Okay guys, I think that I can put this one to rest. I called Allen, the owner of CT Racing a few weeks ago.

He said that without opening up the airbox, there was only about a 5 hp increase. He emphasized the need to do this if you wanted to see much of a HP gain.

Also, I questioned him about the peak power being at a higher RPM than the stock dyno chart. Again, this was due to the fact that the motor could get enough air to make more power at a higher RPM.

Also, as mentioned, I asked him about the CT Pipe's dyno chart showing that it was lower on power on the initial take off. He said that was just an error in when he hit the gas and that they had started recording the dyno info just a split second before he nailed the throttle on that run. He mentioned that he might do it over and post it on the website so that it wouldn't mislead anyone. He assured me that had he been on the gas prior to starting the dyno run, it would have recorded higher HP at all RPM than the stock dyno chart in which he was wide open before they started recording the run.

Lastly, he said that the Raptor was the only bike that they've tested that actually makes more power with the Supertrap disks instead of just a pipe endcap with a large exhaust opening in it.

 

cstark, I'm afraid you're wrong.
Think about this. What's the definition of horsepower? It's a link between force (torque) and speed. I can't remember the exact units, but it's torque x revv = power. So the ways to achive more power are to have more torque (high compression, better explosion...etc) or more speed (revv higher).
For what reasons does an engine stop revving? Lots. But the most common is air flow. If you improve air flow (more comes in...and as much gets out), then your engine will revv higher. Then you have spark firing. It has to be set up more precisely if the engine revvs higher. For 4 strokes, you also have to consider the valve springs, they have to be stiff enough so the valve shuts exactly when the cam "does", but watch out for breaking valves...etc
In ATVs, which engines are mostly underpowered motorbike engines, the easiest to gain horsepower is simply improving airflow. You will get more revv (and more torque also, because more mixture comes in).
It's 100% normal the HP are achieved at higher RPM...and it doesn't necesseraly take a high compresion piston and race cams.

 

Zorro,

Airflow does not restrict and engines redline. The mechanical resistance and tolerances of the engine parts restrict the redline. A motor without a rev limiter will rev tell it blows.

 

A quads airbox is setup like a bottle neck. The intake tubes restrict airflow from getting too the carb. Adding an aftermarket airfilter is going too do nothing, unless you modify the airbox lid, remove it, or remove the airbox all together too increase airflow too the carb. The carb doesen't care what type of airfilter you have attached(as long as it's clean). Too increase airflow, you have too get rid of the bottle neck.

 

With an aftermarket pipe, increased airflow and a properly tuned carb. You are still resticted by the stock engine compression, camshaft timing, and ignition timing. The intake and exhaust valves are still the same sized opening, for the same amount of time. The spark still goes off at the same time, and the compression ratio is the same. More air and fuel doesen't do you a lot of good unless one or more of these are changed. Gasoline engines work on basic principles. You do not get something for nothing.

 

Engine dynamics are certainly not my forte but why would these engine "specialists" (Alan Knowles of CT and Curtis Sparks) spend so much time developing these air mods (exhaust and intake) if they have minmal effect?

I am skeptical though of CT's claim of such a horsepower boost with such minor mods. Too get the same boost in a 400 you have to install a 440 kit.

 

cstark,

I don't normally say this, but you are ignorant (look up the definition of ignorance before you assume this is a flame) as to what makes power. You are correct, an air filter does not make power and neither does it help an engine "breath better" as you stated. It might really come as a huge shock to you, but an air filter, get this, filters air!!! Who would have figured?

Where in my post above did I say that an air filter made the CT Pipe have more power? Opening up the air box means relieving the restrictions of the intake system.

By mentioning a hotter cam, you should at least have some crude understanding of what makes more power. The camshaft dictates when the valves open and close and that is one of the determining factors of how much air/fuel that can be ran through an engine in a specific amount of time and/or revolutions.

Get a book, surf the web, ask someone who knows and then when you have an understanding of internal combustion engines, come back and make some responsible and contributary type posts.

 

I can tell you from experience in switching my airfilter, that you do get more power from just an airfilter.

I switched from a stock airfilter to a Uni filter on my 400ex. I had to change the jetting because it ended up too lean.

I keep the stock one oiled and in a bag in case I have to throw the machines on the trailer and I haven't cleaned the Uni. When I have to switch back to the stock one, the machine definately doesn't rev as quick or run as well.

Also, people change their filter to the K&N filters and get immediate changes. This must to with the change in fuel/air mixture and volume.

Your theory that 'just' changing the filter will not make improvements doesn't make sense or prove correct in real world situations.

I absolutely agree that the airbox snorkel is a restriction on the motor. In fact when you look in the Raptor's snorkel there are two restricion fins in the neck. Put your hand over the snorkel and see how long it runs.

The exhaust can also be restrictive. Your suggestion that improved compression and altering the cam will improve power is correct. However, it is not exclusive to those changes. In order to extract the maximum amount of power, you will need to improve all these areas.

For myself personally, I don't want to change the internals of the engine for reliability purposes. I would only consider changing the header, silencer, modifying the airbox and adding a filter.

If the performance gains are 5hp or 10hp I would be thrilled. Maybe in a couple of years when I get bored of the ride and power, I may dive into the motor. But for now, I will take the comfort of reliability.

RM

 

That's enough evidence for me, you absolutely don't know what you are talking about. Some motors may be able to sling themselves apart, but most of the time, it's their effeciency that won't let them "rev till it blows".

It's funny that you understand there are limitations with a given cam, valves and etc.. but then you are unable to make the connection of what produces power and ends up being the final limiting factor. A Banshee doesn't have a rev limiter, nor does a gas powered weed trimmer (WeedEater) but you don't see them throwing rods thru the engine on a relular basis do you? If they continued to rev until they flew apart then someone would beef up the parts and we'd see 20,000 RPM Banshees. The fact is that the limiting factor is the amount of air/fuel that can be pumped through the engine. Without forced induction, all engines are relying on Barometric pressure to feed our engines.

I'll make this deal with you. Pick your choice of any gasoline fueled vehicle to race against me on my old mountain bike or on foot. Allow me to restrict the intake system to my desire. Then we'll race for titles.

 

A banshee has the TORQ's(spelling)system that does not allow the motor too "runaway". When a condition is hit where it starts revving too the moon, that systems kills the motor. Without that, the banshee motor WOULD blow. It acts just like a rev limiter.

A 2-stroke gas powered weed wacker barely has enough power too cut the grass, let along rev too the moon. The carbs are jetted really rich too cut top end power. Running a gas/oil mixture on a 30cc 2-stroke will kill performance.

Forced induction is a totally different animal. More "fuel mixture" is forced into the combustion chamber, but the motor still runs in the same RPM range as a "regular" motor. Who runs forced induction with a stock motor?

Companies like CT Racing, Curtis Sparks, or who ever, will go too great lengths too make a buck. If they claim something and you believe it, your at fault and not them. People that know stuff about engines, will not be calling them and wasting thier time in the first place.

Adding an aftermarket airfilter will increase throttle response and "seat of the pants" feel. But there is not real HP gain.


People preach that the Raptor kills everything in drag races and is the new king of the hill. But the next day, the performance is really restricted by airbox design and stock exhaust system. So which is it?
Lightning quick acceleration does not equal restictive intake and exhaust.