TTM
Well-known member
From what I can remember just after moving from this turbo to the GTX3076R, the Garrett turbine made a significant difference up top, as I would find myself upshifting a good 1000 rpm later, which came a bit as a surprise. Initial feelings were quite mixed as I needed to rev the engine higher to make it feel alive, which involved rethinking my driving style. Honestly I was a bit disappointed. However, with the previous turbo, the std inlet made for ridiculous mid range torque, and the car was just too fast off boost because of the tall 951 gearing, when I didn't want it to be fast, and the engine was not breathing as much as I felt it could when I was pushing it. With the GTX turbo, the short runner intake later gave the upper room needed for the higher-flowing compressor, and made the car slower mid range, which was just what it was missing to be a fun drive again, but it affected much the overall engine feel and I had to relearn how to control the engine.
Though the rate at which Nick's turbo builds boost is remarkable from the dyno sheet, I would still say that the short ratios of the 968 gearbox don't load the turbo as well as it could - I once saw 17psi at 2700rpm in 3rd gear when I was fiddling with boost settings. I'm sure Nick could get close to that by polishing boost settings. Whether the engine's VE will be high enough to injest that much air at such low revs is another topic though!
My friend with the 450bhp 3.0 8V uses a #8 turbine and runs 1.2 bar of boost, but his compressor is I think slightly smaller than on Nick's turbo, and thanks to a modern BW turbine wheel sees no more than 2.0 bar of back pressure. With a higher-flowing compressor and a less efficient turbine wheel, I bet Nick may now be seeing quite a bit more back pressure than "only" 2.0 bar, which certainly goes in line with the fact he saw no more power with 1.2 bar of boost than with 0.9. At this point this leads me to believe the turbine will affect the upper end more than the intake. A LR intake will shift the curves to the right slightly, but the engine may not be making that additional power any more healthily.
I would measure back pressure some times in the future, but firstly fiddle with the boost settings to perfect the low and mid range capabilities of this turbo. I don't see a GT turbo like my GTX3076R performing quite as well with the short 6 speed gearbox, unless going smaller in compressor size like with a GTX3071R.
PS : I'll make myself available for a beer or two in Blighty should you Pat come over. About time we all have a proper real chat!
Though the rate at which Nick's turbo builds boost is remarkable from the dyno sheet, I would still say that the short ratios of the 968 gearbox don't load the turbo as well as it could - I once saw 17psi at 2700rpm in 3rd gear when I was fiddling with boost settings. I'm sure Nick could get close to that by polishing boost settings. Whether the engine's VE will be high enough to injest that much air at such low revs is another topic though!
My friend with the 450bhp 3.0 8V uses a #8 turbine and runs 1.2 bar of boost, but his compressor is I think slightly smaller than on Nick's turbo, and thanks to a modern BW turbine wheel sees no more than 2.0 bar of back pressure. With a higher-flowing compressor and a less efficient turbine wheel, I bet Nick may now be seeing quite a bit more back pressure than "only" 2.0 bar, which certainly goes in line with the fact he saw no more power with 1.2 bar of boost than with 0.9. At this point this leads me to believe the turbine will affect the upper end more than the intake. A LR intake will shift the curves to the right slightly, but the engine may not be making that additional power any more healthily.
I would measure back pressure some times in the future, but firstly fiddle with the boost settings to perfect the low and mid range capabilities of this turbo. I don't see a GT turbo like my GTX3076R performing quite as well with the short 6 speed gearbox, unless going smaller in compressor size like with a GTX3071R.
PS : I'll make myself available for a beer or two in Blighty should you Pat come over. About time we all have a proper real chat!
