Category Archives: Misc.

New Turbo Project

I picked up a set of used FrankenTurbo F4H’s that are in need of a rebuild so I’m going to have a different center section installed.

FrankenTurbo F4H-BT Turbocharger
FrankenTurbo F4H-BT Turbocharger

Before refurbishing them I am going to have the turbine housings coated with the Swaintech White Lightning ceramic coating so I’ve started to disassemble the turbochargers.

FrankenTurbo F4H Center Housing
FrankenTurbo F4H Center Housing

The turbine housings will be sent off alone, saving a few bucks on shipping, and making it easier to coat them without the rest of the turbocharger.

FrankenTurbo F4H-BT Turbocharger Turbine Housing
FrankenTurbo F4H-BT Turbocharger Turbine Housing

SRM IC Temperatures

I’ve not had much opportunity to assess how the Silly Rabbit Motorsport side mount intercoolers compare with some other IC’s that I have used, under conditions beyond a FATS pull.

Recently temperatures have been in the mid 90’s so I made some recordings of Intake Air Temperature to gauge how these intercoolers fare.

silly rabbit motorsport side mount intercooler

The first chart is of the IAT’s and boost pressure during a session of assessing how boost onset looked at various engine speeds for the Turbo Concepts Stage 1 turbochargers that my S4 is presently operating with.

Boost is repeatedly requested with a short period of recovery taking place while the engine speed settles back to the next starting value.

Not surprisingly during the period of repeat boost events the intake air temperatures are increasing.  During four mintues of steady state driving at 50 mph the IAT’s return back to a value approximately 20 degF over ambient.

The next log was recorded during an afternoon commute.

Once again when steady state driving takes place the IAT’s settle to approximately 20 degF over the ambient temperature.

Is it Real or is it DynoJet?

Recently it has seemed to me that a large percentage of dyno results that have been made public are developed on a DynoJet brand dynamometer.   I like the consistency that a DynoJet has with the measured wheel horsepower and this is the brand of dyno I seek out when I look for a place to have my S4 dyno’d.

The frequency that I have put my car on a DynoJet, along with the abundance of street logs that I have recorded, provides a good collection of results to use to compare the two methods for estimating vehicle wheel horsepower.

The summary below shows the setup that my S4 had and the DynoJet generated whp and the road acceleration derived whp.  The last column to the right shows the amount of change between the DynoJet and road measurement.

DynoJet vs Street

Comparison of Peak Wheel Horsepower Measurement by Method
SetupDynoJetRoad% Change
K03 Stk2372168.9%
K03 Nef2832588.8%
FT F4H3843635.5%

From these seven data points the average change from DynoJet to street is about 6%.

Another source of wheel horsepower also derived from street data is the calculation made by the ECUxPlot program.  The application appears to take into account similar variables, but I suspect something may have been left out, or is assumed to have less influence, as compared to the assumptions I make in my calculations.

Shown below is a series of pulls made by my car with the calculated wheel horsepower displayed:

ECUxPlot Calculated Wheel Horsepower
ECUxPlot Calculated Wheel Horsepower

These same logs when evaluated using my calculations produce the following:

ECUx Calculated Wheel Horsepower
ECUx Calculated Wheel Horsepower

It may not be immediately clear, but the calculations I have made are greater than the results calculated by ECUxPlot.  Out of the four data points, ECUxPlot reports a peak wheel horsepower value about 4.5% less than my calculation.

So which is more accurate?  I’m not sure, I have found that my calculations more closely match the results that were recorded on a Mustang Dynamometer but who’s to say how accurate that dyno was.

TiAL 605 Dyno Race Gas
26 PSI – 100 Octane – No WMI

An outcome of this comparison is, if it is assumed that the commonly used ECUxPlot is more accurate, the difference between DynoJet recorded wheel horsepower and that from ECUxPlot would be even greater than what I have calculated.

Using ECUxPlot’s calculations, the results are on average 9.2% less than that reported by the DynoJet.


I am reasonably confident that the street measured results are more accurate than the DynoJet values.  The DynoJet would seem to read above truth by somewhere from 6% to 9.2%.