metal_miner
New member
- Joined
- Feb 3, 2007
- Messages
- 179
Before I start explaining my dyno results I'll be upfront and state that for the entire comparison I ran out of supply fuel feeding my dual stock CP3's and therefore ran out of rail pressure on the top end with my little Walbro 80 gph pump. This issue will be shortly addressed with a Raptor 150 gph.
That said - I hate lag on the street or towing, especially at my 5,000' - 6,500' driving elevation, but having top end also is nice. I had tried different types of single turbos: HTT 62/12, HTT 62/14, II SPS 66/14, and II SPS 62/14. After spending tons of $ and time, I eventually came to the realization that I wanted a compound turbo setup.
I first had a BD tow twins setup. It was good on the street and towing, but choked up quite a bit on the top end. At my elevation it was good for 50 psi before drive pressure started overcoming boost.
I then had Nathan at MPI build me a compound setup keeping my Super B (57/65/14) on top, but replacing the BD primary with a Garrett GT4202 1.15 AR wastegated turbo. This setup spooled the same as the BD tow twins, but yielded about 25 HP more (600 HP) on the top end before the little Walbro couldn't deliver.
I then started reading about Soulezoo's and Onetun's Garrett ball-bearing compound turbo set-ups and their amazing spool speeds. Via MPI I purchased the GTX4202R with 1.15 AR non-wastegated housing and installed it. The first test drive yielded immediate improvements:
1) Way less smoke off idle because the GTX primary starts spooling sooner than the journal bearing GT.
2) My cold pipe starts registering boost at 8 psi in the intake horn. Before the swap, cold-pipe boost used to register at 12 psi.
3) I hit >40 psi boost in at least one lower gear than before. The turbo is so responsive that I had to learn to apply less throttle input than with the journal bearing GT.
Since this was all SOP, gauge, and visual improvements, I figured a dyno session would tell a better story. See attached files for the comparison.
Settings are exactly the same for the GT4202 (RunFile #12) versus GTX4202R (RunFile #16) runs (TNT/R = #5 and TST 4x0). Any TST setting above this started dropping lift pump pressure and in turn rail pressure.
The ball-bearing GTX spools about 100-150 rpm sooner than the journal bearing GT. Top end power and torque were about the same since both ran out of supply fuel.
From my datalogs of this dyno, the GTX put out 29 psi with 60 psi in the intake manifold at 1225* EGT. At 29 psi the GTX is at PR=3. The maximum air mass flow on the GTX compressor map looks to be at PR=3.5, which holds to PR=4.25.
On the street with the GTX I hit about 65-70 psi total versus 60 psi total with the regular GT.
All the above comparisons were with my truck otherwise set up with Flux 2 injectors, dual Cummins CP3's, Walbro supply pump, Smarty TNT/R, TST PMCR.
I can't wait to get the fuel supply resolved. Then I'll dyno again using the same fueling parameters.
That said - I hate lag on the street or towing, especially at my 5,000' - 6,500' driving elevation, but having top end also is nice. I had tried different types of single turbos: HTT 62/12, HTT 62/14, II SPS 66/14, and II SPS 62/14. After spending tons of $ and time, I eventually came to the realization that I wanted a compound turbo setup.
I first had a BD tow twins setup. It was good on the street and towing, but choked up quite a bit on the top end. At my elevation it was good for 50 psi before drive pressure started overcoming boost.
I then had Nathan at MPI build me a compound setup keeping my Super B (57/65/14) on top, but replacing the BD primary with a Garrett GT4202 1.15 AR wastegated turbo. This setup spooled the same as the BD tow twins, but yielded about 25 HP more (600 HP) on the top end before the little Walbro couldn't deliver.
I then started reading about Soulezoo's and Onetun's Garrett ball-bearing compound turbo set-ups and their amazing spool speeds. Via MPI I purchased the GTX4202R with 1.15 AR non-wastegated housing and installed it. The first test drive yielded immediate improvements:
1) Way less smoke off idle because the GTX primary starts spooling sooner than the journal bearing GT.
2) My cold pipe starts registering boost at 8 psi in the intake horn. Before the swap, cold-pipe boost used to register at 12 psi.
3) I hit >40 psi boost in at least one lower gear than before. The turbo is so responsive that I had to learn to apply less throttle input than with the journal bearing GT.
Since this was all SOP, gauge, and visual improvements, I figured a dyno session would tell a better story. See attached files for the comparison.
Settings are exactly the same for the GT4202 (RunFile #12) versus GTX4202R (RunFile #16) runs (TNT/R = #5 and TST 4x0). Any TST setting above this started dropping lift pump pressure and in turn rail pressure.
The ball-bearing GTX spools about 100-150 rpm sooner than the journal bearing GT. Top end power and torque were about the same since both ran out of supply fuel.
From my datalogs of this dyno, the GTX put out 29 psi with 60 psi in the intake manifold at 1225* EGT. At 29 psi the GTX is at PR=3. The maximum air mass flow on the GTX compressor map looks to be at PR=3.5, which holds to PR=4.25.
On the street with the GTX I hit about 65-70 psi total versus 60 psi total with the regular GT.
All the above comparisons were with my truck otherwise set up with Flux 2 injectors, dual Cummins CP3's, Walbro supply pump, Smarty TNT/R, TST PMCR.
I can't wait to get the fuel supply resolved. Then I'll dyno again using the same fueling parameters.
