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Hey everyone i'm new to this forum but have found it a great source of help on some things/common probs etc.

biulding a custom forward facing plenum for my mates RB20 R32, i know this has been talked bout before and nearly everyone agree's that the standard one is hard to improve on especially in a low powered RB20 but he wants it more for looks and to make everything easier to work and get rid of bout 1.5m of piping so please don't try and convince me to not do it! :cool:

anyway hear's my question what can i do about the stock idle air control that bolts up to the back of the plenum? the car runs quite well without it i just want to know if it's actually needed? has anyone got any pics of what they have done on an RB20? i am keeping the standard bottom runner's and have purchase a top half to modify, i don't want to just wack the throttle on the front of it, i am planning on milling the old top half down bout 10mm off where it bolts to the lower half and then make a custom bell-mounthed top plenum for it? it will be tapered so that it can correctly distribute the air to the back cylinders more evenly and i will flow bench it to check how evern the flow is on each cylinder before fitting it to the car, i will have before and after dyno results to yeah it will be interesting.

so yeah sorry for the rant if you can give any pics for ideas or can help with the idle control issue that would be great

thanks again

how ya going mate. i've got a rb25 in my r32 with a greddy plenuim and i have blocked off where the air bypass valve sits and i've had no problems with the car stalling even with the air con on. even on the old rb20 before if expired it never worked properly either. if you are worried bout the vacum hoses and stuff and just bypass everything. goodluck with it and put some pics up when ya done.

OK THANKS MATE, has anyone else just disconnected the IAC on the back of the standard inlet manifold?? i have disconnected it and the car seems to run fine even when the aircon is on like "116HKS has said above. so my main worry is i've already started making it so i really need to know if i can still use the standard throttle body or do i have to switch to a XF style throttle body????? anyone got any Pics of what they have created for RB20'S?

so you are talking about the AAC then, not the IAC ?

2 plugged unit - from looking at another RB20 plenum i've worked on - the AAC can be installed by simply drilling 5 holes in the flat back section of the plenum - 4 bolts holes and the AAC's plenum feed hole.

hardest thing about it is :

- having a enough room to fit it

- flat surface for mounting

- running the air hose from the IC piping from infront of the TB

so its not that hard, just a little fiddly.

ok, so yeah AAC what does that stand for? would be somthing simple it's just to late for me to work it out! :-) anyway do all aftermarket plenums have the facility to run one of these such as a plazmaman?? JD customs?? CPC?? thanks for the help anymore would be appreciated

an easy way to do it is by using a large nipple threaded into the plenum, and making a plate with a fitting welded onto it. bolt the plate to the AAC unit where it would normally bolt to the plenum and run a hose from the fitting on the AAC to the plenum.

you can also hide it under the plenum, therefore having alot more choice where you can put it.

its how we did it on my RB20 and ive had no problems at all.

i had alot of stalling issues when it wasnt used at all.....

  • 1 year later...

the idle air control is the only one you need. the air regualtor simply balances air between the front and back of the plenum.....throw that in the bin.

Just make another plate to welded on to the plenum, depending what thickness material was used for the plenum and drill and tap it to suit. I have kept all the standard gaskets for when people want me to put them on.

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