Look at the smoke! Turbocharging...
Look at the smoke! Turbocharging might be a great way to gain solid horsepower from your street car. Under the hood, the pipework routes pressurized fresh air to the carb.
The old adage "Speed costs money; how fast do you want to go?" still rings true. If you want to play, you're going to have to pay. For Kevin Alexander, or "Feets" as he's known on Moparts.com and Pentastarpower.com, there were several performance options he wanted out of his '65 Plymouth Belvedere II, with economy to boot.
"The idea was to get three things out of this project," says the 30-year-old Dallas native. "I wanted it to top end at 130 mph in the quarter, I wanted an engine that could make 650 horses, and it needed to run on pump gas. Here in Texas, it gets real hot in the summer, so big cams and big fuel systems are out the question. Forced induction was the only choice."
Weighing the options, Kevin knew Roots-type blower systems would rob a lot of horsepower and dump large amounts of heat into the boosted air, and the modern centrifugal units were a bit better but still make plenty of heat. Turbocharging seemed to be the way to go. Unlike the others, turbos are driven by exhaust forces, meaning they don't rob horsepower off the crank except by creating minor backpressure. The silent running nature of turbos is a big bonus for a street-driven car. Since the 440 in the big, black Plymouth was mildly tweaked, Kevin researched what it would take to rig a set of cast-iron hair dryers to the motor. He obtained most of his information from the book Maximum Boost by Corky Bell, published by Cartech.
"There isn't a lot out there on doing turbochargers on an engine this big," says Kevin. "I read as much as I could to get an understanding to make good choices. Turbo science, especially on a motor with this much displacement, can be a hit-or-miss proposition."
Here's where it begins: through...
Here's where it begins: through an air filter mounting inside the front wheelwell. The pressurized air runs through the pipe, dropping down to the right. The turbine, which is spun by exhaust pressure, is inside the fenders.
Kevin says the idea is to get a large-enough turbo that won't restrict flow, yet small enough to quickly spool up to maximum boost pressure. If the turbo was too small, the engine would choke because it couldn't push exhaust out quick enough. If it's too big, the exhaust gases could past the turbine instead of spinning the turbine wheel quickly enough to get boost at an usable rpm (turbo lag). The result of this mental deduction came via Garrett Research Products through Majestic Turbo in Dallas, where Kevin specified a T3-sized turbine housing (which handles the exhaust charge action) coupled to the larger T4-style compressor (which pressurizes the intake side). The turbine for the exhaust and the impeller for the compressor are mounted on a single shaft; this is how the turbocharger makes power. After he finished, Kevin admitted he was probably a little too conservative on the turbine side, though the idea was to get units that would reach peak efficiency by 98,000 rpm (many won't get to peak efficiency until 130,000-plus rpm). Low efficiency means high heat in the intake charge and big detonation problems.
(A) A set of beat-up Hooker...
(A) A set of beat-up Hooker headers were rewelded to face the front so exhaust pressure can spin the turbine, and an O2 (oxygen) sensor mounted to the exhaust outlet is for an air/fuel gauge mounted in the car. The Tial wastegate is the bypass seen at the lower left of this image (B), which will open to allow excess exhaust pressure to bypass the turbine. The pipe above is the carb inlet. Note the stainless lines carrying engine oil to the turbos.
The pair of Majestic customs were positioned into the inner fenders on opposite sides of the car, taking air into the compressors via filters mounted directly to the compressor inlet from the front of the wheelwell. A set of beat-up Hooker headers were butchered and rewelded to funnel exhaust pressure back to the turbines, which then routed it out to the mufflers under the car. The boost is controlled by a pair of Tial wastegates. The diaphragm inside the wastegate is fed boost pressure. When the pressure builds high enough to overcome the spring pressure on the diaphragm, it pushes open a valve in the header. This allows the exhaust gases to bypass the turbine and to maintain the desired pressure. Without them, the turbos would probably boost the engine into oblivion. Once the compressor side is finished pressurizing the fresh air as a result, the charge funnels to a reverse Y-pipe mounted in front of the radiator, then the single tube runs up to the K&N Filtercharger bonnet atop the carburetor. A pair of pressure bypass, or blow-off, valves on this inlet pipe make sure rampant boost doesn't cause damage when the throttle is closed. These came from junkyard 2.2 turbo cars, cost a couple of bucks at the boneyard, and are mounted about a foot before the carb inlet facing downward; Kevin says they'll blow your hat off if they open at full boost. An oxygen sensor from an '87 Gran Fury was also put to use to monitor the process.
Next was the carburetor problem. Metering fuel/air for forced induction into the carb throat can be a little trickier than having a blower draw air from below the carb. Kevin tried several different carbs, with a modified 650 Holley being the best so far. The fuel metering system needs to react quickly to changes in air pressure, and a vacuum line is routed directly to a diaphragm-type Mallory fuel regulator on the firewall, increasing fuel pressure as the boost increases. Kevin says he is still experimenting to find the best solution in this area and fuel injection would be a much easier way to run turbos in many regards.
A few additional modifications include stainless oil lines coming from the two oil-sending unit holes in the block that now route engine oil into the turbos, returning it to the oil pan when finished. Without lubrication at high rpm, these units are capable of explosive problems. The air plumbing for both the compressor side (up to the carb) and the turbine side (exhaust gases from the headers, through the turbine, and out to the mufflers) is bulky, but was installed in a few days by a local muffler shop. Auto Meter gauges allow Kevin to watch air/fuel ratios, oil pressure, and other vital signs. On the dyno, even this early in the experiment, the engine made 359 horses at the rear tires with only 6 pounds of boost.
Once the two turbines pressurize...
Once the two turbines pressurize the air, it's routed to this pipe layout where a Y-pipe will direct it up to the carburetor.
This is Kevin's first project involving turbochargers; he had a turbo-equipped Shelby Charger a decade ago, but little of that science will platform directly to the big-inch V8 environment. The photos show this car is no trailer rig; still in progress, it doesn't even have the replacement hump for the new four-speed trans welded to the tunnel yet. However, Kevin gets an A+ for ingenuity; he invested less than $6,000 in the entire project, and the engine program set him back a mere $3,500, including a bucks-down rebuild on the 440 mill.
The engine is a .030-over '68 block with 8.7:1 pistons installed. A set of later -452 heads were used, including a custom-ground Comp Cams bumpstick with .488 lift and 10 degrees of overlap. For timing accuracy, a Pete Jackson geardrive was added. A pair of twin electric fans round out the package. Kevin, who has a '92 Cummins D250 pickup that makes 527 lbs.-ft. of torque at the rear tires, plans to add an intercooler to the '65 as soon as possible. This is an air-to-air type unit, which routes the incoming charge from the compressor into the carburetor and produces power by reducing the charge air temperature.
The rest of the car speaks for itself: the type of machine that'll literally blow unsuspecting 5.0 and GM-F-Body guys into the weeds.
After corresponding with Kevin for several weeks on the Moparts' Web site, he brought the car up from the Lone Star State to the 2001 Mopar Nationals so we could get an eyeful of the beast. Speed still costs money. How much may well have its answer here.
Due to the extreme high speed...
Due to the extreme high speed of the turbine impeller, oil is routed from the oil-sending holes at the rear of the block and up to the units via stainless lines, then circulated back to the oil pan.
A pair of blow-off bypass...
A pair of blow-off bypass valves came from junkyard turbo cars and allow the boost pressure in the inlet pipe to escape when Kevin lets off the throttle. Without them, ka-boom!
It might look a little rough,...
It might look a little rough, but don't laugh. It's paid for, and it runs like a scalded cat.