Mi16 Std. Manifold Inlet Trumpets Test

[Vili 17]

I did rather interesting test last week. My engine is 2.1 S16 with 1.9 mi16 inlet manifold and bigger throttle body.

I installed these inside the manifold and did before and after power measurements.

The results are here. The graphs are calculated from the ecus data log and are fairly accurate since the made 187 hp and 213 Nm on the rollers before these tests. However there can be small error since the test were made outside on different days and the wind speed and temperature weren't accounted for.

The red and blue curve are with the trumpets and yellow and green without. Sorry about the colors if you happen to be color blind.

Edited August 25, 2013 by Vili

[Vili 17]

This is a picture from inside the manifold.

[welshpug 1,626]

can you get hold of an RFS inlet manifold to test? that has a similar arrangement inside as standard.

[Vili 17]

Well yes. I could probably borrow RFS inlet manifold from my friend. I'll have to give him a call and ask.

[petert 554]

Great effort. I guess there would be a reduction in diameter? And a lip where the tube ends? It would be certainly interesting to compare to the RFS inlet. Does it feel any different on the road?

[Vili 17]

The inside diameter of the trumpet is 45 mm which is the same as the runner. The trumpets are shortened and only go inside the runners by few millimeters. The head of the std. runners is chamfered and the trumpets only go inside to the depth of the cut.

I can't really tell how much or little different it feels on the road. I made the power measurements by accelerating trough (2000-7400 rpm) the second gear and it took approximately 0,3 seconds less with the trumpets in.

I had to rework the whole ignition and fuel map after the trumpets. My engine is very prone to knocking which is quite understandable if you look at the specs and it got worse after the trumpets. I had to delay the ignition at low revs and at 5k but also got to add fuel for especially to the middle revs 4000-5500. At higher revs, say past 6000 there wasn't such a big difference. It might be due to the fact that trumpets lengthened the inlet tract by circa 30 mm.

I believe there would be lot more horsepower to be gained by shorter inlet manifold and longer duration inlet cam or even just by fitting adjustable cam pulleys.

Edited August 26, 2013 by Vili

[Vili 17]

It might be impossible to tell from these graphs but it think I managed to cure some the typical 3,5k dip in the torque curve. The inlet modification probably didn't contribute that much to it but changed the ignition map that I now have map cells at 3,4k; 3,8k and 4k instead of the earlier 3,5k and 4k. That way I could add some ignition advance to where the dip or area of low VE is.