Built by Jorge Cuartas, Rick Sosebee & Brad Skelton
Building a "Short Course/ Stadium" racing UTV on the heavily wooded East Coast makes about as much sense as building an all out "Snowcross" sled in sunny South Florida, yet for some unexplainable reason, it's exactly what we decided to do with our somewhat beat-up '08 Polaris RZR.
Not long after building our GNCC-specific woods racer (Nov. '08) Polaris released the RZR-S model. The "S" model's wide stance and increased stability make it a natural jumper, and the ideal "Short Course"-style racer. With the woods segment effectively covered, we set out to build an "S" of our own, unfortunately for us, the only RZR left in our stable was a highly abused '08 unit. The allure of MX with a roll-cage was intriguing though, and the abused unit would have to do.
The Fluidyne radiator's 33%...
The Fluidyne radiator's 33% wider water passages keep the Big Bore Holz motor cool enough to run for hours at peak power.
Being that our RZR motor had a hole in it that you could pass a grapefruit through, the decision to start by yanking the powerplant was pretty easy. Seeing that we were going to have to deconstruct a sizeable portion of the machine for the engine removal, we decided to just go ahead and strip the unit down to a bare frame. Two piles were formed, with junk going into one, while salvageable parts would go into the other. And as always, the junk pile seemed twice the size of the other. The junk wasn't necessarily garbage, just parts that we'd rather replace with trick aftermarket goodies. Among them were the stock wheels, tires, plastic, A-arms, shocks, CV axles, seats, steering wheel, exhaust, headlights, roll-cage, taillights, sway bars, radiator, bumpers, seat belts, steering wheel height adjuster, ECU, throttle body, cylinder, head, skidplates, air filter, airbox assembly, battery, clutch and shift knob.
The salvageable parts were either bead blasted or polished on our wire wheel until they looked new. The plastic floorboards, and bed pieces were pressure washed and detailed using Maxima SC1 silicone detailer. While time consuming, the entire process guarantees a clean look, and the detailing offers a great opportunity to inspect the parts for wear or damage. The stock wiring was trimmed down by removing anything that didn't directly relate to running the motor (i.e. lighting and accessory wiring).
The RZR was relegated to a...
The RZR was relegated to a bare frame once the replaceable parts were stripped off.
Just like the rest of the project, our motor would require a complete overhaul. But rather than settle for a stock rebuild, we would be going all out. After all, jumping a 1000+ pound machine requires serious horsepower, and that kind of hp is achieved one of two ways: a turbo or a big-bore kit. We initially wanted to do both and were working toward that end until our conversation with the folks at Holz. A quick glance at their dyno chart provided all of the evidence we would need that the Holz/Kroyer Stage 3 motor kit would be more than enough. The kit runs on pump gas and is comprised of an 81.5mm big-bore cylinder & piston Kit, CNC ported head with oversize valves and springs, billet cam with new lifters and chromoly push rods, 46mm bored throttle body, billet intake manifold, adjustable PRV (oil pressure relief valve), Team Clutch kit, ECU upgrade tuned specifically for the Kroyer motor kit, all of the necessary gaskets, spark plugs, Joe Gibbs Break-in oil, and even an OE Polaris oil filter (core exchanges were required on the cylinder, head, throttle body, and ECU).
The turnaround time on the kit itself was pretty shocking, as everything actually arrived close to the time it was promised (almost unheard of for motor builders). Upon arrival we were pleasantly surprised to see the attention to detail the Holz folks took in preparing their instructions and packaging the components. Everything was labeled, and the instructions were thorough. ATVR staff motor-builder extraordinaire Rick Sosebee tackled the motor assembly task and painstakingly checked and rechecked the torque on every bolt and the tolerances on every part while assembling the beast. Rick's meticulousness was par for the motor package as a whole.
We paired the Holz Stage 3 kit with a few non-Holz parts, the first of which is Dragonfire Racing's RZR Race Filter. The canister-style intake system is a full replacement for the factory intake system. DFR boasts 80% increased airflow as compared to single inlet filter systems, and the velocity fins remove up to 85% of incoming particles before they even reach the filter. The filter element requires no oil (which can cause damage to engine sensors) and removes up to 99.99% of the remaining particles in the air.
Exhaust duties fell into Muzzys lap. Muzzys stainless steel system with dual oval stainless black Teflon mufflers not only looked great but fit like a glove. The full stainless 2-1-2 design, is trick looking and easy to assemble. The Teflon coating on the mufflers offers a nice contrast and stands out against the billet aluminum muffler mount brackets (which are made specifically for long-travel suspension kits). The Muzzys come with an integrated oxygen sensor bung (which allows the addition of an air/fuel meter) and numerous heat shields. The system is USFS approved and sounds about as mean as you could imagine without being obnoxious.
In order to keep the whole thing running cool, we contacted Fluidyne and installed one of their high-performance radiators. The increased efficiency of the cooling system allows the motor to maintain peak horsepower via 33% wider water passages. The Fluidyne radiator cores are a good bit thicker than the stocker, providing increased surface area and better all-around cooling. Choosing Fluidyne was a no-brainer thanks in part to the rugged construction of the radiators themselves: Aircraft-quality aluminum, TIG-welded tanks, furnace-brazed aluminum cores, billet filler necks, and beaded inlet/outlet hose connections all combine for a nearly bulletproof product. We actually opted for the OEM install location since rollcage-mounted radiators scare me half to death. The thought of boiling water that close to my neck and back in a machine that I will most likely be rolling just doesn't sit well with me.