Chapter 2: The Plan for Power

"It doesnt matter if you think you can or you think you can't, you're right" - Henry Ford


This project has been in the works for some time now and I've been lagging a little bit. It's not that I haven't been working on this project, its that the research for engineering this project is the biggest time consumer in the world. I like to do things right, the first time. Everything from the kind of material the fuel lines are made of to calculating airflow through the cylinder heads has been taken into consideration. The smallest detail missed can be the doom of a project like this. What is it they say...patience is a virtue? Not all the posts in this blog will be technical, but just to warn you, this one in particular is pretty heavy on the info.

My goal is to kill a Ferrari in a quarter mile drag race. A lot of people think that the more horsepower a car has, the faster it is. This is generally true, but other things to take into account are a vehicles weight, gearing, aerodynamics, power band, and torque output. Comparing two cars that they weigh the same: if one has more torque, it will be faster than the other at non aerodynamic speeds, respectively. I don't know about you, but how fast do people really think they can go in this country? I mean seriously Holmes, when will you ever drive your Ferrari 200mph? Even at most race tracks cars don't ever hit their top speeds because there is simply not enough room. Don't get me wrong, I like hitting corners, but that's for the next project...WINK*. If i'm getting punked by some guy at a stop light, its all about acceleration. That's where these European sports cars have a soft spot. They just can't launch because all their power is at the high end of the engine speed range and they are missing all the torque. There are some exceptions to this rule, so if a car the price of 7 houses beats me i'm content with that. Here is my first realistic target:

(skip to bottom of post now to avoid a headache)

2004 Ferrari 360 Modena F1
Price: $157,767
Motivation: 400 Horsepower @ 8500 rpm, 275 Lb-ft Torque @ 4750 rpm
Weight: 3200lbs
Performance: 0-60 mph 4.4 seconds. 12.8 second 1/4th mile time. Like I said., who cares about top speed.

*Torque is defined as twisting force. Horsepower is how fast that twisting force is applied. 

The thing to notice is that the cars weight is seriously low. That means it doesn't take much motivation to move it, the only problem is that that motivation comes in at almost 5000 rpm. This will be the first of my mathematical calculations.....though easy, it gets much complicated later.

2004 Ferrari 360 Modena F1:
3200 lbs / 400 hp = 8 lbs/ per HP
3200 lbs / 275 lb-ft torque = 11.63 lbs / per lb-ft of torque

A starting point to beat this car is that mine has to have lower numbers per HP and Torque. To theoretically be equal to it I would have to figure it out using my vehicles weight to find what it needs in terms of motivation. I found me vehicles weight to be around 3700 lbs, but after accounting for adding the turbo system and other parts i'll add 200 to it to be more accurate.

1969 Pontiac Tempest:
3900 lbs / Ferraris 8 lbs per HP = 487.5 HP
3900lbs / Ferraris 11.63 lbs per lb-ft torque = 335.34TQ

On paper and not considering anything else except for motivation numbers, these are the minimal numbers that I need to achieve in order to beat it. I'm not going to get into the design of engines too much, but after tons of research I have figured out that this is where Pontiac V8s show their earth rotating grunt. These beasts always make more torque then horsepower, so if I can put the power where I need it, I should have more torque than a freight train. Based on my research, here is the rundown of the kind of airflow that I need to make the magic happen for a required rounded off horsepower number of 500. It would take forever to explain why I picked the numbers that I did for the formulas, so if anyone wants to know the details an any certain thing just let me know. Bust out your calculator mofo:

Determining required airflow of turbocharger compressor in order to reach my horsepower goal:

Formula: AF = HP x AFR x BSFC/60

AF = the actual mass air flow in pounds per minute

HP = the target horsepower                           500 x 12.5 x .63/60 = 65.6 lbs/min airflow

AFR = the air fuel ratio

BSFC/60 = the brake specific fuel consumption converted to minutes

*Brake specific fuel consumption (BSFC) is the fuel flow rate required to generate each horsepower. Lower numbers mean that the engine requires less fuel to generate a given amount of power.

*Air fuel ratio (AFR) is the amount of air entering the engine compared to the amount of fuel. 14.7:1 is ideal, so that means 12:1 is rich with a lot of fuel and 16:1 is lean with a lot of air. This number greatly effects the performance and operation of an engine and its horsepower.

Determining MAP for required airflow demand:

Formula: MAP = (Wa x R (460 + T)/(VE x (N/2) x Vd)

MAP = manifold absolute pressure

Wa = actual airflow in pounds per minute

R = 639.6 the gas constant                               (65.6 x 639.6 (460 + 130)/(.90 (6200/2) x 412) =

T = estimated air intake temperature                            24755078.4/1157850 = 21.38 MAP

VE = estimated volumetric efficiency              21.38 MAP - ambient air pressure 14.7= 6.68 PSI Boost

N = my maximum engine speed

Vd = my engine size in cubic inches

*Manifold absolute pressure (MAP) is the atmospheric pressure of the air we normally breath + any extra that is forced into the engines intake manifold. 14.7 is the average air pressure at sea level.

*Volumetric efficiency (VE) is how much air the engine can breath while running compared to the amount of air that it can possibly hold as if it were not running. Think of it as how much air your lungs can hold vs how much effort it takes to inhale it to that amount. It's like going for a run and measuring the restriction that you feel while taking a breath. Easier means a higher volumetric efficiency, but if you're running while you are sick, you will have more restriction and have a lower volumetric efficiency.

*Boost is the higher amount of air pressure entering the engine than what is normally available in the surrounding environment. More boost equals more air which means that more fuel can be added to it to make more power.

Convert MAP pressure to pressure ratio:  

Formula: MAP +N / AMB – N2 = PR

MAP = required manifold pressure

N = pressure loss on compressor outlet side      (21.38 + 2 / 14.7 – 1) = 1.71 Pressure Ratio

AMB = ambient surrounding air pressure

N2 = compensation AMB for turbocharger intake restrictions

*Pressure ratio is the amount of air pressure coming out of the turbo compared to going into the turbo. What this means is that for every 1 unit of pressure entering the turbo 1.71 is coming out of it.


Now that most of the math is done, here is quick break down in English. For the engine to make 500 horsepower, the turbo for the motor will need to flow 65.6 pounds per minute of airflow while multiplying any surrounding air to 1.71 times its normal pressure to make 6.68 pounds of boosted air pressure into the engine. And now the exciting part...... How much power is more boost worth? These numbers are only if the air temperature stays the same as when it entered the motor, but because it is compressed it will heat up. Because hot air is less dense, I have to cool it back down using an intercooler before it enters the motor if i want to make this kind of power. After running these numbers multiple times here are the results:

6.68 psi = 500 horsepower
8.83 psi = 550 horsepower
10.96 psi = 600 horsepower
13.1 psi = 650 horsepower
15.25 psi = 700 horsepower
17.37 psi = 750 horsepower

- 487 horsepower is what is required to beat the Ferrari
- If i only make 500 horsepower, my engines torque should be nearly double that of the Ferraris
- 10 psi boost is about the limit that I can go on pump gas with this engine
- 600 horsepower is about the limit that I can go without breaking parts inside my engine

AWESOME:)