While the 8374’s spool-up characteristics is one important reason for choosing it; I also love the efficiency range. By studying the compressor map, I knew this was an excellent choice. Anticipating around 450-500 WHP at what hopefully should be around 18-22 PSI on pump fuel, that should put it right around an estimated 47-52 lb/hr on the X-axis, and at the 2.2-2.5 at the Y-axis (for 18-22 PSI). That puts us in the top two 76-77% efficiency islands, and I can even be off by a 1-2 PSI swing either way and still be at over 75% efficiency. This is very good, and it will help keep charge temps down.In order to reach our sustained top-end torque (power) goal, we’ll need a turbo size that can flow well. Borg offers turbos in its EFR line with inducer sizes ranging from 50mm to 68mm. The 8374 we chose fits more in the middle. This 8374-C, to be exact, denotes the fact it’s the 8374 with internal wastegate and a .92 AR twin-scroll housing.
For those of us not so well versed with the different turbo nomenclatures, Borg Warner’s 8374 may sound like a big turbo, but as you can see it’s actually not. Borg Warner’s names are the largest diameters of the compressor and turbine wheel (the exducer of the compressor and the inducer for the turbine wheel, if you will). If you want to know what the smallest diameters are–the inducer/exducer sizing for the compressor/turbine, respectively–think of the 8374 as really being a quick-spooling “6264” turbo. Perfect!
The EFR turbos include a center cartridge equipped with Borg’s dual-row ceramic ball bearings for quick spool-up and improved transient response between gears. In this picture, we can also see the fact that the 8374 can be water-cooled as well, which Borg and Full Race insist on doing. Lastly, notice the compressor housing’s backing plate. I’ve always had the turbos with six-bolt compressor housings holding it secure, and it was always a big pain to re-clock them. With this V-band setup, it will make life super easy.
Another thing we cannot see in this pic above is the inside–where Borg-Warner technology really stands out. The bearing housing material is made of M50, which is military-grade, and the ceramic bearings are encased in silver for a true motorsport grade. This should come as no surprise since all EFR turbos were engineered for Indycar. This technology means these ceramic bearings can reportedly withstand more than 10x the thrust strength of traditional journal bearings!
Something else not visible is the fact that on the shaft inside are two oil control seals on each side, (instead of just the one more commonly seen in other turbos). This dramatically reduces the potential to have any leaking or oil burning.
While Borg Warner is not against externally mounted blow-off (or recirculation) valves, it offers its compressor recirculation valve to save the customer money and work needed to install an external unit. It also improves transient turbo response. This technology comes from Borg’s OE passenger car experience, with millions of cars on the road today using these types of setups from Borg. This will be my first time with an internally mounted recirculation and wastegate valve.A big part of Borg’s ability out-spool the competition is seen here, in its EFR turbine wheel, which is made of titanium aluminide (which Borg calls “Gamma-Ti” for short). As a result, Borg reports it weighs about half of what you’d normally see out a turbine wheel this size (sometimes even less than some of the aluminum compressor wheels!), reducing the inertia. The reduced weight substantially helps in spooling up a 64-mm (or larger) turbine wheel like this one. There, on the lower side of the exhaust housing, we can see the internal wastegate, which can excavate up to 40% of the flow for good boost control.
I am really glad that you are not going for an all-out TQ number. There’s so much more to an engine than it’s TQ/HP number. Most people don’t really know that there’s much more to an engine than how much TQ it produces.
Case in point: Gordon Murray’s T.50 NA V12 revs at 28,400 RPM per second.
hi guys, thanks for the replies. Next two articles are in the works as we speak!
Joe, I think I understand what you’re saying with the 28400 RPM “per second”, as in the rate of RPM acceleration. Just so others aren’t confused, it’s like–when free-revving in neutral–it’ll *theoretically* rev to 28400 RPM if you floor/free-rev it for one 1sec. Murray’s actual [beast of a] car has a 12100 RPM rev *limit*, which is still insane for that size of a motor. And thanks for the compliments. Yes driving this car is so different from the Supra in every aspect, I’m just having so much more fun in it. I very much want to floor it more often than in the Supra (which is more of an “event”) since it is more top-end based. And I just love the RB’s sound, even moreso now with the wastegate plumbed back into the exhaust. Stay tuned as that’s what I discuss in the next one! 🙂 thanks guys.
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Great Article, Really excited to see how this goes!
I am really glad that you are not going for an all-out TQ number. There’s so much more to an engine than it’s TQ/HP number. Most people don’t really know that there’s much more to an engine than how much TQ it produces.
Case in point: Gordon Murray’s T.50 NA V12 revs at 28,400 RPM per second.
Tease!
hi guys, thanks for the replies. Next two articles are in the works as we speak!
Joe, I think I understand what you’re saying with the 28400 RPM “per second”, as in the rate of RPM acceleration. Just so others aren’t confused, it’s like–when free-revving in neutral–it’ll *theoretically* rev to 28400 RPM if you floor/free-rev it for one 1sec. Murray’s actual [beast of a] car has a 12100 RPM rev *limit*, which is still insane for that size of a motor. And thanks for the compliments. Yes driving this car is so different from the Supra in every aspect, I’m just having so much more fun in it. I very much want to floor it more often than in the Supra (which is more of an “event”) since it is more top-end based. And I just love the RB’s sound, even moreso now with the wastegate plumbed back into the exhaust. Stay tuned as that’s what I discuss in the next one! 🙂
thanks guys.