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Discussion Starter · #1 ·
so i have an idea for moving air into sled engines that i'm thinking about trying on my sled. i haven't been playing with sled engines for very long, but i have lots of experience with tuning impot cars. so thats where i'm coming from on this idea. i want to make a cold air intake for my sled, similar to what you would find in an import car. i'm thinking of getting rid of the factory airbox, and putting in a pipe on each carb that points up and sucks air from the same location as the factory airbox through 2 high-flow air filters. the pipes would be much lighter than the airbox, would free up more room under the hood, provide unrestricted airflow, and act as a resonator that would make for a sweet engine note coming from under that hood. not to mention it would provide a horse power gain.
so does this sound like a decent idea? i havn't seen anything like this on a sled, but like i said, i haven't been around sleds for all that long yet.

ps. if this idea hasn't been done yet, and someone takes this plan, starts mass producing intakes, and makes a bunch of money off my idea, you can expect a call from my lawyer. hahahah.


dave m

93 mxz chassis w/97 440cc LC.
old tunda w/377cc
 

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Discussion Starter · #2 ·
i also have a question along the same lines. when i look at exhaust pipes for sleds, i really wonder why they are designed the way they are. why would you want the exhaust to open up into a big huge tube mid way through the pipe? when i look at this i see a big problem with air flow dynamics. this big chamber would just disrupt airflow, and slow down the velocity of the escaping exhaust gasses. the only reason i can think of why these pipes would be made like this would be for heat dissipation. but i would think that a pipe with a uniform diameter that led into a short, slightly larger diameter, resonator would provide much better power gains. any thoughts on this subject??

dave m

93 mxz chassis w/97 440cc LC.
old tunda w/377cc
 

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Wow, i have so much stuff to say about this.

First off, i think you are forgetting the fact that most snowmobile engines are 2-strokes vs. the 4-strokes in that of import cars. The intake and exhaust on most factory sleds are "tuned" for optimum performance. The exhaust system is actually supposed to have what you call a "bulge" in the pipe. This chamber actually provides a 2-stroke engine with MORE power. The exhaust gases are forced into the chamber and actually resonate backwards forcing more un-spent fuel back into the cylinders where it gets compacted in and cumbusts with even more fuel from the intake ports. This provides a significant power boost over just having a straight pipe. It's actually one of the principles of what makes a 2-stroke engine work. "Rocket" may be able to enlighten the subject even more because he builds custom exhaust systems for snowmobiles.

Secondly, the air box has several purposes, one of which is to keep snow from being ingested which can, if too much enters, cause the intake side of your piston to scorch. But what many don't realize is that the air box is actually tuned for the engine as well. It helps keep a stable air pressure within the box because the hood scoops are forcing air inside the engine bay and there is a constant change in pressure from the wind. Now, you can certainly run a sled without the air box, but you must re-jet your carbs for the adverse effects it has on your carb tuning. Many people run air filters or prefilters over each carb, but i don't recommend just pulling out the air box and slapping in a pair of filters. It may take a bit more work than that.

As far as your cold-air intake idea goes, it's a very good thought, but i think there is enough cold air from the chill of winter to take care of that on its own. Plus, many air boxes are designed with the foam filter on top which (usually) pulls the air in from the outside of the hood where your handlebars are located. I understand that you don't want it to inhale engine heat, but many non-EFI sleds cannot adjust for this change. However, new sleds like Arctic-cat's F7 have place the intake side of the engine facing forward to perhaps get more consistent cooler temperatures, similar to what you would call a cold-air intake.

I hope this clears things up a bit. You have great ideas, and if you want to try them, i say go for it. I also have experience with forced-performance on import cars, so i have a good idea of what you proposed. This again is my opinion, so please correct me if i am wrong.
 

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There was an article in the March 2002 edition of the Canadian Snow Goer by Kevin Cameron on that exact topic. His take was that ram air doesn't work nearly as well as a resonance chamber, which is exactly what your air box is.
So this is why the big three have opted for airboxes rather that big cool looking air-scoops on the hood. I am not sure how 2 tubes would be able to match the resonance of an tuned and engineered airbox that was built for your machine.
These sled designers do this for a living, and are very good at what they do, and that is make good all around sleds, the aftermarket stuff just allows you to tune your machine for the type of riding that you do.

 

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the thing with tuning on an import car is taht it is efi. When you intake colder air it can adjust the fuel input to produce optimum power with this air. A carburated engine can't do that. Also air boxes are usually quite light. A couple feet of PVC pipe would weigh more. And as already said the air boxes usually intake air from right below the handlebars which is intaking cold air anyway. Also intakes from this point often(as with import cars) make annoying noise.
 

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the cold air kit idea has merit, the pipe idea does not. if a 2-stroke pipe doesn't have a bulge, it doesn't have backpressure, it doesn't have compression, it doesn't run, period. without backpressure, your intake gasses escape through your exhaust port before they can be burned.

the intake idea definatly has merit. On the SRX for sumer, we run K&N cones. no power increase over stock becuse your pulling hot air, instead of cold, but you'r pulling more. if you ran a tube away from the engine heat, you could greatly increase performance. BUT there are some inherent problems with this system, which is why airboxes where invented in the first place.

ok, the first problem you'll encounter will be your engine wont be able to start well at all, because the freeze-thaw cycle under the hood freezes the water in the filters. meaning your engine cant breath at all until it's warm enough under there to melt this ice.

second, and more important problem, also relates to your freeze-thaw cycle. there will be snow gets caught up under the hood, which then melts, and since filters like that don't drain the same way airboxes do, that water is makeing it to your engine. engines don't like water, water doesn't like engines.

if you managed to put a drain system at the bottom of you PCV tubeing tho...


if this works, I want a design credit and royalties : )

they may be called snowmobiles, but hiding behind that is a cheap excuse to not grass drag.
 

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Discussion Starter · #7 ·
thanks for the replys guys, and thanks for clearing up my thoughts on the exhaust.

as for the intake,

in terms of making power, i want to have the pipes taking air from under the handlebars just the same way the airbox does. i wasn't considering a ramair setup at all because of the snow ingestion issue. it would make power just due to the unrestricted, cool airflow, and the air velocity created while travelling through the pipes.

in the event of any snow ingestion or condensation build up, i did have a water trap/drain already planned into this design. i just didn't want to give too much of my design away over the course of this post. (sorry, no royalties)

as for weight savings, i was thinking of thin gauge aluminum pipe rather than pvc, so i still think that these pipes are going to be lighter than the stock airbox.

the thought of jetting did cross my mind. and i was thinking that if i made a set of these for my sled, i would put in some fatter jets for the first ride just to be safe.

i just have one more question regarding factory airboxes. i aggree that the guys at the factory are pretty smart people, and that they probably try to design their airbox to produce the most power within the perameters set out buy the company. however, i have also heard of the airbox refered to as the intake silencer. this leads me to belive that one of the functions of the airbox is to reduce engine noise. ussually when you try to dampen engine noise, horsepower is sacraficed. this is also why i am guessing that people will "gut" thier airbox for an increase in power. if what i am saying is true, than a better flowing air intake system would provide a nice power gain, but also increase engine noise. judging by some of the exhaust pipes i have heard up at the mountains, the extra noise created by the intake would be just as welcome as the power it creates.

any more questions or comments are welcome.


dave m

93 mxz chassis w/97 440cc LC.
old tunda w/377cc
 

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like I said before, this cold air intake would make much more noise then your stock box. With the intaking right in front of you you will definetally hear the noise. I think it would be worthwhile myself though. You should just drill a whole in the bottom of each of the tubes so water can drain. Stock airboxes have holes in the bottom for this purpose, it wouldn't allow a large amount of air in so you woudl stil take most of your air from the cold air spot.
 

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Discussion Starter · #9 ·
ya i think i'm gonna give it a shot. i'll let you know how it turns out.


dave m

93 mxz chassis w/97 440cc LC.
old tunda w/377cc
 

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I just found a really cool article that explains more about air boxes. It's pretty interesting, read the bottom.

click here

There are also some other really good articles on that site too.
 

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Discussion Starter · #11 ·
thanks megaman, that is a really great article. totally changes my opinion on this topic. the idea of maintaining positive intake air pressure makes quite a bit of sense.

dave m

93 mxz chassis w/97 440cc LC.
old tunda w/377cc
 

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<BLOCKQUOTE id=quote><font size=1 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>Originally posted by 500fasEnuf:
There was an article in the March 2002 edition of the Canadian Snow Goer by Kevin Cameron on that exact topic. His take was that ram air doesn't work nearly as well as a resonance chamber, which is exactly what your air box is.

[/quote]

Didn't someone say that before.....daaaa
 

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Sheesh, i never even noticed that. I don't pay any attention to the author or publisher or any of that crap. The link shows SnowTech not Snow Goer, but the author is the same.
 
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