the myth of aftermarket air intakes...

[tooter]

Just when you thought your aftermarket SRI would make more power than your stock air box...

http://www.youtube.com/watch?v=PAIxeQUSg-Q

[fnkngrv]

it isn't just about HP

[cali yaris]

I believe their results, with the car they tested. But it's interesting how I documented +12 whp with a CAI, pulley, header and axle-back exhaust on my Yaris.

Something, or combination of things, increased the power output. It's possible the CAI contributed nothing, but I don't think the other modifications alone did it.

It's worthy of discussion. (and no in advance, I only have the 'after' dyno still saved)

[cali yaris]

it isn't just about HP

True, especially of a peak. HP/Torque curves and air/fuel would be a more complete picture.

Tooter's intake, for example made +1 whp (I think), but lost over much of the range (with a stock throttle body). You could just say it gained +1, but that wouldn't be a very complete picture.

[ilikerice]

I gotta dig out my dyno with stock filter and after with aem cai. No other mods and it was only 1.5 whp gain. I have weapon r header and axleback and nst underdrive pulleys. I need another dyno

But the cai sound is nice.

My friend has the new 5.0 mustang. He says you lose hp by going cai. But will gain just using a drop in k&n filter. Must be duct work. It depends on the application i guess. Every car is disigned differently

[fnkngrv]

Originally Posted by ilikerice

It depends on the application i guess. Every car is disigned differently

^ This.

[tooter]

Originally Posted by cali yaris

I believe their results, with the car they tested. But it's interesting how I documented +12 whp with a CAI, pulley, header and axle-back exhaust on my Yaris.

Something, or combination of things, increased the power output. It's possible the CAI contributed nothing, but I don't think the other modifications alone did it.

It's worthy of discussion. (and no in advance, I only have the 'after' dyno still saved)

I would like to have seen that baseline dyno so that the change could be documented. The only way to tell for sure if the CAI did anything would have been to dyno it with all of those other items and the stock air box.

A while ago I put the stock air box back on and couldn't feel any difference. The guy in the video said more than once that you can't feel a change of less than 10%.

[cali yaris]

What does "feel a change" actually mean? And is that universal for all cars, with all power outputs, and all curb weights?

If you drive a certain hill, and your car slows down on that hill, then you make a modification, and the car holds speed on that hill you have obviously produced more tangible power. But I bet you can't feel that on the flat, from light to light.

[fnkngrv]

Originally Posted by cali yaris

If you drive a certain hill, and your car slows down on that hill, then you make a modification, and the car holds speed on that hill you have obviously produced more tangible power.

Excellent point.

[tooter]

That's why a valid driving test includes a variety of conditions, and the 10% was just that one mechanic's opinion.

I thought it was significant that one of their test vehicles was a little stock 1.3 Daihatsu, which is comparable to an underpowered stock Yaris. I run the most unrestricted intake there is, short of running none at all...



...and was suprized at (besides being quieter) how similar the stock air box performed in comparison...



Although I opened mine up slightly with a larger aluminium air horn.

[fnkngrv]

You can say what you want, but I definitely noticed a difference with my AFE in the 3500-4500rpm range. This is where the guys in your video in all honesty as far as I am concerned did folks viewing a disservice. There are supposed to be multiple reasons to change over to an aftermarket intake.

Really they weren't even doing a correct test because they didn't have the filter in the proper spot for solid possible gains. I will grant you that they did say that they were trying to mimic what a lot of folks do, but depending on the kit if it is worth a damned it will have some type of shielding, etc just like the stock box does.

[why?]

there is so many things wrong with those tests. This type of thing is where science and stupidity meet up in the car world.

nothing is proven with 1 dyno run. Repeated runs with the same power, usually within 1 or 2 hp, are necessary to prove anything.

there was nothing remotely scientific about what they did. They took two random filters in the 1.3, mounted them all the way in the back of the engine compartment, and compared that to a stock system that they even admitted looked liked it funneled air from the front of the engine compartment.

now maybe in some lala land people actually do stupid crap like that. but every intake i've ever seen comes with piping to get air from a more reasonable place.

it is also more than a little suspect they did not show the dyno charts together on the screen. They also assumed everyone wanted only peak power. Both are idiotic, and reek of purposeful deception.

now in the real world, a reputable company is not going to sell crap that does not do anything. K&N advertises 4.56 hp gain, shows dyno charts that i am sure are repeatable, because they know competitors will try and prove them wrong. Any reputable company will do the same.

I've spent decades of my life pouring through car magazines with dynos of different things. There is a gigantic difference between scientifically proving something, and doing what those losers did.

[tooter]

Originally Posted by cali yaris

True, especially of a peak. HP/Torque curves and air/fuel would be a more complete picture.

Tooter's intake, for example made +1 whp (I think), but lost over much of the range (with a stock throttle body). You could just say it gained +1, but that wouldn't be a very complete picture.

While your point is well taken, the +1 is incorrect, Garm. The peak horsepower difference between the stock manifold and the tooter manifold is actually +3.4 hp. Both runs were done on the same day with the same stock throttle body, and the tooter being the only component changed.

(stock manifold + stock throttle body = red)
(tooter manifold + stock throttle body = blue)
(tooter manifold + 1ZZ FE throttle body = green)



And speaking of a more complete picture... I still haven't seen your +7hp graph yet.

[CoryM]

A clean factory air filter typically flows at least 150% of what the stock engine can pull through it. I've done the math in the past when building custom cars (and again on my most recent one). The idea is that the stock filters will be left in for 24000km or so before becoming restricted. Go to a filter manuf site and they often post their flow numbers. Compare those numbers to what your engine can do and you will find it's plenty. There are a few stock cars that have filters that are very small (older cavaliers come to mind), but typically anything newer than 98 or so have waaaaay oversized air filters. I would guess the stock Yaris filter (but probably not the airbox) would support up to 300bhp (and yes, that's a guess only. Been a long time since I've done the math.) There are some airboxes/inlets that restrict flow because they decided that "quiet" is more important; Again, not very common. One last thing to consider is that plenum design is HUGE in terms of power, and throttle response. The idea is to have lots of still air sitting there ready to be gulped into the engine as soon as the throttle body opens. This is why the inlet hole in the airbox often seems too small.
Fluid dynamics..... gotta love them.

Cheers.

[TPA5]

I still think that if aftermarket intakes were so amazing for performance, the manufacturers would install them. Instead manufacturers use the design that was created by engineers way smarter than I am, so I'm good with that. I could see the benefit of an aftermarket intake with a turbo or with a slew of other mods, but on it's own? I don't think it does much but make more noise.

[why?]

Originally Posted by TPA5

I still think that if aftermarket intakes were so amazing for performance, the manufacturers would install them. Instead manufacturers use the design that was created by engineers way smarter than I am, so I'm good with that. I could see the benefit of an aftermarket intake with a turbo or with a slew of other mods, but on it's own? I don't think it does much but make more noise.

except that oem has a total different goal than aftermarket. Look at the Yaris' intake. The goal is not sheer power. They have to worry about california's silly carbon in the intake requirement, noise, vibration, and harshness, gas mileage, the amount each one costs, how easily can the robots install it, etc.

aftermarket cares about one thing, either total power, or tourque and power band. They don't have to worry about price point, or dumb laws, or nvh, or any of the many other things that complicates what the oem was doing.