itb's and runners

[feral4mr2]

i have myself some itb's that i want to put on the vermin (hi comp bigport 4age) and i would like to make my own adaptor plate (cant afford the one from the states!). and they space them out some too.
anyways i was thinking about some bend around ~13" runners and mount the itb's onto the end of the runners. or even cut the plenum off my na inlet manifold and weld a flange for them onto it.
longer runners = lower rpm range gain is my understanding. (feel free to correct me, i am not long outta bed!) haha.
from my internet searches some itb's are mounted on short and some longer style runners on different varioations of engine/model of vehicles.

or is the design of the itb's to be used directly to the head and the length of the velocity stacks the determining factor on low vs high rpm gains?


feeling like a noob here....

[roadsailing]

Basically:

Longer total inlet tract = more low end power

Shorter total inlet tract = more top end

Longer distance between throttle and inlet valve = more top end

Shorter distance between throttle and inlet valve = better response.

To get the best of what you want, you will probably have to spend time on the dyno, but copying the standard lengths would be a good place to start.

*plug* I have 20 valve trumpet flanges if you need some too

[MWP]

Longer distance between throttle and inlet valve = more top end

Please explain why that is the case...

[roadsailing]

it isn't always the case, but basically it allows the airflow to "settle" after passing the throttle plate, as this is a disturbance. (you will get the best airflow with no throttle plate at all)

It isnt as simple as this, as the throttle plate can improve fuel "atomisation" when fuel droplets smash into it and so on.

have a read of this, gives a good idea of a number of things.

http://www.jenvey.co.uk/~Tech_QA.htm

oh yeah feral, i dont see any issues with fabricating your own adapter, just bear in mind that 4AGEs love shaking inlet manifolds until they crack and break off, so make it strong and keep bracing in mind, ITBs are reasonably heavy. (another reason to keep them fairly short between throttle and inlet valve)

[takai]

Those CNC manifolds from the US are MIGHTY good. Especially at the current exchange rates.

[roadsailing]

the T3 ones? i havent looked at taht site for ages

[takai]

Yeah, T3 ones. Damn well made, and pretty freaking awesome.

[Rallystanza]

Agree totally with you there chris and with the dorrah as it is, its a bargain.

[oldcorollas]

dunno about T3, but the jap ones are around $400plus del from yahoo (actually, from RSchita but sold thru yahoo)

http://page.auctions.yahoo.co.jp/jp/auction/113964607

http://www.rschita.jp/4renprice.htm

and a different type (NLA?)
http://www.rschita.jp/4renmani_type2.htm

edit: but that $400 is with gasket and all bolts and vac fittings as well... still not cheap, but look well made

[Rallystanza]

I suppose I may aswell link the T3 one for those that are interested.

Bling T3

As you will note, dorrah means varyou.

[oldcorollas]

are the T3s for the 101 or 111 throttles? (they have different transitions...)

[takai]

AE101, silvertops.

[Ben Wilson]

It's a track car, don't stuff around having bends in the runners, just put the air filter in the boot. I can't find the numbers I ran, but with stock cams, a total runner length about 1" shorter than the factory runners should be a good start.

[roadsailing]

Pretty sure T3 make them for blacktop ones too, they make them for big and smallport, its just not very well advertised.

I have a T3 silvertop to smallport adaptor, fairly nicely made bit of gear

[jeffro ra28]