knuclepunk-on a sportbike ie-07 yamaha r1-the intake has two preset settings for under i believe 7k rpms and over-the intake tubes are so many mm longer under the 7k mark as opposed to over to keep up the velocity- now this doesn't even take ram air into effect yet

 

I’d like to see where this is going as well, because I don’t see much gain from the ram air effect in terms of positive pressure when I crunch the numbers until you really get the speed up there quite a bit.

If you’re talking about a performance gain from minimizing pumping losses and tuning the intake to take advantage of capturing energy from resonant conditions, then it’s a different story and there are gains to be had. But actually compressing the air (positive pressure) takes a great deal of speed and you’ll need to go over 200 MPH before you see a gain of 1 single PSI above atmospheric pressure. And then you’ve got to factor how efficient your scoop is. For example, take the NACA scoop commonly found on aircraft and on various performance cars (Dodge Vipers, Ferrari’s, Lamborghini’s, etc). It’s considered to be about 70% efficient, which means that only ~70% of the air is making its way into it. Every little bit helps, but I just don’t see much of a performance gain for our trucks or bikes from the air actually compressing to make positive pressure above and beyond your current atmospheric pressure at the speeds we normally drive / ride.

 

Correct.

The tubes (Velocity stacks) vary in length to smooth out the power curve before the ram air system comes into play. Each system is different from bike manufacturer to bike manufacturer (some use a butterfly valve, etc..), but the end result is the same.

My point is that the velocity stack tuning is designed around RPM and not MPH (Read: ram air). My statement of airflow velocity being affected by the pressure drop between the ram air box (at speed) and the intake valve still holds true.

 

To expand on this topic a bit more for anyone interested (except knucklepunk who I'm sure knows this stuff well), the reason it’s designed around RPM is because you’re tuning the intake (cross section, shape, length, etc) to make a pressure wave of air arrive at the intake valve as it opens for given RPM.

During the intake cycle, you’ve got a nice stream of air flowing past the open intake valve until it closes. Even through the intake valve is now closed, the air coming into the intake doesn’t just stop immediately once the valve closes because an object in motion tends to stay in motion and that includes air. So you’ve got a given amount of air in motion piling up against the closed intake valve and going nowhere. The air compresses upon itself (positive pressure) and moves back the other direction as a pressure wave that has energy. As the intake valve opens again, the air again turns around and this cycle continues to repeat as the intake valve opens and closes.

Tuning the intake so the pressure wave is timed to the intake valve opening at a given RPM is how you can take advantage of this positive pressure energy to gain more performance at a given RPM.

I’m not going to get into the nitty gritty details of all the math, but it’s a matter of synchronizing events based on a given RPM. The basic idea is to figure out when and how long your intake valve is open for each crank rotation at a given RPM that you want to tune for. Once you figure out how long your intake valve is open & closed at a given RPM, you factor in how fast the pressure wave is traveling and how far it travels during valve opening and closing events. You’ll now have your resonant conditions from which you can work with to determine how long of a path the air needs for the pressure wave to arrive at the open intake valve. This is why tuning is designed around RPM and not MPH.

 

Id like to chime in and ask what you guys think about bbk? I looked at pics of the af1 setup and it seems identical to mine with the mandrel bending and blue filter and same open air box.As far as i know the only difference is the af1 is SS and the BBK is crome?Not sure if im right or wrong.The way i see it is the betting looking intake setup attracts more attention and who cares if you lose 2-3 HP because you have SS or alum or plastic.But anyway really wanted anyone thoughts on the BBk set up and how it compares.

 

First off your truck is awesome my brother!! Second, I may not be a number cruncher, but CAI is CAI. Unless you're building a 10 second supercharged bore'd out beast! I don't think Its going to make a whole lot of difference. (But I joined the marine corps infantry, so what do I know hahahahaha j/k)

I do understand there are just some number hungry F150 owners out there and thats cool, I guess its all what you like. But that Volant you have looks SWEEEEET! Are there different stages of that or is there just one model and all is about the same?

Hows it sound, under the hood and out the exhaust?

nice ride again!!! Looks like you make the money! Or you live in a cardboard box haha j/k

 

according to a connection i have with yamaha of europe- you are incorrect on the smoothing out comment above btw

 

Well I hope I didn't screw up....I had intended on buying the Volant intake, but after reading this forum I put my order in at Troyer for the Airforce 1 intake. Hopefully I can tell a difference. Thanks.

 

I thought for an air force one you need the xcal becuase the af1 will run to lean becuase the edge doesnt account for a/f ratios?

 

I may be wrong, but my understanding was that only the new 3V 5.4L engines where having problems running too lean.

Someone that knows for sure, please chime in.

Thanks.

 

Oh ok I think your right I didint know you had a 2 valve motor. My bad.

 

Amazing....Not one word about JLT...That will smoke them ALL!

 

According to Troyer, it can happen with all engines. It varies with the intake.

 

Air Force 1 I think.

 

I've been trying to keep my posts easy to read for everyone, but that might be causing some confusion on your end as well. Here's the deal - The length of the stack will change the air velocity and volume inside each runner. Even a slight change in the mouth profile will change the velocity.

Let's say you install a pipe on your bike or an aftermarket air box. You can "tune" the airflow velocity and the runner length to smooth out the power curve and/or adjust when the powerband comes on. This is especially helpful after installing an aftermarket air box on your bike and you've lost a ton of bottom-end power. Heck, you can even change the stacks to fine tune the A/F ratio.

The fact remains that the velocity stack tuning is still RPM specific and not MPH specific. My statement holds true, so you're "contact" in Europe must have had my statement explained to him incorrectly.

Just to be sure, I asked a couple of my friends to confirm if my statement was true or not. Needless to say, they confirmed as well.

As a side note, one friend works at Porsche Motorsports and the other currently builds superbike engines for very popular AMA rider, so their word is gospel to me. I have an email from a friend of mine at Yamaha too. Once I get approval to post his email, I'll do so inside this forum.

Out of curiosity, what did your contact in Europe say besides I was wrong?

Cheers!