Adding power is often the first place people look when planning out their modifications. It's especially important for the early V8 Vantage with the 4.3L engine, which is often derided as being underpowered and slow. This page will go over the basic modifications you can do to improve the performance of your Aston Martin where engine power is concerned.
DISCLAIMER: As always, follow all safety protocols. Don't undertake this task if you aren't comfortable with it and fully understand it. You are ultimately responsible for anything you do. Neither Redpants, LLC or myself is responsible or liable for anything that may occur.
There aren't a huge number of places to gain power in an Aston. Rather, it's just the basics: Intake, exhaust, and tune. There are ways to improve power delivery, and these are going to be just important (if not more so) than the peak HP numbers most people focus on. The distinction between power delivery and power output is very important because both have a related but different effect on how the car behaves when you get on the throttle.
(A quick note: I'll often say throttle instead of gas pedal, though they're the same thing. The term "gas pedal" kinda bothers me because it isn't a gas pedal, it's an air pedal. You press down on it and it opens the throttle body, allowing more air into the engine. The additional gas is provided to maintain a given air-fuel ratio due to the increased air flow, so it's a reaction to the primary function of the throttle pedal: air. Okay, pointless tangent over, let's continue.)
Power output is how much power your engine is making, and the terms used to describe power output are distinct and important to understand.
Horsepower (HP) comes in two flavors: brake horsepower (BHP) and wheel horsepower (WHP). Brake horsepower is named after the source of its measurement: an engine braking dynamometer (dyno). It's a type of dyno that connects directly to an engine to measure the engine's power output. Brake horsepower has nothing to do with the brakes of the car.
The general term "horsepower" is the same as brake horsepower, but wheel horsepower is different. Wheel horsepower measures the amount of power at the wheels of the car. WHP will always be less than BHP because power is lost between the engine and wheels. The amount of loss depends on a large number of factors, but typical loss for a rear-wheel drive (RWD) car is 15-18%. So a car making 400 BHP will have around 330-340 WHP. All-wheel drive (AWD) cars have an even greater loss of power in the drivetrain, as much as 25%.
Another figure you may see is pferdestärke (PS), which is very close to BHP. A car with 400 BHP would have approximately 405 PS. It's a small difference, so don't worry about it too much.
The other main measurement is torque (TQ), which is expressed in pound-feet (lb-ft) or Newton meters (Nm). Horsepower and torque are related. An easy rule of thumb to help you differentiate between the two is that torque is the power that matters in the lower part of the RPM band - say, when you're starting from a stop or cruising at a steady speed on the highway. The more torque you have, the quicker your car will launch from that stop, and the quicker your power (and speed) will build when you want to pass a car without downshifting. Horsepower is the snappy, quick power burst you get in the upper RPM band.
A massive amount of information is available online about horsepower and torque, and how engine output can be increased (or decreased, or changed in other ways) with modifications like an exhaust system, so I won't rehash that. Instead I'll go over these things as they are specific to an Aston Martin.
The main takeaway from the information above is the difference between BHP and WHP, and the difference between horsepower and torque, as I'll be describing characteristics of various cars and their modifications in these terms.
4.3L V8 Vantage
Of all of Aston's recent cars, the early V8 Vantage is the one most in need of increased power. In fact, the only real complaint anyone had about the car when it was first released is that it needed an extra 50-100 hp. From what I've experienced, it wasn't that the car was under-powered. 380 hp, while not a ton, was on par with other cars in its performance category at that time. Rather, there were two distinct issues that, when combined, made the car feel rather slow. The first is that the Vantage looked and sounded much faster than it was. This affected a driver subconsciously as they expected the car to be faster than it was, therefore making it feel slower than it was. Second, there's a considerable amount of lag between throttle input and engine response. That lag is a much bigger issue than many people realize, so let's address that first.
Let's use a couple of basic diagrams to illustrate what I'm talking about. Here is a diagram showing the power output of two identical engines:
The engines produce the same power at the same RPMs. That means, all things being equal, the cars with those two engines will have the same acceleration. But if we change one engine so it can respond more quickly, it will reach higher RPMs before the other.
The engines still produce the same power at the same RPMs, but one engine climbs through RPMs more quickly. In the above example, the slower engine would have only around 300 HP when the quicker engine has 400 HP. So although the two engines produce identical power, one engine will outperform the other because of how quickly it gets to higher RPMs.
Fixing Throttle Lag
The 4.3L engine throttle lag can be largely remedied with two changes to the car. One reduces the electronic lag that causes the throttle body to open more slowly than the relative input you're giving the gas pedal. The other reduces the mechanical lag caused by an incredibly heavy flywheel. Either one will benefit the car, and both can be done to further improve engine response.
Reducing throttle lag matters because it means you get to the higher power output of the engine more quickly.
Aston Martin uses drive-by-wire throttle bodies. That is, an electrical signal is sent from the pedal to a solenoid on the throttle body to tell the throttle body what to do. It's pretty much the standard setup for all modern cars, having replaced drive-by-cable throttle bodies which had a physical cable running between the pedal and throttle body to pull it open.
The nice thing about drive-by-wire systems is that they can be reprogrammed to give more-or-less response at the throttle body based on pedal input. From the factory, the 4.3L V8 Vantage had a very leisurely throttle response. Engine tuning has the dual benefit of giving increased power as well as a quicker throttle response.
The other big issue affecting the 4.3L V8's engine response is its very heavy flywheel.
4.7L V8 Vantage
In 2009, Aston Martin swapped out the 4.3L V8 engine for the 4.7L unit that would power the car until its replacement with the AMG twin-turbo 4.0L V8. The new, larger V8 fixed the common complaint of the Vantage needing more power, and it did so in a few ways. First is that the larger engine provided more horsepower and more torque. The extra 40 hp was a considerable bump, but what made the biggest difference during most driving was the extra torque. In addition to the extra power output, the factory also fitted a lighter flywheel. This reduced the throttle lag that plagued the 4.3L engines and got the engine into the higher rev range a bit quicker.
V12 Engines (DB9, DBS, V12 Vantage)
The power potential of these engines is greatly handicapped by the factory.