mikstr

Further to some snooping around on the Speedzilla RC51 section, I came across info relating to a chap who makes a custom airbox for RC's (http://speedzilla.com/forums/showthr...hlight=airbox). It has a larger volume and allows the engine to breathe better thus generating more power. This, of course, got me wondering if this basic premise (larger volume airbox) would help the Firestorm/Superhawk breathe better (and, you guessed it, generate more torque and hp).

So, I think I will attempt to build a larger volume box (using all available area under the gas tank) out of fiberglass to test the theory. By doing the work myself, it shouldn't cost too much and as I won't be making any permanent changes I can simply throw it out if it doesn't work. Also, as I have a Flo-Commander, I'll be able to play with the mixture without taking the carbs apart. I am also looking at making some sort of ram-air system (by opening the "phony vents" located in the front of the fairing and feeding them into the airbox). I realize that doing so could potentially create issues with air pressure differences compared to using the stock air inlet but I hope to get around this by borrowing a practice from the snowmobile industry. That is, I will join the fuel bowl vents together with a T and feeding it into the airbox directly with a grommet (thereby making the fuel bowls sense the same pressure as the airbox/carbs and thus keeping the equilibrium between the two). Not sure how any of this will work but it should be fun and hey, I may even uncover some hidden hp in the process (not to mention learn something too).

If all of this works, I may then look at fitting a BMC "race" air filter to capitalize on the better breathing. BTW, doesn anyone know what the difference is between the street and race BMC filters?

cheers

Note to Greg/Hawkrider: I just had a peek at your site and read the info about re-routing the carb vent tube. Any idea what the tube size is? Also, I beleive this would be the tube that I would have to vent into the airbox (as per my little scheme mentioned above), correct?

bluesman

If you will get it all to work - you will be a Shawk tuning hero....
I cn only wish you luck and hope it will work.
As some tip - use lower part of stock airbox, just get rid of stuff you have there (collection hoses etc.). Then you can make blanking plate out of plywood for to "close" lower part of airbox, put clingfilm on underside of tank, put tank on and fill space with construction foam. But make sure you will protect well anything that could be exposed to that fowm - it is horribly sticky stuff. It will give you max. possible volume under tank to model top airbox cover on.
I bought second airbox off ebay and tried that method. Then I kind of gave up because I could not see dramatic volume increase and then I started to think where I ride my bike etc. and told myself to stop messing about...but I wish I'd had a bit of time to work on it.

Hawkrider

Good call on pressurizing the bowls. That's what needs to happen. Though you'll find that you will probably need to run an inline fuel pump to overcome any pressure created while at higher speeds. I don't remember the size of the tubing exactly. Could be like 1/2" OD and something like 1/4" or 5/16" ID. It's thin walled since it doesn't hold pressure.

mikstr

I was planning on using the lower half as it's quite intricate to mould. I am basically looking at using up all of the remaining available space on the top and sides. I have an idea to crate a mould of sorts (an imprint of the available space) that I will use to help me to create the new fiberglass cover (don't want to give all of my secrets away, lol). Either I will build a complete cover or set it up so that the new "cover" creates a seal with the bottom/underneath of the tank itself (as I believe the RC box is said to do).

I would also like to develop some form of a ram-air system. I realize that any noticeable benefit from such a set-up is mostly realized at high speeds but I suspect that the relatively small snorkel used on the OEM set-up may prove to be a limitation to air flow into the box (and hence horsepower). My idea is to open up the front of the top cover and cover it with the water resistant but breathable cloth used on mountain snowmobile to guard against snow ingestion. I then hope to open up the pseudo-vents in the front of the fairing to direct air into this newly crated opening. I will continue to run a filter, however, as I don't feel like sandblasting my engine internals.

All of this could turn out to be for naught but I like to tinker and have come across some functional stuff in the past by doing such expreimentation (such as my intake runner mods). I'll keep you posted

mikstr

Hi Greg,

thanks for responding. You may be right regarding the need for a fuel pump but I doubt that the increase in pressure will be very substantial, thereby allowing the present gravity feed system to do the job. Just a thought but as the current petcock already uses a vaccum feed from the engine, maybe a snowmobile fuel pump (which is run from engine vacuum, in this caes from the engine's bottom end on the two-strokes) could do the job (compact and easy to adapt). Of course, these are unchartered waters....

Can't wait to get the bike home and start the ball rolling (will be picking it up on March 31st weather permitting)

mikstr

BTW, I really appreciate the input guys. Others are welcome too, we may get this going and working after all. If it works, well, I may take orders, lol

shayne

You can buy one. I can't tell you much about it, except that it uses the space taken up by your radiator overflow bottle to get part of its extra capacity, so you need to relocate that. I have a hunch that it was French or German made. Nakedchef has one, but he logs on rarely here.

If you want more info, send me a PM, and I will see what I can find out about it for you.

mikstr

Hi Shayne, thanks for the info. I guess my "pioneering bubble" has been burst, lol Oh well, I may still try it, call it doing it on the cheap (based on the price of performance parts, I am sure the one on the market is likely a bit pricey). I would be curious to know what kind of results Nakedchef has seen (any info would be great, in terms of tuning, ....)

cheers

shayne

Righto, I will see what I can find out. Might take me a while though.

mikstr

More info...

I am toying with two options: make an entire fully enclosed airbox cover, or the sides only and seal it against the tank as the other chap (RC forum) does and you are proposing (in theory easier to do, and truly maximizes volume, also virtually eliminates flex or resonation by airbox walls). In terms of creating the "mold", I will use expanding caulking foam in a plastic bag/membrane (so it doesn't make a mess and stick to everything). It will give me an exact imprint, I can then simply lay the fiberglass on that and presto, perfect match up (should be quite easy and inexpensive to do). I am looking for something to use to seal things up though and not sure what to use (it has to be resistant to gasoline, was thinking weatherstripping/door frame foam but it's likely affected by fuel fumes). Any suggestions welcome...

I may also add filter area to my stock filter (my opening it a hole in the plastic backing and gluing a portion of car (foam) filter in place. I will also see what can be done in terms of force-feeding air to the box.

mikstr

Crazy schemes, part ??:

was wondering about fitting a small high-flow fan motor atop the airbox, with air scoops drawing air from the openings between the tank and frame (mid-tank), resulting in force-fed air into the carbs. Could hook up the motor to a rheostat linked up with the thrpttle so as to vary the motor speed with throttle opening (a poor man's supercharger, lol). Think of it as a way to get mechanical ram-air. The filtration could be set-up at the air entry point, thereby eliminating the present filter and shelf, really opening up the airbox for better volumetric efficiency.

Crazy or what?

Forgive me but I have an overactive mind (really should have been an engineer).....

cheers

Hawkrider

Yes, crazy and it won't work. If you think about the law of conservation of energy, energy cannot be created nor eliminated. It just transfers from one body to another and may change form (heat, potential, kinetic, etc). So whatever power you gain from that fan will be lost through the power required to create it in the alternator. Follow?

mikstr

Hi again Greg,

I have shelved the fan idea, I think I'll have enough issues getting a normal box to work, never mind the fan. In regards to the energy situation, I agree, but how does that account for superchargers and turbos?

Hawkrider

Well, on the turbo you're using energy that is wasted anyway from the exhaust heat and flow and using it to force the air charge into the motor. You lose a little bit of power because of the increased backpressure but gain some torque. Either way the thing spins so fast that it can build enough pressure to effectively overcome any losses involved.

On the supercharger, it's a little different since it's driven off the motor, but still you're creating enough intake pressure to overcome losses.

Keep in mind that the efficiency of either is greatly increased when an intercooler is used. All that energy used to compress the air also creates heat from friction of air molecules.

Now back to the fan idea, if you were to build a fan, or rather air pump, either positive displacement or centrifugal, that could get the pressure similar to that of either a turbo or supercharger then you're looking at a pretty big electric motor. Figure at max boost a supercharger is using at least 5hp from the motor. A loose thumbrule is that every 4hp is equal to 3kw. Do the math and that's 3.75kw, or 3750 watts. The VTR alternator has a rating of 280 watts at 5000rpm, or 7.5% of that required to drive the motor alone, much less the lights, ignition, etc.

With the motor idea you're converting kinetic energy from the motor into electrical, then converting the electrical energy back into kinetic energy. In that process you're losing energy from heat and friction, along with reactive load losses (creating and collapsing of magnetic fields). It's much more efficient to drive right off the motor or use the heat energy from the exhaust.

mikstr

Me again,

I just got off the phone with Kevin Cameron (of Cycle World fame) and discussed my plans with him (I call him on a semi-regular basis to do some work for our magazine). He thinks that increasing the airbox volume should net some gains (of course, experimentation is the name of the game but....).

I am chomping at the bit....

gboezio

I think that the most "tunable" aera on the airbox is probably the velocity stacks length, the ram air effect from their resonant frequency dictate where in the RPM band the slight supercharging effect will peak. Judging by the 2 different length stacks, the engineers probably made the two cylinders peak at different RPM. Now I have to bring the main point, the resonant frequency is designed to work in conjunction with the cams timing, head ports volume (thus velocity) witch have the most effect on where the torque peak actually happens. For a successful modification of the air box design, a cam swap will totally wake up the high end since the ports are already too large and flow too much. The plenum (air box) volume is part of the equation, but the goal is to have enough volume of air so when the engine rams air in, there is no vacuum created in the box. A funny, cheap test would be to remove them (shorten the stacks, raide the resonant frequency, raise the tune RPM) and see if there is a difference in the powerband. I hope you can come up with a few more HP and bow to your engineering will.

mikstr

I have already modded the intake runner length and had success in doing so (do a search as I posted a few threads about this in the past). I am now putting my focus on the box itself. I realize there are a lot of factors at work (scavenging, pressure waves, resonance, volume, shape,....) so I may totally miss teh mark but given the cost of trying something new, I have decided to go for it. I currently have two ideas that I plan to try, both larger volume. Hopefully one or both will work, if not, it's back to the set-up I am running now which is really quite good anyhow.

I would love to run a set of Moriwaki Stage 1 cams but have already spent enough $$$$ on the bike for a good little while. Besides, I am not looking so much for a high-rpm gain as one in the 4-7K range where I do most of my riding.

cheers

P.S. I head to Victoriaville quite often, was there on Friday in fact, we should hook up for a ride sometime

gboezio

Sure, as soon as the beast comes back together and the weather permit I'm all over the idea, I'll tell you about my future turbo project (after the allmighty garage project). BTW what was your bike color and location, I lived on the plateau and regularly saw a red hawk on st-denis street close to mt-Royal, a grey one at the firefighter building on jarry st and a black one around five o'clock everyday on hwy 132 going westbound every day of the week. Was these one of yours ??

mikstr

Nope, mine is midnight blue (the fastest colour btw, lol). There are pics in the gallery

Jonny

Maybe I've got my facts mixed up but didn't they change the airbox and fuel tank on the European '01 and after models? Smaller tank and larger airbox. How much they enlarged it I don't know but knowing that and what kind of power gains would probably be a good reference for you and what gains you will see and in what rev range. Just an idea.

mikstr

Yep, you've got your facts mixed up. In 01 they went to a larger tank on some of teh non-North American models. Some claim that the airbox was smaller on these but I have heard this is in fact not true.

Appreciate the input though.

cheers

Jonny

Doh! I figured I had something screwed up! Couldn't you still look at the differences in volume and hp curves between the two and extrapolate a rough idea of the gains you might see?

shayne

We get the larger tanked models here, and the airboxes are the same.

shayne

As we have discussed previously, my experiments have led me to believe that more air gives more power, however this power is best suited for track use rather than street. In my case 2-3 ft/lb of torque and 5hp were gained with a couple of simple mods. The biggest factor was the airfilter, which was at guess maybe up to 20% larger in area than a K&N (this is only a guess by looking at them). For street use, the constant throttle operation was not perfect. Going to a standard K&N fixed it.

Our (me and dyno tuner) best guess as to the reason for this, is that the bigger filter was changing the airflow, and the standard vacuum slide set-up was not up to controlling the slides causing them to fluctuate, and giving rough constant throttle running, and when you opened it up slowly it hesitated. Give it full throttle though, and it ran clean, and very quickly. So we figure it was the slides that weren't right. As discussed a fit hasn't been found yet, but I will get back to that one day.

My thoughts on your mods, is that you may have the same issues, depending on the airflow levels achieved. Time will tell of course. Perhaps more airflow than I achieved may fix the problem? I haven't tried that.

As a point of interest, with my modded intake set-up, I was runnig 50 pilots, and 205 mains, which were 200 Keihin mains drilled out. I am now running 48 pilots and 170 mains with the K&N. Be prepared to need to step up your fuel delivery a lot.

mikstr

I have a Flo-Commander which allows me to adjust the fuel delivery either up or down at the turn of a screw (as I don't feel like spending the summer pulling the carbs apart to change jets). While I am hoping to generate some gains with a larger volume airbox, it is more of a pet project than a do-or-die mission. I like to ride the thing too, not just wrench on it, lol

thanks for sharing the info

lazn

RE: fan/electric supercharger.. It would work, given a powerful enough fan, however any normal 12V fan you can buy will actually slow down the air and create resistance rather than improve your power output. All any supercharger does (and a turbo is just a fancy supercharger) is put more air into the engine to allow more fuel to be burnt. (they don't create energy) There are electric superchargers on the market that do work, however they draw 60-120 amps!! considering most car alternators are in the 90amp range.. I don't know what the superhawk's can deliver, but I think 60amps would be too much.

gboezio

Gotta haul a trailer with batteries

mikstr

Thnaks for the info. I realize they don't create energy (they just make it act like a bigger engine by moving more air). Again, it was just a lame-brain scheme, lol (a wandering mind, a sure sign that Spring is here and I need to get the bike out ASAP)

shayne

Hmmmmm...... I would have thought that the Flo Commander would give you more adjustability with your existing jetting, but not flow more fuel than the jet is designed for?

How does it work?