Previously I have tested a few different charge pipe products from aftermarket vendors as well as the stock GTI parts. When I was contacted by Vargas Turbo about possibly testing their charge pipes I decided it would be interesting to see how a silicone charge pipe fared against the metal and plastic versions.
As a single piece silicone part the Vargas charge pipe connects the turbocharger to the intercooler, and intercooler to the throttle body, doing away with the hoses and one pair of hose clamps that the stock, and metal options, used.
Flow testing is performed on each charge pipe individually and then by joining the pipes with a small length of silicone hose. This short piece of hose is a substitution for the intercooler. The silicone joiner hose has less pressure drop than an intercooler, which should allow the test to better represent how well the charge pipes flow.
The charge pipes are attached directly to the flow bench using an adapter that is sized to fit inside of the charge pipe and the inlet of the charge pipe has a bell-mouth attached to help direct air smoothly into the pipe/hose.
The flow bench is operated at a depression of 28″ of H2O and the airflow through the pipe is measured at this depression.
Airflow for each pipe arrangement are listed below:
- Hot side charge pipe: 392 CFM
- Cold side charge pipe: 595 CFM *
- Both charge pipes: 362 CFM
Note: The cold side pipe (*) was tested at 26″ of H2O and extrapolated to 28″
These measurements are compared with the stock GTI charge pipe in the chart:
A summary of all of the charge pipes that have been flow tested is shown in the next series of charts:
The Vargas Turbo silicone charge pipes for the Mk7 GTI were flow tested using a flow bench. Compared to the stock GTI charge pipes the Vargas Turbo product produced gains of 43% on the hot side, 30% on the cold side, and 34% with joined charge pipes.
Airflow Sensitivity Investigation
While testing the charge pipes a couple of different arrangements of bell mouth to charge pipe were tried and the results demonstrate the ability of the flow bench to differentiate subtle changes.
The Vargas hot side charge pipe was tested with each configuration of the bell mouth to the hose and shown above and the results are summarized in the chart.
A couple of points to make about the results as they apply to optimizing and testing of these parts:
The improvement in airflow in the “flush” and “inside” cases were 5.5% and 13.6% versus the “over” setup. Relatively subtle changes to the arrangement of the parts can result in decent airflow gains.
Looking at the images of the “over” and “flush” cases does not give the impression that there would be an ~ 20 CFM difference in airflow. This is an example of the type of small changes that the flow bench is able to pick out.
This is very handy when performing detailed work, such as porting an intake manifold or cylinder head, but can give an impression that there is a large change in performance if care is not taken to consider how the resolution of the flow bench differs from other measurement tools that one may be more familiar with.