Dyno result for the risky business Porsche

[vannik]

That is interesting, as well as the change to a Y-connection. I see in the simulation of this setup that with the junction box it is very difficult at lower rpm values to speed up both turbochargers because one has enough capacity to generate the required boost. Then the wastegates open to control the boost from one turbocharger and the other one does not speed up. It can even see reverse flow. The Y-junction goes a long way in resolving this but also where you get the wastegate control signal from is important. I know it is "only" a simulation but it seems to point at what is being done now.

[ptuomov]

That is interesting, as well as the change to a Y-connection. I see in the simulation of this setup that with the junction box it is very difficult at lower rpm values to speed up both turbochargers because one has enough capacity to generate the required boost. Then the wastegates open to control the boost from one turbocharger and the other one does not speed up. It can even see reverse flow. The Y-junction goes a long way in resolving this but also where you get the wastegate control signal from is important. I know it is "only" a simulation but it seems to point at what is being done now.

The motivation for going from the plenum box to Y-pipe was reducing high-rpm high-load pressure losses there. Doing this was possible because we went from a single MAF after the box to dual MAFs upstream of the box.

Are you concerned about part throttle, low rpm operation or full throttle, low rpm operation? Both wastegates stay completely shut until about 2500-3000rpm, depending on the boost program. With manifold vacuum, the bypass circuit opens and recirculates air from the boost pipe to air filter box upstream of the compressor inlet.

We've got a MAF, pressure differential sensor between compressor outlet and inlet, and turbocharger speed sensor, each, on both sides. Therefore, we can observe whether the system is symmetric or not. Both turbos start spinning slowly already at idle, not making any boost, of course. The turbocharger speeds track each other fairly closely regardless of the conditions, and the MAF sensors indicate similar mass flow from both sides.

We've seen one situation in which the system was imbalanced and that was when one of the wastegate signal lines had popped out...

[vannik]

With dP over each compressor and each compressor speed there should not be any imbalance problem. I saw it only when using purely mechanical control with MAP in the center pipe.

Your system has the required sophistication to correctly control the wastegates.

[ptuomov]

With dP over each compressor and each compressor speed there should not be any imbalance problem. I saw it only when using purely mechanical control with MAP in the center pipe.

Your system has the required sophistication to correctly control the wastegates.

We’re actually running a very simple control logic and 30 year old computers, but I agree that we can verify balance effectively with the sensor suite.

[ptuomov]

What Porsche rubber turns into under high heat and 1.5 bar boost:

14D6DA91-EB9B-42EB-BD52-43A8C0940F77.jpeg

[MadBill]

Is that a recent part or an ancient one?

[ptuomov]

Is that a recent part or an ancient one?

This is a new one. We swapped it in a couple years back, while you’re there and for no good reason. The original 30 year old part is still intact and will be going back in now.

[MadBill]

A close comparison of quality and durability might be in order. It wouldn't be the first time that the old OE part was better than a new replacement one...

[ptuomov]

A close comparison of quality and durability might be in order. It wouldn't be the first time that the old OE part was better than a new replacement one...

I would say never and nowhere as true as with the 1987 928 S4, that at the time was fastest and probably also among the most expensive production cars. The 30 year old original parts were made from best materials and held to highest tolerances. Not so with the current replacement parts.

[ptuomov]

Air filter:

CE9035DC-ADA1-45CA-BE8E-20DC1CB28ADB.jpeg

69C6238D-7AC5-445D-84A0-2D5E3BF3811F.jpeg

799B12FC-6A1A-4273-90C6-8519FCBE04CD.jpeg

2B854681-1FBB-4F69-804A-531A30DCA9E4.jpeg

E72BB04A-634F-4E31-AE35-3B5057384596.jpeg

[ptuomov]

Dual MAF plumbing:

1F2F1709-F1FD-42B5-AA4A-1FC84BC537AC.jpeg

30DABCF8-F1D3-493C-AC17-E780188C9BF2.jpeg

99F24185-DEE3-4538-9EE6-728C1890C683.jpeg

C2D4416C-1148-4970-953E-552D4A09EA99.jpeg

44520E07-DBB8-4AA0-8B16-AA626A7F4141.jpeg

D2918D2F-3B5A-451F-B7A6-25A51A4B3325.jpeg

EF325E09-7899-41EF-8708-794B187C046F.jpeg

[n2xlr8n]

Nice work!

It looks like you guys could definitely stay busy.

Would you mind sharing that filter PN? I had trouble finding an air filter that would flow enough for my application and still fit the available space; I'm certain that would work for me.

[ptuomov]

Nice work!

It looks like you guys could definitely stay busy.

Would you mind sharing that filter PN? I had trouble finding an air filter that would flow enough for my application and still fit the available space; I'm certain that would work for me.

It’s a standard part, don’t know the part number. The big non-standard portion of the filter is that it has two 3” inch holes and flared pipes bonded into them.

[ptuomov]

Actually, a custom part but based on RU1500 cross section.

[ptuomov]

Some photos of the filter looks with the cover on:

61D8DA2B-469F-4AF0-805E-D1780FE15581.jpeg

E86E71C7-444D-4647-913E-BD4AE696E74D.jpeg