One of the main goals of PerfExpert is to help you see the impact of your mods on performance when doing engine tuning, as you can see in the 4AGE 20V intake comparison performed on a Corolla GT AE82.
Here it's about another PerfExpert user's car : Georgi's impressive Mercedes 190E. It has a 3.0L 24V engine swap converted to turbo at 0.9bar boost, managed by a MegaSquirt standalone ECU with 660cc/min injectors.
We will see how he used PerfExpert to compare different turbo sizes on his car, when he was looking for the one that will provide the best spooling while maximizing power and torque.
Note that in order to perform accurate comparison, Georgi has carefully followed PerfExpert mounting requirements and measurement conditions. Check out the DIY phone mounting article for more information.
In the app, he created three Setups : one for each turbo. This allows better organization by grouping together results that belong to a specific turbo. Also, he took care of using exactly the same boost pressure, and not changing other parts in the engine or in the car : only the turbo. This ensures that the changes in power and torque are only due to the turbo swapping.
Dyno result with the T66
The first setup was with a T66 (A/R 1.15) turbo :
Max power : 451hp @ 6300rpm
Max torque : 520Nm @ 5900rpm
Not satisfied because of the turbo lag, Georgi decided to replace this big T66 turbo with a smaller one. The purpose was to get full boost at lower rev. In other terms, he wanted to improve turbo spooling.
Dyno result with the smaller turbo
The 2nd setup was with a smaller turbo, that is a hybrid turbo built using Holset turbine and compressor wheels inside Garret housings (A/R .82) :
Max power : 452hp @ 6300rpm
Max torque : 537Nm @ 4600rpm
As you can see, with the hybrid turbo, max power value and max power rev are still exactly the same, but max torque is acheived 1300rpm earlier and is a bit higher than with the T66.
Dyno result with the T6682
Unfortunately the hybrid turbo didn't last long and failed after a few weeks, so it was time to fit back the T66, but this time with a A/R .82 turbine :
Max power : 479hp @ 6200rpm
Max torque : 581Nm @ 4700rpm
Results are very good here : same spooling as with the small turbo (hybrid one) but with more power and torque! With still 0.9bar boost!
T66 vs Hybrid vs T6682 comparison
Now let's have a more detailed look at these different dyno results :
The T6682 setup is definitely the best one through the entire engine rev range.
This comparison has been made using OpenOffice spreadsheet desktop application from data files exported by PerfExpert mobile app (Tabulation Separated Values files).
The PerfExpert comparison feature is still in development and will be available in a few weeks on the PerfExpert Network. It will allow a user to overlay several dyno or timed run results on the same graph inside a web page.