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Air vs Power

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Hello Everyone!

I've heard that More Air equals more power!

If its that true then how could we determine when more airflow is required for the engine during tuning?

Or even when building an engine?

Or just buy a bigger throttle body and tune to see the difference?

Last thing what are the pros/cons for getting a Big:

1.throttle body

2.intake manifold

3. Head valves


During tuning you are maximizing fuel and spark to make power with the airflow you have. Its kinda too late at that point to say I need more airflow. When you finish the tune and you're still wanting more power there are many ways to get more airflow into the motor as you mentioned above each with their own pros and cons. If you start with a power level goal, an engine builder experienced with your platform can recommend what you need to get there.

Hey Kelly!

thanks for your reply,

lets assume that there is no experienced builder for a certain engine.

What is your next step?

What you mean is - more oxidant* for the fuel in the cylinder means more power - or, rather, torque.

For most engines oxidant is the oxygen in the air and the more air, or more accurately, the denser (which is a function of temperature and pressure) the better. This is why we try and keep the air temperature down as cooler air is denser and has more oxygen.

With forced induction it is a bit more complex as the process of compressing the air, to make it more dense, also heats it which reduces the density - this is why charge coolers are used, to lower the temperature of the air before it goes into the cylinder (There are other reasons to reduce the charge temperature, but I will leave that for now). The trick is to get more, overall, oxygen into the engine - it is possible, with very high boost levels, to actually have power dropping off because the density change from increasing boost is less than the loss from compressive heating.

OK, now more to your point, for all engines, the theoretical maximum is 100% of the cylinder volume but, for a variety of reasons, that is rarely achieved with naturally aspirated (non-boosted) engines with a production 2 valve per cylinder engine being around 80-85% and a 4 VpC around 90-95% - but a fully optimised engine can get close to 150% under very, very carefully opimised conditions, such as in the last generation of NA F1 engines - at the end of the 3 litre V10 era Mercedes were rumoured to be getting ~970hp at close to 20k rpm!

Every production engine, such as yours, is a compromise of many different things and, to increase torque and/or power, you need to determine your budget, what sort of power level you want within that budget, identify what the limitations of your vehicle are that are preventing you achieving your aims, and determin the most cost effective means of reaching them AND, if applicably whether they will support further torque/power gains that may be applied later - it is foolish to do the same thing twice - eg, rebore with cast pistons for one power levl only to need to replace them with forged later.

As I said,every engine is different, you should be able to find plenty of foums and other sources of information on your specific engine - what is it, BTW? - and any other modifications - such as clutch, oil pump, or cooling - that are required to keep the engine reliable.

*I said "oxidant" because some fuels, such as alcohols, have oxygen as part of their chemical structure which means they supply a part of that, and there are other substances, such as Nitrous Oxide, which can be used to add ogygen as it breaks down in the cylinder - both these are usually referred to as "chemical supercharging".

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