Felt it would be best to post this question here.
Motorcycle - 07 Harley FLHX
Engine - 96" modified to a 103 " with forged 10.5:1 pistons . 585 gear driven cams.
HP - dyno - 98HP 112 TQ
Pipes - Reinhart true duels
PC III

Found after buying this bike that it didn't have enough torque for my taste. I do a lot of two up riding and touring. I've also installed a hard pack touring package. So I went to the dealer and he said the 103 package you see up top was the way to go. After the mods, I found that I had more mid and top end power but I lacked bottom end torque like I wanted. So I went back to the dealer and ask what could I do. They said a new exhaust system would give me more bottom end but it would take away top end.
Well rather than throwing away my Reinharts, and ordering a good two into one pipe, I decided to try an old school trick and I ordered more baffles and install bolts to create more back pressure . It worked very well after installing two 5/8 bolts cross each other. I had massive low end torque but I lost a lot of mid and top end.
When I told the what I had done he told me I had to let a build like that "BREATH" or I would loose a lot of power. Well I informed him all I was looking for in the first place was Torque that I wasn't interested in drag racing.

So my questions are this. Why does a modified engine have to "BREATH".
And why can't I build back pressure to get more torque with my exhaust? Will this hurt me engine in any way ?

Thanks Guys

 

one question: are you using a powercommander or SERT? or something similar?
if not, that might be another option since you can tune the engine more in the direction of your liking with a new map.
If you do have one of those modules installed, did you get it dyno tuned?

 

ok just noticed I can't read properly...so the only part of my question still valid is whether you got it dyno tuned? or did you get a preset map?

another question, what air filter are you using?

 

I think there was a major misunderstanding between you and the guy at the dealer. It sounds like you wanted more torque at low RPMs. That is much different than "more torque!". An engine produces torque at all RPMs. You can build an engine to produce lots of torque at higher RPMs (which actually gives you more horsepower) or you can build it to have more torque at lower RPMs (the concept you have of torque) which will make it accelerate quicker if you're not willing or are unable to downshift.

As for the guy telling you that the engine would lose power if you didn't let it breathe, he was talking about horsepower. You already described the result that matches what he described. It doesn't have as much power at the higher RPMs. When you introduced back pressure it lost mid and top end torque (commonly known as horsepower). In trade you got more torque at lower RPMs. It shouldn't hurt the engine to run this way.

Are you happy with the result? If you find yourself wanting some of the higher end torque back then consider getting that 2-1 exhaust. Otherwise your good to go.

 

I have a 103" that was set up for my type of riding. Was the motor package a kit or something they pieced together for you? As for letting it breathe, the more air in the more air out. I think (no expert) running too much baffle is actually plugging up the system, where its pulling more air in than it can push out causing the lose of power. I think a cam swap might solve you problem, but like I said I'm no expert.

 

The only way to make ANY power whatsoever, ya gots to have air, fool, and spark. That said, the MORE air and fuel, the more power. Simple, huh??
Not so fast.
I am NOT a cam expert. But I do build motors. I have a buds who is a cam wizard. I fully understand all the technical data, etc, for cams, but not so much which one goes where. So I have him make recommendations.
That said, there are a few engine builders out there, you can access on the net here. Give them the data you have above, and see what they recommend for a low end 'grunt' cam. Without going online and tracking it all down, I do not personally know the numbers on the 585 cam, but my GUESS is it is an RPM cam. Need to get the R's up, for the cam to do it's designed function.
When I built my pan, I went with a low end 'grunt' cam. Less lift and overlap.

Here, try looking at this. Compare the 546 with the 585. The 546 is a low end cam. (Touring and two up) Note the differences in opening and closing degrees, the lifts and durations. Hopefully this will help clarify, some of the issues you are ?ing.
http://www.powersportsuperstore.com/.../tr49-8570.htm

When you baffle it down that much, you are 'strangling' the motor, just can't get rid of the burnt gases fast enough, thus you are not getting a good charge of air and fuel, specially at higher R's.
But you are WAY ahead of the curve, compared to many. You NEED back pressure for a street motor to run decent. Guys who run straight pipes only, are making way more noise, but much less snoose.

"Well, how come dragsters run open header pipes?"
DOH!! They're turnin' THOUSANDS of RPMs. Plus running giant blowers to pack in the 'meat'.

You can try emailing Lee, not sure if he will respond or not, but he is a darned good egg.

http://www.leesspeedshop.com/

And another builder round here, Greg. And they GO good, when he's done.

http://www.pro-performance.biz/

Good luck.

 

Don't quote me, but I think that's .585 lift with quite a bit of overlap and duration. That's the cam that S&S puts in its "super stock" engine, right?

If so, Gumby probably nailed it. An Andrews EV72 has only .560 lift and it's really too much for easy street riding.

I'd be wanting 510 cams, which I have, and which give gobs of grunt without running out of power at highway speeds.

Again, don't quote me on those 585 cam specs, but it's worth looking at...

 

Another thought. There are two basic ways to move air through an engine. Use a big "pipeline" and the air can move slowly and still give plenty.

Use a smaller pipeline and the air has to move faster. The faster the air moves, the more power you will have at low rpms. If the "pipeline" is too big, you have to spin the engine way up to get enough air/fuel velocity to make real power.

That's part of why you lose low end power with straight pipes, and part of why restrictions can help. That's part of why too much cam can hurt low end power.

Everything: Breather, mixture, intake runners, exhaust, cams, etc. have to match as far as purpose is concerned.

 

Im not saying the bike is weak or doesn't have power. What I am saying is I have the best power at 3000 to 4500 rpms. I have to run in higher rpm's to get grunt. So I installed those bolts in the baffles and I found it gave me more low end grunt. A lot of grunt, but it took away about half of the top end. I hardly have to turn the throttle with this set up and it grunts down the road well. Im just worried I might damage the engine or something. That's why I was asking. Plus will it make my engine run richer or leaner that way ?

 

Gumpster pretty much summed it up. The way to move the 'range' is with the cam . look at a ' torquer' cam. this will give you the low end grunt and still let ya spin up the 'R's and have some decent power on top. Also ditch the bolts and baffles and slip in a set of AR cones. Anti Reversionary cones go in the pipes right at the head and tend to cancel out the 'wave' in the pipe and add just the right amount of back pressure to the system. like has been said before too much baffle just chokes the motor with spent exaust. Need to move air to get power and torque. And choking it out like that will make it run rich.