Due to the registration requirements here I had to keep my EFI bog standard and now that I has been on the road fro a while I would like to re-work my manifold so that it all fits more neatly under the bonnet. at present I have this huge and not so attractive bulge in my bonnet.

My idea is to cut off the plenum and to turn it around so that the throttle body is facing the front of the engine then I want to cut the manifold just outboard of the injectors then replace the longish curved manifold sections with shorter straight sections of aluminium tube of course making sure that they are all as close to being the same length and cleaning up the ports inside afterwards.

There seems to be a section that appears to join all of the runners together and there is a hose that connects this to the rocker cover can this just be deleted? (a)
Likewise what is the purpose of the metal pipe that seems to come from the exhaust side of the motor and do I have to ensure that I extend and re-work this? (B)
I know that many here are big fans of things like Mega squirt but if possible I want to continue to use the stock computer (Nissan N16) and The reasons i want to do this are all about packaging rather than absolute performance

thanks in advance

Hi Mate,

I think both a) and b) are about recirculating gases.

a) is the rocker cover breather - oily vapour is being recirculated into the intake of the engine to avoid emmissions to atmosphere. This can be redirected into a catch tank - assuming local laws etc... allow.

b) sounds like the EGR system. Exhaust Gas Recirculation - again it's about emmissions. However this system is usually controllled by the ECU. If you want to keep the standard system you should investigate what the ECU will do if you remove this control. It may do nothing and not notice that the EGR system is no longer there but you should check first.

Also don't forget that by removing the curved tubes in the intake manifold you are shortening the inlet tract. This will change the torque/power characteristics of the engine. Shorter pipes will PROBABLY shift the peak torque/peak power further up the rev' range. Not the end of the world but you should be aware.

Otherwise "Good Luck" with the modifications and keep us abreast of the work via pictures every now and then.

You are right Justin that the best thing to do is to retain the original plumbing as much as possible. and what you say about shortening the inlet tracts altering the torque curve has occurred to me. From my motorcycling days I think making then shorter may make the engine pick up a bit quicker but I do not think that there will be much to be lost over all.
I will look into just how the rocker vent pipe is actually connected to the intake and see if I can re plumb it into the plenem .
Cheers
Iain