Borg Warner EFR Series
First up, a suspiciously familiar one, the BWEFR 6258.
This is a dual row ceramic ball bearing, water cooled, internal wastegate with integrated BOV turbo that flows 44lbs/min. 62mm compressor wheel, 58mm turbine wheel, with a max capability of about 440hp.
I believe that this turbo is probably the model that the IPD 4T4 turbo is based off of. I think it’s probably exactly their turbo, and they have a special exhaust housing for it to bolt to a stock manifold.
This one is available with a variety of exhaust housings, all stainless steel, including T25, T4, and two V-band of different A/R with an EWG. It has a reputation of being extremely quick spooling and hard hitting. Overall, even though it only is capable of 10hp more than the supposed 430hp capable Hybrid K24 Big Wheel turbo, this one is going to be more efficient and make more power all the way across the powerband, and if I had to guess, the area under the curve in the low and mid range would probably be in the 30-70hp range. Overall, if you wanted a great turbo for street fun, you would have a hard time going against this one.
I’m not going to go into a lot of details of the above setup, suffice to say it is a bolt-on STI, and the comparison is between the VF39 (very similar to the K24 turbo, maybe a touch smaller) the the 6258 turbo. The boost level is 24.5psi down low, tapering to 13.5psi for the VF39 and a whopping 20psi for the 6258, as it wasn’t gasping for air like the smaller VF39.
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Next up is the middle brother, one run by a member here with great success, the BWEFR 6758.
Much like it’s little brother, it is known for a quick spool up, although it is going to be a little slower on the draw than the smaller 6258 by virtue of having to spin a bigger 67mm compressor wheel. It utilizes the same 58mm turbine wheel, although this one has a big difference of having an available V-band housing with an IWG. The A/R of all housings are going to be bigger except for the smallish T25 one, which uses the same .64 a/r. This one also uses the dual row, ceramic ball bearing water cooled center housing.
This one is rated at 450hp and 53lbs/min of airflow, but I believe that at higher boost pressures it can make much, much more power. In fact, the below dyno chart (from Full Race’s website, where I’m getting the data) of a VW Golf R 2.0 at 35psi tapering to 32psi, on pump fuel with water/methanol injection.
That’s a big number, well past it’s “rated” horsepower.
(Edit: The numbers on the chart aren’t there, but it is 455whp and 516ft.lbs of torque)
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Finally, the last one in consideration, the BWEFR 7163.
The tale of the tape:
71mm compressor, 63mm turbine, available in T25, T4, or V-band housings, all IWG except for one available with the V-band housing that uses an EWG. Internal BOV as with all the rest, and supposedly the turbo used in the Indy Racing League in 2014/15. The turbo is rated at 60lbs/min.
Another STI, another VF39 turbo compared to the 7163 this time. No boost numbers, but that max power number and how fast it spools is definitely intriguing out of 2.5 liters.
This one has a little more work done to it than the regular turbos, but all three can be had in the $1600-$1850 range, depending on options.