When It Comes to Your Bikes Engine, It’s All About the Air

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January 27, 2011 | By: Scott Holton

Here’s a basic fact about the internal combustion engine: Every single one of them is just a variation of an air pump. As the piston goes down with the valve open, air — mixed with fuel — rushes into the cylinder. As the piston goes up, it’s compressed, spark occurs, power is made, and the spent gases are sent merrily down the pipe. To make more power, we need to get more air in and out of the motor.

“More air means more power” is the mantra for this blog post and the easiest place to show this is with the motorcycle air cleaner assembly. Mother Harley is handcuffed by EPA regulations, but we can let loose of a few ponies by simply changing to a good quality air cleaner assembly The Hypercharger comes immediately to mind, as does the Forcewinder or the Revtech free-flowing air cleaner.

The less restrictive air cleaner allows more air and fuel (more air requires more fuel) into the cylinder, giving us our power increase. One thing to keep in mind: Any time you change the airflow through an engine, the carb (or EFI) must be rejetted or recalibrated.

Next on the agenda are exhaust systems. Now that we’re getting more in, our next objective is to get more out. I know that drag pipes are popular, but the fact is, they actually hinder performance. They work at the rpm for which they are tuned and kill power everywhere else. This can be remedied by adding baffles and reversion cones such as AR Power Cones, but these still aren’t as effective as other systems.

The best choices for making power are the 2-into-1 header systems such as the White Brothers “E Series” pipe, the Thunderheader, or the Vance & Hines Pro pipe. If you don’t care for the looks of this style system, excellent results can be had with the Python 3 series of pipes, or the exceptional look offered by Hooker. An interesting development in today’s exhaust technology is the double-wall constructed Double D’s — pipes that should be very blue resistant. By the way, improper jetting or timing is the primary cause of exhaust bluing. Being too rich is as bad as being too lean (and yes, there is a product out there to remove this called Blueaway).

Up next — if the pocketbook permits it — is a carburetor change. On Evo’s 90 and up, the stock carb is a CV Keihin. This is a great carb if it’s set up correctly. Its outstanding low-end performance is offset by its small size and wimpy top-end pizzazz. This works well around town but suffers in the big roll-ons on the freeway. By far the most popular parts sold by J&P are the complete S&S Super E kits.  Once again “more air, more power.”

These American-made kits are easy to install and come with an outstanding instruction booklet. Another carb to consider is the HSR 42 Mikuni. A strong performer in its own right, it also comes with detailed instructions. Both kits offer well-designed free-flowing air cleaners. The traditional S&S teardrop was developed to increase airflow due to a vane cast into the cover. And as a bonus, it’s good looking, too! The only improvement I would recommend is to replace the foam element that is supplied in the kit with one of the K&N gauze-type elements available from J&P. The Mikuni comes with the K&N-style filter.

For you EFI guys out there, K&N — in conjunction with the fine folks at Dynojet — have developed the Power Commander. This little unit allows you to make whatever tuning changes required after changing pipes or other modifications. Well engineered, this unit is infinitely adjustable and user friendly. Excellent support is offered via the Dynojet website at www.Dynojet.com.

Comments: 11 Comments | Categorized Under: Dynojet, Motorcycle Engines, Tech Tips

Comments (11)

here is your answer boys,its the difference of night and day.all you have to do is get more air coming in and more air/faster leaving going out…pro series hypercharger breather w/2 into 1 exhaust pipe and you’ll add about 18 hp…example:my pro series hypercharger w/ white brothers e-series 2 into 1 exhaust pipe useing no discs and only baffle sounds great by the way,and even better without baffle,sounds and runs like a drag bike…. (can’t get this exhaustpipe anymore). white brothers sold out to vance and hines but you might get lucky or close with another 2 into 1…you know the old saying if it works and works really well they’ll quit making them…..

I have seen data that compared torque and hp changes when you upgrade the air intake and exhaust on another website. This site does not compare harley’s being upgraded though only other manufacturers ie yama, kawa, honda ect. They do use many different brands of exhaust such as monster pro, and many others. you can see the charts for yourself at pacificcoaststar.com just put in a bike and an exhaust and the chart will come up and show you what to expect in hp and torque if you upgrade. I imagine it would be similiar for the harleys too.

Most of you “BIKERS” wouldn’t buy it anyway if it worked great, but wasn’t cosmetic…..and the newest product on the market.

The problem is there is no source of information to substantiate the vendor’s claims about their products. Nor are there any performance claims to compare. I couldn’t find any info from anyone when I went shopping for aftermarket exhaust and pipes.
None of the magazines or catalog sites will post this infomation as they wouldn’t want to ‘bite the hand that feeds them.’ If they ran a side by side comparison and found that a specific Vance and Hines pipe performed better than a BUB pipe, BUB would pull their advertising.
What is needed is a consumer’s union or someone with kahunas to take the time to test and report on these vendor’s products.

I think a source of the problem is that there is NO accurate performance information posted anywhere for the consumer to compare products for their bikes. None of the magazines or catalog websites posts any such figures, I guess, to keep the vendors from pulling their products or advertising. You don’t want to bite the hand that feeds you…
There are many different bikes and vendor products out there, but the engine and transmission combos are relatively few and stable. Why doesn’t someone take one bike, dyno it, then do a modification with new pipes and aircleaner, tune it, and dyno it again? Post the results. Kind of like a consumer’s union for bike products.

TO: Frank Francis,… Take an old spark plug, smash the top off of it, drill and tap the bottom part to match the threads on your compression releases and screw it back in. Think out of the box… just “make” what you need.

I’m running a Shovel head with an S&S 93 cu in sidewinder kit,heads ported and two spark plugs per cylinder. My question is are there any compression release out there that can thread into one of my spark plug holes? I want to make starting easier,the dream of a hot rod scooter isn’t as important in my old age.
Where can i geta couple or sonething i can adapt to a cored out spark plug? This would be a MAJOR find.
Thanks

I’m running a K&N filter on an 06 EGlide with an HD race tuner. Dyno says I’ve gained 5 HP? Who really knows. Didn’t notice a lot of difference in performance however the fuel consumption seems to have improved

I would think with all the air and more gas, the engine might use some extra cubes, or compression boost to accommodate it?

I have a hypercharger on my 06 custom softail chopper, it makes the air draw to the back and rotate around as it goes into motor. This bike has a 110 revtech motor putting 117 HP to the ground! It is not like a ram air tube like you see on alot of bikes , it works better. My buddy has one on his o6 fatboy,works great also!
RW

Does anyone know if this thing actually works any better than a reg breather with a K&N filter,I`ve been told it`s not any different,just for looks

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