Joe Perez

iTrader: (8)

Is this sufficiently big and cheap? http://cgi.ebay.com/ebaymotors/Ford-5-0-Mustang-stock-throttle-body_W0QQitemZ150210361690QQcmdZViewItem?hash=item 150210361690
Or maybe this one: http://cgi.ebay.com/ebaymotors/C4-CORVETTE-THROTTLE-BODY-FLOW-BOOSTER-AIR-FOIL-85-96_W0QQitemZ260207414015QQcmdZViewItem?hash=item26 0207414015
or this one: http://cgi.ebay.com/ebaymotors/C4-CORVETTE-THROTTLE-BODY-FLOW-BOOSTER-AIR-FOIL-85-96_W0QQitemZ130192510078QQcmdZViewItem?hash=item13 0192510078
or this one: http://cgi.ebay.com/ebaymotors/Ford-...em170189738401



1- No synchronizing issues
2- Easier to get a stable MAP reading
3- Less and simpler fabrication required
4- Lower cost
5- Not as ricey

MX5-4me

More air flow

Braineack

iTrader: (62)

Is there more airflow through a 70mm plenum with 4 TBs behind it or a 70mm plenum with a TB on the front?

MX5-4me

None of those TB will flow as much air as 4x~45mm TB. end of story.



1- No synchronizing issues
Easy fix with time

2- Easier to get a stable MAP reading
How so?

3- Less and simpler fabrication required
No, not really?

4- Lower cost
No, not to get the same flow

you can pick up Motorcycle TB or TB off of PWC or ATV for very reasonable.

5- Not as ricey
I'm guessing this is the real reason most folks have issue with it.

It's not ricey if it improves perfomance. IMO
using ITB can do just that in the right application.

MX5-4me

how is that what we are talkng about?

I guess i'm missing something this time.

Braineack

iTrader: (62)

to use a ITBs on a turbo there has to be a plenum right???? so is there more airlfow through a 70TB and no ITBs, or a 70mm opening into a plenum with TBs behind it?

levnubhin

iTrader: (30)

Either way, to spend im guessing around $2000 to put itbs and a megasquirt and gain maybe 10whp is just plain STUPID! Dont tell me about throttle responce it still took him until 6250 rpm to make the 105hp. He may get off the line a little quicker but if im making 105 whp at 3000rpm his chance dont look to good.
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MX5-4me

in no way shape or form am I talking about anything to do with this guys set up.. I don't think ITB are right for an NA Miata

I also don't understand why the ITB have to be limited to a 70mm Plenum for a turbo application.

70mm Plenum for 4x~45mm TB is not near enough.

get closer to 100mm.

MX5-4me

we agree.

Zabac

iTrader: (39)

the way i look at it, 1 TB 1 small restriction when at WOT
4 TBs 4 small restrictions when at WOT

so, one massive TB with a proper sized plenum and runners is greater than ITB with a plenum before them

MX5-4me

so if i used 4x45mm ITB with a 90mm Plenum i wouldn't flow as well as one 70mm TB with a 70mm Plenum?

Is that what you are saying?

bryantaylor

iTrader: (5)

ITBs are really cool, but not on a sub 2 liter 4 banger. little motors NEED F/I. ITBs would be great on a v8, but not a 100 horse 1.6/1.8

Joe Perez

iTrader: (8)

No, but a single 90mm throttle body will flow better than four 45mm throttle bodies.

One 45mm throttle body has an area of 1,590 mm2. Therefore, four of them have an effective area of 6,360 mm2.

One 90mm throttle body has an area of 6,361 mm2. So it's actually bigger to start with.

Assuming that the throttle plates and shafts are of equal thickness between the two, you'll lose twice as much to frontal edge area on the IRTBs vs. the single throttle body.

And of course airflow through the manifold isn't a constant, equally divided among all four ports- it happens one port at a time. So at any given instant, you've got one cylinder trying to fill itself through either a single 45mm TB with an area of 1,590 mm2, or one cylinder trying to fill itself through a single 90mm TB with an area four times as great.

Of course, all of these things are so much larger than the intake ports on a Miata head can possibly be bored out to that it's pretty moot to begin with.

Are there power gains to be had from IRTBs on a "built" engine relative to a stock manifold and plenum? Of course there are.
It's just that the $ to ratio is hugely disproportionate to what you'd get out of pretty much any kind of forced induction known to man.

MX5-4me

This is what i was missing ..That makes good sense.. Thanks..

Pitlab77

iTrader: (3)

My stock 99 makes with a K&N drop in filter, and an axel back makes 110 RWHP and i forget how much tq lol

miataspeed1point6

iTrader: (1)

I like alot of the cars from CR. I actually get alot of inspiration from some of the cars for exterior and interior mods.

But sometimes I look at what they are doing and I just don't get it. $2k for 10hp? I know it's more of the style with the IRTB's on that site....but damn.

m2cupcar

iTrader: (5)

I agree- I think it's more about looking at it that making power. They do look cool, but they're still slow.

The_Pipefather

iTrader: (5)

The general consensus is that

IRTB vs. Stock Manifold+ Turbo: No contest, turbo wins

But lets not debate about what happens when you use IRTB + Turbo. Forget $$ per hp for a moment, if there weren't any gains by going to IRTB, the 80's turbo F1 engines wouldn't be using them. Sure, the gain by going from stock to IRTB on a turbo engine is a lot smaller than if you did it on NA.

There's no question that IRTB's do give gains on a NA engine, when done properly. Most of the JDM-crazy crowd simply uses the shortest possible runner length which, IMO, is not optimal. The Miata stock manifold has a runner length around 10-12" if you figure in the plenum. Typical IRTB lengths are around 5". I suspect there would be a severe loss in cylinder filling due to lack of the "tuned length" ramming effect that occurs with the stock longer runners.

I think the present IRTB setups are compromised both in terms of performance and cost. Someone needs to re-design and re-package the IRTB with some thought towards cost. One way to start is by looking at some of the older carb manifolds out there. The main cost is the TB castings and all the linkages themselves. If those are integrated into a single casting or plate (like this: http://ca.geocities.com/mlvd@rogers....stop_screw.jpg)

and an exhaust-header style manifold is made to join into each individual port, I think the cost can be brought down significantly. If I had the money to build a prototype I would.

Joe Perez

iTrader: (8)

+8.

When Gene Berg and CB Performance first started doing aftermarket fuel injection on the VW type 1 about 15 years ago, they took old Weber carbs with their corresponding manifolds, ripped out the venturis, and drilled holes in 'em for the injectors. The Weber manifold design had, oh, about 30 years of R&D already behind it, and as it happens they were already IRTB to begin with. (The T1 engine configuration does not lend itself well to plenum intake designs, as evidenced by the piece of **** intake manifold design that the factory clung to for 50 years)

When CB started making proper "off the shelf" manifolds and throttle bodies some years later, they simply copied the Weber IDA design verbatim. The manifolds were identical with the exception of having injector bosses cast in, and the throttle bodies were identical save for having TPS-mounting provisions and lacking the float bowls and such.

As an example, here's a picture of an old-school Weber 44IDF carburetor kit for the T1 (the design hasn't changed in decades):


And here's a turnkey fuel-injection system for the same engine (this is a newer design with the injector bosses on the throttle body, designed for people upgrading from carbs who wish to keep their old manifolds):