top pipe removal for my own make need help

[Trust33]

Im thinking of removing my top pipe and replacing it with one of my own makes.The pipe will come from the side return intercooler pipes.I have a few ideas but need your thoughts and comments on this one to be able to get the best setup possible

1.What does the iaa unit on the side of the plenum do?

2.What does this pipe do?can i remove it or do i need to retain it?and what issues are there with removing it (if any) and blocking off the plugs.

3. What would taking off all the bov plumb-back pipes and pluging up the holes do.( there are 2 options due to me having an atmo bov i can retain this system or i can ditch it and get a new plumb-back bov)which one depending on epa regs.Suggestions please.

There are 2 types of pipes that could be made.1 with the bov return or 1 without the bov return with mounting of the one with the bov in the stock location (depends on epa rules).

Basically i have to know all 3 to come to my final conclusion..

See my pics for a comparison..

[Trust33]

http://www.skylinesaustralia.com/forums/at...achmentid=18104

[Sydneykid]

1.What does the iaa unit on the side of the plenum do?

Idle control.

2.What does this pipe do?

Bypasses the throttle body

can i remove it or do i need to retain it?and what issues are there with removing it (if any) and blocking off the plugs.

Not if you want a stable idle.

3. What would taking off all the bov plumb-back pipes and pluging up the holes do.(

The usual return to idle problems (stalling) caused by loosing already metered air (AFM). ie; engines run rich as too much fuel is injected. This is standard vented to atmosphere BOV stuff, there are plenty of threads on it.

For a 100% road car I would always recommend a plumb back BOV, the performance loss is neglible. For a 100% race car it doesn't matter as much, a bit of extra fuel on the down change is OK. For a combo car you could have a removeable return pipe, but I really couldn't be bothered. For people who like the woosh, well I gues a 50% plumb back BOV is a compromise solution.

Hope that helps

[Trust33]

SK would plugging the stock bov have any effect on the idle cause thats the current setup on my car and it runs perfect.Thats what gave me the idea that i could loose the plumback system all together.

And so by leaving the iaa open to the free flowing air from the pipe when the throtle is closed the plenum is fed the right ammount of air to keep it on idle.I see

[Sydneykid]

Hi Trust33, the iaa needs filtered air. Plus I think there is a boost issue as well. But I am not sure on that one, I would have to read up on it some more. As for the BOV, it is a RETURN to idle problem, not an IDLE problem itself. If you have an open to atmosphere BOV, then when you get of the throttle quickly after a burst of accelleration, the engine stutters with the rich mixture, most simply stall.

You can tune around this, but it takes some time and is quite fiddly. Some engines it just doesn't work on at all.

[Trust33]

ok that part i did figure out once the iaa pipe is gone theres no idle nessesitating the need to put it back on and therefore i will retain it currently it is run after the bov you are right it does run a bit rich.To me making a larger pipe to the plenum then and giving the throttle a bore out will be a fix for it.letting the plenum get a bit more air just before throttle is jammed shut i could quite possibly give it just what it needs without having to change the idle.

SK i know everyone tells you this your a great help mate :Dj:

[Sydneykid]

ok that part i did figure out once the iaa pipe is gone theres no idle nessesitating the need to put it back on and therefore i will retain it currently it is run after the bov you are right it does run a bit rich.To me making a larger pipe to the plenum then and giving the throttle a bore out will be a fix for it.letting the plenum get a bit more air just before throttle is jammed shut i could quite possibly give it just what it needs without having to change the idle.

SK i know everyone tells you this your a great help mate :Dj:

I am not a believer in larger throttle bodies on standard plenums, waste of time and money. They are not the limiting restriction (weak link in the chain), it is that simple.

When the throttle is closed, the throttle is closed. The problem does not happen when there is some throttle opening. Whether it is larger or smaller in diameter makes no difference. In fact there is an valid argument that the larger volume in the inlet system decreases the throttle response.

Thanks for the thanks

[Trust33]

So i keep the throttle body std size and upgrade the pipe to retain the idle pipe but i get rid of the plumb-back and std bov.Well now i can use a nice size mild steel inlet pipe to save me plugging the holes and use a catch can.All considering if i retain the atmo bov or not.

[Sydneykid]

Well now i can use a nice size mild steel inlet pipe

Watch the rust, it can be a problem. :innocent:

[Trust33]

Hmmmmm thats ok.Thats fixable.swap for stainless:)

[Sydneykid]

Hmmmmm thats ok.Thats fixable.swap for stainless:)

Aluminium is lighter.

[Trust33]

Aluminium is lighter.

Yes it is,i cant go any further on this yet so it might be a while untill this happens i just brought a front mount from www.slidewize.com zac was very helpfull answering all of my questions.Just waiting for it now.

SK ill call on you if your needed again but yeah ill keep you posted once theres some progress made.

Thanks heaps for your help.

:nowigetit