Thread: CAI Evaluation
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Old 05-16-2011, 03:39 PM
BigOntheBlue BigOntheBlue is offline
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Engine: 2003-2008 345ci (5.7L) Hemi V8 345hp 375lb/ft
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Originally Posted by theweavman View Post
you didn't add the HP & Torque gains posted by the different companies.....Now I agree that you may have to take those with a grain of sand, but it's also a good starting place for comparisons.....
There's no consistent dyno data set that directly compares CAI systems so I don't think its a good starting place at all to compare systems.
Not all dynos use or follow SAE J1349. If they all did then I'd be inclined to trust the numbers but since they don't all follow the same standard, I tend not to trust numbers from manufacturers. And just because they use an independent dyno doesn't mean that the data is any more valid.

My Spectre claims a 12 HP increase on the box. They don't give me any data on how a 12 HP gain was attained or calculated so it's marketing and not engineering. They don't even say if that was 12HP gained on a 5.7L Hemi Magnum - they could be regurgitating 12HP from another application where the gains were good in the opinion of their marketing department.

I've got a great ocean view property for sale here in Colorado....

The engineering reality is this:

When considering intakes - relative air density is the reason for the gains or losses in HP. Relative air density is affected by temperature, air pressure and the relative humidity.

All other things being equal - if you increase altitude by 1000ft (decrease pressure) you'll see about 4.45% decrease in HP.
All other things being equal - if you increase temperature by 10 degrees Fahrenheit you'll see about 1.15% decrease in HP.

However, temperature and pressure affect relative humidity so we can't actually hold relative humidity constant to calculate the effects of the other two variables. The effect is small though with only about 0.5% decrease in HP with a 10% change in relative humidity. Holding temp and pressure equal of course.

So what exactly does that mean and where do "we" the end users get some valid info to base our decisions? Possibly from somebody willing to test every system under the exact same conditions. OR from multiple dynos that all use the same standard and same vehicle etc. that also all correct the output based on an accepted test standard OR don't worry about it at all. Just give your engine the coldest and largest volume of air with the highest static pressure and least amount of water you can possibly give it ..... "where you live".

For Spectre (and applies to most manufacturer's claims) 12 HP is only 3.4% of what Dodge says my motor should be putting out.... I can get 3.4% by dropping the intake temp by less than 10 degrees but I'll never really make up the difference based on altitude since I've dropped over 20% just because of where I live. (Static Air Pressure) I've seen claims of 70% HP increase - Yes, it's possible when you are comparing where the minimum HP output occurs (the worst possible place to drive) vs. where you need to actually drive it in order to get those gains. NOT based on "Where you live" or your conditions. Comes down to standard ways of reporting the data.

Any intake that acts like a compression chamber or funnel will increase the static pressure at the TB which is what we want. Short of that you can install an air "pump" or fan, or a supercharger or a turbo. SC's are better for gains across the full RPM range, but are pretty pricey.

That's all I got for lunch today - I know for sure that there are users everywhere looking to know exactly what intake they should buy without doing any thinking or research. The relative marketing numbers from these manufacturers are pretty much worthless in terms of comparing A and B to C.


Last edited by BigOntheBlue; 05-16-2011 at 03:56 PM.
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