Huge turbines are VERY efficient But not very effective @ low rpm / air flow.
Put that turbo on a 500+ci engine and I doubt it will make less TP than BP.

Still comes back to the old efficiency or response, pick one.

Lighter rotational mass and less bearing friction does allow more efficient components to be used with the same response as older smaller turbochargers.

 

What impact are the new wheels having on cam events and exhaust housing ratios?
I believe the answer is clear, but would like to see the experienced point of view.

 

More aggressive EVO events resulting in higher initial pulse pressure. Tighter A/R's to help with the low shaft speed efficiencies of the wheel.


Ill let you know how it works soon. 365 inch sbf with a s510,.85 A/R and an EVO you wouldnt believe if i told you.

 

I've seen some posts on boats here that have less than 1:1 TP:BP. Boats obviously have a much smoother flowing pre turbine header availability and also super short, huge downpipes too. It seems when space is not an issue it helps significantly reduce BP. Post turbine size seems to be more important than people think also. If I remember correctly one such poster mentioned that his boat motor, which had very short 5ish inch downpipes (twin BW S4xx's), went from less than 1:1 on the boat, to over 1:1 on an engine dyno with the only difference being hanging exhaust ducts from the dyno stand on the downpipes.

 

It has more to do with loading the engine than it does what they did with the exhaust.....

 

^^^ Yep. If the demand is low and RPM high (enough) higher BP:TP is normal.
Boat = strange load, maybe he needed a bigger prop

 

Well they are talking about Mark55/Unchained. He went from a short 5" 90 to 8 feet of exhaust necked down to 3 1/2". He also had to add a lot more to the manual boost controller. I'm not sure on his prop, but he is overdriving it 60% (almost unheard of), but he is also making just shy of 1900hp/tq IIRC.

 

Turbine's job is to provide drive power to turn the compressor. The compressor wheel operating at a certain speed and flowing a certain mass flow of air will require x amount of power to turn the wheel + losses from friction/etc. The design of the turbine wheel will greatly influence its ability to put out power, so the actual drive pressure seen can and will vary. The exhaust system design will likely need to beable to channel the heat and flow in a way to extract the most energy out of the system as possible. So I can definately see where you can have less pre-turbine backpressure vs boost pressure.

Seen this from another forum.

 

Orr,
What forum was the Volvo combo posted on?

 

When you've achieved crossover, the engine can be treated more as if it were naturally aspirated.