I recently installed a Garrett Powermax Stage 2 turbo, which is a GT3782R. It’s a 62/64/.89 turbo. The comp wheel is a 61.4x82mm 6 blade wheel, and is normally found in the GT3582R turbo. The turbine wheel is a 72.5x64mm 10 blade wheel, and is normally found in a GT3788R. The center section is a GT37R water cooled ball-bearing unit. The exhaust housing is a .89 a/r divided and internally gated unit that has the HE351 4.4” outlet on it. This combo is designed specifically for the 3rd gen Cummins.
The kit is a well designed and was quite easy to install. I spent about 5 hours doing the install which included a new (to-me) exhaust manifold. The only issue I had was with one of the bolts required for bolting the turbo to the manifold. It was too long and hit the turbine housing. I had to get another at the parts store. The rest of the kit fit perfectly, the intake, exhaust, coolant, and oil lines all attached easily and no adjustment was required.
Prior to putting the turbo on the manifold you need to attach the inlet coolant line. I had to disconnect the WG rod to get the allen wrench into the banjo bolt.
Turbo ready for install
Manifold ready for the turbo.
Bolted in place.
Where the inlet for the coolant connects to the OEM heater core return.
Where the coolant return goes into the water pump.
To pre-oil the turbo I used one of my kids medicine syringe’s in the oil feed line. It worked quite well, it took about 2 ounces before there was resistance on the oil feed line.
Completed install, wrapped in Turbo Performance blankets.
During the initial idle is was apparent the tone of the exhaust had changed, it is much deeper and there is a faint hint of the turbine wheel. It sounds like a bigger I-6, and reminds me a marine 3406 with an 8” stack. I think that both the manifold and turbine housing are responsible for the change in the tone. The turbo also spins for a few seconds after you shut the motor off, which I think is awesome.
On the first drive around the block I thought my boost/DP gauges had come unhooked because at no load there is no boost/DP, unlike the stock setup. I did another leak check, reinstalled the finder liner and went for a drive.
The turbo howls! From about 2-7 psi is has a howl, which I gather is a characteristic of the Garrett comp wheels. It was different at first, but I love it now. I took it easy for the first 50 or so miles. After the easy miles I got on it a few times. It’s pretty quiet from 7-15 psi then it starts to sing! It’s a very different whistle than the stock turbo made, but the comp wheels are very different in design. My 4 year old will mimic the turbo sound, which I find much funnier than my wife does. It’s only really noticeable at low boost and low speed, it passes the wife test, but the 4 year was told to be quieter…
Despite lower boost at low-no load the engine is much more responsive and revs easier than with the stock turbo. I also noticed that it takes a lot less pedal to get the rpms to 2200-2400.
Under normal DD driving the boost is much lower than stock, as expected, but there is no lag, less smoke, better acceleration, and best of all less timing rattle.
When I get on it the boost builds very very fast. From 0-10 psi from 1,000 rpms in 6th the boost builds about the same as stock, maybe a touch slower. From 10-25 its much faster than stock, and a little slower from 25+. That’s all what I expected, under normal acceleration, not lugging, the turbo is much faster than stock. Even thou the boost is a hair slower to reach 10 in that test the smoke clears much sooner than it did stock. Boost and Drive are nearly 1:1 under all acceleration and cruise. The only time I have seen greater than 1:1 is WOT above 2500 rpms, the DP climbs slightly faster than boost but based on the 3rd event that is to be expected as well, and I am rarely ever above 2400. Even at its worst is better than stock was at its best. Cruise at 80 is 1:1, where stock was 1.5:1. Below is a no load chart of what I get.
The main reason I wanted a turbo upgrade was the DP when towing, it was nearly always 1.5:1 or greater with the stock turbo and the Smarty Jr.
I have about 225 miles on it towing and it’s a great towing setup. Around town acceleration in 2nd-4th gears it runs about 100-200° cooler than my stock turbo did, gets to 800-900 normally and stays there, regardless of light acceleration or heavy acceleration. 5th and 6th it will get to 1000 ± 50 and stay there, light or heavy acceleration. If I short shift it and start off in the next gear at 1300-1400 rpms the EGT's are a little higher but not over 1100°-1150°, but that's driver error and did it stock as well.
6th gear (255/80/17's and 3.73's) at 60 mph it will get to 1225° WOT on a grade, which is what it did stock as well, but the truck has more power than it did stock for the same fueling. There is a grade that I do at 60 in 5th becuase stock it wouldn't hold speed in 6th, I pulled it easily in 6th today at the same speed as always.. still 95-100% throttle but never slowed, rpms were 1700.
I can easily tow in 6th at 60-65 with a TT and a 25 mph headwind and not get too hot on the EGT's.
Where we went this past weekend we go often and there is 1 good sized hill that is 60 mph in 5th, stock turbo would run 1150° at the bottom and 1225° at the top, the new turbo ran 1050° most the way and the last steep part where the truck is at 75-80% load I saw about 1150°.
Boost is slightly lower across the board but EGTs are generally down and power seems to be slightly up.
IAT's are up to 25° lower on long grades with similar boost (+25° vs +45°), so the turbo is much more efficient than the stock HE351. Cruising in 6th at 60-65 mph with the a/c on the IAT’s were +10° with this turbo, where stock would have been approx +20°. I attribute that to the efficiency of the compressor wheel and less heat in the engine bay from the manifold/turbo blanket, but at highway speeds it’s mainly the compressor wheel.
Drive pressure, what drive pressure?? I never saw more than a +2 psi difference on drive pressure over boost for the entire tow. When I hit a grade drive will get about 2 psi ahead of boost and hold there until boost stabilizes, then it will drop to about 0 to -2 psi, which is amazing if you ask me. Even at 2400 rpms, 75% load in 5th gear DP would drop to 2 below boost; where with the stock turbo it would have been +12 at the lowest.
Slow speed is an absolute joy. I did about 70 miles of 20-30 mph towing mostly in 3rd, but 2nd -4th were used. The truck responds better than stock and has all the air I need at low rpms and low speed. I never saw over 650° in all those miles, not many hills but some small ones.
The truck is also much smoother at higher rpms. At 2000-2500 rpms the truck drives like it did at 1500-2000 with the stock turbo. Downshifting is easier and does slow the truck as much. Cruising at 5th at 2200 rpms the motor is much quieter than it was, and the boost builds and drops off easier and makes for a more constant speed and smoother operation.. I know I used the word smooth a lot, but it really is quite amazing.
My low boost “Smarty signature” smoke is 90% gone. I still see a minor haze right at the shift, but its nearly gone. If I try I can still roll some black, but normal driving the difference is huge.
Normal driving in lower gears keeps the turbo ahead of the air demand, and shifting so that your at 1500-1600 rpms after the shift is perfect in upper gears, which is where you should be shifting anyways to stay above peak tq rpm.
My mileage seems to be a hair better for the driving I have been doing, but time will tell on that.
All in all I am very happy with the turbo. I have yet to experience a situation where the stock turbo was superior. In the 350-400 rwhp range this turbo seems to do it all with ease!
The last I have noticed that I didn’t expect is oil pressure is a 2-4 psi higher all the time. I figure this is from less oil going to the turbo and more to the block. The BB turbo’s use very little oil and have a restriction built into the inlet fitting.
More to follow as I put some miles on the truck.