Cubic Inch vs. Boost ?

[Steve Roseman]

While explaining to my 12 year old the effects of boost and how it theoretically increases displacement, he had to ask me how much.

What I need to know is, is there a formula for figuring out boost and displacement on the little 5. 9?

I know the displacement isn't actually increased, but the boost has the same effect.

 

[Snow man]

Im not sure buy i thought for every 14. 7 psi,atmospheric pressure you effectively are taking in twice the air an otherwise normally aspirated engine could,so you effectively can double the power with the same displacement if you add the proper amount of fuel with the air. I used to have a dodge daytona shelby Z,an 87'model,it was intercooled. It used to run high 14's at 93 mph,bone stock,and gave Mustangs/Camaros fits,with just afew mods. It only got 16 psi of boost,and you could feel its power more than double going from off boost,roll on in 5th,to full boost,so i tend to believe its true. That little 2. 2 was rated at 175hp(conservative),its performance was definetely equal to a an engine double its size (4. 4) liters. With the CTD the boost allows as to add more fuel and burn it all,giving lower EGT's,less smoke,and the abiltiy to add even more fuel. My 5. 9 with over 400hp,and about 40PSI of boost,is the performance equal to the older normally aspirated engines of more than twice its size,although i doubt the smaller engine will last as long.

 

[Don M]

Hi Steve,



The more hydrocarbons you can unzip the better.

The extra air helps to cool the hydrocarbons your unzipping.

Boost alone wont make much extra power in every case.

Alot of guys feel that the boost is the thing making the power.

The fuel is, actually. Most diesels are set up to give more fuel with more boost via the AFC or some computer controlled fueling curve.



Boost generally goes up our trucks from the extra heat of the combustion process. Heat makes boost. Fuel makes heat.

Having more fuel to unzip is the key.

Example is the performance injectors, cam plates or delivery valves. Heat always comes up and the boost follows, depending on how you have your wastegate set up, etc.



So just packing in boost is not the reason we see power from higher boost. The fuel starts the process.



Don~

 

[Forrest]

Somebody equated psi to displacement. The #'s may have been 40psi in our motors equated to 1100cu".

 

[Steve Roseman]

Thanks Guys,

That's about what I thought but wanted to double check.

Don, I'm aware of the fuel=power, not boost. I was just being theoretical, with the motor using every bit of air supplied to it.