Who doesn’t love mods (modifications) that increase horsepower and torque and/or fuel efficiency? Heck, I love mods! But has anybody ever thought, “wait a minute … if adding an airfoil to my throttle body on my TPI engine will increase CFMs, how come the manufacturer didn’t design the throttle body that way to begin with?” Or, “removing the screens on my MAF will increase air flow, why did they put them in there?”
Well, for some mods, I agree. The airfoil can be added with no risk of any part getting damaged as a by product. The MAF screen removal mod, can damage the MAF if not careful, or if an air filter becomes damaged enough where it will not prevent foreign objects from damaging the filament.
Most American vehicles are designed with reliability in mind. Yes, adding headers and a free-flow air filter will improve efficiency as well as power, but can the drive train handle the extra ponies? In most cases, this would be a yes. But another example is a Pontiac Grand Prix GTP. This 3.8L engine is equipped with the Eaton supercharger pumping a moderate amount of PSI for that little extra (35HP) boost. You can get a smaller pulley for it and increase the PSI for horsepower gains of nearly 50HP. Why didn’t GM do this to begin with? Well, they sort of did. Their prototype GTP was rated at 300HP. They felt that if this amount of power was sustained too long, damage to the transaxle would, very likely, happen. To the auto manufacturer, it would be more cost effective to reduce the amount of power output, than to redesign the transmission to handle that much sustained power.
Which kind of leads to other modifications.
I have seen modifications done from simple free mods to complete rebuild of engines that include ported and polished heads, 800CFM double-pumper carbs, performance cams, headers, bored out cylinders … the whole works. And if done right, that engine will put out some pretty serious power and reliably … BUT … what about the rest of the car? The transmission, the rear axle (especially), the twisting of the frame (or unibody construction)?
Mods have to be done responsively. Let’s add more power so we can go faster! But who thought of the brakes to stop it?!
Most mods can be done with little worry to the rest of the car. Most transmissions and rear axles are rated far more than the stock engine can put out for the extra “comfort” zone. And probably the main reason why most cars do not come with the little extra mods that we do to our cars, is cost. Let’s face it, if the auto manufacturers would add all of our mods to a car from the factory, what fun would it be then?