Interesting turbo technology on Mazda CX-5
Dec 22, 2018, 10:51 AM
#2
Evolved Member
Good to see this variation of stuff finally hit the streets. We've seen this before on experimental stuff or thing guys do.
From the Article:
"... developed this ‘dynamic pressure turbo system’ employing two important concepts: variable flow area and exhaust scavenging by way of ejector effect. Other technologies that have been implemented in the past to combat turbo lag in a similar fashion has been a VGT/VNT (Variable Geometry Turbine in Borg-Warner speak, Variable Nozzle Turbine in Garrett speak). Until recently, only the Porsche 911 Turbo has gotten VGT turbos on a gasoline engine as the vanes and rings and all the moving things in the turbine housing required exotic and expensive materials to prevent from seizing up and failing at high gasoline exhaust temperatures. There are newer and cheaper gasoline VNT turbos now from Garrett which are paired with VW and GM engines which have to be combined with engines running Miller Cycle which helps bring down the exhaust temperatures. Either way, VGT/VNT turbos have a lot of moving parts in the turbine housing which drives up cost, complexity, and durability issues from many wear points in the mechanisms. Another technology used back in the day by Honda/Acura was a variable A/R turbine housing. The turbine housing used a flapper valve to divert flow to inner and outer flow paths which where created by a wall and vanes cast into the volute. Looking at the design, it looks difficult to cast, probably had poor turbine efficiency, and lots of places for cracks to start to form from thermal cycling. It’s probably telling Honda/Acura only used the technology for one generation on the RDX before ditching it. The Mazda design uses a twin-entry flange with one port being small in cross-sectional area and the other being large for high flow. No difficult to cast, low durability, flow impeding walls and vanes down in the volute of the turbine housing. Below 1600 rpm, valves close off the big port flow paths forcing all the flow into the small port. Good ole Fluid Mechanics tells us that for a constant mass flow of fluid, the velocity of fluid will accelerate when you reduce the cross-sectional area it flows through. So, the thumb over the end of the garden hose. So that’s how Mazda attacked the issue of turbo lag."
From the Article:
"... developed this ‘dynamic pressure turbo system’ employing two important concepts: variable flow area and exhaust scavenging by way of ejector effect. Other technologies that have been implemented in the past to combat turbo lag in a similar fashion has been a VGT/VNT (Variable Geometry Turbine in Borg-Warner speak, Variable Nozzle Turbine in Garrett speak). Until recently, only the Porsche 911 Turbo has gotten VGT turbos on a gasoline engine as the vanes and rings and all the moving things in the turbine housing required exotic and expensive materials to prevent from seizing up and failing at high gasoline exhaust temperatures. There are newer and cheaper gasoline VNT turbos now from Garrett which are paired with VW and GM engines which have to be combined with engines running Miller Cycle which helps bring down the exhaust temperatures. Either way, VGT/VNT turbos have a lot of moving parts in the turbine housing which drives up cost, complexity, and durability issues from many wear points in the mechanisms. Another technology used back in the day by Honda/Acura was a variable A/R turbine housing. The turbine housing used a flapper valve to divert flow to inner and outer flow paths which where created by a wall and vanes cast into the volute. Looking at the design, it looks difficult to cast, probably had poor turbine efficiency, and lots of places for cracks to start to form from thermal cycling. It’s probably telling Honda/Acura only used the technology for one generation on the RDX before ditching it. The Mazda design uses a twin-entry flange with one port being small in cross-sectional area and the other being large for high flow. No difficult to cast, low durability, flow impeding walls and vanes down in the volute of the turbine housing. Below 1600 rpm, valves close off the big port flow paths forcing all the flow into the small port. Good ole Fluid Mechanics tells us that for a constant mass flow of fluid, the velocity of fluid will accelerate when you reduce the cross-sectional area it flows through. So, the thumb over the end of the garden hose. So that’s how Mazda attacked the issue of turbo lag."
Dec 25, 2018, 10:58 AM
#4
EvoM Guru
iTrader: (1)
Originally Posted by SharkyPR
Can you say engine lugging?
I wonder how many blocks will blow up after producing all that torque on top gear and low RPMs.
I wonder how many blocks will blow up after producing all that torque on top gear and low RPMs.
Dec 27, 2018, 06:51 PM
#5
Evolved Member
From the article:
"The CX-5 is everything to Mazda these days. It is very nearly outselling the rest of the automaker's entire lineup in the United States—combined—and it has become perhaps the clearest representation of the tiny Japanese company's ambition to become a premium brand."
https://www.caranddriver.com/reviews...by-the-numbers
"The CX-5 is everything to Mazda these days. It is very nearly outselling the rest of the automaker's entire lineup in the United States—combined—and it has become perhaps the clearest representation of the tiny Japanese company's ambition to become a premium brand."
https://www.caranddriver.com/reviews...by-the-numbers