Category Archives: Flow Tests

Flow Testing Y-Pipe Prototypes

Background:

It’s been some time since I tested any parts for the B5 S4 but when I was contacted by Torque Factory (TF) Consulting wondering if I would be willing to flow test a Y-pipe they are developing I agreed to.

Audi B5 S4 Y-Pipe Flow Testing
Y-Pipe Flow Testing

Previously I have tested the stock S4 Y-pipe as well as the B5 RS4 Y-pipe. For this test the products would consist of the Torque Factory prototype as well as The Tuner Y-pipe.

Audi B5 S4 The Tuner Y-pipe
The Tuner Y-pipe

Two MAF pipes were supplied, one 4″ and the other 4.5″ in diameter. The 4.5″ pipe contains a removable flow straightener.

Because these products are larger than the S4/RS4 parts I have previously tested I needed to make a new adapter to attach the products to the flow bench.

Flow Bench to MAF Pipe Adapter

3D printing comes in handy for creating the adapters needed to join parts with the flow bench.

Test Procedure:

Prior to measuring the airflow through the parts a calibration plate is installed on the flow bench to check for accuracy. Once that has been completed the Y-pipe is attached to the MAF pipe using a silicone coupler and the MAF pipe is attached to the flow bench using another silicone coupler that attaches to the flow bench adapter.

A MAF sensor is installed in the MAF pipe and the PCV port on the Y-pipe is blocked off.

The previous testing with the S4/RS4 Y-pipe had been performed at a depression of 10″ of H2O. I found with the larger components used during this test that the flow limit of the bench, roughly 650 cubic feet per minute (CFM), was being met before reaching 10″ of pressure drop through the test article.

Audi B5 S4 THE-Tuner Y-Pipe Flow Test
THE-Tuner Y-Pipe Flow Test

For this reason 6″ of H2O was chosen as the default test depression for taking measurements.

Several combinations of Y-pipe and MAF pipe were flow tested.

Torque Factory Consulting Y-pipe Flow Test
Torque Factory Consulting Y-pipe Flow Test

Test Results:

The table summarizes the readings for each of the combinations tested:

Y-Pipe
Test Case
MAF PipeFlow
Straightener
Airflow
@ 6″ of H2O
TF-14.5″Yes641
TF-24.5″No686
TF-34″N/A644
THE-14.5″Yes560
THE-24.5″No537
THE-34″N/A518

This data is presented in bar chart format along with the measurements for the S4 and RS4 Y-pipes:

Torque Factory Y-Pipe Flow Test Bar Chart
Flow Test Results Summary

A calculation can be made with the measured data to predict the airflow at a higher depression than what was tested.

Because the S4 and RS4 Y-pipes were tested at 10″ of H2O an extrapolation is made with the data for the Torque Factory and THE Tuner Y-pipes to estimate what they might flow at a depression of 10″ of H20.

The predictions are shown on the chart below, represented by the segment of the lines that are dashed.

Conclusion:

A flow bench test was performed to measure the airflow through different combinations of Y-pipe and MAF pipes using a Torque Factory Consulting prototype Y-pipe and a production version Y-pipe manufactured by THE-Tuner.

Comparing the results of this test with previous results using the S4 and RS4 Y-pipes both the Torque Factory and THE-Tuner Y-pipes flowed significantly more air at the test depression.

Of the various combinations tested, the Torque Factory prototype using a 4.5″ MAF pipe without a flow straightener produced the highest airflow, 686 CFM @ 6″ of H20.

Audi B5 S4 Prototype Y-Pipe Flow Test
Prototype Y-Pipe Flow Test

References:

THE-Tuner product page

Torque Factory Consulting

Silly Rabbit Motorsport and White Dog Racing Intercooler Matchup

As mentioned a few posts back, I have access to a pair of the latest SRM side mount ICs for the B5 S4 along with the White Dog Racing side mount intercooler option for the B5 S4.

Silly Rabbit Motorsport and White Dog Racing Side Mount Intercoolers
Silly Rabbit Motorsport and White Dog Racing Side Mount Intercoolers

Yesterday I took the opportunity to measure the Silly Rabbit Motorsport IC on the flowbench.  Before taking similar flow measurements on the White Dog Racing side mount ICs I took some dimension measurements of the two products to see how they compare.

The table below summarizes how the specs match up:

Silly Rabbit Motorsport & White Dog Racing IC Specification Matchup
Silly Rabbit Motorsport & White Dog Racing IC Specification Matchup

Deciding upon a standard arrangement to test these two intercoolers with was not entirely straight forward.  Each is supplied with a hose kit that differs substantially from the other.  The SRM ICs are delivered with a set of silicone hoses and the WDR ICs have a set of metal inlet pipes along with silicone hoses.  The silicone hoses between the two vendors differ in shape and length.

Because I had already measured the SRM intercoolers I chose to utilize the SRM hoses with the WDR intercoolers.  As the goal was to determine how the intercoolers compared, keeping a standard hose arrangement seemed to be the best way to measure on a level playing field.

The two configurations I chose for comparison were first with the core having no inlet pipe and the SRM hump hose connecting the core to the flow bench.

White Dog Racing Audi B5 S4 Side Mount Intercooler on Flowbench
White Dog Racing Audi B5 S4 Side Mount Intercooler on Flowbench

Then the second setup was with the same silicone hose on the outlet, with the addition of inlet piping.  The inlet piping consists of the hose that joins the hard pipe with the turbocharger compressor housing outlet, the hardpipe, and the SRM silicone hose.

Silly Rabbit Motorsport Cast End Tank Intercooler
Silly Rabbit Motorsport Cast End Tank Intercooler

All tests were done on the driver side intercooler and inlet piping.

Under these standard arrangements the following results were measured:

SRM vs WDR Flow Test Results
SRM vs WDR Flow Test Results

The White Dog Racing intercooler produced slightly greater airflow in each test case.  The gains in each are approximately 4% over the SRM intercooler.

Conclusion:

As mentioned when I first saw the SRM IC with cast end tank, I liked the way the tank had smoother edges than the previous end tanks, but the reduced cross section of the inlet and outlet piping was concerning.  It cannot be determined from these tests what design differences led to the outcome, but a reduced cross section into and out of the intercooler versus the competitor is not going to help.

Airflow is an important aspect of intercooler performance, but the device is called a ‘heat exchanger’ for a reason – in the future I plan to assess how well the WDR intercooler cools.

More SRM SMIC Flow Testing

I have a set of SRM SMICs on hand that differ from the ones on my S4 with respect to the end tanks.  These new arrivals have cast end tanks.

The cast end tanks look smoother than the end tanks I am using which might lead to a slight improvement in airflow, but something else that has changed is that the inlet and outlet piping are a bit thicker than on the welded end tank.

The inner diameter of the inlet/outlet on my ICs is 2.375″, on these cast tanks the inner diameter is 2.18″, this could be a detriment to better airflow.

I put the driver side intercooler onto the flow bench to get a reading without any piping on the inlet side.

SRM Cast End Tank SMIC
SRM Cast End Tank SMIC

This arrangement flowed 301 CFM @ 28″ of H2O.

Next I attached the supplied SRM intake coupler hose and retested.

SRM Cast End Tank SMIC
SRM Cast End Tank SMIC

The flow dropped as expected, down to 279 CFM @ 28″ of H2O.

As a final check I attached the rest of the inlet piping that would connect the intercooler to the turbocharger.

Silly Rabbit Motorsport Cast End Tank Intercooler
Silly Rabbit Motorsport Cast End Tank Intercooler

The airflow dropped further, down to 228 CFM @ 28″ of H2O.

The drop in airflow with additional inlet piping is not unexpected and lacking a comparison intercooler these numbers don’t tell much.

SRM Cast End Tank Airflow Summary
SRM Cast End Tank Airflow Summary

Tomorrow I plan to run a similar series of tests with the White Dog Racing side mount intercooler to see how it compares.