Why Beyond the Numbers is Important

In this day and age of better, faster, cheaper the inevitable question of why certain things cost what they do always crops up.  Clearly the price of an item is one constituent in the equatio to its overall value.  We stress the term value here because that's what really matters.  So what is value?  Value represents what you get for your money.  Let's not confuse value with price.  Price is just that, what you have to pay to get the goods or services.

The systems we build here represent the best value in the realm of forced induction.  While it is hard to not start rambling on about the inherent benefits the turbo has over other forms of forced induction, we will stay focued on the topic at hand, that being value.  So, therefore we present below some of the hidden features on our flagship Porsche 32V M28 Twin Turbo system.

Let's talk about exhaust manifold for a minute.  These represent the starting point of any turbo system, twin or single.  Our manifolds are backed by hundreds of hours of development time and have been designed to fit into the cramped engine bay of the Porsche 928 without causing the power robbing features found in some turbo manifolds.  We present the photo below of our latest design coupled with the Garrett GTX3071 turbocharger.  The manifolds have short runners, but with smooth transitions into the main flow and are ceramic coated to cut down on radiant heat in the engine bay.  Cast versions of these parts are currently in development.  Realize that the exhaust manifold is the starting point for any turbo system.  The starting point if you will in the chain series of events to take the engine from normally aspirated to forced induced condition.  The job of the exhaust manifold is to deliver an as in-tact as possible exhaust pulse to the turbine wheel to power the compressor.  It has to do this job over a wide range of temeratures and pressures in a brutal environment without sagging, warping, cracking or just simply falling apart.  Thin walled tubular manifolds are great for race cars where limited hours of use are expected, but on a vehicle like the 928, durability is as important as performance.  Our designs acheive the perfect balance of the desirable attributes of a turbo manifold.

Where the intake manifold has the task of delivering the pulses in-tact to the turbine wheel, the wastegate and downpipe have the test of bypassing and getting the spent gasses away from the turbine wheel.  Proper wastegate function means picking off the pulses in an area where all pulses have combined.  Internal wastegates do this well, but can limit flow on a big power engine thus causing a boost creep issue.  Remote wastegates are almost always a more desirable solution as they maintain a higher diaphragm to vale area ratio thus making them easier to control and modulate.  Smooth transitions here are key, as is cross sectional area and the ability to control the thermal expansion.  Let's talk about that for a second.  The gasses leaving the turbine can be in excess of 1000F and are always lower than the gasses entering the turbine (gas temperatures across the turbine drop due to engery given up in powering the turbine).  Restriction on the back side of a turbine housing is a big no-no.  Restriction here will always show up as more heat.  More heat into the charge and more heat against the heads.  If you study our designs closely, you'll see a very clean approach.  Downpipes are a full 3" right from the turbine and include expansion joints for compliance thermally as well as mechanically into the remainder of the exhaust system.  Wastegate pipes are fully divorced and are 1.75" diameter.  Notice how the wastegate pipes intersect the main exhausat pipe at a shallow angle and on the inside of the radius?  That's not a coincidence of the layout, but rather part of the functional design of the part.  Consider for a moment what happens to the wastegate pipe as the wastegate transitions from closed to open.  You can easily see that the pipe goes from a lower to a higher temperature, perhaps by several hunderd degrees.  The change in length is a function of the alphs value of the material, the length of the material and the temperature change of the material.  Clearly an expansion joint here is mandatory, not a "nice to have".  We see downpipes all the time that inject wastegated gasses into the main downpipe with no provisions for thermal expansion and at right angles.  How well do you suppose that works and how long will it last?

 Once the turbo is properly supported and hung in a manner such that the hot side can get the maximum possible amount of work from the enthalpy in the exhaust gas, it is important to then feed the compressor side with air which is as close to ambient temperature and pressure as possible.  This becomes incredibly difficult in a cramped engine bay, but we have made every effort to get the air to and from the turbocharger in the best possible manner.  This is one reason twin turbos were selected for the 928s engine bay instead of a single.  Two 2.75" suction side pipes outflow one 3" suction pipe...ever time.  Likewise, two 2.25" pressure side pipes outflow one 2.5" pressure side pipe.  You get the picture here after working in a cramped engine bay for any length of time.  We start by routing cold air in front of the radiator through large high-flow air filters.  Let's dwell on this seemingly simple aspect for a moment.  Consider what makes a good air filtration system.  In the ideal world of the automotive aftermarket, the air filtration woudl; provide ample filtration to allow a long service interval between cleanings, pick-up cool air, place the filters where visual inspection is easy, place the filters where replacement or repair is easy, and finally add to the overall aesthetics of the system.  We believe our design hits all of these details eloquently.  Again, it's about finding the best possible solution that meets or attempts to meet all of the desirable features.




© 2011 Kuhn Performance Technologies.