November 11, 2009
March 21 Mod Shop Makeover
AOPA's "Win A Six in '06" Sweepstakes airplane has been spending the past two weeks at LoPresti Speed Merchants' shop in Vero Beach, Florida. There, two main modifications are being made to the airplane - both designed to improve the Six's cruise speed.
The first mod to be installed - LoPresti's newly designed wheelpants for the Cherokee Six and Saratoga - went on quickly. Though they may look bulbous and chunky, the "Speed Spats," as LoPresti likes to call them, do a fair job of reducing drag.
Test pilot and Speed Merchants President Curt LoPresti made his first test runs in our/your Six and came up with some interesting data. First, he discovered something that I already knew but hadn't fully quantified: that the stock airplane yielded cruise speed numbers faster than those advertised in the pilot's operating handbook (POH) - before any speed mods had been installed.
The POH says that you're able to cruise at 162 mph/141 knots true airspeed at 6,000 feet and standard conditions. But the newly overhauled engine pushed cruise true airspeeds to 171 mph/148 knots. LoPresti calculated that Ultimate Engines' custom overhaul upped engine power by approximately 16 horsepower, in effect transforming a 260-hp engine into a 276-hp mill. This was with the engine set at maximum continuous power and exhaust gas temperatures (EGTs) set at 100 degrees rich of peak.
As usual for a newly overhauled engine, cylinder head temperatures (CHTs) register hotter at this high power setting. Where I was seeing 388-degree CHTs with my super-rich cruise power settings on my cross-country delivery flight from Arkansas to Vero Beach, LoPresti was seeing an occasional 400-degree reading during some of his test flights.
After the Speed Spats were installed, LoPresti charted a 10-mph/9-knot increase in cruise speed compared with stock wheelpants. This made it a 181-mph/158-knot cruising machine. So the big news is that first tests showed a 17-knot hike in cruise speeds! And LoPresti's new Six/Saratoga cowling mod had yet to be installed! (LoPresti claims a 6-mph/5-knot increase in cruise speed with the new cowling.)
The cowling comes with some distinctive design elements. Most noticeable are the round cooling inlets and large cowl flap. The former accelerate cooling air as it enters the engine; the latter helps dissipate engine heat. Less obvious are the belly fairing and new induction air system ductwork. This cowling is not just a bolt-on, turnkey project. It involves a lot of components and requires 55 hours of labor to install. We'll also be adding one of LoPresti's Boom Beam Xenon high-intensity discharge landing lights to the cowling.
At this writing, LoPresti's flap seals and flap hinge fairings ("Speed Splitters") have yet to be installed. But when they are, LoPresti says we can add another 5 mph/4.5 knots to the cruise speed. If projections hold up, that means we'll have a 192-mph/167-knot Cherokee Six. As LoPresti likes to say, the speeds mods will give the fixed-gear Six the cruise speeds normally associated with the retractable-gear Piper Saratogas, which have 300-hp engines.
See the Win-A-Six at Sun 'n Fun I'll be able to check those new cruise speeds on my way to this year's Sun 'n Fun Fly-In at the Lakeland-Linder Regional Airport in Lakeland, Florida. This year, the event runs from April 4 through 10.
If you plan to attend - and we hope you do - make sure to stop by AOPA's big yellow tent. Parked right out front will be the Win-A-Six. Come on by and have a look at the new engine and propeller and the LoPresti mods. They make an impressive sight, and while the avionics, paint, and interior have yet to be completed, we'll have mockups of these for you to look over.
The LoPresti cowl has two large, hinged access panels that swing open to reveal the engine. Good thing, because they afford a good look at the level of detail that Ultimate Engines lavished on the Six's Lycoming O-540 decked out with ECi Titan cylinders. For the motorhead in you, it's a visual feast.
Another aspect of the Win-A-Six static display will be the daily presentations scheduled to be given by contributors to the sweepstakes project. At 1 p.m. each day from April 4 through 9, you can hear from those who donated or discounted their products and services to the sweeps effort. Don't miss them!
We'll also have AOPA Pilot staffers on hand to show off the Six's many features, and yours truly will be sure to be there to fill you in on the latest project details. See you there!
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