X-Prize Sonata Cylinder Head Modifications

2008 Hyundai Sonata Cylinder Head Modifications

For Performance & Economy

This paper is designed to cover cylinder head modifications commissioned by Randy Timmerman on a 2008 Hyundai Sonata 2.4 liter DOHC 4-cylinder head.  The head work and this paper were done by Mike Holler.  The objectives of the modifications are to dramatically improve fuel economy and performance while reducing regulated exhaust emissions in the normal street driving range.  The four areas of interest are the intake ports, exhaust ports, combustion chambers, and valves.  This paper outlines the modifications performed, and the objectives these modifications are intended to address.

Shown in the next several pictures are the stock ports and combustion chambers.

The combustion chamber and bowls represent a typical 4-valve arrangement.  This same style of configuration is typically found on hundreds of different engines throughout the world.

The exhaust ports are somewhat unusual in that the two individual ports converge into a round discharge opening, where the exhaust gasses enter the exhaust manifold.  Several other head designs incorporate this style, but it is certainly not the majority of heads represented in production.  It does offer unique opportunities to improve performance and exhaust emissions as will be outlined forthcoming.

The intake ports represent the industry standard lay-out.  Considering the intake valves only open to 0.172” (43.8 mm), it became obvious that the velocity in the intake ports was extremely low.  Higher velocities would improve the areas of concern.  Modeling clay was used to create a profile that would improve velocities, and induce higher swirl inside the cylinder.

The clay represents a technique of raising the port on the one side while lowering the port on the other.  One of the ports will allow the air/fuel charge to enter the cylinder in a straight-in fashion at the tangent of the cylinder bore, while the other port will force the charge high, arching in and splaying off the back side of the intake valve.  This dramatically improves the homogenization of the air and fuel within the intake charge, while inducing a motion that carries through the ignition cycle.  This assists in flame propagation for a better burn.

After testing on the flow bench, the design was deemed appropriate and the clay was removed and replaced with epoxy.

This bias is obvious in the pictures.  The “screw threads” (called “Powre Lynz”) add a boundary layer characteristic that promotes higher velocities, better fuel vaporization, and better homogenization of the air and fuel.  As will be shown later, this same principle is applied to the backs of the intake valves.  These modifications were done by hand and were time consuming.

A bias was also applied to the exhaust ports.  The intake ports allow the use of epoxy, whereas the extreme heat found in the environment of the exhaust ports prohibit the use of epoxy.  Therefore it was decided to meet the objectives by removing material only.

Also shown in the last 2 pictures is the radiusing of the sharp edges where the “squish pad” transitions into the open area of the combustion chamber.  This was performed on both the intake and exhaust sides.  There is usually a small lip or ridge surrounding the exhaust valves.  This lip was opened up to the edge of the cylinder wall to enhance exhaust flow past the valves by removing a source of unwanted turbulence.  Here is a side-by-side to compare modified combustion chamber to stock:

The next area of attention is the valves.  The intake valves were modified by adding concentric rings to the back sides (called “Powre Valvz”).  As the air and fuel enter the cylinder, the fuel tends to bounce off the intake valves.  By adding a texture, more of the fuel is broken up into smaller droplets, and even vaporized as it interacts with the hot textured valve.

The exhaust valves were cleaned and electroplated with a flash coat of nickel.  The exhaust valve is the hottest part of the combustion chamber.  By adding a catalyst to the hot exhaust valve, ionization prior to ignition enhances the rate and quality of the burn within the combustion cycle.

Development for this cylinder head was done with the aid of a Super Flow SF-1020 SB flow bench.

Porting the exhaust improved flow at valve lift by 12 CFM, or 9.5%.  Measurements were done at 28” WC depression in the exhaust direction.

Using only clay no material was removed from the aluminum ports.  A net loss of 2 cfm resulted at valve lift (@28” WC).  Using the epoxy and reshaping the ports a net gain of 3.2 cfm resulted.  Adding progressive pitch Powre Lynz brought the flow bench numbers back down to a net loss of 4.2 cfm.

The intake valve was opened to 0.170” and flowed at progressive depressions.  The above chart compares the epoxied and ported intake with the normal as-ported texture, then with the Powre Lynz using stock intake valves, then with the addition of the Powre Valvz.  At 28” WC pressure, the flow is only -4.6 cfm from the stock numbers (139.6 cfm stock versus 135.0 cfm in final configuration).  The objective is to make better combustion efficiency through better air/fuel preparation versus improving volumetric efficiency through higher flow numbers.

Return to X-Prize Sonata