Race Engine Forum UK

Measured at 15mbar constant
Done by http://www.flow-improver.de

1)
1301cc standard manifold with 42mm throttel body
I 124,6 kg/h
II 127,0
III 128,4
IV 126,6

Max Delta 3%

2)
asymetric design with 52mm delta throttle body
I 152,0 kg/h
II 151,4
III 157,1
IV 153,2

Max Delta 3,6%

The flow is higher on the second, clear because of the bigger throttle body BUT the delta between the channels is only 0,6% more than stock!
I had never thought this.

Hi Acki,

Thats very interesting, and surprising that the difference across all four would vary so little.

Clearly worth the effort!

Good work.

Tom

Just fantastic info!
Fromn which car is that "asymetric design" inlet manifold?
I see that there is on both manifolds more flow on 3. intake pipe, is it worth of try to increase flow of other pipes to make the flow over all pipes as same as possible?

It's a welded standard manifold. Throttle body is Lancia delta.



When you install a bigger intercooler you have shorter pipes when you don't need to go in the middle of the manifold :)

Great write-up Acki. Good work and good info to share with everyone.

I believe that at a modest .5bar the sidedraught manifold design you have should be fine and give good fun without issue. There would be some matters to consider if you ever decided to increase the pressure. I understand your dilemma concerning plumbing and intercooling. Track cars=bigger intercooler, traffic cars=less plumbing.

Positive performance manifold design is similar to Nat-Asp only as far as having a power target. Different considerations are made for resonance, volumes, chamber dynamics, etc. etc. Basically the unit will be catering to a different type of machine. Some serious manufactures have solutions, but most require exceptional flow studies.

I do believe you will be very happy with your design in your present intentions though. And I'd love to see more pictures of your car and the turbocharger.