The FrankenTurbo F4H turbocharger is no longer offered, but I had it for a while on my S4. During that time I collected a significant amount of basic performance data on the car. Recently I have been looking at turbocharger alternatives to the BW K04 and the metric shown below, 2-11 time, is something I have recorded for the candidate turbocharger systems.
Just to see how the F4H stacks up I pulled this data to compare the F4H to one of the top contenders, the TTE550.
FrankenTurbo F4H vs TTE550
The F4H uses a smaller compressor wheel and turbine wheel as compared to the TTE550, so the outcome is not surprising.
Below is the F4H under a range of ambient temperature conditions.
F4H 2-11 time with grouped by Ambient Temperature
No surprise that as the ambient temperature increases the 2-11 time grows longer.
Taking advantage of some unseasonably cool weather I had the opportunity to record the boost onset characteristics of the TTE550 turbochargers under conditions more like those when the BW K04’s (and FT21’s) were logged.
Shown below is the 2-11 time for the BW K04’s and TTE550’s. The 2-11 time represents how much time passes during boost buildup from when pressure reaches 2 psi and then builds to 11 psi. This measurement is made beginning at a variety of engine speeds typical of my normal driving state.
BW K04 vs TTE550 2-11 time
While the TTE550 clearly trails the BW K04s at all engine speeds the difference becomes less pronounced with increasing engine speed.
Ambient temperature does come into play when measuring boost onset. The chart below illustrates the response from the TTE550 under different ambient temperature conditions.
2-11 time with ambient temperature represented
The various measurements are grouped in range categories (degrees F) to make the presentation clearer.
This does obscure the fact that some of the differences in ambient temperature may be minor, or significant. For example, a reading can be made at 48 degF and compared with another at 50 degF that resides in a different category despite there only being a 2 degF difference. Also, within the same category one reading could be made at 50 degF and another at 59 degF.
Looking at this boost onset in a more familiar form, I have charted the boost onset at various starting engine speeds against engine speed. This chart was made from measurements taken at an ambient temperature of 41 degF.
TTE550 Boost Onset
Impressively, at lower engine speeds the TTE550 is reaching approximately 17.5 psi at 3000 rpm.
Prompted by a suggestion that a different orientation of the water shock / anti-surge accumulator would be better for this setup I took the time to rearrange the hoses for the accumulator and the nozzle supply.
The new orientation of the accumulator off of the tee has the fluid exiting the pump proceeding directly toward the accumulator, and then veering off 90 degrees to go to the nozzles.
A log with this new orientation is shown below:
Overlaying the two accumulator orientations leads to the chart below:
The difference around 3000 rpm is almost certain to be related to the manner in which boost built during the two sessions, rather than a result of the different orientation.
It is hard to discern if there has been any change to the quality characteristics of the flow with the change to the placement of the anti-surge accumulator; but there has not been any detrimental effects from the change so I plan to leave the accumulator in the new location.
