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Old 02-04-2009, 03:14 PM   #1
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Default 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!
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Old 02-04-2009, 04:57 PM   #2
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why flame? ITBs and a turbo is the best its gonna get
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Old 02-04-2009, 04:59 PM   #3
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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
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Old 02-04-2009, 05:01 PM   #4
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Quote:
Originally Posted by mazda/nissan View Post
why flame? ITBs and a turbo is the best its gonna get
seriously. It's a great idea and has been down on alot of different cars with respectable gains.
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Old 02-04-2009, 05:16 PM   #5
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seriously. It's a great idea and has been done 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
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Old 02-04-2009, 05:30 PM   #6
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Depends. If you want top end, it's probably worth it. Stock intake manifold suckssssss. Building custom **** 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.
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Old 02-04-2009, 05:35 PM   #7
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Originally Posted by Rafa View Post
Fixed

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

Feel free to correct me any time! lol
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Old 02-04-2009, 05:38 PM   #8
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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 ***.
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Old 02-04-2009, 05:43 PM   #9
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If you can get it going consistently and reliably, it will be the ****.
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Old 02-04-2009, 08:20 PM   #10
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Quote:
Originally Posted by Braineack View Post
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
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 *** way possible, investigate runner sizing, ideal literage of plenum, etc.
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Old 02-04-2009, 08:52 PM   #11
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Quote:
Originally Posted by N3v View Post
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 *** way possible, investigate runner sizing, ideal literage of plenum, etc.
Please keep us updated on your progress!
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Old 02-04-2009, 10:58 PM   #12
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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...
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Old 02-04-2009, 11:02 PM   #13
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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)
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Old 02-04-2009, 11:17 PM   #14
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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.
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Old 02-04-2009, 11:46 PM   #15
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maybe, run the whole thing using a MAF sensor....
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Old 02-05-2009, 12:26 AM   #16
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Quote:
Originally Posted by Corky Bell View Post
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.
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.
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Old 02-05-2009, 01:33 AM   #17
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sounds like an interesting project with badass potential. make sure you take lots of pics
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Old 02-05-2009, 01:42 AM   #18
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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
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Old 02-05-2009, 03:03 AM   #19
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Why not go quad turbo with each fed into an individual throttle body...
Best of all worlds.. no lag and awesome throttle response
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Old 02-05-2009, 03:35 AM   #20
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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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