RE: Four-cylinder Cayman at the Nurburgring
Discussion
kambites said:
Is there actually any advantage in equal length headers if you're going to turbocharge though? I'd always assumed that turbo-charging made scavenging almost impossible because of the damping effect it has on exhaust gas pressure.
You need to time the exhaust pulses into the turbine wheel so they don't interfere and hamper response. Particularly with a twin scroll turbine housing. Any delays result in pulse overlap and lost energy.zeppelin101 said:
kambites said:
Is there actually any advantage in equal length headers if you're going to turbocharge though? I'd always assumed that turbo-charging made scavenging almost impossible because of the damping effect it has on exhaust gas pressure.
You need to time the exhaust pulses into the turbine wheel so they don't interfere and hamper response. Particularly with a twin scroll turbine housing. Any delays result in pulse overlap and lost energy.kambites said:
Ah OK, so instead of scavenging to increase volumetric efficiency, you want to maintain constant exhaust pressure to keep the turbo spinning at a constant rate/pressure? Makes sense.
Kinda, it's about maximising the energy that each pulse can provide to the turbine wheel.This site here shows the difference in exhaust pulses (rough, but accurate enough to get an idea) between a mono scroll turbine and twin scroll turbine.
http://www.autozine.org/technical_school/engine/Fo...
Scavenging can still be used on a turbo engine to good effect to get rid of exhaust gas in the chamber and increase airflow at very low engine speeds. Makes some interesting shapes on the compressor map doing so.
Thankyou4calling said:
George29 said:
Emissions had nothing to do with the Cygnet.
Correct but don't let the truth get in the way of a good myth touted in many a pub.Edited by Thankyou4calling on Wednesday 22 October 15:47
Which is it?
zeppelin101 said:
That's quite well explained, cheers. JDMDrifter said:
Really interested in this, taking Porsche in a newer direction that hasn't been seen for a while. What price do we reckon these will start?
About the same as the current base Cayman, would be my guess. I don't think it'll be a lower entry model, it'll simply replace the current entry model.Gassing Station | General Gassing | Top of Page | What's New | My Stuff