v8440
Well-known member
This time with the new turbo, an HTB2-64 with the 14 cm exhaust housing. In 4th gear, without nitrous, it posted: 392 hp, 694 ft/lbs. These figures are at the wheels, with the air filter on, and exactly as I drive it every day.
I started dynoing this truck back before I knew that you should dyno diesel pickups in overdrive whenever possible. Accordingly, I make most pulls in 4th so I'll be able to make valid comparisons to previous pulls. The reason you should pull in overdrive is that the rollers have weights appropriate for many passenger cars. That is, the intertial resistance of the drum is reasonably close to the resistance the engine sees accelerating the actual vehicle down the road. Not so for a diesel truck-they are much heavier. The drum's relatively light weight cheats them by forcing them to rev much quicker than they do in real life, which soaks up power in speeding the drivetrain/engine up faster than the vehicles sees on the road.
Anyway, I did make one pull in 5th. It made 399 hp and 814 ft/lbs. Again, this is without the nitrous and with the air filter installed.
Then, I ran it on the bottle. I found that with the bigger turbo, the engine won't accept nitrous at as low an rpm as before. By won't accept, I mean it will buck and shut off if you spray it too early. With the stock turbo, I had been able to spray it at about 1100 rpm. This spooled the turbo REALLY fast, and led to it making 920 ft/lbs at about 2100 rpm. Since spraying it so early is now not possible, the peak torque actually dropped off. On the best bottle pull for torque, it made 906 ft/lbs, and 430-something hp. On the best bottle pull for power, it made about 890 ft/lbs, and 450 hp. I don't know why there was so much variation in torque and power between those two runs, but that's what the dyno said.
All said and done, without nitrous, the turbo alone picked it up 52 rwhp compared to the stock turbo. Nothing else was changed-I even set the wastegate on the new turbo to the same boost level as the stock one was set to.
In any case, it was fun. I can hardly wait to get the 2nd turbo on there-twins spool much better than a big single, and can still produce much more boost.
I started dynoing this truck back before I knew that you should dyno diesel pickups in overdrive whenever possible. Accordingly, I make most pulls in 4th so I'll be able to make valid comparisons to previous pulls. The reason you should pull in overdrive is that the rollers have weights appropriate for many passenger cars. That is, the intertial resistance of the drum is reasonably close to the resistance the engine sees accelerating the actual vehicle down the road. Not so for a diesel truck-they are much heavier. The drum's relatively light weight cheats them by forcing them to rev much quicker than they do in real life, which soaks up power in speeding the drivetrain/engine up faster than the vehicles sees on the road.
Anyway, I did make one pull in 5th. It made 399 hp and 814 ft/lbs. Again, this is without the nitrous and with the air filter installed.
Then, I ran it on the bottle. I found that with the bigger turbo, the engine won't accept nitrous at as low an rpm as before. By won't accept, I mean it will buck and shut off if you spray it too early. With the stock turbo, I had been able to spray it at about 1100 rpm. This spooled the turbo REALLY fast, and led to it making 920 ft/lbs at about 2100 rpm. Since spraying it so early is now not possible, the peak torque actually dropped off. On the best bottle pull for torque, it made 906 ft/lbs, and 430-something hp. On the best bottle pull for power, it made about 890 ft/lbs, and 450 hp. I don't know why there was so much variation in torque and power between those two runs, but that's what the dyno said.
All said and done, without nitrous, the turbo alone picked it up 52 rwhp compared to the stock turbo. Nothing else was changed-I even set the wastegate on the new turbo to the same boost level as the stock one was set to.
In any case, it was fun. I can hardly wait to get the 2nd turbo on there-twins spool much better than a big single, and can still produce much more boost.
