Gutted Pipes and goats Belly??

[josh]

I recently bought a full set of gutted pipes for my bike. I have installed the gutted exhaust pipes and was trying to decide if I should also install the gutted goats belly. As I look around I see some people run into power issues or possible valve problems due to lack of back pressure?? Before I try it can I get a opinion??

PS I have a cobra fuel module thingy so I can adjust that as well if needed

Also I have both a stock goats belly and a gutted one to clarify

[cactusjack]

I've heard of a lot of people who gutted their goat's belly. I've yet to hear any of them say it was worth the trouble.

[ringadingh]

If you have both you could try them and see which one you like better. If they are just debaffled pipes you should still have more than enough back pressure.

[redjay]

I gutted the goatbelly and debaffled the mufflers on a spare exhaust system I bought. I like the sound of just the debaffled mufflers. With the debaffled goatbelly on as well I did not like the sound. The performance was flatter as well. I put the stock goatbelly back on and the debaffled muffflers. Sounds just right for me. Gutting the goatbelly is a lot of work for no gain in my opinion.

[macmac]

I gutted the goatbelly and debaffled the mufflers on a spare exhaust system I bought. I like the sound of just the debaffled mufflers. With the debaffled goatbelly on as well I did not like the sound. The performance was flatter as well. I put the stock goatbelly back on and the debaffled muffflers. Sounds just right for me. Gutting the goatbelly is a lot of work for no gain in my opinion.

Just based on the quote I would say the back pressure loss is too much. In that case of no more parts, some other form of baffels would need to be made up and put back as a minimum to re-gain back pressure.

I am trying to plan out some form of discussion on back pressure, but it is a harder topic for me to present.

There are just so many varriables, and I am not any engineer.

[leadbelly]

That would be an interesting topic macmac, even if you just covered the basics of why backpressure is neseccary.
I was told once but have since forgotten, something about scavaging exhaust?
Can't remember now, guess I could look it up but I'm not interested in some overly detailed white paper thesis writen by some engineer.
I'm sure your explaination will be sufficiant.

[snarleybill08]

exaust systems are like women, very finnicky. i have built many performance systems, some worked some did'nt. exaust systems are so complex in design that you really have to have a dyno to get them right. there are two things that have to be considered when designing a system. do you want lowend usable torque for all around street riding or do you want the maximum horsepower for racing? you can't have both. exaust systems and camshaft durations have to work together. there are two things that affect exaust systems. one is the frequency of the exaust pulse and the other is back pressure. for tractible street motors back presure is somewhat important. in all out race motors back pressure is a no no. the frequency is important because it will actually suck the exaust out of the engine. on a street motor back pressure is important because it will prevent you from losing a good part of your intake charge on valve timing over lap. basically if you don't know what your doing leave it alone. you can do more harm than good. often time if it seems like it should really work you may lose efficiency. i bought a v&h two into one for my v-star, anf one month later put the stock system back on. it sounded like crap to me. i put cobras on my nomad, with a procharger and cobra module. it runs great but my v-star will put it in the weeds. the nomad is in a very mild state of tune. i think the cobra or any other module will give the most bang for the buck. i also think a crossover pipe in the cobra exaust and v&h would be a big plus for exaust scavenging on the nomad. road house leads the others with this. i have gutted a goat belly and i can attest that they are very restrictive for a big pulsing v-twin like the nomad. will it put out more power? only a dyno can tell. i don't put much faith in seat of the pants. i would guess that a gutted goat belly on a dyno would best a non modified one on the dyno, just from looking at it. now this is just a speculation from an old fart whose done it all. the nomad ain't no race bike but has lots of room for improvement in rideability. the fuel module tuned in gives the biggest improvement. the aircleaner mod will give the upper end improvement. the stock aircleaner is great at low rpm's, but is very restrictive at the upper rpms. the mufflers in stock form will handle all the exaust this motor will put out, cuz both mufflers are passing the exaust for both cyl.s at the same time, do to the siamezing effect of the goat belly. my nomad is tuned absolutely perfect for the riding i do. i have the cobra true duals with the non modifiable baffles, the cobra module, and a kurakyn pro hypercharger. this is an under square motor, that is capable of very smooth lowend pull, and has a very mild cam profile. for it's size it is quite under powered. that is the price you have to pay for good rideability. why do you think harleys are so slow. lol. ps. my bike sounds great to. bill

[AlabamaNomadRider]

Thanks Bill for the explaination of how the exhaust system functions. It was very informative.

[josh]

I ended up staying with the stock goats belly and love the sound with just the pipes. I have the other pieces and may play with switching stuff around later but for now I really like it.

Leave the bike as it is. The debaffle is great for some. Aftermarket are also great. And the stock setup for folks like me is plenty great. If I wanted something else I would just buy it, but I dont. We just rode 350 miles Saturday on the parkway, me and the wife on the Nomad and 5 others. A Vulcan 2000, nice bike, a Fat Boy, a Gold Wing and a Vulcan Classic. Mine led like a champ and it was so peaceful on the parkway because I had the Fat Boy, with Screaming Eagles riding last. :)

[mrimpala]

I debaffled the mufflers and removed the goat belly. I then fabbed in a crossover to connect the pipes. Sounds great, and runs pretty good. I will not put aftermarket pipes on. I've spent $30 in all and I'm happy with it.

[nomad]

how about a pic of the crossover or diagram of some sort?
i would be interested in something similar on my 2003 1500fi.

[lw]

how about a pic of the crossover or diagram of some sort?
i would be interested in something similar on my 2003 1500fi.

I would think the enterprising individual might find a market for such a fabrication.... I know I'd be interested.

[mrimpala]

Wow, I didn't expect that kind of response. I'll try to get some pics posted. It was really quite simple. I did use a lot of welding wire, and did a lot of grinding.

[mrimpala]

Ok, lets see how this works. Any questions or comment, please reply or send me a message.

http://i996.photobucket.com/albums/af86/mrimpala/100_0246sm.jpg
Crossover from the left side.

http://i996.photobucket.com/albums/af86/mrimpala/100_0247sm.jpg
Crossover from the right side.

http://i996.photobucket.com/albums/af86/mrimpala/100_0248sm.jpg
Crossover from under the bike, from the right side.

I should add that I also made the flanges out of 1/4 or 3/8 inch stainless, and used a '69 Chevy Corvair exhaust donut between the two flanges. I am also going to wrap the pipes with black wrap.

[AlabamaNomadRider]

Thanks for the pictures it looks like you did a good job. How has removing the goat bladder affected the performance of your bike?

[mrimpala]

I have not noticed a real difference in performance. Until I do something with the intake part of the air pump, I probably won't notice a difference. It sure sounds better, though. The TFI really smoothed out the idle. Once the intake is modded, I'm sure a difference in performance by the "butt dyno", will be noted. Does that translate into actual increase in performance, not hardly. Also doing this allows you to use the longer oil filter.

Ride safe.

[Makula76]

Why did u go with making the y pipe? Why not just put straight on the rt side and just cross over from the other head pipe to the Lf sidewhich would b same as buyin aftermarket set up.and not near enough welding unless u didn't have access to a pipe bender

[redjay]

Hi. Just a heads up, this thread is from 2010.

[Makula76]

Hey ty I didn't even pay attention lol..do u have idea whhy he did this instead of just a crossover

[mike07nad]

Hey ty I didn't even pay attention lol..do u have idea whhy he did this instead of just a crossover

I almost believe the reason that there is not 2-pipe true duals has something to do with back pressure in the exhaust. The way the engine functions it requires a certain amount of back pressure which is created by the Y-pipe.. That's kinda what I remember - Note: I am by no means an engine/exhaust Guru. Hope that helps.

Mike
Red_VGR