Thanks Reeb. I am mostly after the weight...if I get a couple extra HP...great. Did you have to change jetting?? How does it sound?
CPI Pipe for XP
- Thread starter Throttle Junkie
- Start date
I think it sounds awesome. It's hard to describe. Half way between twin pipes and a throaty single is the best I can describe it.
I did play with jetting throughout the year. 2 sizes down on the mains. Seemed to be the best all around for our elevation. 4-7k
I did play with jetting throughout the year. 2 sizes down on the mains. Seemed to be the best all around for our elevation. 4-7k
go with the cpi pipe i put one on my xp and i like it a lot it is about 10hp and you can feel it it was a big dif
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dynotechjim
Well-known member
www.dynotechresearch.com/techarticles.asp
anyone who really wants to know the actual power gained or lost by aftermarket things like this needs to follow the technical data on my website. This is a listing of independent dyno test information available to subscribers, who by subscribing ($20/yr) support our Consumer Reports-like testing.
anyone who really wants to know the actual power gained or lost by aftermarket things like this needs to follow the technical data on my website. This is a listing of independent dyno test information available to subscribers, who by subscribing ($20/yr) support our Consumer Reports-like testing.
......no problem with your results, but what's your elevation? pipes developed 5000 feet higher than you will probably result in different outcomes...cpi pipes are developed at over 5000 ft, and are tested and modified for riding in the 7-11 k elevations, where they work very well....
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Keithcat
Member
Jim,
Your site is a wonderfull place for information. I have been a member for years and will keep on renewing my subscription. It takes away most of the hype on inflated dyno numbers. I have used your information as a tool for a few motor builds with great results. Thank you
I myself ride mostly at elevation even with living in Michigan. Do you feel that in general if the pipe is tested at low elevation with great results. You will see good results up on the mountains with the same pipe?
I see it as like this. Stock xp 800 makes say 150 hp. Take the sled up to 9000 feet and you now have 109 HP. So if a pipe was designed and tested at near sea level to produce say plus 4 hp. By taking that same pipe up on the mountain will the pipe be effective? I say no. I feel the pipe would have needed to be tested as a 109 hp motor and then modded to find the extra 4 or so HP. Right or wrong?
The guys running the 860r motors are in the same boat. Start off with say 180 at sea level and end up with 130 at 9000 feet. Im sure this is why the stock pipe seems to work so well for them. It gets closer to the intended HP level of the pipe.
I have seen a few pipes that are ALT specific. But it looks like the stinger size is just adjusted a few mm smaller to hold a little more heat. So does this mean that if the pipe was tested at sea level that its design would prove good as well up at 9000 feet?
Anyone?
Keith
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dynotechjim
Well-known member
My facility is 1000 ft, and you can see that the Stock, CPI, Aaen and DynoPort single pipes all flow within 1/2% airflow CFM.
How is the CPI pipe "modified" to work well at 7000 ft? we should dynotest that same modification to see if that might help here as well.
How is the CPI pipe "modified" to work well at 7000 ft? we should dynotest that same modification to see if that might help here as well.
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dynotechjim
Well-known member
in the next day or so, I'll be testing our first production Dragon 800. Exxtreme performance in CO/ UT sent me a stock RMK 800 single pipe and an SLP single pipe that they have modified to be good for mountain riding (their dyno is at 5500 ft I think), and they want to see how it works at 1000ft compare to stock, unaltered.
They choke the end of the pipe down for more back pressure. Most people have said the CPI is too "tight" for lower elevations and works well at higher elevations 7,000'+.
Some people have even said that the CPI is even too tight for higher elevations for certain modded motors.
i've been working with mike at cpi for over 20 years on pipes for several mod engine applications....i've been able to watch as pipes were designed, tested, scrapped, and done over a great many times....when we get a pipe that developes the power curves, output, and reproduceability, i (if it's for my sled) take it to the mountains above 8000 ft for side by side comparison with a test mule, a sled of comparable acceleration and speed....i then ride it in practical situations....frequently it needs to be adjusted to add or take away some specific characteristic.....in regards to keithcats' comments, the stinger size plays an important part and is one of the main reasons that flatland and altitude dynos' results are frequently different.....and that reason gets into the propigation of sonic waves and air density....a pipe developed at low altitude, where the air is denser, is going to process the air volumne and speed differently than at high altitude where the air is not so dense.....a pipe developed at altitude frequently doesn't do well down low, and vice-versa.....so as i have said before, it's not the results of a particular dyno or operator that makes the difference (although that's very important), but the conditions (in this case altitude) that makes one pipe superior to another in the application for which it is intended........i originally got into this hobby because i couldn't get the results i wanted from pipes that were developed in california or the mid-west (and believe me i tried many), when i started working with mike at cpi, i immediately got better results, and have used cpi or slp pipes exclusevely since then....another thing about cpi that i appreciate, is if a pipe doesn't do what i want, with a good description of the problem, i can get it modified so as to be satisfactory
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So was the dynoport mountain or low alttitude pipe used?? Dynoport offers two different pipes and I would assume their high altitude pipe would not dyno very well at low alltitude and would explain the "tightness" of the CPI.
Just talked to CPI. The pipe was designed at 5,000 feet. They see about 3 sled lenghs over a stock sled in a uphill pull. Weight savings is close to 15lbs.
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dynotechjim
Well-known member
All four pipes we dyno tested on the XP800 had backpressure nearly identical as indicated by the airflow CFM of the engine during testing. We need to find out from Dynoport what is different about high altitude pipe.
So the SLP is tighter. Jim I believe you have one on the way.. Would like to see it on the dyno. At this point I am leaning toward leaving the stock pipe on with a HPS can. Jim do you have any plans to dyno the stock motor with twins??
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dynotechjim
Well-known member
the stock pipe has an internal stinger (short hunk of pipe that protrudes into the rear cone). That internal stinger adds to airflow restriction, so we need to know if the SLP single has one to estimate total backpressure. A larger diameter outlet pipe that protrudes into the pipe internally can be more restrictive than a smaller diameter outlet pipe that just attaches to the rear cone. We'll know quickly on the dyno since the tighter pipe will usually have less airflow CFM through the engine. Looking forward to testing the SLP single.
Is anyone selling twin trail pipes for the XP800?
Is anyone selling twin trail pipes for the XP800?
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Jaws is. I heard guys have ordered them but they never showed up
http://www.jawsperformance.com/perexh5.html#xp%20800
http://www.jawsperformance.com/perexh5.html#xp%20800
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Keithcat
Member
Jim,
I knew the stock pipe had the internal stinger. I was not aware that it had any effect on airflow. Humm...... Good info.
As for the SLP, it does not have the internal stinger. Now this could very well be the reason for the smaller stinger size.
Just looking at the SLP exhaust can its a dual chamber design. Looks like it had been engineered very well. The intake ID opening is the same as the stock BRP muffler. However the exit outlet is about quite a bit larger. Seems like a very loose can. Overall running the SLP pipe and SLP can together may complement one another.
I hope to see one on the dyno shortly.
Keith
I knew the stock pipe had the internal stinger. I was not aware that it had any effect on airflow. Humm...... Good info.
As for the SLP, it does not have the internal stinger. Now this could very well be the reason for the smaller stinger size.
Just looking at the SLP exhaust can its a dual chamber design. Looks like it had been engineered very well. The intake ID opening is the same as the stock BRP muffler. However the exit outlet is about quite a bit larger. Seems like a very loose can. Overall running the SLP pipe and SLP can together may complement one another.
I hope to see one on the dyno shortly.
Keith
Jim one more question was the stock pipe through the stock can also?? I know a couple guys grass draging this year and had agressive setups in for dragging, turning 8150 - 8200 with a can. They made them pull the can and run stock can in the stock class and once they did that lost 200 - 300 R's. Normally I would call total BS, but it seems they do have a little more hp with the can vs stock can.
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dynotechjim
Well-known member
one bit of useful instrumentation for you mountain guys who run for minutes at WOT is a pipe center section pressure gauge. Pressure will climb as the pipe gets hotter from front to back, gas expands and that fixed outlet acts smaller as temp climbs.
At 1000 ft some of the cans are tight, lose CFM, lose HP, HP peak slides up to a higher RPM because average temp of the gas in the pipe is higher (baro pressure and backpressure has no meaningful effect on the speed of sound, but temperature of the gas has dramatic effect of the speed of the soundwaves). Tight cans can hurt EFI sleds even more since airflow drops, fuel flow stays constant and A/F ratio becomes fatter for even less HP. Loose cans just blow too much good stuff out the muffler, since the engine needs a certain, ideal amount of backpressure to supercharge the exhaust port on closing. But loud, loose cans also lean out EFI sleds helping optimize A/F ratio if they're fat to begin with.
Now you can see why after 22 years of doing this stuff I still, on occasion, get bewildered!
Rich Daly at DynoPort uses a pipe center section pressure gauge to help develop pipes/ cans. Since most new sleds leave little on the table (like the XP800), if you can match the stock muffler's backpressure with a can, you can ALMOST match the stock muffler's HP (we're thinking that there may be some funky tuning going on inside the stock XP800 muffler that we don't understand). We weld a brake line fitting to the fat part of the pipe, screw on a foot or two of 1/4" brake line to insulate a 1/4" rubber pressure hose from pipe heat, then tie-wrap a low pressure acetylene gauge to the handlebars (0-15psi very cheap at welding supply houses). Check stock backpressure first, then choke things down with tight stingers/ can mufflers to where performance is best.
Maybe at high altitude, the stock muffler which is perfect in the flatlands, might be too loose. If that's the case, then a can too tight here might be beneficial at high altitude.
I will bug my pal Bill Davis at Exxtreme Dyno in Utah about this. Since he sent me several RMK800 modified pipes that work dandy at 6000 ft (to see how they fare at 1000), I may in turn send him some stuff that is dandy here to see how thin air changes things.
I'm wondering now if, say, 4.5 psi of backpressure is optimum for max HP for an XP800, what is optimum at 6000 ft?
Perhaps one more line of data can be provided in my test results--pipe backpressure. If we find that a given backpressure is ideal at all altitudes, this will be something that mountain riders can monitor, and easily adjust.
At 1000 ft some of the cans are tight, lose CFM, lose HP, HP peak slides up to a higher RPM because average temp of the gas in the pipe is higher (baro pressure and backpressure has no meaningful effect on the speed of sound, but temperature of the gas has dramatic effect of the speed of the soundwaves). Tight cans can hurt EFI sleds even more since airflow drops, fuel flow stays constant and A/F ratio becomes fatter for even less HP. Loose cans just blow too much good stuff out the muffler, since the engine needs a certain, ideal amount of backpressure to supercharge the exhaust port on closing. But loud, loose cans also lean out EFI sleds helping optimize A/F ratio if they're fat to begin with.
Now you can see why after 22 years of doing this stuff I still, on occasion, get bewildered!
Rich Daly at DynoPort uses a pipe center section pressure gauge to help develop pipes/ cans. Since most new sleds leave little on the table (like the XP800), if you can match the stock muffler's backpressure with a can, you can ALMOST match the stock muffler's HP (we're thinking that there may be some funky tuning going on inside the stock XP800 muffler that we don't understand). We weld a brake line fitting to the fat part of the pipe, screw on a foot or two of 1/4" brake line to insulate a 1/4" rubber pressure hose from pipe heat, then tie-wrap a low pressure acetylene gauge to the handlebars (0-15psi very cheap at welding supply houses). Check stock backpressure first, then choke things down with tight stingers/ can mufflers to where performance is best.
Maybe at high altitude, the stock muffler which is perfect in the flatlands, might be too loose. If that's the case, then a can too tight here might be beneficial at high altitude.
I will bug my pal Bill Davis at Exxtreme Dyno in Utah about this. Since he sent me several RMK800 modified pipes that work dandy at 6000 ft (to see how they fare at 1000), I may in turn send him some stuff that is dandy here to see how thin air changes things.
I'm wondering now if, say, 4.5 psi of backpressure is optimum for max HP for an XP800, what is optimum at 6000 ft?
Perhaps one more line of data can be provided in my test results--pipe backpressure. If we find that a given backpressure is ideal at all altitudes, this will be something that mountain riders can monitor, and easily adjust.
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in our testing of the internal stingers, i tried them on a set of triple pipes on a 780 rotax that was bb to a 925...the objective was to tone them down to reduce the size of the can (for weight).....while they were effective for noise and power, any time a long hill in deep snow was attempted, they would squeak a piston, jetting them up to very rich levels didn't help...after numerous rebuilds (the engine would squeak at just over 1 min at wot), i decided that the airflow restriction increased suddenly, probably due to a sonic wave blocking the internal flow exit, causeing a rapid pressure spike and resulting detonation....after the internal stingers were removed, the pipes worked fine......relative to coming up with an ideal backpressure for a can, i think that the pressure required is going to depend largely on the design of the pipe and the state of tune of the engine, length of the y-pipes and head pipe....as engine/pipe/can systems have developed more hp in recent years, the backpressure that the can holds has become less tolerant of variations.....hence the days of slapping a glass-pack on the pipe and having it work are long gone....it normally takes several attempts to find a can that won't lose power, and still have a weight reduction that is worth producing
