Supercharger Disadvantages

While the benefits of supercharging can be great, these benefits come at a cost in terms of expense and complexity. Adding a supercharger to a car that wasn’t originally equipped with one from the factory (and no Mopar was), means adding equipment under the hood that not only takes up space, but generates heat as well. Also, since most automotive superchargers are driven from the crankshaft, either by a belt or gear-drive system, the normal engine accessories like the alternator, power steering pump, water pump, etc. nearly always need to be changed or modified in terms of position and belt routing. Compressing air also generates heat, so supercharger kits often come with an intercooler, which must also be placed in the engine bay, usually in front of the radiator, to cool the intake charge back down prior to ducting the air into the engine. The car’s fuel system including the pump and injectors (on fuel injected vehicles), or carburetor (on carbureted vehicles), must also be up to the task as any time more air is supplied, more fuel must be provided as well to ensure the proper combustion mixture. Tuning of the ignition timing is also a consideration, as the additional cylinder pressures experienced with supercharging will require a reduction in total advance to prevent detonation.

Of course as boost pressure increases, additional modifications such as forged pistons, forged connecting rods, and a forged crankshaft become necessary to ensure engine durability. In extreme cases, a supercharged engine may need to be “O-ringed” which involves installing a stainless steel wire on the deck or head surface around the combustion chamber, which is used with a copper head gasket to ensure combustion chamber seal in highly boosted applications. And while supercharged engines generally don’t need aggressive stall converter rpm or gear ratio, at some point the converter, transmission, U-joints, gears, and axles will need to be upgraded to handle the additional torque that the engine is making.

Normally Aspirated Advantages

Simplicity is likely the biggest advantage of a normally aspirated (non-supercharged) performance engine as there is no supercharger, ductwork, intercooler, or drive system to fit into the engine bay. Making horsepower in the 600 range without forced induction can be tricky, however, and often requires some fairly major modifications to the engine both internally in the way of a stroker kit and/or forged internal components, and externally in the way of aftermarket cylinder heads, headers, and induction. To make high power levels without supercharging or other power-adder systems like a turbo or nitrous, an aggressive camshaft is necessary and the engine must be revved higher which sacrifices low and midrange torque.

Lower cost is another distinct advantage of building a normally aspirated engine as superchargers and associated equipment like drive kits, intercoolers, ducting, and accessory drives can be expensive. By choosing not to add a supercharger to an engine, the money saved can be applied to the engine itself as items like high-flowing cylinder heads, headers, high-compression pistons, a roller cam and lifters, and other items necessary to make big power without the benefit of forced induction. Achieving high power levels without a supercharger generally requires a cam with narrower lobe separation, more duration, and higher lift to allow the engine to rev higher and ingest more air and fuel, so oil system modifications can be necessary as well.

Normally Aspirated Disadvantages

Normally Aspirated engines are limited to atmospheric pressure when it comes to manifold pressure, so power must be optimized in other ways. Extra expense must be spent on cylinder head porting, and more aggressive cam profiles require heavy springs which will cause quicker wear to guides and seats, as well as more frequent spring replacement. Compression levels must also be higher in a normally aspirated engine, which causes more aggressive wear to rings and rod bearings. The higher compression required in a normally aspirated engine also leads to higher cylinder pressures any time the engine is running, not just when under boost like a supercharged engine, requiring more frequent maintenance or freshening of the engine comparatively.

A second disadvantage of a powerful normally aspirated engine is the requirement of parts like a loose stall converter or high gear ratio differential to optimize the performance of the vehicle. Since normally aspirated engines generally make their peak torque and horsepower at a higher rpm level, and in a narrower rpm band than a supercharged engine, the gearing of the car and stall speed of the converter become much more important. Often the higher gear ratio required will lead to high engine rpm when cruising on the highway, causing more aggressive engine wear. Of course an overdrive of some sort can alleviate this issue, but then the expense of the overdrive transmission must be added to the cost of the build.

Conclusion

The purpose of this article is not to draw a conclusion as to whether supercharging is better or worse than building a powerful normally aspirated engine, but rather to give you the information so you can decide which is right for your Mopar. For some of us, having a fast car that looks fairly stock is a desirable aspect of a vehicle build, so a normally aspirated engine may fit our needs better. For others, the whine of a supercharger and the intimidating look of a blower sticking through the hood may be just what we’re after, and the broad power band of a boosted engine can certainly be worth the expense. And if you’re still undecided, we suggest building one of each!

SOURCE
Comp Cams
3406 Democrat Road
Memphis
TN  38118
800-999-0853
http://www.compcams.com
Auto Performance Engines
1479 Berkley Rd.
Auburndale
FL  33823
863-967-8781
Indy Cylinder Head
8621 Southeastern Ave
Indianapolis
IN  46239
317-862-3724
www.indyheads.com
The Supercharger Store
314 W Highway 82
Huachuca City
AZ  85616
520-456-9706
www.thesuperchargerstore.com