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David S. Wallens
David S. Wallens Editorial Director
10/19/21 8:00 a.m.
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Can we share a secret with you? When we originally built our 1992 Mazda Miata back in 1999 or so, part of the wish list included individual throttle bodies.

We already had the Flyin' Miata/Link ECU and cylinder headwork, so why not go all the way? Figure in the expense and complexity, however…

Read the rest of the story

maschinenbau
maschinenbau UltraDork
10/19/21 8:41 a.m.

Does the pope E36 M3 in the woods?

gumby
gumby Dork
10/19/21 8:43 a.m.
maschinenbau said:

Does the pope E36 M3 in the woods?

Do bears wear funny hats?

JAdams
JAdams Reader
10/19/21 8:50 a.m.

Yes! Yes! Yes!

 

I'd love to do ITBs on my NA and would love if you guys led the way so I could follow. 

alfadriver
alfadriver MegaDork
10/19/21 8:51 a.m.

Need or want?  

I honestly think you don't NEED it.  But 100% on the want thing.  Go for it.

mmcvay
mmcvay New Reader
10/19/21 9:16 a.m.

Putting itbs on my 92 was probably the best thing I did to it. They made the B6 feel like a real sports car motor unlike stock. It's worth it just for the intake noise.

Colin Wood
Colin Wood Associate Editor
10/19/21 9:35 a.m.

I think ITBs are one of those things that won't always add power, but they can add fun–and isn't that why we play with cars in the first place?

frenchyd
frenchyd UltimaDork
10/19/21 9:39 a.m.

In reply to David S. Wallens :

You are aware that air has mass?  That an object in motion tends to stay in motion and an object at rest tends to remain at rest. 
 Individual throttle bodies will need to start and stop intake air  4 times per revolution more often than air inducted through one  throttle body.  It's far easier to divert air already in motion than to start and stop air. 
   You can make up for that loss by increasing duration on the camshaft at the expense of low end  power. 
 OK 4 injector stacks look sexy. But cost you power.   What is your priority ? 
 

ps I don't see Ferrari, Aston Martin etc. using individual stacks. 

APEowner
APEowner SuperDork
10/19/21 9:46 a.m.

I think it's a bad idea and not worth the time and money.  I totally think you should do it and I'd be thrilled to be proven wrong.

maschinenbau
maschinenbau UltraDork
10/19/21 9:55 a.m.

In reply to frenchyd :

You may not be aware, but they're used in plenty of modern exotic and sports cars. Mclaren F1, Ferrari 355, many Lotuses, BMW M N/A engines, RB26 (which was turbo AND ITB), and my favorite, the Lexus LFA. Not a magic bullet, but there is power potential there.

Junghole
Junghole SuperDork
10/19/21 10:00 a.m.

Does the hp gain outweigh the torque loss? 

Keith Tanner
Keith Tanner MegaDork
10/19/21 10:14 a.m.

I've been offline for a couple of weeks, did not expect one of my videos to get posted here :) 

Frenchy, I have repeated dyno charts on several Miata engines that show they do not cost you power but provide some gains. Proper A-B tests. The airflow you're imagining is the same regardless of where the throttle body is.

My BMW M5 also has 8 individual throttles and does okay on power. 

ITBs are fun but most aftermarket implementations are not great street options. They work much better if you run a plenum like the BMW or like I did on one of my Miatas. On a high compression engine, they make quite the hammering noise. But they do sound good when you're in the mood and have the ability to play. They're also a great magazine project because people love the idea.

The Link ECU that's in the Miata in question can run ITBs -BTDT - but it's definitely not ideal as it can't use anything but MAP. Worked well enough on my Locost but you accept certain compromises on a car like that :)

I will admit that I have a set stashed away that I'm thinking of putting on one of my Miatas just because. 

Keith Tanner
Keith Tanner MegaDork
10/19/21 10:22 a.m.

Don't have the before/after charts for one engine handy (I'm 2000 miles from home) but it went from 134 to 146 rwhp with throttle bodies. Should have gone higher, I realized years later that I never ran it all the way to redline on the dyno for some reason.

Here's an A-B of a ported intake manifold vs a set of throttle bodies on a high compression stroked Miata engine. Yes, I know about the torque dip in the middle - but the point is the before/after. Shortly after, I failed sound at Laguna due to intake noise :)

http://targamiata.com/images_lrg/targa%20IRTB.pdf

ah, found a dyno video. I have some driving videos somewhere as well.

 

DeadSkunk  (Warren)
DeadSkunk (Warren) UltimaDork
10/19/21 10:34 a.m.

Wanna screw with people? Put four SU carbs on it with the pistons locked up in place so that they're just throttle bodies.........I've seen it on an NA and everybody was freaking out because they failed to notice the injectors sitting right behind each SU. I'll bet somewhere someone has hidden injectors inside the SUs for giggles, too.

z31maniac
z31maniac MegaDork
10/19/21 10:50 a.m.
frenchyd said:

In reply to David S. Wallens :

You are aware that air has mass?  That an object in motion tends to stay in motion and an object at rest tends to remain at rest. 
 Individual throttle bodies will need to start and stop intake air  4 times per revolution more often than air inducted through one  throttle body.  It's far easier to divert air already in motion than to start and stop air. 
   You can make up for that loss by increasing duration on the camshaft at the expense of low end  power. 
 OK 4 injector stacks look sexy. But cost you power.   What is your priority ? 
 

ps I don't see Ferrari, Aston Martin etc. using individual stacks. 

Many vehicles still use ITB's, but are fed by a common plenum. 
 

Keith Tanner
Keith Tanner MegaDork
10/19/21 10:58 a.m.
DeadSkunk (Warren) said:

Wanna screw with people? Put four SU carbs on it with the pistons locked up in place so that they're just throttle bodies.........I've seen it on an NA and everybody was freaking out because they failed to notice the injectors sitting right behind each SU. I'll bet somewhere someone has hidden injectors inside the SUs for giggles, too.

Jenvey makes a range of stealth throttle bodies that look like carbs with hidden injectors and throttle position sensors. The current owner of my Locost plans to install a set at some point. 
https://store.jenvey.co.uk/heritage

Rodan
Rodan SuperDork
10/19/21 11:01 a.m.

The juice isn't worth the squeeze... but it will sound spectacular! wink

alfadriver
alfadriver MegaDork
10/19/21 11:05 a.m.
DeadSkunk (Warren) said:

Wanna screw with people? Put four SU carbs on it with the pistons locked up in place so that they're just throttle bodies.........I've seen it on an NA and everybody was freaking out because they failed to notice the injectors sitting right behind each SU. I'll bet somewhere someone has hidden injectors inside the SUs for giggles, too.

The other idea is to put EFI on cars that already have ported mechanical injection.  With ITBs.  I know you can get Weber like EFI systems, but for some cars, that's kind of a step backwards. (not in terms of performance, in terms of looking original)

alfadriver
alfadriver MegaDork
10/19/21 11:06 a.m.

In reply to Keith Tanner :

Makes a Miata sound more like an Alfa.  :)

californiamilleghia
californiamilleghia UltraDork
10/19/21 11:07 a.m.

i love the idea of using  throttle bodies off a production car or motorbike , 

but the "brain" is a problem and  I  think beyond most of us :(

if there was an cheap Arduino type board  that could run it  maybe it be more popular , 

Even something that replaced a stock single 'smog' carb that is worn out......

I know.....dream on  !

DeadSkunk  (Warren)
DeadSkunk (Warren) UltimaDork
10/19/21 11:08 a.m.
alfadriver said:

In reply to Keith Tanner :

Makes a Miata sound more like an Alfa.  :)

This made me chuckle.

alfadriver
alfadriver MegaDork
10/19/21 11:23 a.m.
californiamilleghia said:

i love the idea of using  throttle bodies off a production car or motorbike , 

but the "brain" is a problem and  I  think beyond most of us :(

if there was an cheap Arduino type board  that could run it  maybe it be more popular , 

Even something that replaced a stock single 'smog' carb that is worn out......

I know.....dream on  !

While Keith figured out a speed-density solution, an alpha - N solution does a good job, which can be done with even a microsquirt.  It's a little harder to calibrate, but with air temp, water temp, and BP corrections, it can run really well.  Heck, my Alfa is Alpha-N but with a mechanical computer.  I would imagine that it's an option for Speeduino.

(but I will 100% admit to being nervous about doing it, too.  I've never pulled the trigger)

frenchyd
frenchyd UltimaDork
10/19/21 11:43 a.m.
maschinenbau said:

In reply to frenchyd :

You may not be aware, but they're used in plenty of modern exotic and sports cars. Mclaren F1, Ferrari 355, many Lotuses, BMW M N/A engines, RB26 (which was turbo AND ITB), and my favorite, the Lexus LFA. Not a magic bullet, but there is power potential there.

Well technically most EFI  injectors  turn the cylinders into individual throttle bodies with a common plenum.  Most use one throttle plate ( per side) rather than individual throttle plates. 
      The individual throttle plates will create severe headaches. Placement is critical, the potential for a lot of air leaks, binding in one or more throttles caused by vibration, misalignment, wear.  Then the throttle linkage itself!  The weight of all those throttle plates. Plus the added turbulence of individual throttle plates.  
     Finally every time the intake is removed the potential is there  to bend, warp,  or damage something. And thus the need for once reassembled to synchronize the whole assembly. 

captdownshift (Forum Supporter)
captdownshift (Forum Supporter) MegaDork
10/19/21 12:08 p.m.

Secondary emissions, manufacturering cost and maintenance are the main reasons manufacturers aren't too interested in them. It has nothing to do with performance potential. 

 

I'd be very curious about an E85 setup on a stock intake, versus a skunk 2 plenum intake, versus itbs. 

David S. Wallens
David S. Wallens Editorial Director
10/19/21 12:29 p.m.

Good chatter. Thanks, everyone, for the interest. 

Some follow-up comments:

Need it? Who needs any of this stuff? I'm thinking pure emotion (and editorial, of course).

Keith, good point about the Link needing a MAP. Hadn't even gotten that far, but Ed and I figured we'd need to replace the ECU anyway. (And please tell me more about that set that you have stashed away. laugh) And what do you think about the Jenvey setups? Is that a turnkey solution? 

We've discussed bike IRTBs but Ed noted that he could feel the drivability issues from his house. (Which is not near my house as he was making a funny.)

That's the "problem" with the current setup. The engine is totally cold right now. If I turned the key, it would fire right up and then immediately set to a nice idle. No weirdness, no drivability issues--and that's with the Link, the cam gears, the lightened pulley, the aluminum flywheel, the bolt-ons, the headwork, etc., etc. Side note: The engine used to sometimes stall when returning to idle, but replacing the throttle damper seems to have totally solved that issue.

The Skunk2 intake sounds very cool but, sadly, they don't offer it for the 1.6L. Sad face. 

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