custom intake deign and build

[goodall]

Over last month or so I have been designing a intake manifold for my 7a powered lotus 7 replica. The reason for the custom manifold is that the oem one would poke out and just sorta wanted to do it. I have also changed the length of the intake so that the intake is tuned at 5500rpm, rather the 4500rpm the stock one seemed be when i worked the numbers backwards, this will hopefully mean same torque but more power. Its also shorter so I can fit under the bonnet. Its made from 3mm plate and 10gauge (3.2) round tube, the base plate of the plenum is 1/2" (12.7mm) all of which is 6000 series aluminium alloy. For the manifold flange I just cut the stock manifold since I dont need now, also they only seem be worth £5 on ebay which cheaper than buying alloy.
The throttle body i'm using is of a alfa v6 and 70mm diameter at the blade, which is quite an increase from the stock 7a which is effectively 63mm.

I have started to fabricate it in last few days so far iv made the plenum and the plenum base plate. The base plate I have cut out using a £50 wood router form argos, which is amazingly good at cutting aluminium. The plenum so far has been mig welded, by me however I have ground the welds back see how good they are and they seem to not be porous however I not 100% on them.
I need some way of bending the tubbing i have for the runners, thinking of a ring roller however not sure if know anyone with one or even if would bend the radius i want. Other option is a mandrel bender but again dont know anyone with one and you have bend to what ever size the die is...



These two CFD's show the flow if the engine was consuming 5 times the air it would at 100% VE at 7000rpm

[gnutz2]

How are you going from square to oval?

I read somewhere that a D shape port flows better than a round one? This could apply closer to the valve.

[goodall]

plan is to tubing with ID of 32mm, which is same the radius of the ovals of the intake ports, then then using the press squish it into a oval at the plenum end with a radius of 13mm same as the on the plate, then the length of the flat side made doing this should be 30mm the same as the vertical side of the cuts side on the plate, then im going cut the runners down the middle and add in a strip. the squished bit will taper for about 150mm back to the round shape and the strip will taper aswell, which is meant to help on NA intakes

[quattro84]

Nice, FloWorks results

[goodall]

Thanks, they should with any hope hold true in the real world, fingers crossed!
I just put the volume flow way up, rather than programming in each valve opening ete as I had teach myself how use it which had taken long enough, so i didnt bother spending any more time setting up the simulation. This is my 11th design, between side entry, dual plenum, and centre entry, as well as tapered and straight iterations. This design flowed best to what i had perceived difficulty of fabrication