New BW EFR Turbo Thread
Dec 1, 2011, 02:41 PM
#1141
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This is why I want to see more results
For what its worth, Perrin's dyno testing suggests the GT builds shaft speed up faster when the engine is allowed to accelerate at a constant rate when comparing two open housing units (with a "76mm" GTX comp wheel). On Buschurs test, the units are much more comparable when the GT turbine is driving an HTA 76mm compressor when comparing a with a twin scroll EFR7670.
Dec 1, 2011, 04:05 PM
#1144
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Your results assume a 70mm EFR turbine wheel performs identically to a 60mm Garrett wheel. You need to weight your findings based on the performance of the wheel (I can guess that turbine efficiency and flow rate would be two good performance indicators)
Your post's content and perspective have always been interesting...I'm curious who you work for.
Your post's content and perspective have always been interesting...I'm curious who you work for.
A GT30 turbine wheel in a 0.82 A/R T3 housing chokes at 23.5lb/min corrected flow
According to BW's Matchbot,
A 7670 turbine wheel in a 0.83 A/R T3 housing chokes at 24.3lb/min corrected flow, and A 7064 turbine wheel in the same 0.83 A/R T3 housing chokes at 20.0lb/min, which is a little less than what the GT30 does in a 0.63A/R T3 housing, so makes perfect sense to compare the GT30 with the 7670... The only remaining unknown is their respective turbine efficiencies
To answer your question I'm self-employed, http://www.facebook.com/pages/Hydra-...e/156778955724
Dec 1, 2011, 04:27 PM
#1146
Evolved Member
Alas we don't have the luxury of comparing much else, Perrin datalogged both the GTX and EFR equivalents on the road and that didn't show any advantage to the EFR either. I am not sure what else we could hope for?
Dec 1, 2011, 04:30 PM
#1147
i respectfully disagree with some of the assumptions you posted above. of course inducer will affect the system, thats why i posted the "rule of thumb" up. i have no clue where your 40% claim comes from, but its nowhere near accurate - id classify that as absurdly inflated to be honest. maybe try not to post conjecture/misinfo .. just wait for more people to run these turbos like you said.
edit - the reason most drag racing classes measure inducer is so that the turbo doesnt have to come apart for tech inspection... it would be highly unusual to expect racers to disassemble their turbos every morning for tech
edit2 - if you take those buschur results serious, and honestly believe a T3 undivided hta30r will wax a twinscroll efr... im wasting my time responding here.
edit - the reason most drag racing classes measure inducer is so that the turbo doesnt have to come apart for tech inspection... it would be highly unusual to expect racers to disassemble their turbos every morning for tech
edit2 - if you take those buschur results serious, and honestly believe a T3 undivided hta30r will wax a twinscroll efr... im wasting my time responding here.
Dec 1, 2011, 04:34 PM
#1148
Let me walk you guys through this again...
GT30 turbine has 60mm inducer and 55mm exducer
7670 turbine has 69.5mm inducer and 61.5mm exducer
both of them have 10-blades
GT30 has a mean diameter of sqrt(55x60) = 57.44mm
7670 has a mean diameter of sqrt(69.5x61.5) = 65.38mm
rotational inertia = geometric constant depending on shape x m x R^2
m = another geometrical constant depending on shape x density x R^3
to sum up,
inertia = geometric constant depending on shape x density x R^5
in the real world, blade thickness does not go up directly with radius, and inertia is proportional to R^4.333 if the section is stiffness-limited, or R^4.666 if the section is strength-limited , which is probably the case here. Nevertheless, we will take the average of the two and use R^4.5 instead (which would work out in the 7670's favor)
density of inconel = 8.1
density of gamma-Ti = 4.0
assuming the geometric constants are the same,
I GT30 / I 7670 = (8.1 x 57.44^4.5)/(4.0 x 65.38^4.5)
I GT30 / I 7670 = 1.131
So a simplistic analysis shows that the GT30 turbine wheel has 13.1% more rotational inertia than the 7670, but this does not take into account the MUCH greater thickness of the 7670 blades, the superback section of the 7670 (which puts mass where it affects rotational inertia the most), and the longer/thicker nut section (which would have a minor effect on rotational inertia) The superback section ALONE has got to be worth more than the 13% difference between the two turbines, and we STILL haven't taken into account the thicker cross section of the gamma-Ti wheel!
The worst case scenario conclusion we can draw from the above is that the 7670 turbine wheel does NOT have a lower PMOI than the GT30, in fact its probably higher... The 7064 would have a significantly lower PMOI than the GT30 but then again it flows less given a similar housing... I hope I've made my point clearly
PS - I'm not passing judgement as to which of the above turbine wheels is "better", or more efficient, or faster spooling, just comparing their relative rotational inertias.
GT30 turbine has 60mm inducer and 55mm exducer
7670 turbine has 69.5mm inducer and 61.5mm exducer
both of them have 10-blades
GT30 has a mean diameter of sqrt(55x60) = 57.44mm
7670 has a mean diameter of sqrt(69.5x61.5) = 65.38mm
rotational inertia = geometric constant depending on shape x m x R^2
m = another geometrical constant depending on shape x density x R^3
to sum up,
inertia = geometric constant depending on shape x density x R^5
in the real world, blade thickness does not go up directly with radius, and inertia is proportional to R^4.333 if the section is stiffness-limited, or R^4.666 if the section is strength-limited , which is probably the case here. Nevertheless, we will take the average of the two and use R^4.5 instead (which would work out in the 7670's favor)
density of inconel = 8.1
density of gamma-Ti = 4.0
assuming the geometric constants are the same,
I GT30 / I 7670 = (8.1 x 57.44^4.5)/(4.0 x 65.38^4.5)
I GT30 / I 7670 = 1.131
So a simplistic analysis shows that the GT30 turbine wheel has 13.1% more rotational inertia than the 7670, but this does not take into account the MUCH greater thickness of the 7670 blades, the superback section of the 7670 (which puts mass where it affects rotational inertia the most), and the longer/thicker nut section (which would have a minor effect on rotational inertia) The superback section ALONE has got to be worth more than the 13% difference between the two turbines, and we STILL haven't taken into account the thicker cross section of the gamma-Ti wheel!
The worst case scenario conclusion we can draw from the above is that the 7670 turbine wheel does NOT have a lower PMOI than the GT30, in fact its probably higher... The 7064 would have a significantly lower PMOI than the GT30 but then again it flows less given a similar housing... I hope I've made my point clearly
PS - I'm not passing judgement as to which of the above turbine wheels is "better", or more efficient, or faster spooling, just comparing their relative rotational inertias.
Dec 1, 2011, 04:46 PM
#1150
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Dec 1, 2011, 04:58 PM
#1151
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Seriously though, what I don't understand is why these BW Ti-Al wheels have to be so thick/bulky? MHI's Titanium Aluminide TD05HRA turbine is the same size as the inconel version, and I don't think it flows much if any less... A 7670 turbine is comparable in size to a GT35 turbine wheel, yet it flows like a GT30, and spools somewhere in between... Disappointing :/
Last edited by hydra; Dec 1, 2011 at 05:00 PM.
Dec 1, 2011, 04:59 PM
#1152
Originally Posted by David Buschur
What overlay are you and your boy geoff wanting to see exactly? Go figure you spend a lot of time typing and not much time actually doing any racing or proving of anything.
Lets see your HTA76 dyno pull on it's HIGHEST power output versus the best BW EFR dyno pull on your dyno from leet's car. Overlay them with boost plots.
Last edited by R/TErnie; Dec 1, 2011 at 05:17 PM.