Nothing against you four-stroke guys, but I want to point out something. You fret over dyno charts way to much. Not all of you do this, but to those of you who do, I think you are silly. Everyone buys pipes, but the horsepower doesn't start showing up until you start sinking some money in the head, carbs, and big bore kit, etc.

 

I see you are Trinity guy as well. Thats fine I had work done by Trinity two years ago. Lets say I won't be back....If thats what you like thats fine. DMC Graydon and Sparks are all excellent choices. I don't look down on other pipes. My reasons are valid to me and you can get an opinion or whatever w/ it. I at least spent the time MYSELF, not what somebody said or did, and found my own results.

 

Actually ZRWhat-- This post is starting to sound like a I like Chevy vs. Ford contest.
- I have made numerous posts with supporting data on different web sites and in private e-mails. Sure, the dyno is a controlled enviroment but that is the point. Beyond that, I will stand with the post by KingRaptor as he has a way with words.

Pipes tested: Big Gun, Graydon, Sparks, GYTR, Trinity, FMF, Yoshi, HMF, CT, White Bros and a couple of others, including two that were developed on one of my 686 motors. I have not tested the DMC or Pro Circuit and the HMF was not tested on one of my motors.

Pipes tested on 686 and/or 720 motors: Big Gun, Graydon, GYTR, Trinity, Yoshi, CT, White Brothers and a couple of others.

Results: I still have a strong liking for the GYTR although the Yoshi and Trinity pipes also seem to fit my requirements.

 

OK Sandgod, just for you I will find a BG pipe and do a dyno pull against the GYTR and Trinity pipe on a 686 or 720. I will then post the results for you to enjoy. This may take a few days as it is difficult to find anyone who has a BG these days.

Sorry you don't like Trinity. Going somewhere else could be one reason why you are still looking for performance improvements in this site.

 

raptor720,
I as well look forward to your dyno results between the various pipes. I have a hard time believing in the magazine tests since they all have advertisement space to sell. Some un-biased results would be nice.

 

I dont want to get caught in the middle of what seems to be a Hatfield-McCoy conflict over pipes, and I dont have any real world dyno proof, but what I do know is that I very frequently ride my trusty old Warrior in the midst of my buddies all slathered with Raptor goodness. On a good day of trail riding and then some all out drag racing in a construction area flat, one Raptor in particular took the drags every single time.

My friends that were competing had all different types of pipes. The one that won all the time was a 2002 Raptor with a GYTR pipe. The lead can be contributed to rider experience, but all of us are fairly skilled riders for what we do. If nothing else, we are all on about the same skill level. The GYTR was visibly faster than the Pro-circuit and Trinity, which truthfully is the only pipes I remember other than the GYTR. Granted also, I think I remember hearing that the '02s are geared differently than the '01s, but I'm not sure if that's correct or not. If it were, I can maybe see the slight advantage.

All in all, I saw with my eyes that a GYTR on an '02 Raptor that hadn't been jetted, beat out other pipes that were "properly" jetted.

 

Darn good news for me in Davedough's post!!! I was going to cancel my name on the waiting list for the GYTR Carbon pipe yesterday and order something else. When I went to the dealer to do that, they had it! Somebody had screwed up and I got the order in right before they went on backorder. I put it on last night but haven't had a chance to ride it yet. One thing is for sure: LOUD!! I'll have fun tomorrow! Thanks everybody for the input.

 

O.K., here's my take on the situation. First, I do not have an aftermarket exhaust on my 1 month old '02 Raptor yet. I am paying careful attention to all these kinds of posts because I am buying one soon. From what I can tell, the motor, WHEN STOCK INTERNALLY, does not flow enough to take advantage of a full exhaust over the entire rev range. The full exhaust systems do make an extra 1-3 peak HP over the slip-ons at a sacrifice of low end torque. This is because they flow so well, they are not providing enough backpressure to allow the engine to run properly at low RPMs. If you ride in wide open spaces and spend most of your time above 5000 RPM, full exhaust probably is the way to go. If you ride tighter stuff where you are on and off the throttle, spending a lot of time in the 2000-5000 RPM range, you gladly sacrifice a few peak HP for more and smoother low end torque. This is where the slip-ons work better and is the point that I see Raptor720 trying to make. If you are running big bore kits, high compression pistons, and hot cams the engine now has the mods to make more power over the entire rev range with the full exhausts. Less back pressure is not always better. Look at 2 stroke pipes. The whole point of the different pipes is how the backpressure is controlled (and how much) to optimize the power over a specific rev range. That is why companies like ESR or FMF have multiple pipes for different uses. This is whats happening with 4 strokes, just to a much smaller and less significant degree. Finally, sound plays a big part. The human mind loves to play tricks on itself. If it sounds faster (louder) it must be faster[img]i/expressions/face-icon-small-wink.gif[/img]

 

CBUS660R,

Let me correct a few of your beliefs concerning the 660 and some basic exhaust theories. Not that you are too far off base -- just that you need a touch of fine tuning. lol

First, it is not that the 660 "does not flow enough to take advantage of a full exhaust..." What happens is that the 660 exhaust ports in stock form substantially out flow the intake ports. In the ideal world, we would want to see the intake flow more than the exhaust. "Back pressure" is something that really does not play a part in the works.
The reason why a full exhaust may make 1-3 extra hp in high rpm is partly a result of "their high flow abilities" but has nothing to do with "providing enough back pressure to allow the engine to run properly at low rpm's."

What is really at issue in the one cylinder 660 is air speed/air velocity. Picture a garden hose -- with a small hose, the water moves faster than in a large diameter hose moving the same volume of water. On the engine, with a large pipe, the air speed is slow vs. the stock head pipe that has smaller tubing. We want the exhaust to stay hot and move fast. This causes a vac in the cylinder and helps pull additional new fuel/air into the cylinder during valve overlap. The result is more torque/power/bigger smiles, etc. With the big primary tubes of the full systems, you have lower air speeds and usually colder exhaust. Both of these things will give you less torque (as demonstrated in countless dyno pulls) simply because less fuel is pulled into the cylinder by the exhaust vac.

The 1-3 peak hp gain with a full system results from the ability of the larger pipe to handle more high pressure exhaust and thereby allow for a greater vac at high rpm. Problem is that it is peak only and usually beyond your shift points.

With the big bore kits, compression and cams, you should have more exhaust gas volume. This is the only reason why a larger diameter head pipe may (I say MAY) help. In this case, you have given up some low end torque by the design of the cam. You hope that the high compression piston helps restore the loss but there still is a loss.

NOW for your 2 stroke theory. Back pressure is not what makes the 2 stroke pipe work. What you are interested in on a 2 stroke is the sound waves and speed of sound. Using math, you calculate the lengths of pipe and angles to reflect sound waves back to the exhaust port at a specitifc time. When the sound is reflected back to the exhaust port at the correct time, it will work like a wall (back pressure) to prevent the loss of the next fuel charge into the exhaust. Port timing and pipe length are critical to a specific engine operating rpm. In some PWC systems, they inject water to change the speed at which the reflective wave hits the exhaust port. This gives the rider a large power range.

The reason why ESR, FMF and others have various pipe lengths on 2 strokes it to help the consumer match the sound wave timing to their port design and desired power range. On a 4 stroke, you can also set some pipe lengths to tune for a specific power range much like a 2 stroke. Typically, a short 2 stroke pipe is top end and a long is bottom end power. This may not be true for the 2 stroke.

Finally, on the sound issue, I agree, a loud pipe may add 2" to a man even if it does not increase power. This is one of my gripes about the 2 stroke crowd and their desire to run open pipes thinking it makes more power. In reality, they can tune their pipe to provide the same power with a silencer it will just need to be a different length pipe and possibly different diameter tip. The off road boyz learned this by accident with their Mazda powered off road cars. They ran open LOUD systems for years. Finally, one team discovered that they could make it quiet and when they did, they had more power!! Now Mazda's are one of easiest listening machines off road.

I am by no means the end all expert on this stuff. I learned theory and made application to what I learned. After years of testing and having fun, I believe that I have a good grasp on what exhaust is all about. Most pipe builders can get away with large pipes and other "stuff" on most engines. Problem is that the 660 single is so critical concerning air speeds that the pipe men cannot dip chrome on a pipe and get away with it. If it was a 2 or 4 cylinder engine, the exhaust from other cylinders helps create the vac needed to make torque. Not on the single.

 

I'm with you Raptor720. I realized that I was oversimplifying the principles at work (just enough knowledge to be dangerous), but I wanted the discussion to include some technical info and now we are getting there. Of course, we are trying to condense a subject (thermodynamics) that engineers spend years in college learning and applying into a couple of short paragraphs [img]i/expressions/face-icon-small-shocked.gif[/img]. All of the bickering that was going on was not helping me make a decision on what to spend my money on. Finally, I see in hindsight that I left out a critical factor on mods when I failed to mention porting and polishing the heads (duh).