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Old 11-18-2007, 06:52 AM   #1 (permalink)
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Washer trick for more low end Torq?

I Had the bike on a dyno for 1 pull a while ago (then the pushrod broke) and the torq seemed to cross 100 lbs at approx. 3200 rpms. Now I havnt had the bike tuned yet so with a tune im hoping to get it over a 100 at maybe 2700? But dyno tells me this thing rips at 3500 +. Im wondering if I were to try this thing with a washer in the rear of each muffler could/would it make a difference with my setup. I did the y pipe mod and im thinking I shoulda not have done it, because the partial obstruction may actually give you more low end torq hehe.I Know I dont have drag pipes but im just wondering??? Particulars of my build are at bottom.

Solving the big problem with drag pipes

--------------------------------------------------------------------------------

Difficulty: Easy to Moderate (some welding) Time Required: .5 hour Cost: $0 - $20

One of the first modifications most riders make to their motorcycles is a set of aftermarket exhaust pipes. Many opt for drag pipes, which are basically just a length of chrome pipe (by comparison, the stock mufflers on my 96 Intruder had three baffle plates and a core of fiberglass packing). These pipes make a LOT of noise, so people often assume that they make power also. But a completely open exhaust attached to a stock motor will actually reduce horsepower by 5%-10%. Usually a significant throttle lag develops also, making the bike hesitate when the bike is accelerated from highway speed, such as when you pull out to pass someone. Adding a free-flowing air intake system and re-jetting the carbs will make the motor work well with the pipes, and correct some of the throttle lag, assuming that you have: 1) the money, 2) the desire to further modify the bike and perhaps void the warranty, and 3) a bike with an external intake system or the desire to add one to your ride. If you do these other modification, and keep the open pipes, overall horsepower will be better than stock.

On paper.

The maximum horsepower on a motor with free-flowing intake and exhaust is impressive on paper, but maximum power is achieved at very high RPM. Power in the RPM range that street motorcycles live in is actually unimpressive, as the open system makes very little torque in the low and mid ranges. Open exhausts (and the matching open air intake system) are designed to work at high RPM and with a wide-open throttle, like at a drag strip. After all, that's why they are called "Drag Pipes!"

But you like the noise ( insert argument here: "Loud pipes save lives!", "I hate my neighbors", or "But chicks dig it') so the drag pipes are going to stay. So here is how you can make them work on the street.


Materials Needed:
2 * 3/4-inch washer
2 * 1 1/4-inch length of 1/4-inch threaded rod OR a 1 * 1/4-inch long 14-20 bolt
4 * lock nuts to fit the threaded rod (or regular nuts with lock washers)
1 * 1/4-inch drill bit and an electric drill (not a cordless one)
A friend or co-worker with a welder, or a bottle of beer for a guy at the local muffler shop
Some high-temp flat black paint (optional)
The procedure:
Step 1: Weld the washers onto the heads of the bolts, or to one end of the threaded rods. Then thread one of the nuts onto each from the other end, stopping about 2/3s of an inch from the bottom of the bolt head/ washer. Paint them flat black if you want it to be less visible once its installed. After a whopping two minutes of work, you should have two assemblies that look like the drawing below.


Step 2: Drill a 1/4-inch hole in each drag pipe, 1-inch from the end. Drilling up from the bottom is easiest, but if the pipes are off the bike you could drill them so the hole is towards the bike so no one can see it. Use a center punch or nail, and add a drop of oil or some WD-40 to the drill bit to keep it cool while it cuts.

Step 3: From the inside of the pipe, stick the bolts/ threaded rods through the holes in the pipes, and put a nut on each from the outside. Play with it a little until the washer is in the center of the pipe, and then tighten it finger tight. Looking down the pipe, it should look like the drawing below. DO NOT USE THREADLOCKER! You'll know why in a minute...

Step 4: Congratulations! You have just installed a set of baffles in your drag pipes that can be tuned for the type of riding you are doing. For maximum mid-range torque, put the washer directly across the pipe at a 90-degree angle to the exhaust flow and tighten the nuts. Fire the bike up: do you hear any difference in the noise level? Probably not! But take the bike for a spin- you can feel the mid-range torque! Doesn't the bike pull better, and more smoothly, when you roll on the throttle? Dyno tests have proven that this little device boosts low and mid-range torque by creating just enough turbulence and back pressure to keep the airflow continuous, which lets the exhaust system suck the gasses out of the combustion chamber more efficiently, improving airflow over a completely open system.

If you are planning on doing some racing on the dragstrip, loosen the nuts and turn the baffles so they are parallel to the pipes. This will reduce the back pressure and free up top-end horsepower at very high RPM, like drag pipes are supposed to do, but the turbulence helps the pipes work better than if you removed them completely.

If you have changes the final drive ratio or put on a very small diameter back tire, start with the washer at about a 45-degree angle to the exhaust flow, and a little trial and error will help you find the ideal angle to get the most out of your ride.

Well, there you have it: with ten minutes of work and about $2 worth of material, you have modified your drag pipes to work on the street while keeping the noise. The result is a quicker, more streetable bike that will still piss off your neighbors.
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Old 11-20-2007, 12:55 PM   #2 (permalink)
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anyone out there wana take a stab at this ? It musta been tryed before on many different bikes, heck Joe (hillsides tuner said he does this type stuff when he is tuning if he doesnt get the low end results he is looking for). So would ya put a washer in both pipes or just the pipe coming from the rear cylinder or what? I saw dyno where Mike from Latus did this (partially plugged left pipe) and the torq shot up on the bottom end from like 2500 to 3200. Im may be getting bike tuned next week so I just thought I might try this before I bring it. I know I should just get a fatcat and be done with it but I love the way the stockheadpipes look. I figure a heck of alot of peiople must have tryed this so someone please chime in and give me your thoughts!!!
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Old 11-20-2007, 02:06 PM   #3 (permalink)
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Bolts

What we do here on our Dynojet 150, when forced to work with drag pipes, is use a 1 1/2" long 1/4-20 bolt (for 1 3/4" pipes) and stack 3, 5/16" nuts on the bolt and then nut it with a 1/4-20 nut. The sound stays, the bottom end torque comes up, and all is well.
BTW, we were the ones that intially alerted Joe to that little trick, as well as our "Torque Nozzles" that are a tapered exhaust venturi, that are installed in the end of those 2 1/4" power-killer pipes.
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Old 11-20-2007, 04:47 PM   #4 (permalink)
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Question. I have the Cobra Slip-Ons on my 07 FLHRS and I pulled the baffles and took the fiberglass wrapping off. Better sound although it really killed the low / mid torque.

The stock baffle is about a foot long, sort of looks like a Samson baffle, but it is a straight thru with cheese grater slots.

So, is there a good alteration I can do, add some restriction inside the baffle (washer trick, etc.) or would a different baffle work?
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Old 11-20-2007, 05:58 PM   #5 (permalink)
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claydbal is reading this now saying WTF is this?
thats not a permanent fix. its to determine if the pipes are the culprit. if some tomfoolery like that gets your power right, you know the pipes aint right. we did this in the 70's till we discovered mufflers made more power for street racing.
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Old 11-20-2007, 07:20 PM   #6 (permalink)
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Quote:
Originally Posted by claydbal
thats not a permanent fix. its to determine if the pipes are the culprit. if some tomfoolery like that gets your power right, you know the pipes aint right. we did this in the 70's till we discovered mufflers made more power for street racing.
Well Claydbal: considering the fact( I believe it to be fact) that there are only a handful of really good 2-1 pipes and all the rest of the pipes are not up to snuff in the performance area in comparison. Then ill take that non permanent fix, get it tuned and then ride with that non permanent fix for the rest of the bikes days hehe. I just need to know if the non permanent fix im looking at will or might do anything? And i would love to have the fatcat #s but as of this moment I just cant change the look of the bike with that pipe cause I love the way it looks with the current setup. Heck I believe a good tune and no playing with the pipe is gona get me where I want to be, cause when this thing hits 3200+ rpms I always smile. But if a bolt and a washer are gona make me smile more then heck Ill spend the 75 cents.
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Old 11-21-2007, 06:02 AM   #7 (permalink)
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claydbal is reading this now saying WTF is this?
Quote:
Originally Posted by Qhorin
Well Claydbal: considering the fact( I believe it to be fact) that there are only a handful of really good 2-1 pipes and all the rest of the pipes are not up to snuff in the performance area in comparison. Then ill take that non permanent fix, get it tuned and then ride with that non permanent fix for the rest of the bikes days hehe. I just need to know if the non permanent fix im looking at will or might do anything? And i would love to have the fatcat #s but as of this moment I just cant change the look of the bike with that pipe cause I love the way it looks with the current setup. Heck I believe a good tune and no playing with the pipe is gona get me where I want to be, cause when this thing hits 3200+ rpms I always smile. But if a bolt and a washer are gona make me smile more then heck Ill spend the 75 cents.
the great thing about forums----you ask for opinions, you get em. you make your decision, all is good. and i agree with your opinion of pipes, yep, only a handful actually work, the rest i call centerfold pipes. these centerfold pipes were the reason someone discovered the bolt/washer trick.
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Old 11-21-2007, 06:17 AM   #8 (permalink)
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Drag pipes................there is your answer.............
Generic open tubes made to irritate the general public....not one math calculation even used in the design process.

Drag pipe R&D time 15 minutes, dyno runs 5~10.
2:1 R&D time over 500 dyno runs.
Which one would you really want on your machine?
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Old 11-21-2007, 06:47 AM   #9 (permalink)
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I once read in AIM (American Iron Mag), that you could test this by holding a screwdriver or some similar impediment in the exhaust and take your readings. I don't know exactly how you would do this, but I have a set of Hooker Header drags (not 2 into one) on my softail, put some 1 1/2 inch 1/4 20 screws near the ends and it feels better. I have not put it on the dyno, but I can definately feel an improvement. The nice thing is, that if it doesn't work, or if for some reason, makes it worse, you can easily remove the screws.
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Old 11-24-2007, 03:01 PM   #10 (permalink)
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Here are some pics of my bike with the longer screws in the tailpipe.

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Old 11-25-2007, 03:51 PM   #11 (permalink)
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thanks for the pics fender. And thanks for your input to clayd, I always appreciate anybody trying to help out
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Old 11-27-2007, 04:43 PM   #12 (permalink)
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Hi George, Yep ,you remember i had the fatcat in the garage ,sent it back (cost me $120 restock fee)hehe. Im about to get it tuned at Jds I think it is. Bethlaham penn. The fellow that Dock just taught. I wanted to bring it to Joes but he wont let me bring it in the morning and take it home that night which means driving 7 hrs then going back (another 7 hrs) . Cant do it !!!!
So im doing some last minute experimenting to see if I can feel anything different in the low end. I have stuck a couple pieces of metal in the rear of the 2 pipes but havnt rode it yet to check it out. So just trying to make sure its all done before I spend for the tune.
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Old 11-27-2007, 10:02 PM   #13 (permalink)
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Quote:
Originally Posted by Qhorin
Hi George, Yep ,you remember i had the fatcat in the garage ,sent it back (cost me $120 restock fee)hehe. Im about to get it tuned at Jds I think it is. Bethlaham penn. The fellow that Dock just taught. I wanted to bring it to Joes but he wont let me bring it in the morning and take it home that night which means driving 7 hrs then going back (another 7 hrs) . Cant do it !!!!
So im doing some last minute experimenting to see if I can feel anything different in the low end. I have stuck a couple pieces of metal in the rear of the 2 pipes but havnt rode it yet to check it out. So just trying to make sure its all done before I spend for the tune.
I'm a little confused here. If you're talking about JDS in Roselle Park NJ, where the heck do you live in NJ that it takes 7 hrs to get there? I know we get some heavy traffic here, but you must be keeping it under 20 mph. lol
Even Bethlaham Pa is only about 1 1/4 hrs away from Joe's place.
What am I missing?
(I had Joe dyno my Deuce. He did a real nice job)
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Old 11-27-2007, 10:07 PM   #14 (permalink)
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He was talking 7 hours to joes cycle repair. Near albany ny.... www.joescyclerepair.com Is he really that far from you Qhorin?
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Old 11-27-2007, 10:29 PM   #15 (permalink)
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Quote:
Originally Posted by TXCHOP
He was talking 7 hours to joes cycle repair. Near albany ny.... www.joescyclerepair.com Is he really that far from you Qhorin?
I knew I was missing something there. thanks I can be in Williamsburg Va in 7 hours. lol
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