BoostJunky

I understand if minimal gains are gained with the Y-pipe, but when couple'd with a full exhaust intake and some type of programmer the gains should be much better through out the board, is any body using this with all the supporting bolt ons? Dyno numbers?

vteckiller2000

I have a hypothesis on the smallish gains.

When I removed my exhaust to test any gains at the track, the exhaust was revealed to hiss extremely loudly as soon as the wastegates opened. This sounded like a heavily modified turbo car with stock exhaust, i.e. a restriction in the exhaust stream. I think maybe that the manifolds are so small that the exhaust downstream from the turbos cannot do much to assist in evacuating the exhaust.

Anyone have any ideas?

ADDF150

Aftermarket manifolds will help with that. The small manifold diameter is used to keep exhaust gas flow rate quick, resulting in minimal lag of the turbos. Larger diameter is increased flow, but not necessarily increased "speed" in exhaust flow.

BoostJunky

Yes, I think aftermarket turbo manifolds will help quite a bit, but after talking with a shop that's developing some turbo kits/upgrades for the EcoBoost, was told that a replacement for the oem manifold would be pretty difficult to make other then just making another cast Mani and porting it as much as possible, and a tubular Mani would be even worse(harder to make)

But if it can be done, not only would it help the power gains/spool, but it would effect the tone drastically, and may help take away some of the raspiness that the Eco is notorious for

vteckiller2000

I know why they make them small, and they are in fact really, really nice manifolds. I just can't for the life of me figure out why it hisses so much...

engineermike

It hisses when the wastegates open because the flow reaches sonic velocity. At sonic, the pulses you know as exhaust noise no longer exist. It's called "choke" flow. It can happen in either snail also. Gas can not physically flow through a hole faster than sonic velocity, and it doesn't take that much dP to reach sonic.

The exhaust downstream of the turbine is not really related the the manifold size. I know it's couner-intuitive, but it's two different and nearly unrelated piping systems. We will discover with time that gains from upgraded manifolds will be meager or non-existant until very high hp levels are reached.

vteckiller2000

Why does my Audi and every other turbocharged car I have owned not sound this way then? I pulled off my exhaust from the Audi today and it just gets louder and fuller sounding when the gate opens.

Centexguy

Also depends on where the gate dumps to. And fwiw, my diesel never made a hiss noise with the exhaust off. Just loud pitche howl. It was also a 72mm HAHA

I ported the stock manifold out on my diesel once. It was a 5.9L cummins (inline 6). Only turned 4000rpms. I ran a 66mm compressor with a 71mm exhaust wheel and a 13cm exhaust housing with dual internal waste gates. I gained right at 250rpm of spool up and dropped 100* on my egts just by porting the stock manifold. Power never increased but it came on sooner. It was a very nice difference. Some folks have tried equal length tubular headers and they helped on the top end but destroyed the bottom end. It's not always about flow. Velocity is a major factor to consider.

engineermike

The exhaust going through the wheel is usually not at choke flow. This allows the normal noise through and it can overpower the wastegate hiss. However, it's entirely possible the EB turbine housings are so small that it's reaching sonic in the wheel or snail.

vteckiller2000

Intriguing. I would think that my Audi would have been the same way then with it's tiny little k03, or even the current k04 hybrid.

Strange.