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I’ve been working on some calculations for possible air box mods—does anyone know off hand what the air box volume for the 1WG is?... I can’t find that figure anywhere.

Thanks

Don't have an answer to your question, but would be interested to hear your thoughts on air-box modification..

Tape off the carb throats, measure how much water is needed to fill the airbox. You may want to measure before and after the filter in two sections - the filter HAS to affect the Helmholtz resonance. Taping the bejeezus out of a filter (on both sides) and then installing it should do the trick.

Welp, since you asked…
My thought on the 1WG air box is that it’s a brilliant, well thought out unit stuck in an absolutely miserable location.
I’ll spare ya the list of what I think it does great, but the short of it is, it pretty much does (really well) everything a modern air box is capable of (as an effective plenum chamber).
The problem is where the box is placed.
The body of the box takes on a lot of heat from the engine (which can be controlled some by wrapping it in a heat shield, etc) but the real problem is from where it draws air—from between the back of the box and the front of the gas tank. The inlet hovers over an area where nothing but hot, low-density air rises, then it sucks it up.
As great of a box it is, it has diminished returns because of this-- it doesn’t get a steady supply of cooler air (or any really) and engines that receive an inadequate supply of air in poor condition simply will not supply the same amount of power as ones that do.
I clipped this from an article last week:
Less density means fewer oxygen molecules in each liter of air; less gas can be burnt, making less torque and power. So, if an air box has its inlet at the front of the nosecone rather than right next to the super-hot radiator or exhaust pipes, it'll get more oxygen in and more power out.

Last week I cut an inch and a half diameter hole through the tank cover, directly above the box’s snorkel. I cut it because I’m rebuilding all the bodywork anyway and just thought I’d see what would happen. Theoretically, the carburetor saw a little “better” air but what I didn’t expect was the incredible amount of heat that poured out the hole at idle after the bike got hot. What was once just getting trapped there (then getting eaten up by the inlet) before I cut the hole was still rapidly sucked into the box at higher RPM. It just kind of seemed absurd to just let it stay that way, so…
I’m keeping the box-- I don’t want pods or any kind of forced induction system, neither of which I think is a better alternative to a well sorted out air box system.
I did some experiments in reconfiguring the intake and had a few pretty satisfying results, one of which absolutely gave the bike more juice, so to speak, at 100mph +.
I think I’m just gonna pull air through the top of the tank cover, perhaps with some type of shroud to shield rain from the inlet I build which will go straight down into the box, but I’m still doing some layout and math (hence my request for “box volume” info).
I need to tinker with the inlet/ diffuser, but I need to know a few more numbers before I can calculate the shape and length for ideal deceleration of air and for tuning the frequency of the whole package. The diameter of the ideal inlet (not where the duct hits the box but where the air first enters the duct) however, I know. It’s 2.79 which is a calculable dimension knowing just an engines displacement and its required rpm for max power (and the formula to figure it out).
And that's where I'm at with this thing.
If anybody’s interested in any of this I’ll post some photos of what I end up doing and any further thoughts— and any of yours would be greatly appreciated.
Thanks.

Take s look at the OW01 air boxes. They're similar shape to the standard air box but have ram air on them. Ram air doesn't add much to an airbox other than volume which is important. As I understand it the air box is a flowing unit and the air is dynamic all the time, added volume is good for when you open the throttles quickly. The snorkel is good for dynamics it gets the air moving faster, maybe you could mount the snorkel above the tank shroud or venitlate the shroud form the front to cool the air under it.
There should be a FZR600 3he top fairing about 1989 with ram air pipes it should fit your bike (you might need the full fairing) that should help keep things looking stock.

I’ve given some thought to a ram air system and they’re obviously not without virtue. You can position the intake in a high-pressure area away from engine heat and the box will ultimately “ram in” the mixture better then the configuration I have now (at certain speeds). Also, like Ducati has been doing recently; you can stick filters in the ducts and capitalize on the largest box you can fit by making the volume all air with no internal obstructions. They have other benefits as well…
But they have momentum losses and, because ducting will not be 100% efficient, some (a lot) suffer a little at some point in the rev sweep where they “choke” a tad.
I’m taking that information on faith however as I’ve never done these kinds of induction experiments on testing equipment (See John Bradley’s Racing Motorcycle “Technical guide for constructers”— there’s not of ton of air box stuff in there but he does reprint a few informative testing results.)
The reason ram air type set ups are used on performance bikes now is because the reason they couldn’t effectively be used in the past (when they were basically a novelty waiting to be developed) has been sorted out. You need a good fuel injection system that can articulate the air/ fuel mixture at different road speeds… without one (which I don’t have) you’re bike will typically operate great above X amount of speed/ less well under it. Some of this (like mid-range) however can be handled a little with a well shaped/ sized box.

I found this online that speaks to this:
“Valve overlap will naturally have a dip in the torque at about a third to a half the red line rpm. If the air box is tuned to have minimum resistance to air flow at this rpm, the dip in the torque curve will be partially filled in by the ease of pulling air into the engine.”
“So, your air box is most likely designed to add horsepower in the mid-range. The air box will have little or no effect on peak hp.”

But there’s still gonna be disruptions to power deliver characteristics at different speeds (with no F.I.).
I just think a good box setup can do more all around with out an intentional ram effect going on (again, especially with no F.I)
But I may decide otherwise as I’m still thinking about it all/ I'm checking out the system on the OW01 now.

I'll post some photos of what I did last night later... I can't seem to post 'em right now.

The air filter takes up space in the airbox, thus will impact system resonance as Don suggests. I've also considered using water to measure volume. However, I have not seen any data to support the theory that Yamaha actually "tuned" the FZRs system resonance for optimum performance. No doubt, it was deemed an acceptable compromise given cost, space limitations, and noise requirements. It works well enough, but I wouldn't try too hard at replicating the OEM volume and port resonance. It's interesting to note that Yamaha made a "kit" airbox for racing the FZR. (Granted, they were likely used with different cams, but still...) I don't think Yamaha's production induction systems started getting optimized until more recently (T-cat). I agree with Evil, that "ram-air" has minimal pressurizing effect, but it adds volume, and it draws air from a cooler source.Yamaha's kit airbox incorporates these elements.

I'm sure the YZF600 motor in my FZR400 would like a better air box, so I've given some thought on this issue. If I could route a duct from the front and over the radiator, I would do it, but that looks like a serious challenge. I would go the OW01 route if I could deal with the cosmetic change.

Interesting article here also. http://www.thunderproducts.com/AirboxesDynotech.htm

Thanks for the article-- I'll look it over tonight.

And ya, I think I'm not gonna worry too much about retaining/ duplicating the OEM volume. I’ll probably end up pulling up that channel in the top of the box and create a larger volume area. I'm guessing that provision is only there to give space for the snorkel to point backwards. Now that I'm going to change the inlet layout I’m taking that stolen area back! (It looks like there's a good 5x5x5in. available there.) I would think any after the filter-wall volume increases will provide more still air for the engine to grab at high speeds.

If you haven't already, check out BDK engineering's take on all this. They've got a pretty smart carbon fiber, ram air box available that draws from the bikes nose. As I remember it, I think the duct work sits over the radiator/ under the front ends bottom yoke like you mentioned.

Here are a couple more.

http://motorcycleinfo.calsci.com/Airboxes.html
http://www.saltmine.org.uk/randy/airboxdesign.html

Problem for me with trying to optimize tuning via Helmholtz principals is that it would require careful measurement (including length of intake tract to the top of the valve). Determine at what rpm the midrange dips occur and a bunch of math just to get in the ballpark. Then construction of an airbox that will likely need adjustments. Unfortunately, I'm just not that motivated....

The BDK box is pretty trick, but no way is it going to work on my 1WG. R6 yokes and YZF radiator fan obstruct the path for the intake duct. Would be sweet on the 3TJ though. (If it clears the R6 yokes there also).

The BDK snorkel needs the radiator to be notched or dropped down, BDK do a specific rad for this and racing so it's bigger volume too.

The 600's cam cover sits higher than the 400 so you can't get the snorkel in. You can cut a hole in the bottom headstock bracing though (this 3TJ frame) and strengthen around it then put in a little quarter turn scoop. You probably wouldn't need it to come any further forward than the bottom yoke, you can bastardise the snorkel with an airbox or fibreglass a base to seal to the tank or airbox cavity and keep the carbs and coils inside the box.

FZRRDRZ wrote:Thanks for the article-- I'll look it over tonight.
I’ll probably end up pulling up that channel in the top of the box and create a larger volume area. I'm guessing that provision is only there to give space for the snorkel to point backwards. Now that I'm going to change the inlet layout I’m taking that stolen area back! (It looks like there's a good 5x5x5in. available there.) I would think any after the filter-wall volume increases will provide more still air for the engine to grab at high speeds.

I've had the same thoughts.

Evilchicken0 wrote:The BDK snorkel needs the radiator to be notched or dropped down, BDK do a specific rad for this and racing so it's bigger volume too.

The 600's cam cover sits higher than the 400 so you can't get the snorkel in. You can cut a hole in the bottom headstock bracing though (this 3TJ frame) and strengthen around it then put in a little quarter turn scoop. You probably wouldn't need it to come any further forward than the bottom yoke, you can bastardise the snorkel with an airbox or fibreglass a base to seal to the tank or airbox cavity and keep the carbs and coils inside the box.

Good info. So it's a "no-go" on the 1WG/600. Guess that leaves two other options; go the OW01 route, or cut holes in the frame like the 3EN2 to route fresh air to the airbox.

I've had two 3en2 and have to tell you the ram air tubes are dummies, the holes are in the outer wall of the frame and even those are half the diameter of the pipe.

This is what I did two nights ago:





Simple, but a good start...

The top of the inlet will sit flush with the tank cover (I guess this isn't a mod for those stock purists out there but I'll be able to live with a pretty small hole in the tank cover, especially if it all "works").

The tube is just straight with no internal profile--- this will change when I have some further idea about what it's exactly doing.

It’s a good “tunable” model as I can change the inlet length by cutting longer/ shorter tubes, slipping them down into the filter as opposed to going longer and having it stick further up from the tank cover.

The tube shape will most likely change toward the snorkel type diffuser used on the 400’s which should decelerate the drawn air and raise pressure, etc.

Yesterday I put 50 miles on it and I absolutely felt smother acceleration from high RPMs to higher... and more persistent power at the top of the higher gears. I guess it's just breathing better.

The results in power delivery are not what I would call earth shattering (yet?) but the bike, absolutely, just got a little better. I'm gonna mess around with it more (inlet length and shape, and increase the box volume) but even if I stop here, there was nothing quite like the feeling yesterday when I felt all that hot garbage air poring out from under the tank cover knowing my bike wasn't eating it.

Interesting. Try to find some sort of 'trumpet' or bell-mouth for the intake end; the pressure drop across a flat / parallel inlet is actually rather surprising. It looks like you've beveled the inlet somewhat; this will help a little. I realise this is a track bike, but races are run in the rain - you are going to want a rain hat, standing well off the inlet, as well as a squirrel screen. Are you going to run a filter, or wide open? The GP racers I played with lo these many years ago ran open carbs, and smeared a thin layer of grease all over the inside of the airbox; it caught a surprising amount of gravel and debris! You'll need to rejet if you do, and it will also affect your resonant frequency. If you're looking for a place to put a duct, and you're already coming straight up out of the tank cover, the highest pressure point is typically between the tip of the nose and the windscreen. Look at a car with 'ram air' - poser cars have the intake pointing forward; old-school muscle cars have the intake pointing at the windshield, with the mouth just a few inches off the glass, because THAT's where the highest static pressure can be found.

There've been several suggestions and plans discussed; I'm afraid I've lost track a bit. If I might suggest, a design perhaps worth investigating is a hollow shell that incorporates the carbs, with sealing foam that presses against the underside of the tank cover. A bell-mouthed 90-deg long-radius elbow snorkel comes up out of the cover; it can be recessed into the cover so long as the overall shape is maintained (part of the snorkel extends down into the tank cover / airbox. Run a duct (as big as you can get it) from the front of the fairing OVER the clamps, ending in a bell-mouth diffuser that stops short of the snorkel. This will allow you to tune the length of the snorkel, while still running cold high(er) pressure air to the airbox. You would need grommets for the throttle cables, and a bulkhead fitting for the fuel line (trying to pack the pump into the airbox would be tedious). This is in addition to the normal drains and breathers normally attached. You might want to consider running the crankcase breather off to its own catchcan; you're after power here, not clean emissions. Sucking in hot oily vapours shouldn't be part of the deal.

Hope I’m not getting too far into the weeds with inane detail for you guys but…

With just the inlet sitting near flush to the top of the tank (no scoop) I took the front fairing off and tried to run the bike hard. I couldn’t and got entirely different results then with fairing on (which were really good).

Above 8000/9000 rpm, nearing 55/60 mph, it ran fine. Same RPMs above 65 (different gear), the bike basically wanted to shut off (in rough fashion). The bike stuttered and, well, started to act “confused”, like if you somehow swapped out a carb. (with different jetting/ bore size, etc.) at 60mph. The engine suddenly had no idea what to do.

I made this thing yesterday/ old Harley parts can serve a purpose.






Mounted it. The inlet sits tall under there but it will be flush when done.







I had it pointed both ways (opening toward the front then toward me) and amazingly, they nearly work equally well.


The problem with ducts that run 90 deg. to a surface (that surface at 90 deg. to travel-- like the side of a fairing, or tank top in my case) is that they are profoundly influenced by the slipstream being created as it rushes over the bike at high speed. And that’s what contributed to the above 65mph dilemma.

Like Don mentioned, the pressure drop across a flat / parallel inlet is rather surprising, and this is primarily true (I’m assuming) because of this slipstream effect. Without doing something about it, like obstructing its path with a front fairing, air is dragged away at speed toward the bikes tail before anything can “grab it”, especially a poorly designed duct. The scoop changes all this.

And why I was getting so similar results with two radically different scoop positions (I figure) is that both ways split the difference of this slipstream problem equally, but in opposite direction-- opening facing backward: slipstream disrupted and no air is stolen. Opening facing forward: air is supplied by getting trapped then sucked down.

It seemed kind of amazing to me to turn it one way then the other and have the bike perform the same.

What’s mentioned in the post above about poser cars and old-school muscle cars concerning “highest static pressure areas” is absolutely true and I expected my experimenting to support this in some way but I think I’m going with scoop pointed forward (it works good all over/ great at high speeds). There seems to be something to the way air hits my frontend (w/ front fairing or not- I tried it both ways), then hits the top of the tank that lends itself to scoop forward. I’m not exactly sure why, other then no windshield behind the opening (like in the car world where the setup should theoretically work best), or maybe, seemingly minor obstructions influence the dynamics, like the top of my front end and clip-on’s sticking out the side.

I went searching for something I read years ago about this in A.G.Bell’s four stoke book and when I found it I remembered how he started to influence my negative opinion about ram air systems on non-F.I. systems. He infers the problem when he writes that he dislikes front pointing hood scoops because they create undo turbulence in the system and upset fuel metering. I don’t think he is considering a well sorted air box systems in that passage but I use to read this guy as gospel.

What I have now is kind of like a ram set up but I’m more comfortable calling it a “half-a-ram system”. The ducting is not situated in a high-pressure area like, near/at the bikes nose. It’s kind of in a “mild area” in respects to a zone like that, and it seems to be working brilliantly right there.

Bell-mouth shape is next then I start cutting down the height of the scoop just to the point it still works as desired and just past the point it stops looking like the Pontiacs my uncle used to drag in the eighties.

I think I can drop it a bit and fully retain its function.

Thanks for everyone’s input, and keep it coming if ya got more.