Turbo + ITB's on a miata.
 

been thinking about this for awhile, and have been reluctant to post the idea/thought of it because of fear of getting a new asswhole ripped but whatever, its just a talk/discussion.

so to start off with what got me thinking!

i was working on a friends Celica and looked at his motor and noticed it is has ITB's from the factory with a plenum on it, and i know that people turbo the 20v engine.

http://www.4age.net/gallery/engines/031.jpg

4AGE 20v turbo

http://www.padandwheels.com/mr2/blac...oject/4age.jpg

http://img696.imageshack.us/img696/6105/jamie164.jpg

with all the chat about intake manifolds, using the 99-00 heads and retrofitting honda intake manifold to our cars. maybe there might be some advantages to this, maybe not.

what are some of yalls opinions?

There would be advantages, question is would it be worth the lots of time and cost it would need?

There are a lot of unorthodox things I would do to my turbo setup before ITBs

If my car had a hamburger logo and a 6 cylinder and twin turbos. Then I'd fux with the ITB Turbo combo.

i know there are plenty of other things that can be done to a car before ITB's. i.e. meth injection, custom intake mani and :hustler:

question is, would a ITB setup with a plenum be more effective than just a custom intake manifold or than the ones that are already out there.....

as far as the cost. im pretty sure if the right parts were sourced and deals were to be had it could be done for rather inexpensive. still may be more than a custom manifold or the ones that are already available for purchase, but what if that cost could be justified with a higher yield of efficiency and what not.

People mention advantages, I'd like to know what they are. More importantly I want to see HOW MUCH of an advantage this would be over a custom sheet metal or retrofitted honda manifold. I'm willing to bet said "advantages" would be so insignificant that they wouldn't even come close to justifying the time/money that would go into something like this.

For the time/money you'd spend on this you could just go bigger turbo and more supporting mods:D

Just my .02 tho

i fully understand your point and logic. in my head i think about this subject in the same way as you. i have just been tossing the idea around in my head for a while and just got tired of keeping it bouncing around in my cranium.

i may see if i can get ahold of a ITB setup off one of these 4AGE 20v's and see where things go, there are a shit ton of them at the local junk yards and i have a friend that runs the celicatech forum so there is a possible place as well for me to get what i need.

i may or i may not do it so we will see.

Short answer:

Do ITB's for feel, not for power. They're good for throttle modulation, as in corners rather than straight lines.

lol @ people who "need ITB's" for modulation.

According to Sav it cost him around $400 to convert to a Honda manifold... for that much an IRTB setup could be built using GSXR throttle bodies. It would take the same or less time than making a sheet metal manifold.

Sometimes MT.net is as bad as M.net when it comes to new ideas...

here are a few that i found. looks kinda cool.


http://www.haywardperformance.com/im...prototype1.jpg

http://www.clockwisemotion.co.uk/ima...bre-airbox.jpg

http://i380.photobucket.com/albums/o...c/IMGP1287.jpg

How do you get a good MAP/vacuum signal from independent throttle bodies?

lol @ people that don't want a more controllable turbo Miata mid corner, it's not a need.

Usually ITB people go Alpha-N, avoiding that problem. BMW got around it in 1989 by putting a VAF in front of the ITB's. There are ways to get vacuum, involving four hoses and a block, but the best way is to put a MAF before the ITB's.

Great, another fix for a problem that does not exist.

Uh, what part of not a need are you not getting here? It's not a problem, just an incremental improvement over the standard system. This is like 9" 6UL's vs 8" 6UL's. Yeah, it's not a need, but it can get you a bit more speed. Control counts, that's why Savington was so fast on the Rotrex car. i'm not saying you or anyone else should buy this, just that there is a reason to do this if you have the infinite money cheat.

That's what I figured, a barbed fitting in each runner to a fuel rail looking tube above each fitting, making a little plenum for a vacuum signal, for things like brakes (or a map sensor). Thanks for the reply :)

1) Sav has access to parts and services at bigger discounts than the typical enthusiast afaik
2) Your average joe can't cut/weld/fabricate so that 400 price tag would be more like 600. most itb setups I've seen are being sold for 1000 or so.
3) Everyone here has a "guilty until proven innocent" attitude. At least most of us. Sure we're skeptical of new ideas because its much better/easier to use a tried/true method and not fuck up our cars.

But hey, when someone shows us proof/results we're more than happy to become believers. At least I am:)

Sav spent 400 bucks putting on having a BP flange welded on a honda manifold...

Man, it sounds like you want to do it so go for it. If the spacing is right on the runners maybe you can graft it onto a Miata flange pretty easily. Be sure to do some before-after dyno tests, on the same dyno, no other changes, etc and see how it compares to stock. The throttle modulation report will be more subjective.

i didnt intend for this to turn into a argument/debate/fight.....


i just wanted it to be a friendly discussion on theoretical pros and cons of doing this. im not telling anybody they should do this or that it is gonna make uber amounts of power gains, this thread was more of a what if.......

What size throttle bodies are ideal for a 1.8 ITB setup?

no one is fighting. but if its proven that they significantly enhance and increase power and its delivery we'll all be looking into doing likewise on our setups.

i was thinking what ever size comes on the 4AGE 20v that motor is a 1.6 so it should be okay for the 1.8. alot of people that have done the ITB's on a miata get them off Liter bikes.

i know its not happening right now, i just want it to be ovoided. im gonna do some more research on ITB's and see how cheap i can source parts out for this.

i can probly get away with choping the flange off a old intake manifold, source the ITBs and make a plenum. it seems simple enough right now...

As did the LS1 swap to me when I wanted to do it:giggle:

When you get ready,I will machine as much of the parts as I am capable,Just buy the material.Ive often thought about this,it seems to me that it would offer an improvement in throttle response on the same order as on a N/A motor.
(G)

thanks Greg, ill keep you posted. i have some other priorities right now but i think ill be getting my hands dirty with this one day soon!

thats why i said RIGHT NOW.... lol

1) Kind of immaterial, as I was advocating building a DIY IRTB setup not buying one. I'll stick by my contention that one could be built for $400 or less without any special discounts.

2) Welding I'll agree with, but anyone who can fab up their own DIY turbo setup should have the skills to make the pieces I'm talking about. You then take them to your favorite welder and have him stick then together. Basically you've got to make an aluminum plate with 4 holes in it the shape/size of the ports (plus the thickness of your runner tubes), four short tubes for the couplers from plate to TB, a plenum box, and some misc spacers between the TB's (early GSXR TB's come in paired barrels but they unbolt into separate units). None of it is rocket science and anyone who can run a drill, a file, and a pair of snips could make it with some patience.

3) I know and it's sort of funny because they all also complain about how M.netters won't listen to new ideas... then they do the same thing here.

In my opinion the "idea" of IRTB's and turbos is well enough proven, look at any turbo era inline-4 F1 engine. They pretty much all used IRTB's (mostly slide valve) and made upwards of 1200hp out of 1.5 liters. From my viewpoint it's a question of whether there's enough benefit to be had to make it worthwhile for our level of power. If I were to guess I'd be inclined to say you might notice a difference at about the same point as it becomes useful to ditch the stock intake.

For the record, I really meant you should try it. If you want to, and you can do it inexpensively, why not?

no promises yet. i want to see how inexpensive i can get it done first!

You're very welcome. :)

Like most things having to do with passage of air going into an engine, it depends. :)

This is stolen from someone who quoted it, on what throttle for horsepower, may or may not be right, seems to make sense to me though:

"...this guide is from A Graham Bell's Forced Induction Performance Tuning:

50mm: 250
56mm: 310
62mm: 390
70mm: 500
75mm :600"

You'd just divide the area of your intended goal by four and choose a width that gives you that opening area. i know you probably know better, but i should remind anyone reading that you'll need to use Area = pie * Radius squared, rather than a linear progression.

Honestly, most any bike throttle body will be good enough, for instance in GSXR's, the 600cc has 38mm, the 1000cc 42mm and the 1300cc 46mm. Believe this is due to keeping air intake velocity down while the bike is under high rev, but don't quote me on this.

That depends on discplacement and rpm. That is one of the advantages of an IRTB or carb with replaceable chokes. Cast intakes do not have that advantage, so it is impossible to control the speed of intake charge entering the cylinder head with a fixed intake. I currently have 40mm chokes. Forced induction cars use different chokes, but I do not know how to calculate for it.

I would like to add that it depends on what one is doing with the car. I never see IRTBs on the highest horsepower drag cars, but I see them on road race cars. I think, that it has to do with the throttle response advantage IRTBs have, which is not really necessary on drag cars.

Not 'pie' but pi. Also pressure drop, all else being equal, is inversely proportional to diameter raised to the 4th power, not diameter squared.

The misspelling was trying to type after 12 hours of working on my car, quite tired, sorry. -.-

Another OEM ITB turbo setup.

RB26DETT

http://img236.imageshack.us/img236/5751/11855mgap2.jpg

On my old RB26, the map sensor was just off the plenum. Before the throttle bodies. But stock runs two MAFS.

I was running a map sensor based PowerFC.

There is also a MAF though IIRC, so the MAP reading isn't as important for a stable idle/low load part throttle like it is in a speed density setup.

I think I might be missing something. It seems that everyone wants better flow, thus the aftermarket IMs. Wouldn't ITBs be a restrictor? I can understand how they would be better on a NA car, but a turbo? My little pea brain can't wrap itself around this.

Anyone?

I just realized I wrote that before reading second page.:facepalm:

If its been covered sorry

Lets take the 62mm TB. Area is 4.68in^2, divided by 4 that's 1.170 in^2, which is a 31mm diameter. I have some ~36mm VFR750 carbs in my garage. Hmm...

My only experience with them is on a RB26 so it relates a bit I guess. I'll explain it this way. Large single throttle body = BIG hp. Guys running big singles (think T88, T51R etc) on the RB go with a single large throttle body to aide in HP/ max flow. Most of the time these are dyno queens or drag cars.

Now, if you stick with twin turbos, say GT2860's like I had built.. and you want better throttle response you keep the ITB's. You loose a bit of peak horsepower but your tip-in response is lightyears better and with two smaller quick spooling turbos it makes the car much more fun to drive. The car still made 530awhp with ITB's so I wasn't complaining.

so we know that Turbo ITB combo is not unheard of, and that it helps throttle response but it hurts flow with a really high HP setup.......

question is....is it worth it.

should one go with a ITB's w/ a plenum or just say my idea/thought blows and one should go with a bad as Honda manifold and make it fit. possibly putting a bigger throttle body on.

One point of data is not proof, per the "hurts flow." Did you see my area calcs? Even small bike throttles give huge entrance area.

Also, ITB F1 Turbo engines make your point fail.

i was just doing a lil recap.

i think if i do this ill try to utilize 62mm TB's

Ok, if you put on ITB's with 62mm inlets, you'll be good for 1560 horsepower.

Not exactly what i'd recommend.

oh shit! NVM :bowrofl:

im bad at math....

whats good for 400 whp?

Hey, if F1 engines can do 1500 horsepower with 1.5L just imagine what your Miata can do with 1.8. :D

You should be fine using GSXR 600 throttles, they're 38mm, which is about the same as a 70mm single throttle body, which is good for about 500 horsepower. :)

fuck yeah, with my extra .3L of displacement! hehe

what is the measurement for our factory throttle-bodies? im gonna start looking at ITB's....

The factory throttle body is 48mm if i remember correctly, there's an upgrade from GoodWinRacing that's 60mm.

so 4 38 mm is = to 1 70mm TB

or is it

1 38mm is = to 1 70mm TB

38mm x 4 about equals one 70mm throttle.

thats what i thought, just checking.

what would be better, the 2 in one Throttles

http://www.epicwelding.com/auto_images/honda_itb.jpg

or 4 individual?

http://www.obxracingsports.com/produ..._image-711.jpg

Not sure exactly what you mean by "2 in one" but i'd go with one for each cylinder. That's what ITB's mean, after all.

Also, those big turbo cars? Willing to bet those are mainly drag cars, where throttle is either on or off most of the time. Throttle arrangement wouldn't matter there. Might be wrong, but that's the feeling i get.

EDIT: You just put up pictures, nice. It's not two in one, those are just different construction methods.

picks added!

2 in one meaning to separate TB's joined together

Edited my post, but it doesn't really matter in either case. :)

Tubes are tubes, doesn't matter how they're supported (as long as the support doesn't fail) as long as how the air travels is the same.

if it will be easier for me to go with 2 constructed together ill do that.


i just looked on egay. there is a set of GSXR 600 ITB's going for 110 bucks! most of them all range between 110 to 200 price range.

Just do make sure that you have your tuning method figured out before you start on the construction. Welding four tubes together and getting plates to turn is the easy part, tuning it is the hard part.

the ITB's wont get installed till after my car is back up and running and dynotuned. after that the ITB's will go on and it will be back to the dyno for tuning and comparing of the before and after.

See you're using MSPNP.

Will assume you're using speed density.

You may be able to get away with using the method i described earlier to get vacuum, but do make sure the people you take it to get tuned know how to tune for ITB's.

If I recall correctly the early 2000's (like 2000-2001ish) GSXR's have 2 paired TB's that each consist of two singles bolted together. This allows you to unbolt them and space them the same distance apart as the intake ports on the Miata head... making the manifold much easier to fab. The downside to that is some spacers need to be made and some fiddling with the linkage would also be necessary. Later GSXR TB's don't come apart... so be sure of what you're looking at.

Do a little google searching, it's how I found the info on which TB's come on which bikes.