ADVANTAGES OF TURBOCHARGING

By 460-BBF-Turbo-In-CC

 

Car Crafters often ask why turbocharge instead of building a bigger engine or using nitrous oxide as a "power adder."

 
Here are some of the advantages of using a turbo over "all motor"

1. "Area under the curve"-- A proper turbo engine can have a huge advantage in midrange and top end torque compared to a naturally aspirated engine.

For example, Here's the torque curve for a Dodge Viper 8.4 liter engine:

RPM Torque
3600 500 lbs/ft
4000 530
4400 545
4800 560
5200 560
5600 550
6000 525

Here's a torque curve for a turbocharged 4.6 liter Ford tested by Richard Holdener at 14 psi:

RPM Torque
3600 490 lbs/ft
4000 615
4400 720
4800 730
5200 755
5600 740
6000 705
6500 670

Here's the torque curve for a Gale Banks turbocharged 6.0 liter SBC on 91 octane at 8-12 psi:

RPM Torque
3800 590 lbs/ft
4400 605
4800 650
5200 650
5600 675
6000 650
6500 625

2. Fuel economy -- a smaller turbo engine with the same peak power as a radical big block is obviously a smaller engine when its off-boost. In cruise conditions, the turbo mill can yield 3-5 m.p.g. better fuel economy, or even better.

At $3.00+ per gallon, that can add up fast on a daily driver. For example, let's say you wanted to run the Hot Rod Power Tour at a round trip of 2,500 miles. With a 11 m.p.g. big block, it would cost $682 at $3.00/gallon. But with an 18 m.p.g. turbo engine, it would only cost $417. And a 22 m.p.g. turbo mill would run the trip for a paltry $340.

3. Drivability -- a 750 lbs/ft "all motor" engine is going to require a fairly big cam, carb and head combo. That usually means a rough idle and fairly crude low-speed manners. A loose torque converter and steep gears are generally necessary to keep the engine in its narrow powerband.

A 750 lbs/ft turbo engine can run a mild cam with a near-stock idle. Off-boost it can be so docile that you could let your grandma drive it. Turbos tend to work well with tighter torque converters and highway gearing.

4. Greater use of stock parts -- big "all motor" power typically requires high r.p.m. That means thousands for valvetrain and induction parts that can stand the revs. The lifespan of these parts is often much less in street driving than stock components.

The same power from a turbo mill can be achieved with mostly stock valvetrain parts. Reliability is measureably increased. Moreover, because high r.p.m, isn't necessary, the rest of the engine can use more stock parts.

For example, the April 2011 issue of Hot Rod magazine features the turbo build of a 150,000 mile GMC Denali engine (5.3-liter 5.3 LM7 engine). With nothing more than a mild LS6 camshaft (203.8/ 212.1 duration; .523/.522 lift; 115.9-degree Lobe Separation Angle) and a cheap Chinese turbo, the engine reportedly produced a massive 594 horsepower and 585 lbs/ft of torque.

5. Power density -- A turbo engine can be smaller and lighter than a big block of similar peak output. That can mean better weight distribution and more power-per-pound of engine.

6. A turbo engine can actually be cheaper to build -- Unless you're building a stock-based combo, building a big block can be expensive nowadays. It's not uncommon for an 800+ h.p. "all motor" big block to cost in excess of $15,000. The same level of power with a turbo engine often costs a fraction of that.

Now for nitrous

7. More tractable than nitrous oxide -- Most nitrous systems are on/off. A sudden 100-300 h.p. can be hard to manage. Even an expensive multi-stage nitrous system can have harsh transitions. Turbo engines can be more tractable because they can be modulated with the accelerator and boost controllers.

8. No bottle to run out-- A nitrous rule of thumb is 1 lb for 10 seconds = 100 h.p. A "200 shot" burns through 15 lbs of N20 in about 75 seconds. That can get expensive in a hurry.

75 seconds of turbo power doesn't really cost anything more than the fuel burned. And the turbo is still there for another 75 seconds . . . and another . . . and another . . . .

9. No nitrous backfires or other accidents -- Many heavy squeezers have stories to tell about intake manifold explosions, fireballs, clogged jets, melted pistons and other horrors of living on the edge with spray. A dialed-in turbo system simply doesn't have the same level of "drama." Many serious turbo racers report much longer engine service intervals than with N20.

10. Nitrous on the street is illegal in 38 states. And nitrous is banned in many forms of competition (drag racing is one of the few places where N20 is legal). There are a lot more places where you can run a turbo.

11. Less "prep" before a pass is needed with a turbo -- Turbos require no "purging" and no bottle heating. They're always ready for immediate action.

12. Easier to adjust for track conditions -- Dialing back a nitrous system for a "loose" track can be time-consuming (especually if it's a staged system). Dialing back a turbo system usually only takes a couple of seconds.

13. You can still have fun without race gas in the tank -- A big-power nitrous 'plant will require race gas to keep detonation at bay. On pump gas you've either got to change the jets or keep off the bottle.

But you can still make decent power with most turbo systems even when there's no race gas in the tank.