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Discussion Starter #1
Hello Turbo gurus,

I'm in the process of installing the K&N air filter for my CX500T. I picked up this kit awhile ago from CXTCs and never got around to installing it until now (my old OEM filter element is now shot). I've removed the reed valve assembly, and installed the filter on the end of the intake tube.

I have a couple of questions about this upgrade:

1) Can the airbox assembly be removed completely from the bike without removing the front fairing bracket entirely? Is it worth the hassle? To my thinking, it can't hurt to lose a couple of extra pounds of unneeded weight, especially from within the upper fairing for an already top-heavy bike.

2) Does anyone know the part number or source for the vapor separator filter that Dan Topping used to sell? Or an equivalent replacement? In expect that this is a necessary accompanying modification to the K&N filter.

3) Are there many folks running this mod currently, or anyone who has? I'm not sure there's much power to be gained, but I have read about an increase in intake noise. Is this noise mostly increased under acceleration, or is steady throttle cruising also noisier? Any other easy mods that are recommended to get the most out of the filter upgrade?

Thanks
Sean
 

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This was Dan Topping's mod.
Claim was faster spooling.

I'm planning on leaving the air box in the bike, blocking off the holes, and making it into a glove box by using some kind of adapted wing nut in place of the large screws nut to hold the cover in place.

The upgrades I would consider very strongly with this mod:
1) Blow Off Valve (This will save your turbocharger a lot of undue stress).
2) Exhaust Mod (take off rear cover plates, and drill 3/4" hole in baffle plate), reinstall rear cover plate.
3) Boost Valve. This ensures that you are at optimum boost pressure before the wastegate opens.
 

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2) Exhaust Mod (take off rear cover plates, and drill 3/4" hole in baffle plate), reinstall rear cover plate.
Never heard of this modification. :confused:

rear cover plates ? Are this the plates holding the "TURBO" emblems ? Or do you mean the aluminum exhaust end caps ?

Are the holes to reduce exhaust backpressure ?
 

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It's the aluminum end caps.
This modification has been done in the British CX Turbo forum on Facebook. I'm surprised that you haven't joined them yet.
Tim Boutle runs the page. (He has the various CX650 turbo drag bikes)
A good page for asking performance questions, as Tim has done a lot of work wringing performance out of these bikes.
 

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Here is an excerpt from Jay Kavanaugh, a turbosystems engineer at Garret regarding automotice turbochargers,
"N/A (naturally aspirated) cars: As most of you know, the design of turbo exhaust systems runs counter to exhaust design for n/a vehicles. N/A cars utilize exhaust velocity (not backpressure) in the collector to aid in scavenging other cylinders during the blowdown process. It just so happens that to get the appropriate velocity, you have to squeeze down the diameter of the discharge of the collector (aka the exhaust), which also induces backpressure. The backpressure is an undesirable byproduct of the desire to have a certain degree of exhaust velocity. Go too big, and you lose velocity and its associated beneficial scavenging effect. Too small and the backpressure skyrockets, more than offsetting any gain made by scavenging. There is a happy medium here.
For turbo cars, you throw all that out the window. You want the exhaust velocity to be high upstream of the turbine (i.e. in the header). You'll notice that primaries of turbo headers are smaller diameter than those of an n/a car of two-thirds the horsepower. The idea is to get the exhaust velocity up quickly, to get the turbo spooling as early as possible. Here, getting the boost up early is a much more effective way to torque than playing with tuned primary lengths and scavenging. The scavenging effects are small compared to what you'd get if you just got boost sooner instead. You have a turbo; you want boost. Just don't go so small on the header's primary diameter that you choke off the high end.
Downstream of the turbine (aka the turboback exhaust), you want the least backpressure possible. No ifs, ands, or buts. Stick a Hoover on the tailpipe if you can. The general rule of "larger is better" (to the point of diminishing returns) of turboback exhausts is valid. Here, the idea is to minimize the pressure downstream of the turbine in order to make the most effective use of the pressure that is being generated upstream of the turbine. Remember, a turbine operates via a pressure ratio. For a given turbine inlet pressure, you will get the highest pressure ratio across the turbine when you have the lowest possible discharge pressure. This means the turbine is able to do the most amount of work possible (i.e. drive the compressor and make boost) with the available inlet pressure.
Again, less pressure downstream of the turbine is goodness. This approach minimizes the time-to-boost (maximizes boost response) and will improve engine VE throughout the rev range."


The same theory applies to motorcycle turbochargers. In a nutshell, the backpressure comes from the front portion of the turbocharger exhaust, and you want the back as free flowing as it can be. This modification allows that to happen.
 

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British CX Turbo forum on Facebook. I'm surprised that you haven't joined them yet.
I am past 40 so not allowed on facebook :p

I don't believe in an internet within an internet and stay far away from Facebook :pottytrain5:
 

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I am starting to collect information on the performance upgrades for turbos, and adding them to my own Facebook, which allows me to post them here.
As I document my build, I'll keep it updated.
It'll take time, because I want to make sure that the bike actually runs first (and I have to get the rear frame straightened), but I'll be doing this exhaust mod, the K&N mod, a Blow off Valve, and a Boost Valve.
 

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Does any one know what blow off valve will work on the cx500tc. I recall seeing one that just slips on the pipe the resonance chamber is on. Information will be greatly appreciate.
 

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Most of them can do that with a rubber collar. When you buy one, look for an adjustable model designed to handle 19 lbs of boost.
 

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Discussion Starter #10
I've wrapped up the K&N install, and figured out the answers to most of my questions.

1) Can the airbox assembly be removed completely from the bike without removing the front fairing bracket entirely? Is it worth the hassle? To my thinking, it can't hurt to lose a couple of extra pounds of unneeded weight, especially from within the upper fairing for an already top-heavy bike.

No, you need to pull the fairing bracket. I ended up deciding to leave the airbox in place for now, until I decide whether the K&N is a permanent modification. In the event that it is, and that I'm looking at doing the boost or blow-off valve mods that Timothy_D references, I'd likely pull the box to lose the weight the next time I have the fairing off.

2) Does anyone know the part number or source for the vapor separator filter that Dan Topping used to sell? Or an equivalent replacement? In expect that this is a necessary accompanying modification to the K&N filter.

Uni Filter UP-101 5/16" clamp on breather filter. $13 shipped through Amazon.

3) Are there many folks running this mod currently, or anyone who has? I'm not sure there's much power to be gained, but I have read about an increase in intake noise. Is this noise mostly increased under acceleration, or is steady throttle cruising also noisier? Any other easy mods that are recommended to get the most out of the filter upgrade?

The exhaust mod is likely my next step, to help make the most of the K&N, but I'm looking forward to watching Tim's progress on his upgrades when the time comes.

So how does the K&N seem to work? There is a very slight increase in intake noise as boost builds relative to OEM, and then there's a pronounced turbo chatter/chirp between upshifts due to the loss of the reed valve assembly. I think it actually sounds pretty cool, and I'm pleased to report that otherwise, it's just as quiet as stock. I can confirm that the Turbo seems to spool up a bit quicker than before, so overall, I'm pleased with the install!
 

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I am going to go with Dan Toppings K&N Mod and Tims Exhaust mod. I have gone over 50+ threads and can´t find the K&N Part number for the Air Filter. Can anybody please advise. I got the little filter already.

Thanks Riq
 

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I thought I would answer my own question for others to use. The swap K&N for the 650 is part number R1050. This filter is 6in long and 3.5in diameter and has a wider id flange 1.7in. The filter for the 500TC is RU75 this is a similar filter 6in long but with a tad less diameter 3.0in and a smaller id flange to fit the small pipe of 1.5in. Also, you can get an oval type filter from mike´s xs filters.

HTH others in the future.
 

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Just my two cents worth... I did not like the K&N installed on my CX650T at all. It took much longer to spool up, almost painfully so, and when the bike is hit with very strong gusty side winds (Santa Ana winds) from a particular angle, the bike would stutter momentarily. Most definitely was related to strong side wind cavitating air to the inlet. Those two things alone did not make the mod worth the small increase in top-end. I removed it, converted it back to stock, and sold my other K&N's I was going to use on my other CXT's.​
 

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I have pretty much taken the entire plate out that is shown in Tim's post #5 above. My theory is that I am not concerned about noise like Honda was and want to reduce an restriction in the exhaust that I can. The bikes that run in modified at Bonneville take the entire muffler off for a speed increase, so my theory is to get as close to that as I can but keeping a legal muffler on my bike. I am also looking at the best way to modify the end cap to increase flow without opening the holes up anymore. All this will be verified on the dyno, or at Bonneville.

I am still playing with the intake to optimize that too. For race purposes I have to keep the stock air box and the bike must appear stock, so I can't just fasten a K&N to the intake of the turbo.
 

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Just my two cents worth... I did not like the K&N installed on my CX650T at all. It took much longer to spool up, almost painfully so, and when the bike is hit with very strong gusty side winds (Santa Ana winds) from a particular angle, the bike would stutter momentarily. Most definitely was related to strong side wind cavitating air to the inlet. Those two things alone did not make the mod worth the small increase in top-end. I removed it, converted it back to stock, and sold my other K&N's I was going to use on my other CXT's.​
Here's my two cents, when I bought these filters from Turbo DV8, he promised me 20 more horsepower. I am still looking for a Honda CB175 at my front door.
 

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No, I said it would lose 20 horsepower in sidewinds. Sheesh, the nerve of some people...
 

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That's alright, it looks faster. I have put all kinds of items on the bike that each promise ten or twenty horsepower, so I figure at this point the bike is making about 200 horsepower. Thank you for all the speed ideas JC Whitney!
 
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