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Voided76

Ram Air Vfr?

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All things considered, our bikes have a very limited top end push and we hit a wall around 140 mph realistically.

Has someone modified their fuel tank, to facilitate a ram air duct to the front fairing area? I saw bodywork for the RVF that indicated this was happening then. Has anyone undergone this now?

http://www.airtech-streamlining.com/hondaz/RVF75093.html

case in point...

One could maybe use a duct under the front fairing, or repurpose the rather gigantic turn signal spots for ducting. A turn signal 2-into-1 setup would yield positive pressure at 80 and above, no doubt. and since the ducting would be travelling up a decent ways I don't think water ingestion during bad weather would be much of a factor in not running a setup like this at all times. Does anyone have 2 cents on the matter?

F__1700_zps7c609376.png

As it so happens, this is the RC45's airbox design. Note the crazy looking air filter, identical peripheral vacuum accessory setup, and the seemingly one-intake top box setup.

Maybe if I got ahold of those intake stacks.... :)

nah. they're like 44 pounds sterling each on the site I found this fiche on.

like holy shit.

Edited by Voided76
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I'm no expert by any means, nor do I claim to be, but I think you may run into tuning problems with a new fuel injected motor. By the mid 90's I think most carbureted sport bikes had external ram air intakes. Carbs deal with changes in air intake pressure/rate quite a bit better I think as they depend on a Venturi to bring gasoline into the carb body. Modern efi systems have a predetermined fuel injection rate that could result in your bike running too lean when you get to that magic speed where the extra air pressure makes a difference. I don't know enough about power commanders to know if you can program them to account for this, but I would imagine a lot of re-tuning would be required. I think they usually program based on rom, not speed? Again, I don't know enough about the power commanders. I try to avoid the very slippery mod-slope :-)

I think there's room for improvement in the way of cold-air intake in general. I haven't looked much into the vfr intake, but looking at the fiche for the airbox, the 6th gen has 1 intake duct (which I think collects air from directly in front of the air box), whereas my old 954 had two intake ducts which collects air for, inside the failing, but on the outside of the frame where I would assume the air is colder.

Here is what the 6th gen box looks like (part 3 is what I'm talking about):

http://www.partzilla.com/parts/search/Honda/Motorcycle/2007/VFR800A+AC/AIR+CLEANER/parts.html

Vs the 954, for an example (part 17):

http://www.partzilla.com/parts/search/Honda/Motorcycle/2003/CBR900RR+A/AIR+CLEANER+%2802-03%29/parts.html

There quite a bit on the google about ram air and sport bikes. I think the thing is carbs vs efi. I may very we'll be wrong. It's been known to happen.

If you find anything, do share!

Cheers,

~Dave

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I've equipped my 5th gen with Ramair, I've had it to a true 140mph & it's was still accelerating hard. If you look up my 10 year refresh threads, then 1st & second versions are detailed there. I basically sealed the under tank area to the airbox & sealed the edges to the tank to the frame where the original intake was. Then fitted a scoop below the head stock, between the oil cooler & the cross rad hose.

Edited by Mohawk

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I would think, at least with the carburated VFRs, without some sort of fuel metering compensation system to deal with the increase in air pressure/volume, would you be in danger of getting too lean a fuel mixture at higher speeds which could mean burned valves and such??

IIRC, the ram air on the carburated CBR 600's had some sort of balance tubes coming from near the ram air openings at the front of the bike and connected to the float bowls in some way to do this.....

Which kinda makes doing ram air on 4th and earlier VFRs a not so simple thing to do, I think....

Edited by Beck
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When you ram air a carb bike you have to balance the pressure in the carb throat and the float bowls or the increased air pressure pushes the fuel backwards and causes chaos... like Beck stated.. not hard to compensate but hard to fine tune for different speeds... it is easier to ram air a fuel injected bike
@vioded... I'm hoping to cut some NACA ducts into my track bike top fairing like an RC45 wih a remodeled fuel tank for the air ducts

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I've got a beat up fuel tank from a highside already.

^_^ I might just buy a nice one, empty the beater, sand it down, cut it for the ducting, have someone patch in some stainless sheet and weld it nicely, get it resprayed and do a 2into1 ramair on the turn signals, while using signal mirrors.

with the rapidbike it'd be SO EASY to enrichen 4-5-6 at a rate condusive to speed compression.

it's something I could do myself once I had a shop do a decent baseline even.

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I thought about removing the front blinkers,installing a duct of some kind and attaching it to the air box some how .

not easy .

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Not Easy?

How hard could it be?

the only actually tough part would be pulling your tank, to cut it up and make room for ductwork. It would also be kinda sad after having done the snorkel removal, losing that awesome intake sound again. lol.

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Remember our frames on the 6th and the 8th gen's our much much bigger than the 5th gens(gotta get that in there) so it completely in closes the air box well almost .

Not unless you can pipe it in from behind .

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Some of the OzVFR guys were running a 4th Gen trackbike at Eastern Creek for a while, and they experimented with ram air - they ran tubing from the 'intakes' above the front indicators, under the frame and up into the snorkel hole, and sealed it all up.

The bike choked at high rpms when at track speeds... so they ditched the ram air. As said earlier, it's a bit more complex than just forcing air into the airbox.

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Does the vfr800 use a mass airflow sensor MAF or a manifold absolute pressure sensor MAP to determine how much air it is breathing?  If there s a MAF somewhere I do not see it in the diagrams.  Too bad.   That means that for airflow improvements there needs to be some remapping.   MAP sensors almost work as well but may need some remapping for something like a cold air input.   MAP + IAT the ecu could theoretically calculate the mass as flow.  Now I see dry NOS systems which simply depend on the o2 sensors but I would not want to risk doing NOS without a PC.  Do power commanders all have switchable maps that could be triggered at the same time as the NOS?

 

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Its not that the bike needs more power,  it is that I need to tinker.

 

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3 hours ago, CathyEveridge said:

Does the vfr800 use a mass airflow sensor MAF or a manifold absolute pressure sensor MAP to determine how much air it is breathing?  If there s a MAF somewhere I do not see it in the diagrams.  Too bad.   That means that for airflow improvements there needs to be some remapping.   MAP sensors almost work as well but may need some remapping for something like a cold air input.   MAP + IAT the ecu could theoretically calculate the mass as flow.  Now I see dry NOS systems which simply depend on the o2 sensors but I would not want to risk doing NOS without a PC.  Do power commanders all have switchable maps that could be triggered at the same time as the NOS?

 

If I am not mistaken, the VFR800 uses a MAP sensor. In regards to the Power Commander, the PC5 has the ability to switch between two maps and is done via a contact closure. Open circuit = Map 1, Closed circuit = Map 2.

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One reply stated "a true 140 mph". Just how much error exists in the 5th gen speedo?

Sent from my GT-N5110 using Tapatalk

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About 10-15% same as with most bikes, never believe a stock speedo. I've since had the bike up to a real 155mph & it was still accelerating, I had to back off because what I thought of as a smooth road before was not that smooth & the bike was wheelieing off the small crests in the road !  My bike makes 120hp on a known good dyno, so I assume the ramair adds a bit more ! I keep trying to arrange a top speed run to find out how fast it really will go.

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@Mohawk, is there a photo of your ram air setup someplace? I seem to recall reading about it a few months ago but search function not playing ball. 

 

If I recall you also installed dual velocity stacks but again search function can’t find it now. I’m assuming you can’t fit dual velocity stacks in a standard airbox as it is too close to the air filter. So are you running them without a filter? 

 

Im toying with the idea of ramair myself, possibly through the dumbo indicators, but they are a bit too low for comfort. Mohawk’s scoop setup seems better protection against water ingress but the air is probably mildly warmer there than fresh air from outside the bike. 

 

Nevertheless, at the speeds ram air operates there won’t be much cold air trapped in the engine bay at all! 

 

Stray 

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