< PWR-EFI Refinement - Pat Williams Racing (porsche)

  With the drivability refinement tuning process complete on our stock 3.3litre shop engine equipped with PWR-EFI-1 complete, it's time to reinstall this car's original engine, a 3.3litre converted to PWR-EFI-1 and built with our package motor optimizing the benefits of our EFI for street and PCA DE applications.

  Though we cover this in more detail at our PWR Package Engine page, this package consists of the following:
PWR design pistons, valves/keepers/collars
38mm Intake system
Headers, BOV, intercooler, PWR mod'd turbo

  Pictured to the right, we've just finished transferring all the pertinent EFI conversion components and transmission from the stock engine to our package engine which is now complete on the cart with the exception of the air cleaner and pipe elbow ready to install back in the car. As with the EFI equipped stock engine, starting with our base engine dyno map, we'll perform drivability refinement mapping.

  With our ECU running in closed loop mode via interface and wide band lambda sensor, now dynamically enabled to self-write its map to our AFR targets, we've performed daily drive cycles manually monitoring our AFR when replicating operating segments needing improvement so that we can make manual table adjustments before saving the map to the ECU and repeating the process. After completing our map for this engine equipped with the typical performance muffler we repeated the entire process running an open exhaust to ensure that if an entirely new map was required, we would have one in our archives for PCA club racers and DE participants desiring to have their ECU's re-programmed for a driving event.

  So what kind of results can you expect with a PWR package engine built to optimize your PWR-EFI-1 conversion? Here's the dyno chart for this first developmental engine from February 2004 in which it produced 544hp at the crank at only .9 bar boost on 91 octane pump gas. Here also is a dyno chart taken in Mid October 2006 for one of our first customer installations now with 14,000 trouble free miles. It's loosened up nicely...478RWHP and 399lbft of torque.

  The fallacy of focusing strictly on peak horsepower only and why a broad torque band is better for the street. Your engine is an air pump. Turbocharging enables engines not optimized in their build criteria to develop high horsepower levels by literally stuffing air into them to produce high torque figures, albeit only attainable at low rpm levels. Boost cannot overcome breathing inefficiencies at higher rpm. The narrower your rpm range for a given peak torque number, the less operating flexibility you'll have - tolerable for racing conditions but unrewarding for the street.

  Correspondingly, cylinder pressure is proportional to torque because torque measures force and work output. The lower the rpm point at which greater torque is produced the longer the dwell time for each combustion event producing this torque resulting in higher sustained bearing/ring land loading and heat generation/retention - the latter driving up octane requirements to produce detonation free performance in this more demanding operating environment.

  One thing you'll note about the above dyno chart and any we publish. Most any large capacity 930/911 turbo engine dyno chart you've seen heretofore shows power flattening off around 5,700 to 5,900rpm as the engine loses breathing efficiently above this rpm, thus the torque begins to flatten and the power falls.  In the pursuit of a broad torque curve,  pushing that torque up the rev range also bought us more horsepower because only torque is measured, horsepower is calculated (torque X RPM divided by 5252)). Therefore, you don't have to produce more torque to get more horsepower, just maintain a strong torque number under the graph curve and hold it higher up on the rev range, you'll register that appealing horsepower number, but most importantly for street gain superior drivability, it's that same RUF yellowbird 134mph quarter mile result with "only" 460hp analogy again.

As of December 09, our first EFI system you saw on the dyno in 8/03 is still in this car with the same package engine and in daily use. No components have been replaced and any ECU mapping changes have been limited to adding refinements we have learned over 6 years of installing many systems on engines ranging from 2.4 litres to 3.8 and from stock to full race.