Vintage Spyder - Show And Go

Few engines have been bored, stroked, and tweaked as much as VW’s aircooled flat four. But harder isn’t the only way to go. Beauty and brains can be a great combination as well. If you want your Bug-based car to look sharp and run smart, check out CB Performance’s electronic fuel injection (EFI), all spiffed up with a custom Porsche 911–style fan shroud. We recently followed along as Vintage Spyders assembled a formidible flattie to power one of its Porsche 550 Spyder replicas.

Beginning with the appearance package, the Vintage fiberglass shroud is more than skin deep. As most VW enthusiasts already know, on pre-’71 engines the oil cooler obstructed airflow to the No. 3 cylinder, so it tended to become a hot spot, especially on a high-performance mill. Of course, on ’71-and-later flat fours the cooling problem was corrected by a wider fan and doghouse shroud, and also by relocating the oil cooler.

Even so, the Porsche shroud is more efficient, and as this Spyder’s owner Gene Leister admits, “We like it for cooling, but to tell the truth, we also love the looks. Everybody comes up to us at the racetrack and wants to know ‘What the heck is that?’” The shroud has an 11-blade fan and integral alternator. The extra juice isn’t really needed (the electronic fuel injection draws about only four amps, and runs on HEI, a breaker point, or a solid state ignition), but the higher airflow is literally a breath of fresh air. Fitting the shroud around the intake manifolds requires a bit of trimming here and there, but otherwise it’s basically a bolt-on piece.

Okay, so the cooling system looks slick, but just how hot an engine are we talking about? Here’s the fun part, because this digital dynamo downloads 224 hp at 7,000 rpm. Peak torque at the flywheel is 183 lb-ft at 6,000 rpm—all of this in a 1,420-pound flyweight of a car that kicks butt on BMWs and Porsches costing nearly twice as much.

What are the vital stats on this street fighter? Displacement measures 2,275 cc, with an 82mm stroke, a 94mm bore, and a 10.5:1 compression ratio. Pounding away inside CB’s dry-sumped, shuffle-pinned Super Case are 5.600 chrome-moly race rods, ARP 2000 bolts, 94mm forged Cima pistons, and a forged and counterweighted chrome-moly crankshaft. The No. 2288 camshaft has a 0.320-degree duration by 0.550 lift with 1.35 rocker arms and 0.108-degree valve centers.

For maximum respiration, the intake manifolds are match-ported Pro-Comp units. Also, CB reshaped and flow-benched the ports on its 044 Supermag heads so they inhale 225 cfm and exhale 180 cfm, using stainless steel valves (42mm intake and 38mm exhaust), nickel-chromium alloy seats, titanium retainers, 1.440 diameter Chevy springs, and 1.35-ratio Manton chrome-moly pushrods. According to CB, these heat-treated heads are cast from permanent molds, a process that allows for tapered cooling fins for improved heat dissipation. The company also says the alloy contains high percentages of copper, silicon, and manganese for higher stability to resist heat and cracking.

Outfitted with a custom exhaust system from Vintage Spyders, this contender growls unlike any flat four you’ve ever heard, and the bolt-on Super Trapp allows for a quick change to suit track conditions. Of course, a lightning-quick counter-puncher needs a good manager, and this one just happens to be a computer, basically the same unit found on a Geo Storm. CB calls it the Digital Power Star. Smaller than a cigar box, the unit keeps track of cylinder-head temperature, the throttle position (by sensing the angle of the butterfly valves), and the engine revs (measured at the distributor).

In addition, a connector adjacent to the electronic control module accepts a plug-in for engine diagnostics and troubleshooting (but not progamming—that’s done by CB, based on the engine specs provided by the customer). The fuel injectors are fitted into the 48mm throttle bodies and can be located inboard or outboard, depending on the need for clearance.

The “closed-loop” models of CB’s EFI also have MAP, oxygen, and air-inlet temperature sensors. However, these have been done away with on this “open-loop” Ultra Competition model to create a much simpler bolt-on setup that costs $1,795. Other changes include a tougher brain box with GM weatherproof connectors, since most of these EFI units are installed in offroad vehicles.

CB claims that a 15-percent power gain is not unusual with its EFI compared to a carbureted engine, but the real advantage overall is driveability. Unlike a carburetor, an EFI system doesn’t have any carburetor jets to get flooded or starved. Consider that the carburetor design on a VW was developed about four decades ago, and the popular Weber 48IDA was actually intended to be installed transversely in water-cooled vee engines! Weber’s cardinal rule that the float bowl should be located forward of the venturi is violated when these carbs are installed on a flat four. Not surprisingly, CB’s modern EFI systems now far outsell its carburetors.

CB Performance’s Bob Tomlinson, the mastermind behind the company’s VW componentry, points out that the reason for the increased power is simple. “There’s no resistance to the air/fuel flow,” he says. “It’s also a better mixture, more precise. The injectors atomize fuel in the exact ratio. EFI doesn’t rely on vacuum and fuel sloshing around in a carb. That’s even more of an advantage in offroad conditions—when you go downhill, the front two barrels flood and the back two are lean; and then you have the reverse problem going uphill.”

As every high school auto shop student learns, the ideal air/fuel ratio is about 14.7:1 by weight. When your engine is running this mixture, it is theoretically producing its maximum efficiency, and for maximum power the ratio ranges from 11.1:1 to 12.5:1. A carburetor is a passive mechanical device that relies on the flow of air through a venturi to create suction to draw in and meter fuel to the engine, but in real-world use it simply can’t maintain this optimum air/fuel ratio.

In contrast, electronic fuel injection works by squirting an exact amount of fuel into the inlet port at the right moment. It sounds simple, but timing and metering the flow are complex tasks. That’s where the open-loop computer system comes in. It constantly receives input on several parameters affecting an engine, and then it calculates how much fuel to spray into it. The computer alters the air/fuel mixture simply by determining how long and when the injector sprays fuel into the port. This injector pulse rate is measured in milli- seconds that the computer changes with fluctuations in rpm, engine temperature, and throttle setting.

As mentioned above, CB’s closed-loop EFI system has an oxygen sensor, but it’s not used on open-loop, high-performance applications because alcohol-laced racing fuel contaminates the sensor. Tomlinson also points out that it’s easier to make more power without it, and it adds to the cost and expense of the system, so he prefers to leave out an oxygen sensor.

In addition to providing more power, EFI really improves cold starts. They can be difficult with a conventional carburetor jetted for a “typical” operating temperature, with no ability to adjust for varying conditions. But that’s exactly where an EFI system excels. When the electronic control module senses a cold-start condition in the cylinder head, it richens the mixture to between 11:1 and 12.5:1, and then leans it out to 14.7:1 once the engine is warmed up and cruising down the highway. During heavy acceleration, the ratio may drop down to 12.0 again.

A key feature that allows the EFI to function is CB’s progressive fuel-pressure regulator that senses engine manifold pressure and can work with only 10 inches of vacuum or less. Reduced vacuum during acceleration causes the fuel pressure to increase, and the increased vacuum produced at idle decreases the fuel pressure for a cleaner burn. The fuel system’s rotary fuel pump, with an output ranging from 35 to 60 psi, has close tolerances and thus requires a 10-20 micron filter mounted ahead of it to catch any impurities.

CB’s Dash Module allows the driver to adjust the air/fuel mixture at both idle and WOT. No laptop is needed to calibrate the EFI—just twist the knobs to the optimum setting. Note that the WOT setting on this Spyder requires a good stretch of road, because you’ll be pushing close to 120 mph with your foot to the firewall. Top speed isn’t really what the driveline is set up for, though, since this 550 repro is a road-course racer with ’50s-era aerodynamics. Even though the driver can tweak the air/fuel mixture manually, when a customer orders the EFI kit, Tomlinson says he likes to know as much as possible about the engine—displacement, heads, valves, cam grind, and so forth—in order to figure the fuel flow and determine the right-size injectors and fuel curve. The injectors can range in capacity from 21 to 64 lb/hr—with a dozen or more choices within that spread of settings—and CB has about 30 different fuel curves it can use. Fortunately, CB has done dozens of dyno tests on customer engines and has a good baseline of comparison. This particular engine has 35-pound injectors.

If all this high-tech engine management still leaves you power hungry, CB also offers turbo motors that pump the output to as much as 450 hp. But that, as they say, is another story.