Ram air on a 750 Vulcan? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 9 (permalink) Old 06-03-2018, 01:34 PM Thread Starter
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Ram air on a 750 Vulcan?

OK, no, not really. Not at all actually.

I've owned 3 VN750s over the past 28 years. From the very first one I purchased new back in '89, I thought, why not fab up something to get cooler air to the engine when sitting or slowly moving thru heavily congested traffic. In Virginia, along the I95 corridor between Spotsylvania and Alexandria, commuting traffic is a joke. Way too many hours spent at a standstill, and worse yet, moving along for long periods of time in bumper to bumper traffic from 5mph to 35mph.

So, instead of the engine sucking in hot air from between the cylinders in the summer months while idling thru traffic, why not design something so the engine is at least drawing in cooler air that has not circulated thru the radiator and the two cylinders? All modern cars do this, why not the Vulcan? Yes, I understand, my design also makes great rain scoops. Hence the reason why, perhaps, this mod has never been done or considered. But rain be damned, with a spare set of air filter boxes, I moved forward.

I've always been a fan of the muscle cars I grew up with in the '60s and early '70s with hood scoops. So my idea centers around this concept, and to some degree, I think I pulled it off.

If you're one who does not like the air filter boxes on our Vulcans, please, stop reading here. You will not be able to un-read what you're about to read, or un-see the pictures provided.

This project is for my new to me, 2006 VN750 Vulcan I picked up this January.

To start...

I removed both air filter boxes from my dead '02 VN750 Vulcan. I took the top off of each air filter box. The black, ribbed, rubber insert in the cover is secured to the chromed plastic top with 5 black plastic rivets. Using a drill and 3/8" drill bit, I gently drilled out the melted plastic rivets. Careful not to drill completely thru the chromed plastic top.

Then I measured the inside diameter of the rubber inlet on the back side of the air filter box. The inside diameter is 30mm x 30mm or 900 square mm.

On top of the chromed plastic top of the air filter boxes is a dimple; visible after removing the black, ribbed, rubber insert. Between the outer edge of this dimple, working my way back to the rear lip (area the ribbed insert was removed from), I measured out a rectangle 15mm x 60mm or 900 square mm. This rectangle will be vertical to the ground when the air filter cover is mounted on the bike. Using a Dremel tool, I cut out the inside of these 15mm x 30mm rectangles. I then rounded and smoothed the lip of the cut out with a file and very fine sandpaper.

I then removed the ID 30mm x 30mm, rubber inlet from the back of each air filter box. Out of 1/8" aluminum sheet, I cut 2ea, 2" x 2" pieces. I then drilled 4ea, 6-32 screw thru holes thru each plate at the corners. Then attached one 2" x 2" x 1/8" aluminum plate to the hole I removed the rubber inlets from. These are block off plates. I used 6-32 stainless steel, socket head screws and lock nuts to secure the block off plates to where the rubber inlets were.

With a sheet of 8" x 8" x 1/4" black anodized aluminum plate I had, I cut 4ea long triangles. I don't have the dimensions with me now. These long triangles make up the top and bottom intake runners for each air filter box. I then rounded the leading edges of each intake runner.

In between the two outer raised ribs of the inserts, I measured and drilled 1" apart, 4ea 6-32 thru holes. Using these holes as a template, I transferred these holes to the top of each intake runner. Then drilled and tapped 4ea 6-32 holes in the top of each intake runner. Three of these holes go straight thru the intake runner. The top hole nearest the front, leading edge of the intake runner cannot be a thru hole as it will poke thru the metal.

Once I assembled the upper and lower intake runners to what was once the ribbed insert, I transferred the two middle holes to the chromed plastic top of the air filter box using stainless steel, 6-32 screws and hardware.

After I test fit everything, I applied outdoor rated, clear Silicone RTV between where all of the pieces join. All of the holes where the black plastic rivets went thru the cover were filled with the silicone as well. After the silicone set up, I went back to the stainless steel, 6-32 screws, removed them one by one and applied a very little bit of Lock-Tite, the blue kind if memory serves.

My mod is not perfect, I'm not an engineer, nor do I have a CNC machine, but the mod serves my purpose. I installed these on my 2006, VN750 Vulcan as seen in the pictures.

Anyway, I know I can't drive the bike in the rain anymore. Although, I still have the original factory, unmolested air filter boxes for my '06, and can install them when needed for long distance trips that may involve driving in inclement weather.

Please, keep in mind, this is not ram air, despite how my mod may look. The bike would have to be traveling roughly 188mph to see something like a .7psi increase over atmospheric air pressure to the carbs. And that's if true ram air were designed for this bike by a group of engineers working with a wind tunnel and tuning the bike to handle any increase in air flow like that seen at 188mph. Not to mention the modifications to the carbs themselves to work with the increased air pressure.

This project was only to satisfy an idea of mine, one that I've been thinking about for many, many years for my Vulcan.

I hope you enjoy the pictures. Any constructive criticism is welcome.

More pictures to follow, that's if I'm doing this correctly.

Enjoy,

RustyFuryIII
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Last edited by RustyFuryIII; 06-03-2018 at 02:14 PM.
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post #2 of 9 (permalink) Old 06-03-2018, 01:42 PM Thread Starter
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Additional pictures...

More pictures to follow....
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post #3 of 9 (permalink) Old 06-03-2018, 01:47 PM Thread Starter
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Additional pictures...

There will be three more pictures following this. If interested, I can disassemble one of the air filter boxes for additional pictures of where the new air inlet is, and the block off plates.
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post #4 of 9 (permalink) Old 06-03-2018, 01:52 PM Thread Starter
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Final pictures for now.

I forgot to add, I have looked on both this forum, youtube and out in the wild. I have not seen anything like the mod I've made to my Vulcan. If someone else has done this, understand I'm not stealing your thunder. Like I said, never seen the mod before, an idea I've had in my head for a long time that has finally taken shape.
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Last edited by RustyFuryIII; 06-03-2018 at 02:11 PM.
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post #5 of 9 (permalink) Old 06-03-2018, 09:53 PM
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Not a bad idea if you're keeping the airbox and ears. Well done mod, looks ok.

Maybe a little larger opening? Don't know if there's any added benefit, but the VMax had some fairly big snorkels, one for each carb I think. (have no idea if it actually worked but it looked wild) I know the stock ears just have a small square hole in the back.

Rain might not be a problem, aren't the filters oiled? My foam pods are right out there and rain has no effect. Pressure washer is a different story. I suppose maybe the ear could fill up with rainwater over time/miles. Drain plugs?

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post #6 of 9 (permalink) Old 06-04-2018, 05:02 PM
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Interesting build. The big question is does it run cooler now?
Years back there was someone who installed a different fan to help with cooling on "stuck in traffic" situations.
Also not sure rain would be a problem, but I think I'd add some kind of drain hole to each box in the event you get an unexpected shower while riding.

I think there was a company that did make replacement covers that were advertised as a "ram air" system years back. (Highway Hawk?)

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post #7 of 9 (permalink) Old 06-04-2018, 06:29 PM
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I've seen the solid Highway Hawk covers, they cover the whole ear. Haven't seen any lately. Looks like HH went out of business, looking at their website, everything says zero in stock. I think I got one of the last coolant tank covers to be listed on ebay.

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post #8 of 9 (permalink) Old 06-05-2018, 12:30 AM Thread Starter
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RE: Ram air?

Yes, it does have the OEM oiled foam air filters. I'll have to take it for a few short runs in the rain to see if it is going to be a problem. I just assumed that since I had these openings facing into the oncoming air, debris, bugs, rain etc, that I'd pick up whatever was directed into them. If need be, perhaps drain holes might be in order.

The opening at the mouth of the modified air filter cover measures 7/8", so no, not a really big inlet. I felt that until I got a handle on how this was going to affect the performance of the bike, I wanted to start small and work my way up, if it's what's needed in the event the openings do not allow enough air into the engine at normal cruising speeds and WOT.

Since I have the original air filter boxes intact, and the modified set off of the '02, I plan on taking some before and after measurements.

1) I'm going to put the original air filter boxes back on the bike. Going to pick up an air temperature probe and insert it into the air plenum/chamber in between the two air filter boxes and ride the bike as I normally would when the outside air temp is north of the '80s and log air temperature inside this space during normal driving here in Spotsylvania in day to day traffic. Then I'll put the modified set of air filter boxes on the bike and repeat the testing/logging of data.

2) I've picked out a dual port manometer that I plan to order here shortly. I'll put the original air filter boxes back on the bike, set up one port of the manometer to monitor air pressure in the air plenum between the two air filter boxes and the other port to measure air pressure in the float bowls. I'll again drive the bike around in normal day to day commuting traffic and log the air pressure in both locations as well as determine the differential between the air box and float bowls. Then I'll put the modified air filter boxes on the bike and repeat testing.

It probably won't amount to a hill of beans, but from what I've read online, and I'm sure I haven't read everything on the VN750 Vulcan, it doesn't appear as though anyone has done this to the VN750. However, if I don't take these measurements, I won't know anything. It will be fun just the same though.

Thanks for the comments.

Last edited by RustyFuryIII; 06-05-2018 at 12:46 AM.
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post #9 of 9 (permalink) Old 06-05-2018, 07:31 AM
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Quote:
Originally Posted by Spockster View Post
Not a bad idea if you're keeping the airbox and ears. Well done mod, looks ok.

Maybe a little larger opening? Don't know if there's any added benefit, but the VMax had some fairly big snorkels, one for each carb I think. (have no idea if it actually worked but it looked wild) I know the stock ears just have a small square hole in the back.

Rain might not be a problem, aren't the filters oiled? My foam pods are right out there and rain has no effect. Pressure washer is a different story. I suppose maybe the ear could fill up with rainwater over time/miles. Drain plugs?
Speaking of snorkles, one day I may have to try this with my KLR.


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