Category Archives: Testing

Dynocom accuracy estimating

The recent posts about JAEInnovation’s builds have introduced a dynamometer that I previously had not heard of, a Dynocom.  As those posts pointed out, I did not have data available to crosscheck the accuracy of this dyno, so statements about vehicle wheel horsepower are of low confidence.

I was in touch with a person who had their S4 measured on this dyno (operated by Doman8 Performance), and they informed me that data logging was showing a FATS of 3.2 seconds and the dyno chart produced by the Dynocom measured a peak of 480 whp.  The wheel horsepower curve is reproduced below:

Dynocom 480 whp pull
Dynocom 480 whp pull

To try and estimate what the accuracy of the dyno is I began correlating the wheel horsepower curve with the FATS time.  The first step was to pull samples of the wheel HP data over the FATS pull range, taking samples at every 250 rpm beginning at 4250 rpm and continuing to 6500 rpm.  These points are shown in the chart above highlighted in red.

The average whp of these ten points is 412.  The median value is 435.  I decided to use the median because the peaky curve allows the low figures at the start to pull the average down substantially.

The dyno chart showed that a 6% correction had been applied for atmospheric conditions.  As has been previously mentioned, this correction should not be applied to a boosted engine.   After backing out the atmospheric correction factor the result is 410 wheel HP.

Now I look at how the FATS average wheel HP calculator compares with this value.

Chart produced by rktskicar

A FATS time of 3.2 seconds should be the product of an average wheel HP over the FATS range of approximately 380 whp.  The result I estimated from the dyno chart was 410 whp.

If the Dynocom has a similar difference to road values as the Dynojet, which I have found to differ by approximately 6%, the Dynocom average wheel horsepower is more likely 387.

The FATS estimate of 380 whp compares well with the adjusted Dynocom estimate of 387 whp.

If the peak wheel horsepower reading of 480 is adjusted in accordance with this process the result is a peak of 427 wheel horsepower.


A single data point is not something to rush out and use to define the accuracy of the dyno.  On the other hand, it’s better than nothing, and the results obtained point to agreement between the two methods of arriving at the average wheel horsepower.

Wrapped Turbo Inlet Pipe – Part 2

The latest component to get wrapped is the upper half of the turbo inlet hard pipe, this is the section that connects to the Y-pipe coupler hose.  I wrapped this section in the DEI Reflect-A-Gold tape.

DEI Reflect-a-Gold Wrapped TiAL Inlet Pipe
DEI Reflect-a-Gold Wrapped TiAL Inlet Pipe

At this stage most everything from the inlet snorkel to the turbocharger compressor inlet is now wrapped in some way or another.  The part that isn’t wrapped is the airbox snorkel, and I’ll probably do something with it next.

DEI Reflect-A-Gold tape wrapped TiAL inlet pipe
DEI Reflect-A-Gold tape wrapped TiAL inlet pipe

I went and drove my usual route recording the intake temperatures.  Rather than post up the composite chart, because it is getting very busy, I’m going to post the temperature deltas of the last two and first two recordings that I made.

Chart of Wrapped Hard Pipe Morning Drive
Wrapped Hard Pipe Morning Drive

The morning drive has two fewer data series than the afternoon drive, only going up to 7.  Drive 1 is in the normal configuration that I had prior to doing any of the wrapping.  The 2 series is the same but with the Darintake holes covered.  Series 6 and 7 are with most of the wrapping in place, through to the Y-pipe in 6 and the hard pipe in 7.

The afternoon drive data with similar data series is shown below.

Chart of Wrapped Hard Pipe Afternoon Drive
Wrapped Hard Pipe Afternoon Drive

These results show very little difference between the ‘untreated’ inlet piping and the ‘treated’ pipes with all of the wrapping in place.

Wrapped Y-Pipe Temperatures

Continuing down the intake I’ve gone and wrapped up the RS4 Y-Pipe.

Foil Wrapped B5 RS4 Y-Pipe
Foil Wrapped B5 RS4 Y-Pipe

It’s quite the beaut now, with Duct Insulation wrapped around the entire thing.

Duct Insulation
Duct Insulation

Seeing as how the Y-pipe is an ‘air duct’ applying this material seems proper.  It consists of a foam layer about 3-4 millimeters thick with a reflective coating on one side and adhesive on the other.  The advertised R value for the material is R-3.

Taking the S4 out for my usual drives produced the following results in the morning:

Morning Drive with Wrapped Y-Pipe
Morning Drive with Wrapped Y-Pipe

Later in the day I repeated the procedure recording in higher ambient temperatures.

Afternoon Drive with Wrapped Y-Pipe
Afternoon Drive with Wrapped Y-Pipe

Adding these latest drives into the collection that I’ve got going yields the following charts:

Morning Drive Comparison
Morning Drive Comparison with Wrapped Y-Pipe

Afternoon drive:

Afternoon Wrapped Y-Pipe comparison chart
Afternoon Wrapped Y-Pipe comparison chart

I was hopeful that this extra heat protection would produce some benefit, the Y-pipe sits directly on top of the engine and seems like a good candidate for some insulating material.

There are moments in the drive when the temperature with this latest modification is lower, around approximately 5 degrees F.

Without digging deeper into the data my initial call is that the wrapping did help some.