ITBS + plenum + turbo = worthwhile gain?
 

alright, I've got another thread that might potentially fire up the flamethrowers, but here goes. The facts are, I'm putting together a forged internals bottom end, but I haven't got pistons yet. Got carillo A rods though.

Basically, I've been studying plenum design and building one, and if I decide to go 9:1 CR or something, in the humble opinions of knowledgable people on this forum, will a plenumed ITB turbo setup show the benefits that it's worth? I could sell the whole setup for probably 1k, but I figure it'll at least be as good as a custom intake manifold, which would have a similar cost I figure.

the setup has 45mm throttle bodies, and a plenum would be attached to my 50mm air horns. If I wanted to dial in more torque, I figure I could add velocity stacks into the runners, but I doubt I'll need to worry about it with a turbo.

I would love to know the diameter of the runners on braineack's setup, for reference. Anyway, happy flaming!

why flame? ITBs and a turbo is the best its gonna get

1.75" IIRC.


but of course adding a turbo to an otherwise stock motor will can net you well over 100% power gain easily :P

seriously. It's a great idea and has been down on alot of different cars with respectable gains.

Fixed ;)

Sorry but English is a second language for me so it's twice as complicated to follow :)

Depends. If you want top end, it's probably worth it. Stock intake manifold suckssssss. Building custom shit like that always ends up being a bitch though. But if you did it, it would be badass. Most here don't like IRRRRRRRTBS because people with them think they're gonna runs 12's in the 1/4 with their throttle response.

haha, its cool man. I'm just using the little time I have in between classes to get my stuff done and not really thinking about my grammar because I keep it gang like that:cool:

Feel free to correct me any time! lol

I wouldn't want to deal with trying to tune it on my own car but if you got it to work well it would be bad ass.

If you can get it going consistently and reliably, it will be the shit.

awesome. 1.75" = 44.5mm, so it seems like ~45mm is the ideal torque/horsepower tradeoff range. What kind of gains did you see after switching out that manifold from stock?

I'm gonna take my time with this setup, probably run regular ol' itbs while i'm breaking in the motor for a while, while I try to figure out how to do this in the baddest ass way possible, investigate runner sizing, ideal literage of plenum, etc.

Please keep us updated on your progress! :bigtu:

Ok, maybe a silly question (ok, I know it's silly) but what is the benefit of IRTBs? Faster throttle response is one, but I never thought it was that sluggish to begin with...

I dunno, all I know is high end cars use them and they look cool and are technically nifty so why not :) (only on FI cars though)

The only difficulty I know of is tuning on vac side. The four tb plates will confuse the vacuum signal to the ecu's map sensor. Instead of a single tb vac of about 20 inches, you are going to find about 10 to 12 inches. Combining the four signals into a damper can might raise that to 13/14.

The consequence is that you must tune the entire span of vac side operation over 12 to 14 inches instead of 20, thus making the incremental changes more coarse and clearly needing a finer calibration.

This is tough on the guys that must have a magic system run perfectly right out of the box.

You are on the right track, it is worth doing.

maybe, run the whole thing using a MAF sensor....

The difficulties you're talking about are also present with NA IRTBs, but I figured it'd be easier to tune on a 'closed' system, where the ITB's aren't just sucking whatever is on the end of the runners (small atmospheric pressure or temp changes) I dunno though, I guess I'll figure it out as I go along.

sounds like an interesting project with badass potential. make sure you take lots of pics:)

Can be done successfully, search JeremyS on the pointy board.
His homepage

His top speed run, I don't know what he was running at the time though.
MX-5 Miata Forum - View Single Post - Fastest Miata?

ITB's are on my long term projects list.


Chris

Why not go quad turbo with each fed into an individual throttle body...
Best of all worlds.. no lag and awesome throttle response

4 tiny turbos would take just as long as one turbo 4 times as big ... well actually i think it would be worse due to the way the exhaust pulses would be hitting the turbines. Think about it, instead of 1800cc to power a turbo, now for each you have 450cc.


whatever, you were just joking anyway, and i ruined it lol.

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I find myself posting this site yet again :)

(not my homepage btw)

Dude if the Veyron can do it a Miata can do it better

i was thinking about doing twin turbos just for the awesome factor, where each one is on it's own system and is fed into two ITB runners. seems expensive, and twice as many points of failure. But it sure would be one engine bay packed to the gills with awesome.

just dont forget a balance tube.

What about a cross? the turbo hooked to cylinders 1,2 feed 3,4 and the turbo running off 3,4 feed 1,2... No idea if there would be any benefit, but it might add to the cool factor.

Tune the spark and fuel maps using a Mustang 5.0 MAF sensor. The calibration values are already available in megasquirt. I am unsure of how you would do boost control and other MAP based functions without a MAP sensor though.

Hybrid Alpha N?

Isnt that what its for?

I didnt know u were planning to run a turbo itb setup or was this a recent thought?

ill be there whenever i can to snap pics! actually need to post up the pics i havd of ur setup when i get home.

MAF is a way more elegant and reliable way of doing it. You have a single air inlet on a turbo car anyway, might as well use it to measure airflow directly.

BTW not a single OEM uses speed-density these days.

I'm always playing around with ideas. last week I was thinking high compression and nitrous, which would work and get me all the power i'd want on the street, then well into turbo power on the track, but turbos are just really damn fun, and an itb turbo setup would be monstrous. I don't have anything here at school besides my car and its current setup. I need to gather parts for my engine build though, cause I'm getting paranoid about the condition of my current shit. I need a job like yesterday.

I'm gonna toy around with the idea of using a mustang 5.0 MAF in my setup, it would instantly make tuning a snap. I don't really trust my current IAT sensor anyway, which is installed into the #1 runner, literally an inch and a half from the engine head.

I just worry about unequal pressure, so a balance tube for the tow manifolds would make sure all cylinders see the same amount of boost. it's common in TT v6 and v8 setups.

idle would suffer with hybrid alpha n. off boost would be in alpha n while on boost would be in speed density.
ideally, i would like to tune idle in speed density, above 85 kpa in alpha n (which is how i have my itb setup) and boost in speed density. it doesnt seem doable that way. so, maf might be the best option with "boost sensing" for timing retard during boost.

I talked with Jeremy about his setup sometime ago and he basically told me the complexity of the system wasn't worth the gains. All in all a well designed single TB setup would do just as well. Plus with a turbo, you really don't hear the ITB's. :)

well, i don't really care, I already have the ITB's. I'll just do it for the cool factor. It might flow better because the pressure is being regulated right at the runners, and it might also have better response. I really don't know though. What is certain though, is that it'd be beastly. As long as it performs as well as an aftermarket manifold I'll be happy.

If you try the setup, please let us know how it comes along.

Don't be too disappointed if you find less gains than say, bumping the boost up by 2 psi, which is a lot easier to do.

Well that was kind of how Jeremy came to it. He purchased a former CSP car that had the ITB's and a bunch of other parts. Took what he needed, so other parts to friends, and then sold the car itself (making money in the end).

ITB whoring time!

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lol what happened to your carbon fiber plate?

all this car needs is a turbo now