Here’s my critique of the design
TMS Website said:
The four branch manifold is a work of art and on its own generates 8-10bhp on even a bog standard car. Developed in conjunction with Primary Designs who are best known for their work on F1, F3000 and GP2 cars the design brief was simple. The 2.2 already had decent torque levels (it was designed with torque in mind) but to gain upper end power more akin to a sports car a 4 into 1 manifold is needed. The crucial concept is that each branch must be of identical length to maximise power and airflow which is no easy feat considering the lack of space to work in.
The design is perfect, it bolts straight onto a Milltek cat section without modification, requires no cutting to the clam in any way and has shown to be one of the best ways to gain power on any configuration of VX220 NA, in fact we're kicking ourselves we didn't do this earlier! On a standard NA it gain 12bhp, on a stage 2 it gained 10bhp on a stage 3 it gained 8bhp - this is one of the most consistent methods of gaining power we've ever seen.
Yes the manifold is an intricate design that does well to fit a decent length of runner into the space, however it is a flawed design as for the length of the runner could be far more easily accommodated by moving the flange location down as Meldert’s 4-1 and my quick sketch showed.
This over elaborate solution is only required to maintain the current flange position, meaning there are a lot of unnecessary tight bends in areas of high gas velocity, in particular runner 3, which while looking good is just going to introduce extra pressure loss. I wonder why they kept the flange position? Couldn’t be anything to do with making it fit with a miltek could it?
Onto which point I don’t really see the point of linking a high flowing 1.75” or pos 2” manifold to a 2” cat section surly you should be looking at 2.25” or 2.5” to see the real benefit?
As for Primary Designs, in my experience F1 teams design there own manifolds very carefully by first doing a 1D Engine simulation using Software like Lotus Engine Simulation or GT power to determine the runner lengths, followed 3D modelling and CFD* of a couple schemes, then linked simulations between the 2 packages this requires huge computing power and very expensive software licences and experienced users. Looking at the company’s website they have none of these facilities, the only computer software mentioned is Solid Edge which is a cheap and easy to solid modeller better suited to CAM applications. So to me it looks like they are more of a manufacture of F1 exhausts rather than designers.
The fact that the exhaust gives more power for the normal engine indicates to me that either runner length is tuned for the peak power rpm of the std engine and that the effect is less evident for the higher rpm of the later stage engines or that all the tight bends are causing extra pressure loss at the higher gas velocities.
As for the price Mandarin VX and I have been quoted £650-700 for a 4-2-1 from MIJ that has twice the material and incorporates a sports cat!
*This is the job I used to do at Lotus
