RCVTR

I haven't seen oil analysis data. The fact that the analysis showed no increase in wear metals or silica changes my opinion. Maybe I'll have to put the K&N back in my Tundra. Lots of filter data out there. Hard to know how to filter it!

Test data I saw with the VTR showed about a 1-2 HP increase at the top end, but at the expense of a loss in midrange torque. The tradeoff was deemed undesirable.

superhawk22

If there's a dip it isn't a noticable one when riding. I had my bike with the stock filter and exhaust jetted and then aftermarket exhaust, k&n and jetted for that and it still pulls hard from all ranges. No noticable flat spots or dips.

shayne

G'day NOrrTH.

The theory behind velocity stacks is to increase air speed, which in turn promotes good cylinder filling. Any increase in the air intake to the airbox is not going to achieve the same result as the stacks.

I reckon if you are running stacks then you are going to need more airflow. Whether or not the stock airbox and filter can deliver this for an engine with stock internals is something none of us can agree on, so it looks like we don't know!

What is known is that on modified engines they need more air.

The other thing I cannot understand is why a K&N filter would show an increase in power but lower torque. Changing the airbox could do this, because if you increase the intake too much you slow down your air speed which is bad, but how can a filter do this? I don't get it. I reckon that a possibility for the torque loss is the tuning when the filter was installed.

Those velocity stacks you speak of are good thing for an increase of 3-4 hp in midrange according to a dyno sheet I used to have. Mildly tuned or stock engines need the long stacks, not the short ones.

Is that along the lines of what you were thinking?

NOrrTH

Thats exactly what I was thinking. Good answer thanks

mikstr

Don't know how I misssd this one, lol

The local speed shop (reputable and authorized DJ POwerCommander center for Eastern Canada) told me that there are essentially two bikes that LOSE horsepower with the K&N's and those are the VTR and Suzuki TL's. Based on this and the DynamoHumm dyno info, I have elected to stay with the stock filter and have no regrets. It should be said that I do not live in a dusty environment and so frequent replacement costs are not a big issue.

In regards to the intake runners, as I have posted before, replacing the short front OEM intake runner with a long OEM unit (rear cylinder runner) yields a definite increase in low-end power and response. The improvement is unmistakable and can easily be felt in the seat of the pants. The only negative side effect I found was an increase in vibration in the 400-5000 rpm range (my highway cruising speed). I would imagine that there is a slight decrease in top-end horsepower however, based on the findings that installing two short runners apparently increases output by about 2 hp on top-end. It should stand, then, that going to two long runners should decrease top end power by about 2 hp over the OEM set-up. In the end, these are cheap mods and one can choose on increased top end or bottom for a very cheap price (and at no risk to the engine).

cheers
Mikstr

jschmidt

Lots of bikes lose power with a K&N.

mikstr

that could very well be but I was quoting from a reliable source in terms of the bikes listed. Also, as I own a VTR, to be honest I don't really care how other bikes react to a K&N

CNI Dawg

AH HA !!!
The obvious answer is for us to develop a variable length velocity stack that changes length with engine RPM automatically!

mikstr

The MV Agusta 1000 has just such a system

Mikstr

Loco

I'm officially fed-up with the unpredictability a K&N filter has given my bike. There may be a slight seat-of-pants improvement in power, but I would rather have a bike I can tune at all rev ranges than one with good points. I'm going back to stock, and the K&N will be up for sale either here or EBay.

mikstr

Hello Loco,

while I know many seem content with their K&N's, your comment sounds almost identical to the one made by my local dealer/speed shop when I contacted them to enquire about getting a K&N. That, and comments by RCVTR and hte dyno sheet on the DynamoHumm web site helped me make my mind up. I am now running a stock filter with the lip cut (search for Bernie Morgan mod on Google) and am very happy with the results.

cheers
Mikstr

P.S. Further to getting a lightened (and precision balanced) flywheel and a Flo-Commander, I just re-tried the two long intake runner combo and am pleased to report that the results are awesome. The engine is now quite smooth across the board (albeit slightly rougher than with the interim length runner I had built and was running on the front cylinder) and wonderfully responsive at low and mid-rpms. I am happy with the result and will be running it this way from now on. Woohoo!!!!

Loco

I've seen this term thrown around a bunch.. Are you talking about those black velocity stacks inside the airbox, or is this something that attaches to the airbox snout? What is a long intake runner?

mikstr

the velocity stack (ie. the plastic funnel-like that runs from the end of the carb venturi into the airbox)

cheers
Mikstr

shayne

Changing of the intake runner is a known modification, and one that Moriwaki make parts for. The consensus is that for a relatively stock engine internally, two long runners are the go. For an engine with higher compression and cams etc, short runners deliver the best.

Short runners on a stock motor do not work. Long runners on a stock motor produce the results milkstr speaks of.

Loco

Are either of the stock ones considered long?

RonVTR

Let me see...

Using the K&N, power will increase as it gets dirty (reduces air flow).

Using the stock filter, power will decrease as it gets dirty.

Hmmmmm... Paradigm shift anyone...

shayne

Yes. I have some billet ally ones, and they are the same length as the rear one. The mouth is much wider though than the stocker.

mikstr

When I use the term long I am referring to an OEM unit as found on the rear cylinder. Short refers to the OEM unit found on the front cylinder (30 mm shorter than long one).

Shayne: how do the Moriwaki runners compare to the OEM? Are they both the same length?

cheers
Mikstr

Loco

What the average price for a set of runners?

mikstr

I purchased a long OEM runner from my dealer last year for @ $40 CAN. I just picked up a set (OEM long and short) on eBay for $10 US plus shipping.

cheers
Mikstr

Loco

It is really just a simple as remove the short one and replace it with the long one? I thought there were locating arrows and other crap preventing that from working?

mikstr

It really is that simple

Mikstr

shayne

The runners I have are made by an Aust guy, who I suspect has copied the Moriwaki design (he sells Moriwaki stuff too). To my knowledge Moriwaki make long and short runners, however each pair are the same length for each cylinder. The long runners I have are about the same length as the longest OEM runner.

The results are just as you report, much better and smoother power in the midrange. I used to have a dyno sheet to back that up that he supplied to me. He also reports that these longer runners help a lot in jetting as you don't need to run as big main jets. As an example, he had a full race engine that ran 185 mains.

Revolution Racing in the UK is one place I think that will sell these parts.

My local guy has a web site which is "hpower.com.au". Not a lot of info on there, but there is a pic, and not sure if he would ship os, but I don't see why not. This business is a sideline for him, so if you send him an email you will need to give him a few days to respond to you. Very knowledgable and a nice guy too. He has done a lot of development on the VTR, including building race engines.

Carnage

I've read how you're all reacting to the K&N filters and I figured I'd put in my two cents. First of all I've read how some of you don't trust a filter that you can see through. Yes you can see through it but that's the beauty of the K&N filter. The media is thin enough the catch the large particles which would damge an engine while allowing for more air flow, while the oil on it catches the fine particles keeping the engine clean. In my experiances with engines (automotive, motorcycle, & aircraft) the K&N filter can cause different effects. This is what I've learned, the more air you can get into an engine the more potential you can get from it. This is why you put forced air induction on an engine such as a supercharger or turbocharger to get more out of it. The one thing you have to remember is that the more air you put into an engine mean that you have to put more fuel into it too. The optimum fuel to air ratio for maximum power is 12:1. So for example if the K&N filter is capable of doubling the air flow from 1 to 2, then the fuel needs to be doubled as well from 12 to 24. This is just a starting point for any engine, you just have to fine tune this ratio for your specific engine. One more note before I close this putting a filter with more air flow on a engine with EFI is so much easier, because the ECU realizes this extra air flow and adds more fuel. Carburated engines don't have this feature so it's just harder to get the mixture at the right ratio.