mean the shaft sorry, thanks for the correction. Idle screw on the brain jibbering here about another car.

 

Can't find any information online but I guestimate the hole spacing to be at 65mm x 65mm centered around the throttle opening. I think there would be enough meat to drill and tap those hole centres into a stock manifold. It would probably just bolt up.

 

update on this: we dyno'd the car, immediately ported the IM, and re-dyno'd asap

picked up a few hp

then leaned it out a little bit (12.2->12.5afr) and picked up a few more hp

The biggest power bump was 6500-7000rpm as expected

pics/plots later

 

 

Ugh. you are such a tease. Where. Are. My. Flapjacks.

 

on mah phone lolz

I keep forgetting to upload

 

We care not about your failures. Your memory lapses are disturbing our flow of free internet entertainment!

 

About how far did you port the upper? graph pics?

 

How do you tag people in a thread?

@18psi

 

#18psi

 

@aidandj

 

@18psi

Ha!

 

I texted the pictures to him he will upload them

 

Why can't you just post them to the thread?

 

Because we are in the garage right now soldering his OEM barometric pressure sensor in to work with the ms3

I'm on my phone

 

^lol



marked up, pre porting





just starting





part of the way done






mostly finished

 

CORRECTED
this is corrected with temp/baro and Air/Fuel is actually displaying MAT
Car picked up power with the porting. Multiple back-to-back runs resulting in these gains.