surge question
Postmaster
Joined: Jun 2006
Posts: 2,647
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From: Fulltime RVer
The thread below is a good review on surge, and ways to eliminate or reduce it. Remember, surge is what kills turbos, and the following quotes are from this thread...
Turbo Surge, Turbonetics T61, GTP38R, & GT38 w/ 99.5 & Early 99 Wheels.
https://www.ford-trucks.com/forums/6...99-wheels.html
Basically this means to downshift early and often as you tow a grade! Don't push the boost too high in 4th (assuming an auto) before pushing the OD lock out button and downshifting to 3rd, and likewise if the grade is steep enough, don't push the boost too high in 3rd before grabbing the shift lever and manually downshifting to 2nd.
If you wait for the PCM to command these shifts automatically, you'll get some surge, and cause needless wear on the tranny as well. Note, when executing these downshifts, first let up on the throttle to unload the drive line so the tranny isn't shifting while under a heavy load. This technique will save wear and tear on both the turbo and the tranny!
Turbo Surge, Turbonetics T61, GTP38R, & GT38 w/ 99.5 & Early 99 Wheels.
https://www.ford-trucks.com/forums/6...99-wheels.html
...Even though surge is a momentary condition, the wear and tear on the turbo bearing accumulates. It's not like being pregnant, you can have a little surge and not even realize it. It takes significant surge to make the noises that people report, and for sure this is the most damaging surge condition, but surge comes on gradually in the vicinity of these surge lines, and if you keep pushing it, then surge announces itself with the tell tale noises that indicate a higher level of more immediate damage...
...You can see from the pic #2 graph what the "poor mans" solution for surge is. You just downshift to 3rd, and now at 65 MPH you're turning about 2800 RPM, and now you're operating on the pink 2800 RPM curve at about a BP=16 psi to have the same HP as for 2000 RPM at 17 psi. The volumetric and thermodynamic efficiencies are maximum at 2000 RPM, and lower at 2800 RPM, however, at 2800 RPM you can increase BP by an additional 7 psi, to 23 psi before hitting the red surge line. So in 3rd gear you've got some surge margin to play with...
...You can see from the pic #2 graph what the "poor mans" solution for surge is. You just downshift to 3rd, and now at 65 MPH you're turning about 2800 RPM, and now you're operating on the pink 2800 RPM curve at about a BP=16 psi to have the same HP as for 2000 RPM at 17 psi. The volumetric and thermodynamic efficiencies are maximum at 2000 RPM, and lower at 2800 RPM, however, at 2800 RPM you can increase BP by an additional 7 psi, to 23 psi before hitting the red surge line. So in 3rd gear you've got some surge margin to play with...
If you wait for the PCM to command these shifts automatically, you'll get some surge, and cause needless wear on the tranny as well. Note, when executing these downshifts, first let up on the throttle to unload the drive line so the tranny isn't shifting while under a heavy load. This technique will save wear and tear on both the turbo and the tranny!
