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Location:
Finland
Registered:
November 2002
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ITB plenums
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Tue, 30 December 2003 18:37
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I'm making ITB's for 3T and I have few questions that occupys my mind.
1. What is ideal plenum volume for charged/atmo?*
2. Where to take vacuum to brake booster?**
*I'm going to make bell-mouths and try to run them with plenum and cold air intake for awhile. Until I'm ready to turbo-charge my engine. I'm thinking triangle type plenum to get even flow but trying several type plenums is no problem.
I think that this is poor plenum considering even flow between cylinders.
**I have made "balance pipe/box" that connects the four runners and this is the easiest point to take vacuum line to brake booster but this is where I'm taking MAP vacuum already. Does brake booster mess MAP sensor if they are too close?
I'm taking this ITB project as a practical semi-scientific research to amass my experience  . So dont entirely knock out my ideas.
Pictures wanted!!!!!
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Location:
Finland
Registered:
November 2002
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Re: ITB plenums
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Tue, 30 December 2003 18:38
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And intake manifold above isnt mine.
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I supported Toymods
Location:
melbourne.victoria.austra...
Registered:
June 2002
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Re: ITB plenums
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Tue, 30 December 2003 20:51
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jayem, why not adapt the 20v throttle bodies by use of your own built adaptor plate?
dunno about the MAP/brake booster vac being seperate....a cruise control setup years ago i did got the vaccuum from the brake booster line and that was OK - suggest it might be the same.
the pic (although not yours) has a port in the end on the left hand side for the brake booster line to be attached to. you could maybe do only this (thinking about my 100kw motor the port for the brake booster comes off no1 cylinder runner, on the 86kw motor it comes off number 4) - and keep your MAP seperate?
hope my ramble helps mate.
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: ITB plenums
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Tue, 30 December 2003 22:09
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I have a vacuum line from one runner to the booster with my ITB setup. It hasn't been a problem.
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Location:
Brisbane
Registered:
May 2002
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Re: ITB plenums
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Wed, 31 December 2003 01:29
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Yeah, my 2T-G took its booster vacuum from a single runner and it seemed to be ok. Not sure if this would be such a good idea if you're running a wild cam though...
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: ITB plenums
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Wed, 31 December 2003 04:01
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Friend is running his booster from a single runner with 304 degree cams. Also no issues.
Think about it for a second - the capacity of a booster is quite small - it wouldn't take too much time to evacuate it with a car running at WOT. Then also consider that there is enough vacuum 'stored' for at least a couple of stabs on the brakes. Remember that when you are on the brakes, you will generally be OFF the throttle (but the engine still at highish rpms) - this situation generates a large negative pressures (in a runner).
I'm talking about NA motors of course. Also use a one way valve and I don't see there being a problem.
And Jayem, don't post any pics of L series ITBs here again without showing the rest of the car - it's like ringing a Dial a Fantasy line and being put on hold! 
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Location:
Finland
Registered:
November 2002
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Re: ITB plenums
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Wed, 31 December 2003 11:29
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Thanks guys you're always helpful!
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jayem, why not adapt the 20v throttle bodies by use of your own built adaptor plate?
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Grega: my throttle bobies are ready except plenum and bell-mouths. Secondly, I live in Europe so 20v falls into "virtually non-existing" category, along with 4A-GZE, 1G, JZ and so on. Hell! even 3T's are really hard to find. We have lots of VW, Fiat, Volvo and Saab stuff floating around thou  .
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And Jayem, don't post any pics of L series ITBs here again without showing the rest of the car - it's like ringing a Dial a Fantasy line and being put on hold!
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I find that pic(which isnt mine ) somewhere on the net. It was some Californian performance shop selling those ITB's.
BTW. First question is still valid.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: ITB plenums
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Wed, 31 December 2003 13:18
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| Jayem wrote on Wed, 31 December 2003 05:37 |
1. What is ideal plenum volume for charged/atmo?*
2. Where to take vacuum to brake booster?**
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the nuber that sticks in my head for plenum volume is 3x engine capacity... which is bloody huge. so 'as big as you can' is about as close as i think youd want
for the brake booster, as some have said, you MAY get enough volume off one runner to charge the booster, but you probably 'should' run a post butterfly line from each runner.
cheers
ed
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Location:
Finland
Registered:
November 2002
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Re: ITB plenums
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Wed, 31 December 2003 16:23
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I remembered that it was 1.5 x engine capacity. This was for single throttle body plenum but how does it affect/work on ITB's. Was it that smaler the plenum and more torgue or vice versa? Too big would cause slow throttle response into the charged engine, I quess. How remarkable factors these are?
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Location:
nth ringwood, Victoria
Registered:
August 2002
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Re: ITB plenums
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Thu, 01 January 2004 00:40
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my booster is a AP racing item and for fronts only and as dave said its connected to no4 only but its for racing only
norbie your 2tg ran a balance pipe over the 4 cyl so that equals it up to make it idle better
fwiw we did a turbo setup on a 18rg years ago blow through webbers including intercooler and big airbox what we could fit into a RA40 worked fine motec was in its infancy then so not as good it made 360 rwh back then as a sports sedan but we had to change the bearings after every race weekend or blow up at next race meeting
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Location:
Brisbane
Registered:
May 2002
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Re: ITB plenums
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Thu, 01 January 2004 05:04
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I was under the impression that multiple-throttle engines don't need a plenum as such, at least not for the same reasons a single-throttle engine does, so the internal volume probably doesn't matter as much. Having said that, I could be completely wrong...
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: ITB plenums
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Thu, 01 January 2004 07:06
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I think Jayem wants to use ITB's AND turbocharging (a la GTR).
Like Ed, the number that seems to stick in my mind is 3 times the engine capacity. Bellmouths within the plenum are helpful (although there are rules about how close they can be to the sides and floor of the plenum) and the plenum should be tapered towards the rear (for an in-line motor).
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Location:
Rocky Mountains, Canada
Registered:
May 2002
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Re: ITB plenums
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Thu, 01 January 2004 07:47
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I cant think why size of a plenum would matter with ITBs.
It might not even be called a "plenum" in such a situation... just an air box.
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Location:
Brisbane
Registered:
May 2002
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Re: ITB plenums
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Thu, 01 January 2004 08:32
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Exactly what I was thinking. 
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Toymods Board Member
I supported Toymods
Location:
Turramurra, Sydney.
Registered:
May 2002
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Re: ITB plenums
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Fri, 02 January 2004 12:56
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The plenums or airboxs used on the only 2 factory turbocharged ITB equipped cars that spring to mind are either small (on the GTR) or almost non-existant (on the GTi-R). I reckon as long as the shape of it encourages equal flow between the cylinders volume shouldn't be a big concern.
Of course I have no theorys or experiences to back me up, just observation.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: ITB plenums
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Fri, 02 January 2004 13:52
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ITB's will still benefit from the basic harmonic tuning properties of a well designed plenum (not just an airbox)
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Location:
Finland
Registered:
November 2002
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Re: ITB plenums
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Fri, 02 January 2004 18:05
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Sorry about my obscure English. I should have been more clear in the first place.
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I think Jayem wants to use ITB's AND turbocharging (a la GTR).
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Correct! This is what I want to try.
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ITB's will still benefit from the basic harmonic tuning properties of a well designed plenum (not just an airbox)
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This is what I had in my mind!
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I was under the impression that multiple-throttle engines don't need a plenum as such, at least not for the same reasons a single-throttle engine does, so the internal volume probably doesn't matter as much. Having said that, I could be completely wrong...
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I disagree but I could be wrong.
I'll get back with some sketches.
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I supported Toymods
Location:
melbourne.victoria.austra...
Registered:
June 2002
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Re: ITB plenums
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Fri, 02 January 2004 22:02
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just gunna throw my 2c worth in.
i can understand why you'd create an airbox with quads and turbo charging no issues there.
but if you think about it ala VN commodore shitty intake manifold design, the last 2 cylinders always ran lean as they got majority of the air first followed by the remaining four.
why not create a set of "tuned length" runners to feed each throttle body and collect them at an airbox/pod filter/intercooler - this was ensuring each cylinder gets the same around of air flow..
thinking about the 20v airbox, them plastic things that connect to the t/b's that basically end up in that silver/black chamber which is fed from the end there - wouldn't that have been what yota were trying to do (keep the same amount of air where possible to each tb?)
this also depends on how much room you have in there too. also on bill sherwoods site there is a really good graph which helps you design optimum runner length...
my 2c for the morning. HTH...
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Location:
western queensland
Registered:
September 2004
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Re: ITB plenums
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Tue, 04 January 2005 09:46
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exactly what is the perpose of a plenum? i liked the tuned length runners idea with a collector and even a singleTB like a reverse extractor set up
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Location:
Montrose, VIC
Registered:
May 2002
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Re: ITB plenums
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Tue, 04 January 2005 10:22
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I think a lot of the time, people use enormous plenums not only because they're shiny, but also because being big is an easy/lazy way to even up flow, as well as mask other deficiencies in the intake system. With the RB26, for example, the intake system presumably underwent a lot of development on the flowbench, then dyno etc. to come up with that shape - and many will testify that it works great, even on engines making huge power. Meanwhile others will rip it off, and stick a massive shiny box on there with a single throttle up front, often because they couldn't tune the thing
On my 4AG now I'm using 20v throttles, and have just finished making my plenum. It isn't a very large item (although it IS somewhat shiny.... damned aluminium!), does use bellmouths and will be turbocharged. I'm going to be using an idle speed controller, and plan to run the booster off of number 4. The cams are 280. I'll letcha all know how it goes WHEN it goes... Hopefully only a week or two away now!
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I supported Toymods
Banned User
Location:
Brisbane
Registered:
May 2002
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Re: ITB plenums
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Tue, 04 January 2005 10:36
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| mrshin wrote on Tue, 04 January 2005 20:22 |
I think a lot of the time, people use enormous plenums not only because they're shiny, but also because being big is an easy/lazy way to even up flow, as well as mask other deficiencies in the intake system. With the RB26, for example, the intake system presumably underwent a lot of development on the flowbench, then dyno etc. to come up with that shape - and many will testify that it works great, even on engines making huge power. Meanwhile others will rip it off, and stick a massive shiny box on there with a single throttle up front, often because they couldn't tune the thing
On my 4AG now I'm using 20v throttles, and have just finished making my plenum. It isn't a very large item (although it IS somewhat shiny.... damned aluminium!), does use bellmouths and will be turbocharged. I'm going to be using an idle speed controller, and plan to run the booster off of number 4. The cams are 280. I'll letcha all know how it goes WHEN it goes... Hopefully only a week or two away now!
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Pictures bitch!
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Location:
Montrose, VIC
Registered:
May 2002
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Re: ITB plenums
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Tue, 04 January 2005 11:41
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Hmmm, one of these days I must get a camera of my OWN, rather than using other peoples ones, ey...
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I supported Toymods
Banned User
Location:
Brisbane
Registered:
May 2002
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Re: ITB plenums
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Tue, 04 January 2005 12:16
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Yes
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