UWE Bristol Engineering showcase 2015

Chris Baguley
BEng Motorsport Engineering
Project Supervisor
Dr. Rohitha Weerasinghe
Investigating Naturally Aspirated Exhaust Manifold Design, to Develop
an Optimised Manifold for Motorsport use, using a VW Golf "KR" Engine
Case Study
Engine Analysis
As a starting point for exhaust design it is necessary
to first take a detailed look into the technical data for
the engine in question. For the purpose of this
investigation the engine being used is a Volkswagen
“KR” engine, consisting of a “051” cylinder head.
Initially, the standard “Kr” cams haft lift profiles were
plotted; as well as combustion chamber volume
measurement and a silicone exhaust port geometry
mould. These are combined with other engine
specific parameters to formulate an engine
specification sheet used for further testing.
Computation Fluid Dynamics (CFD) Simulation
Using figures recorded from flow bench testing of the
Volkswagen “051” cylinder head at peak lift, constant
volume flow CFD testing was conducted on a number
of collectors. To determine the most efficient as a
basis for 4-2-1 and 4-1 manifolds to be analyzed.
Comparing the results against the standard
manifold/downpipe system.
STD – Cylinder 1 Velocity Streamline
4-1 Cylinder 1 Velocity Streamline
4-1 Cylinder 3 Velocity Streamline
STD – Cylinder 3 Velocity Streamline
4-1 Cylinder 4 Velocity Streamline
STD – Cylinder 4 Velocity Streamline
4-1 Cylinder 2 Velocity Streamline
STD – Cylinder 2 Velocity Streamline
CFD Transient Flow Freeze-Frame of Standard Manifold and 4-1 Systems; at Peak Mass Flow Rate Time Steps.
Numerical Thermodynamic Gas Exchange
Model for Transient Flow Simulation
Formulating a numerical model for the incylinder
pressures during the exhaust phase
enables an effective series of data to be
produced, showing the blow down period. This
is the sudden drop in cylinder pressure, after
compression, at the point the exhaust valve
opens. Converting this into mass flow rate,
enables time dependent flow to be replicated
in both the standard manifold/downpipe and
4-1 system.
One Dimensional Engine Simulation – Ricardo
Wave
This case study models the Volkswagen “Kr”
engine, using all data gathered throughout the
previous processes, to enable a comparison of
power and torque curves for both the standard
manifold and 4-1 design. Providing an initial
indication of how the change in exhaust
geometry affects engine performance.
The 4-1 manifold has given a small increase in
top end horse power, at the expense of some
mid-range. Comparing the peak indicated
power figures of:
• Standard Manifold – 149.3hp
• 4-1 Manifold – 153.8hp
Shows a performance increase of 4.55hp,
equating to a 3% increase.
Project summary
Proper exhaust manifold design is a subject
often overlooked by even the most
knowledgeable tuners; so while it may look
impressive, appearances can be misleading.
This report investigates and details the design
criteria to be considered when developing an
exhaust manifold system for motorsport use.
Project Objectives
• Complete a numerical thermodynamic
engine simulation – to determine exhaust
gas flow.
• Plot “Kr” camshaft profiles – for
optimisation of the manifold system
designed
• Conduct a collector CFD study
• Compare 4-2-1 and 4-1 manifold designs
• Analyse transient and constant volume
flow of the standard “Kr” exhaust system
against the 4-2-1 and 4-1 designs
• Investigate the effects on engine
performance figures – using one
dimensional engine simulation
Project Conclusion
After completing a number of analysis tasks
on the Volkswagen “Kr” engine the results
suggest that is has the capabilities for
effective motorsport tuning. The 4-1 manifold
system designed offers a number of beneficial
flow characteristics, along side an indicated
engine power increase.