K&N filter, exhaust change = performance boost?

Woodswoman

Member
K&N filter + exhaust change = performance boost?

Over on a Facebook group for owners of the CTX700, CTX1300 and NC700, someone made this statement today:

"Throw a Coffman exhaust and K&N filter on it and performance is drastically changed. Will run all day and no more need to change down from 6th for inclines."

Anybody who rides a DCT model tried this combination? Do you agree that performance improves? Is there a downside to doing this on the DCT model? I'd gladly take a boost in performance, but not at the cost of messing up the DCT's behavior.

Thoughts/debunking/endorsements welcome.
 
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ponydrvr

Member
I haven't tried this on a CTX. I have done something similar on a Piaggio MP3 400 and several 500's. My experience is that the power and mid-range responsiveness is improved and mpg took a slight hit (~5%). I noticed the primary effect in the mid to upper rpm range.

IMHO: It is not needed.

Now, If you were to modify compression, change the fuel mapping and ignition. Then maybe, only maybe, there would be some increase in performance. Since this is not a racing platform, and I'm to stingy to buy premium fuel, I don't believe the gain is worth the pain.
 

randy1149

New member
i agree with ponydrve, any improvement (if there is any) would not be a "drastically" changed one. Any noticeable "drastic" changes is in the riders head. I'd like to see a before and after on a dyno especially with the removing the back pressure with the Coffman exhaust. In any case I don't think there's any noticeable improvement to justify the cost.
 

MJC

Super Moderator
I changed my exhaust by using a 2' long pipe with a baffle, it is just like a Coffman but longer and does have back pressure. When I need too I will change the Air Filter to the K and N, removing the air box and have open air flow. There is no change with just the exhaust pipe, just more sound, which that is what I wanted. To open up the exhaust you would have to cut out the front of the header pipe and replace it with a open pipe, (to remove the cat), then change the exhaust. If you did all that then you could open the Air box, using a K and N filter. All of which would do nothing but make more sound and more then likely have you spend more on fuel. At that point you would need to have the fuel mapping (ECU) done. Good luck finding someone to work on that!

There is this person Ivan, who I know does the ECU rework on Vulcan 1700's and some other bikes. I took my CTX700 to him to look at and he said because I have the DCT, there is no way he would try the rework on my bike. On a CTX700 un-DCT he could work on the ECU but would need a bike for about 6 months and because there is little demand it would be costly. He also said that on the bikes he has done, he gets them to run better overall, cooler, use reg gas, with just a small amount of power but people feel like it is more then it is because the bike is running better overall. He also said that 90% just redo the ECU so the bike does not backfire and runs better (adjusted fuel mapping) with aftermarket pipes and air filter. To which he said the CTX700 DCT comes from the factory just about set about the best you can get. So change your pipe and air filter if you want but you are not going to get anything more then more sound out of the bike, and maybe save the heat that the cat makes. And I think he is right.

I changed my exhaust pipe for more sound, and that is what I got, I will change my air filter to K and N only because I have one that will work on my bike and I do not want to buy the Honda one when I have one already that will last longer and can be cleaned and reused. I am not going to remove my Cat, but I would if for some reason it needed to be replaced, I am just to cheap to spend the money on a new cat when a pipe coats $10. So IMHO, only install a exhaust pipe (make your own) if you want more sound or need a new muffler, replace the air filter with K and N if you plan on keeping the bike so you can clean instead of replacing (around 50K miles), if you are looking for better or improvements to the bike, sell it and get something with better performance.

BTW, Rebel, (you know that guy who knows all), removed his Cat, muffler, remade his own open Air box and uses a open K and N filter. And did you know that he now has the most powerful CTX700 6 speed in the world? And guess what? He says " the bike does not need to be re-mapped" and his buddies say "With the exhaust mods And Air mods, the ECU adjusts to the changes" Yes on its own, it just does it..... And now on FACKBOOK people who have read or heard about it think "let me try this", please people, the ECU on the ctx700 or ctx700 dct will not adjust to these changes. The only thing that will happen is the bike will be louder, slower, use more gas and you may think it has more power but it will not. Oh, and if something does go wrong you can always bring your bike to Rebel for repairs, RIGHT? .........
 

Woodswoman

Member
Thanks, guys!

It sounded like a big, fat overstatement when I read it, but I honestly wouldn't mind a little more 'oomph' outta the motor when I need it. (Hey, Honda, give us another 100 CCs, wouldya??)

But I'm certainly not interested in making all those changes, and maybe not getting what I want when it's all done.

As for Rebel's methods, no thanks. If I did to my bike what he did to his, it wouldn't pass state inspection.
 

MJC

Super Moderator
Hey Woodswoman, I agree do not do any Rebels methods!

BTW, Was thinking of riding the Catskills (again) for a few days, do you know of any good cheap, motorcycle friendly hotel/motels I could stay at. Group would be a 2, 3 maybe 4 people. We would stay in one hotel and ride deterrent roads in the area. I was thinking maybe 100 miles from here (Hopewell Jct) would be a good area, then explore the Catskills from there. What do you think? Time frame would be 9/2017, during the week. Thank for any info, mj
 

randy1149

New member
If you want a little more umph change the sprockets to get a lower ratio. But there goes your gas mileage.
 

Steven

Member
I've been down that road on other bikes, changing exhausts and going to K&N air filters. Of course I had to rejet the carburetors too. The power increase is marginal at best. It matters if you're racing against others, but on the street, you're not going to notice it.

Someone correct if I'm wrong, but in normal driving the engine can only take in a certain amount of air/fuel, changing the intake and exhaust doesn't change that. Where it matters most is at higher rpm where the intake and exhaust become more restrictive. Since the CTX is not a high reving engine, the gains are modest to almost nonexistent.

Compare that to another 100cc and higher compression pistons, now that is a major increase on power. Then it would make sense to open up the intake and exhaust to accommodate the extra air/fuel mixture going into the engine. Of course, you can change the cams, but again, that in itself isn't going to be a huge change. Doing that would also probably move the power band upwards and you would loose all of that bottom end torque. Nothing is free.

If you want more power, the easiest way is to do what Randy said, change the sprocket.
 
I think a lot of the air filter hoohah is a holdover from days of yore, when filters were often very small and in very cramped airboxes that weren't very well designed. Look at the classic 650 Triumph filter in the attached photo. The back plate of the filter can is not doing the breathing any favors. Some later bikes would breathe better if the air box top or the "snorkel" into it was removed. That doesn't seem to be common in these modern times.

I looked at the K&N catalog. The CTX filter and the Ducati 1199 Panigale filter both have 7/8" deep pleats. The size listed for the Honda (presumably overall to the outside edges of the flanges) is 5" x 12.5" and the Ducati is 6.875" x 7.281. I popped the cover off the air box on my CTX and the actual filter area on the HiFloFiltro OEM replacement is 4" x 9.125". The photo of the Ducati filter looks like it would be safe to assume a roughly .5" flange around the filter, so I'll round it off at 6" x 6.25".

That gives an actual 36.5 square inches for the Honda, and an estimated 37.5 square inches for the Ducati. Is that close enough to call pretty much even?

Both engines have the same crankshaft phasing and they are both twins. The Ducati is 79% larger on displacement and makes about 4X the horsepower and breathes through about the same amount of filter.

I don't think the CTX is likely to be so starved for air that a small increase in flow from a possibly slightly less restrictive filter element is going to make any difference in power.

cheers,
Michael
 

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K&N claims longer maintenance intervals, and with accessing the Honda filter being such a chore that might be some justification for switching. On the other hand, some people claim that the K&N is less restrictive because it doesn't filter as well as a paper filter, and you can easily find years' worth of long flame wars about that. The K&N can last the life of the vehicle with periodic cleaning and reoiling, but that is probably more of an issue for a very small number of people who put a lot of miles on their bikes. There seems to be a lot of used bikes for sale that have not managed to hit the service point for the original air filter.

I'd rather have a K&N or foam filter on a dirt bike that might get water on the filter as a paper element doesn't deal well with that. I don't see that as an issue on most street bikes. I've used plenty of K&Ns in the past but I bought a HifFloFiltro OEM replacement filter for my bike, and I don't see a reason to put anything different in the air box.

cheers,
Michael
 
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randy1149

New member
IMHO the miles recommended for air filter motorcycle replacement is nothing more than a gift for Honda and the dealers. To make the issue worse it takes hours just to get to them behind all the snap on tupperware that needs to be removed.

The size of the air filter on the CTX is almost as big as my Genesis. The replace recommendations are Honda CTX16K miles, the Genesis 30K miles. If you could factor in the amount of air filtered between the lives of these 2 recommendations the Genesis filter is working hundred times of the Honda. So why do I change the Honda at 16K? I don't! 30K miles is the miles I change(ed) all my MC air filters. Of course this is road bikes only with normal riding conditions.

When replacing these filter I've never come across a filter that I would say should have been changed sooner. On bikes that I could get at the filter I've air pressure cleaned the filter around 15K and put them back in for another 15K... works for me.
 

randy1149

New member
Here's the real skinny of dirty filters in today's engines. The test where performed by the Oak Ridge National Laboratory in Tenn. LINK Read the "Conculsion" on Page 25 if you just want the end results.
 
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ponydrvr

Member
So, if I read the report correctly, and in an electronically closed loop FI system, a dirty air fliter will not cause a significant reduction in MPG but does cause a reduction of power and WOT response? Conversely, does it mean that opening the air input loop will produce more response but not improve MPG? I wonder how a change in the exhaust flow restriction would factor into their calculations.

Hmmmmm? Perhaps further scientific study is needed. Or ... maybe the engine designers would release some of their information. Surely someone somewhere has already asked these and even more questions.

However, the conclusions seem consistent with empirically obtained results from my prior efforts.
 

Steven

Member
I've been using K&N filters for 30+ years. I've never had a problem with them or any engine problems because of them and I've never notice any performance change except one time. I installed it in a Pontiac with a 6 cylinder engine. The one thing I noticed right off is that the engine was more responsive with less throttle, but I couldn't detect any change in performance beyond that. Why that happened, I don't know.
 

randy1149

New member
What I get out of it is a dirty filter will cause a reduction in power but MPG will remain the same do to the ECU compensating for the air reduction.

I also get out of it there's no way all that's going to happen at 16K miles on the CTX700
 

Woodswoman

Member
BTW, Was thinking of riding the Catskills (again) for a few days, do you know of any good cheap, motorcycle friendly hotel/motels I could stay at. Group would be a 2, 3 maybe 4 people. We would stay in one hotel and ride deterrent roads in the area. I was thinking maybe 100 miles from here (Hopewell Jct) would be a good area, then explore the Catskills from there. What do you think? Time frame would be 9/2017, during the week. Thank for any info, mj

MJC, finding cheap/good motels isn't as easy up here as you might think. Many places, being small, charge quite a bit to make up the difference. For instance, hotels in Hunter and Tannersville charge at least $100/night.

You could consider the bed and breakfast route. Even if the price isn't the lowest, it does take care of one meal each day. Here in Tannersville, there's the Snowed Inn (https://www.yelp.com/biz/snowed-inn-tannersville), which members of my family who have stayed there call quaint. And I have seen riders staying there. Not the best bike parking (sloped, gravelly), but it's do-able if you are careful.

Or try these folks: http://colonialmotel.biz/

They're family-run, and you might be able to bargain decent mid-week pricing for multiple rooms. There's a gas station/convenience store practically across the street, and two quite good restaurants (Sundae's and the Creekside Cafe) less than a mile away.
 

Merlin III

New member
Over on a Facebook group for owners of the CTX700, CTX1300 and NC700, someone made this statement today:

"Throw a Coffman exhaust and K&N filter on it and performance is drastically changed. Will run all day and no more need to change down from 6th for inclines."

Anybody who rides a DCT model tried this combination? Do you agree that performance improves? Is there a downside to doing this on the DCT model? I'd gladly take a boost in performance, but not at the cost of messing up the DCT's behavior.

Thoughts/debunking/endorsements welcome.

IMO, if anything, you would expect to see nothing from a change in oil filter and maybe a decrease in performance with the exhaust change. I am not real familiar with the Coffman exhaust, but in general your performance, or "tune", is a product of the whole engine system from the carbs to the exhaust. Change one element and you could theoretically diminish how all the elements work together. The computer's ability to make a meaningful correction is questionable.

Could the original FB OP be confusing sound and appearance with performance?
 
Could the original FB OP be confusing sound and appearance with performance?

That reference to a K&N filter is for an air filter, not an oil filter.

Many people do seem to equate loud with power. Since modern bikes can deliver 200hp/liter with fully legal (including CAT) OEM exhausts there's probably little benefit to changing the exhaust unless you are building a full-bore race bike (and even then how many club racers can use all the power of a standard bike?). Some of the OEM sportbike exhausts are reasonably light too so there's often not a significant weight savings.

Some ECUs are pretty smart, and I think most that are closed loop will adjust for changes in altitude and should be able to deal with small changes in back pressure from a different muffler. I don't know if the CTX ECU falls into that category.

I'm planning on changing the stock muffler on my CTX, but I'll be putting on an NC OEM muffler (slightly dented but cheap) as I'll be doing it to improve ground clearance and I'm fine with the stock noise level.

cheers,
Michael
 
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