[svcook]

I think the oxygen sensor regulates the ratio of air:fuel. The ratio that is re-occurring in my reading is typically 14.7:1. If this is correct then I'm confused as to the benefit of a CAI? Would't the ECU compensate for the change in air volume/density resulting from temperature variance and alter the amount of fuel introduced to maintian 14.7:1? Can the terms volume and density be interchanged in this discussion?

Thanks.

 

[brown7]

I may be wrong because of the only experiance i have with the computer/tuning is on my early model Fuel injected mustang which was pretty basic when comparing todays cars.

From my understanding a Stock car will have a the factory A:F. Any mixture less than 14.7 to 1 is considered to be a rich mixture, any more than 14.7 to 1 is a lean mixture (as taken from wiki)

When you Introduce say a CAI the computer can only compensate so much as to effect the final A:F ratio.

The Benefit of adding a CAI is replacing the Restrictive factory intake which is usually where the gains are being made. kinda like upgrading your coffee stirrer to a full blown straw. Some factory parts will not offer as big of a gain because the factory usually does a good job in the design of the part.

LIke i mentioned the computers (well back then) would try to compensate but could only go so far. so adding the CAI would lean it out or make the mixture rich and leaving you with a problem only a computer tune could solve.

it is typically advised to Get a tune after any game changing modifications are done. i.e. head(s), cam(s), header(s), etc

 

[Bigmoney890]

Well a cold air has is more dense than warm air, so effectively more oxygen is in cold air than the warm/hot air coming off your engine. The more oxygen, the more power and better the performance. Just because the air/fuel ratio stays the same, doesnt mean the oxygen entering the engine is always the same. Hope that helps, and someone please correct me if im wrong!

*Edit* and yes it is always beneficial to get a tune after any sort of modification, but not always necessary

 

[svcook]

Well a cold air has is more dense than warm air, so effectively more oxygen is in cold air than the warm/hot air coming off your engine. The more oxygen, the more power and better the performance. Just because the air/fuel ratio stays the same, doesnt mean the oxygen entering the engine is always the same. Hope that helps, and someone please correct me if im wrong!

*Edit* and yes it is always beneficial to get a tune after any sort of modification, but not always necessary

But isn't the theory of a cai that the ratio of air:fuel is changed by the cold air? If the ratio remains the same what is the benefit of a cai?

 

[Bigmoney890]

I was always under the impression that the a/f stayed the same, just that the cold air make the engine run better... But then again im not an expert by any means

 

[bespurcell]

But isn't the theory of a cai that the ratio of air:fuel is changed by the cold air? If the ratio remains the same what is the benefit of a cai?

The theory isn't to change the ratio. The theory is to get more air in the engine. When you add more air your ecu adds more fuel to keep the ratio the same(within it's limit's of course). The ratio isn't what is really giving you power here. It's the fact that your car can breathe more air which in turn allows it to burn more fuel. More fuel burned equals more power. The stock intake is like running a marathon while breathing through a straw(the stock intake is a cai btw). The difference is an aftermarket intake is alot less restrictive.

 

[svcook]

The theory isn't to change the ratio. The theory is to get more air in the engine. When you add more air your ecu adds more fuel to keep the ratio the same(within it's limit's of course). The ratio isn't what is really giving you power here. It's the fact that your car can breathe more air which in turn allows it to burn more fuel. More fuel burned equals more power. The stock intake is like running a marathon while breathing through a straw(the stock intake is a cai btw). The difference is an aftermarket intake is alot less restrictive.

Okay.

If I expand the air flow capacity of the intake, where is the next bottle-neck for air flow? And does this next bottle-neck prevent more air from reaching the combustion chamber even though I've opend up the in-take?

 

[brown7]

ford is pretty good about matching everything to within its power limits. anything you change or add only helps with the efficiency. i.e. port matching.

efficiency is what is making the majority of your power.

bolt ons usually help with this up until a point.

 

[bespurcell]

And does this next bottle-neck prevent more air from reaching the combustion chamber even though I've opend up the in-take?

No. You will get more air into the combustion with a good cai than with the stock intake.