[TDIwyse]

Loving the technical exchange here. Thanks for all who are participating.

I was curious to test some of the comments about the hot side of the stock turbo being a limit, and the stock wastegate being able to control boost creep. I had collected a lot of data previously when moving to the EWG, but never done a back to back test like what is attached.

I reconfigured my system so the EWG was no longer in play, and went back to the IWG. Reset things and did a few days of driving and many drive cycles. Then yesterday I did some testing to compare back to back impact of the IWG vs the EWG config. Well, there was ~1 hr between the tests. But same fuel, same day, exceedingly similiar weather, no wind (but lousy low pressure system on top of us).

Notes about differences from early PerExpert dyno sheet: It's middle of winter and I'm using blended winter fuel (lower BTU's). I reduced my water/methanol blend to 50/50. I lowered the EWG setting to limit drive pressure to ~48 psi range. Using winter/tires with different diameter (had to correct that after noticing the rpm's weren't lining up quite right).

First I did the IWG pull and logged some parameters. Using DWR's Torque PIDs for this (note ... my analog boost gauge reads a bit higher than the reported boost from the PID).

The shape of the IWG power curve showed what I think is evidence of the hot side "choking" at the upper rpm's. Higher drive pressures, higher EGT's and even though the boost was higher, lower peak wheel power.

Drove home, swapped the configuration around so the IWG is out of play and the EWG is doing all the boost control. Drove back to the testing ground and did another pull. Even though the peak boost is slightly reduced, there's much less drive pressure. Result was lower EGT's, and continually climbing wheel power numbers to shift point at ~4600 rpm. This is similar to the air flow measurements I made using pressure drop data (the OEM MAF clips at the mid rpm region for my vehicle as configured).

Also including the configuration for PerfExpert (I think 1750kg is actually lite for what things weight so these should be conservative wheel power/trq #'s) and drag coefficient, and also showing the ambient weather and correction factors.

Interestingly, I don't think my IWG with stock wastegate had issues controlling boost creep at the upper rpm's. This would seem to agree with Bob's experience, but is different than iaknown's experience.

As an aside, this morning and afternoon I did more testing with the EWG setup to allow the drive pressure to go up to 52 psi, which resulted in more peak boost, but not much more peak power (~4-5 whp).

This and some other recent threads have me thinking about turbo upgrades again...