Power Stroke Turbo for Towing

December 21st, 2011

Text and Photos by J.S. Hansen

BD Power’s Direct Replacement for the 7.3L


Nearly 10 years after its demise, the 7.3L Power Stroke is still one of the most sought-after diesel powerplants. The 1994-2003 Ford Power Stroke was the most popular light-duty diesel ever produced, and with new truck prices cresting over the $50,000 range, more and more owners are willing to invest a little money into those old 7.3L trucks to improve their overall performance and efficiency.

Knowing this, the folks at BD Power are always looking for ways to improve their product lines to help fill the needs of the market, and the 7.3L Power Stroke has not yet been forgotten. BD Power has recently released an all-new direct replacement turbocharger for both the 1994-1997 and 1999.5-2003 Ford Power Strokes. Labeled as the “Turbo Thruster II,” this new unit replaces the original Thruster with some pretty nice improvements in both construction and performance.

The new Turbo Thruster II will bolt directly onto the factory turbo pedestal and connect right to all the factory plumbing, with the exception of the intake duct, which has been upgraded from the stock 3-inch compressor inlet to a favorable 4-inch piece. BD Power supplies all the needed O-rings, replacement bolts and the 4-inch hose to connect the new turbocharger to your current air box system.

Turbo engineer at BD, John Todd, spent numerous hours trying to develop the perfect turbocharger to improve the 7.3L’s usability on the street as a daily driver and especially its performance while towing. His main goals were to first eliminate all surging issues the stock turbocharger is known for and second, lower exhaust gas temperatures on both stock and mildly modified power applications. To meet those goals, Todd looked at ways to improve compressor airflow, exhaust flow and bearing durability of the stock turbocharger.

On the intake side, the new Thruster II uses a Garrett 66mm HIP’d (“hot isostatic pressed”) compressor wheel that flows 40 percent more air than the stock wheel and has improved durability.

Next, they went to casting their own compressor housing which has a tighter A/R ratio and a 4-inch ported inlet, which effectively eliminates any surge problems and helps improve turbocharger spool-up time.

On the exhaust side of the turbocharger, BD had its own turbine housings made and machined to optimize flow and help generate the needed turbine flow to limit turbo lag time. BD spent the time to fine-machine the transition from the turbine wheel section into the housing volutes. While this may not sound like much, the attention to detail and the 1.0 A/R ratio offers a happy medium for spool-up and drive pressure control in the higher engine rpms.

The center section of the turbocharger was also upgraded with an in-house-designed 360-degree bronze thrust bearing that improves oiling and reliability under extreme conditions, such as heavy towing and sustained high-boost situations. The use of this new journal bearing design not only offers improved durability, it also allows for easier and more cost-effective servicing, should the turbocharger ever need it.

BD Power markets this turbocharger as a stock replacement or upgrade to the stock GTP-38 turbocharger. While we were told that the turbo showed a 10-horsepower increase on a stock vehicle, BD Power also indicated that it is not targeting the high-performance crowd with this turbocharger. The company is offering it to guys planning to use their vehicles on a daily basis, whether that is for regular daily driving or for heavy towing needs.

After installing our new Thruster II turbocharger, we were able to recreate our previous tests to compare our before and after performance data. With the truck unloaded, we made some wide-open throttle runs from a dead stop up to 75 mph in our 60hp towing tune.

The test mule is fitted with a cold air intake, 4-inch turbo back exhaust and a rebuilt transmission. Testing showed that with the stock turbocharger, we peaked at 24psi boost and 1,100 degrees on the pyrometer gauge.

The BD Power turbocharger brought our peak boost numbers up to 28psi and dropped our EGTs to slightly more than 1,000 degrees at 60 mph. At that point, the pyrometer climbed to 1,025 degrees and just stopped—rather than continuing to climb the longer we were in the throttle, as with the stock turbo.

Because this turbocharger is marketed to those who use their vehicles for towing, we really wanted to see how the turbocharger affected our overall drivability and EGTs with our 36-foot fifth-wheel travel trailer in tow (around 15,000 pounds).

For our test hill, we chose a 3-mile-long 6 percent grade just outside of town. There is a mile-long straightaway, so maintaining the speed limit at 75 mph before the start of the grade is no issue. The climb starts out at around a 4 percent grade for the first mile, levels out for about a half-mile and then climbs to a 6 percent grade for the next 1 ½ miles, until you crest the top and level out.

With the stock turbocharger on the truck—again in our chip’s tow setting—pushing 1,200 degrees on our pyrometer gauge was easier to obtain than the speed limit. So for our testing, we disregarded the speedometer and used our pyrometer gauge (maintained at 1,200 degrees) to control our throttle input.

We started up the grade at 75 mph in overdrive. About halfway up the first 4 percent incline, we had to downshift into third gear and slowed our speed to 69 mph. As the grade leveled off, we had to stay in third gear and were able to accelerate back up to 72 mph before the 6 percent incline started. We were unable to accelerate any harder because of the extreme turbo surge, which we know can be detrimental to a turbocharger. As we started that climb, still in third, our speed slowed to 60 mph as we crested the hill.

Three days later, and with the BD Turbo installed, we recreated our previous testing with our trailer on the same grade. Again, we started at the bottom of the climb in overdrive at 75 mph. We kept a close eye on the pyrometer gauge, keeping it at 1,200 degrees for the duration of the 3-mile climb.

Going up over the first 4 percent grade, we again had to downshift into third gear, and our speed dropped to 70 mph. However, once things leveled off, we were able to get back up to our desired 75 mph and into overdrive before the steep 6 percent section started. That speed and overdrive were unobtainable with the stock turbocharger, because our exhaust temperatures were hard to keep under control.

Shortly into our 6 percent grade, we again needed to command a downshift to bring engine rpms and boost pressure up to help keep the load moving and EGTs in the safe zone at 1,200 degrees. We were able to pull third gear for the length of the climb—and to our surprise, our speed only dropped to 65 mph, compared to the 60 mph we dropped to with the stock turbo.

While these results don’t tell us how much the turbocharger actually helped drop our exhaust temperature, it does prove that the increase in allowed us to use more fuel and throttle while towing up steep grades, since we were able to climb the same hill with the same load at a noticeably faster speed. We should also note that our cruising EGTs while towing ran (on average) 75 degrees cooler, and the new Thruster II eliminated all surging issues.

Overall, we are very pleased with our final results with the addition of our BD Power turbocharger and Crank Case Filter Kit. The new turbocharger has made an improvement in drivability and helped increase our pulling power—both of these are strong attributes to any aftermarket installation. Spool-up time is slightly slower than our original stock turbocharger, but the increase in airflow and drop in EGTs more than make up for that.

Source

BD Power

www.dieselperformance.com

800.887.5030

This is in the December issue of Diesel World magazine.

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