| Author | Message | ||
     Electraglider_1997 |
My brother has a twin cam bagger and is pretty much a mechanical/electrical engineering savant. He hooked up a fuel pressure gauge and found that the pressure was consistently wild because of the injectors firing on each cylinder. Each time an injector fires the fuel line pressure dips. He theorized that if an injector fired when the pressure was low that the cylinder would get a weak charge of fuel and that was why at low rpms the bike was like how our Buell are at low rpms and that is jerky. He hooked up a fuel pressure damper (FPD) on the fuel line fairly close to the throttle body. The approx $50 FPD he purchased was meant for a BMW car. He fired up his Harley and instantly the pressure gauge held rock solid at 40 psi (if my memory serves me correct) where before it was jumping from 30 to 50 psi. He says now the bike will run on down the road at idle smoothly where before it was just like our Buells at under 2000 rpms bucking all over the place. He has a friend in Milwaukee at Harley research and development that told him that they don't put a damper on the fuel line because it would cost too much. And it helps give the Harley that Potato Potato sound. $50 to smooth out running at low rpms is pretty inexpensive in this case. Our service manuals show how to hook up a fuel pressure gauge but I'm wondering if any of you guys have done this already or have access to a gauge and could see how unsteady our ULY's fuel pressure is while running. My brother lives about 280 miles away and I was visiting when I saw his Harley on the gauge with the FPD installed. I woke the next morning wondering if my brother had just solved a big problem for us Buellers. Can you imagine if all it took was a FPD installed to make our bikes run smooth at low rpm, that would be a miracle. It seems that the hp/torque would be improved at the same time. The FPD could probably sit on the airbox base plate. My brother says the closer to the fuel injectors the better. What do you guys think about this? (Message edited by electraglider_1997 on November 15, 2016) | ||
| Electraglider_1997 |
By the way, a FPD is a rubber diaphragm and a spring encased in a metal body with an input and output tube to push the fuel line onto. http://www.bmwbuddy.com/z/part/16121178035-bmw-fue l-pressure-damper | ||
| Smorris |
within the past 6 months someone on this forum (i think) had a pressure gauge hooked up on a xb . i think they had made it with a EBR CR1125(?) fuel line. they sold it after someone inquired about making one for their bike. hopefully someone with a better memory can recall this and help out here | ||
| Jim2 |
I recall the thread. He was just using it to verify the fuel pump was working. There was not talk about pressure fluctuation or FPD's. I've always heard that below 900 RPM the oil pump cannot provide enough flow for our Buell's. At least the old tubers. That is why we idle high. | ||
| Sagehawk |
Are the dampers vacumn operated or am I thinking of a regulator? Or are some both items in one unit? | ||
| Electraglider_1997 |
The Uly's fuel pressure regulator is located in the fuel tank with the fuel pump and fuel filter canister. All fuel injected cars have a FPD according to my brother to take care of the pulsating pressure caused by the fuel injectors firing. The BMW FPD my brother is using is not vacuum operated, it works with the fuel pressure and flow by way of a diaphragm and spring. It looks a lot like the Uly's fuel filter canister. | ||
| Electraglider_1997 |
The idle on my brother's Harley was not what was causing the pressure fluctuation, it was there because of the injectors pulsating the pressure when they fired. The damper instantly got rid of the pulsating pressure. In fact the Fuel Pressure Damper is also called a Fuel Pulsation Damper. A fuel pulsation damper is a device used to regulate the oscillation of fuel caused by the injectors opening and closing and smooth this out. Sometimes referred to as a FPD. Fuel Pulsation Damper - Injector-Rehab Fuel Injector Cleaning Services injector-rehab.com/shop/fpd.html | ||
| Nillaice |
That'd be better than slipping the clutch thru town | ||
| Phelan |
So the next question is, where to get one and where to install it in line? | ||
| Electraglider_1997 |
I personally am going to take off the airbox base plate this morning and try to figure this one out. | ||
| Electraglider_1997 |
I quickly got the airbox base plate off and see the fuel line button that connects to the throttle body fuel rail. The best place to add a fuel pressure damper is on the fuel line just before the so called "button" connector located on the end of the fuel line hose. How do I disconnect that button from the fuel rail male part?? The service manual says to first get the fuel pressure removed by disconnecting an 86 connector down by the fuel pump and then start the engine and run the bike out of gas. Maybe that makes the button easy to disconnect from the fuel rail. | ||
| Reepicheep |
Heck, given what it does, I don't see why you couldn't make one that attached to the button and stayed there. | ||
| Hughlysses |
Craig- If you haven't cranked the bike for a couple of days, the pressure bleeds off on its own (at least in my experience). Just push forward on the plastic connector (towards the fuel rail), squeeze the two tabs on the fitting inward, pull back, and it'll come right off. If you're worried about residual fuel pressure, make sure the bike is cold before doing this and wrap a rag around it to catch any spray. | ||
| Hughlysses |
BTW- Amazon lists a wide variety of FPD's starting at ~$20: https://www.amazon.com/s?ie=UTF8&page=1&rh=n%3A156 84181%2Ck%3AFuel%20Pressure%20Damper I guess you'd just put a tee in the fuel line between the pump and the fuel rail and connect it there. | ||
| Reepicheep |
Easy fix. It would be nice to see somebody do some good objective investigation and see what impact it has on XB's. Doesn't the FI have a schrader valve type relief thing? If so, it seems like it would be easy to make a screw on regulator setup that would have a near trivial install. Just screw it on the relief valve. Take it off when you need to use it as a relief valve. | ||
| Electraglider_1997 |
I'm glad I got the creative juices flowing here. Hugh, the fuel pressure had dissipated like you said. I went out to the garage this morning and after snipping off about three zip ties I used a hose gripper plier http://www.bowerstool.com/product-p/5049.htm and the button came right off the fuel rail without any fuel coming out. I inherited the pliers and they grip and depress the plastic levers on the button like they were made to do this. | ||
| Electraglider_1997 |
http://www.harborfreight.com/3-piece-long-reach-ho se-grip-pliers-37909.html | ||
| Electraglider_1997 |
Reepicheep, I'm looking at the schematic of the fuel rail in the service manual and can't see any relief valve. There is a bit of space between the rail and the inside of the tank/frame but not really much space to be able to add a FPD. You'd have to remove the fuel rail, modify (if that is even possible) and then reinstall. Looking down at the top of the engine it looks like a possible place to put the FPD is right to the rear of the coil. That is where the fuel line passes on its way to the button connector on the fuel rail. There is a hollow space there that might be adequate. If that isn't feasible then the other place would be on top of the air box base plate. Place it right outside the air cleaner to the left rear. It also depends on the type of FPD. Some, like the type my brother is using, have an input and output tube. Others look to have just a t-type fitting that Reepicheep must be theorizing about. | ||
| Electraglider_1997 |
Here's one from Autozone for a 2014 Chevy Cruz with a 1.4 liter engine. $20.00http://www.autozone.com/fuel-delivery/fuel-injecti on-pressure-damper?CJPID=3966477&temp_skip_roadblo ck=true&cmpid=cj I'll have to go and see what the size of this is in person. The price for an experiment will not break the bank. Every thing I've read about FPD's if for smooth idle. They get rid of the water hammer effect of the injectors slamming shut. | ||
| Electraglider_1997 |
Might be able to just pull the button fitting off the hose and then just push the hose onto this Cruze FPD input tube and then just add a section of fuel hose between the output tube of the FPD and the button fitting. No harm no foul. Probably won't be that simple, nothing is. | ||
| Reepicheep |
I thought I remembered spraying myself in the face putzing with something. But maybe that was on the Saturn or the Saab. I'll look next time I am in there. I remember (perhaps wrongly) it being up near the heads. | ||
| Firemanjim |
I have run these bikes with my fuel pressure gauge hooked up on the dyno and seen no real fluctuation, suspect you will be doing all this for nought. The fuel lines are a pain to get off because the darn engineer in charge did not bother to notice if he had clocked the release tabs 90 degrees it would not take an act of God to get fuel line off, and on top of that the fuel line is vacuum formed(?)to the fittings and another pain to try and get apart. The schraeder valve was on the tubers,Reep. | ||
| Electraglider_1997 |
Firemanjim, You may be right but I ordered the FPD and with tax it's only $21 and change and it is supposed to be at the Autozone by tomorrow afternoon. I'm going to see if I can get it installed without too much fuss and then fire the ULY up and witness what happens. As for doing something for naught, it wouldn't be the first time that has happened and certainly not the last if it turns out as you say. Nevertheless I'm sure there are a few here that are interested in what happens so I'm going to do it. Certainly, smoothing out any pressure pulses can't be a bad thing and that is why all cars have them. | ||
| Electraglider_1997 |
My brother's email this morning regarding the FPD on his Harley twin cam bagger: I put 250 miles on the last two days. It definitely runs smoother, especially under 2000 rpm. Even sounds better. Very happy. The one thing you need to be aware of is that it will need to be installed as close to the injectors as possible. I moved mine all around and found that the farther away from the injectors the less it dampened. That makes sense though since it is absorbing the weight of the moving fuel as the injector closes and releases pressure when they open. The best place on mine would be right on the opposite side the fuel enters the upper injector housing. A screw in one like shown would work if there is enough room. I put mine in the line just before it enters the injector hold down housing. | ||
| Electraglider_1997 |
Ran into a problem I did not foresee and may be news to most here. The fuel line is an apparent one piece affair made of a tube of nylon(?) covered by a rubber sleeve. The 90 degree button fitting that push/clicks onto the fuel rail cannot be removed from the nylon tube at least not so as I've been able to figure. The banjo fitting at the bottom of the fuel tank is somehow attached to this rubber sleeve covered nylon fuel tube. It all looks like some Buell specifically made fuel line that cannot be easily messed with or maybe impossible to modify. Here, and I thought it was just a regular rubber fuel line. Wish I would have known about this specialty part. I learned all this by trying and trying and failing to pull of the 90 degree fitting off the fuel line. Finally I peeled back the rubber to find the black nylon tubing that doesn't seem possible to detach from the fitting. At the bottom end this rubber sleeve covered nylon fuel line seems to meld with a banjo fitting. It's nice that Buell went to all this trouble but made my task of installing a FPD way more trouble than I think I want to get into. Anybody already know about this fuel line already? If so, I wish you would have spoken up. I put everything back together and it fired right up but now fear that all the twisting of the button fitting probably wound the nylon tube like a rubber band on a rubber band powered model plane. What a pain in the arse this has become. I'll take back apart and see if I can de-twist the tube. Dammitohellanyway. | ||
| Hughlysses |
Craig- I think that's a pretty common setup for FI fuel lines. I ran into an issue on a 940T Volvo I had a few years ago and discovered this. I was changing the fuel filter, which was located on a rubber mounted frame under the car below the driver's seat, along with the fuel pump. The filter hadn't been changed in some time and the bolt that connected the line to the filter twisted the banjo fitting along with it, damaging the hose right at the banjo fitting. Since I didn't want to be without the car for a week while a replacement line came, I removed the old line and tried to figure out how to repair it. I cut off the damaged plastic end and tried to insert the barbed end of the banjo fitting into the hose, but the hose was much too stiff. Finally, I got a pot of boiling water and submerged the freshly cut end in the boiling water for a few minutes. Then I pressed the hose onto the barbed banjo fitting and let it cool down. It lasted at least another 100,000 miles without issue. You might be able to do something similar with your hose if you can find appropriate T fitting to insert into your hose. Alternatively, you could make up a new hose with new fittings. The only other thing I can think of would be to add the accumulator directly to the fuel rail. Is there any kind of fitting or plug on it that could be used as a connection point? | ||
| Reepicheep |
I wonder to what degree a nylon fuel line already does what you are trying to do? It's already an anti-hammer device. | ||
| Firemanjim |
I tried to warn you about fuel line | ||
| Electraglider_1997 |
Vacuum formed to the fitting is not the same thing as what I detailed. I was able to peel back the rubber sleeve far enough to discover the black tubing underneath. I personally think that hooking up a pressure gauge also might create a damping effect of the pressure pulses. Some thing is responsible for the jerky idling on our Buells. My 97 Electraglide is smooth in comparison to my ULY when comparing the 2500 rpm and below running. It also has two lines on the gas tank, one output and one return. A more expensive setup but probably better. | ||
| Mark_weiss |
Could it be that an Electra Glide has about ten times the flywheel mass of our Thunderstorms? | ||
| Hughlysses |
I believe the isolators for the Big Twins (assuming your Electraglide is rubber-mounted) are tuned for minimal vibration at idle, while Buell tuned theirs for minimal vibration at speed. Here's another way you might be able to tie in the damper: Get a longer banjo bolt for where the hose connects to the fuel pump. Add a second line with a banjo fitting "stacked" and another sealing washer at this point. Connect your damper to the other end of this new hose. I believe this is how they do twin front disks from a single master cylinder. You'd probably have to order a custom built hose from someplace, and the location probably isn't optimum, but it would be a simple install. | ||
| Tootal |
Your EG also has a compensator nut on the crank that quells the low rpm jerking. Sportsters and Buell's are direct drive. | ||
| Electraglider_1997 |
Tootal, you are absolutely correct about the compensator nut on my Harley and what it is there for. My jap bikes had a large rubber damper in the rear wheel hub that probably served the same purpose. Our Buells not having any drive belt slack just makes things more pronounced. Hugh, I think the damper has to be ideally placed as close to the injectors as possible. There actually is room for a screw on damper at the front of the fuel rail but that would entail modifying the fuel rail to create enough mass on the end to bore and tap. There is a hollow area between the fuel rail and gas tank/frame that would probably accommodate a damper. |
