Can anyone shed any light on why my torque curve stays below 90 until 3,750 then climbs again - most posts I see have a flatter curve that is more consistent. I have 2008 fatboy with 103", SE 211 cams, V&H BSS, PC5, SEAC/Heavy Breather, SE 50mm tb

The tuning shop reckons it's the exhaust but someone was telling me the cams might be the issue? Would a 2 into 1 exhaust help? Not much clarity to be had in this!

 

Some exhaust cause what I have heard it refered to as torque dip. Yours doesn't look like a dip, more like the cams haven't started to come on yet.

 

I had the 211 cam in a factory 95 inch with stock heads, stock tb, SE Heavy Breather, and V&H BSS and a Power Commander. The bike made 88 hp and 95 tq but it didn't come on until 3800 rpm. I put on T-Man Stage II heads milled .30 for a 9:8-1 compression ratio, a T-Man 50 mm tb, and V&H BR with Thunder Monster Baffles and it went to 102 hp & 100 tq coming on around 3600 rpm. This combo went above 90 hp at 4700 rpm and 90 tq at 3800 rpm. I wanted the power band to be more to the "left" so I changed to a T-Man 625 cam and a D&D Fatcat with the Performance Baffle. Now things are getting interesting with 107 hp and 105 tq coming on almost immediately. This combo goes above 90 hp at 4400 rpm and 90 tq at 2850 rpm and is still above 90 hp past 6000 rpm. The 625 cam should be going above 90 around 2500 rpm so after talking with T-Man and geting some tips timing adjustment my tuner was going to do the final tune with some "fine tuning". Before I could get it back to him I was rear-ended by another bike while at Myrtle Beach back in May. So my bike has been in pieces waiting on parts and now paint. Hopefully it will be done this week or next and I can finally get back to riding and get this tuning issue resolved.

The 211 cam sounds awesome and is a hot little cam if you like winding it up. That's just not my riding style. I really tried to make the 211 work because it was already in the bike when I purchased it but it just wasn't for me. The 211 likes a boost in compression so that would help you more than anything. Of course I am assuming you are at stock compression when making this statement. If my motor had around 10:5-1 with the 211 cam it may have been ok but when I decided to change the pistons I also decided to switch the cam and go with a proven combination. At that point I was tired of messing around with trying to make something work. A good 2 into 1 pipe like the Fatcat would help also. It would defintely smooth out the curve. I'm not sure if it would move your ower band any because I made the pie and cam change at the same time.

Sorry to go on but if someone had given me this info in the beginning it would have possibly saved me some trouble.

 

Thanks guys. Harleyheaven - thanks for sharing that as my setup is very similar to your original although mine is 103 it is very similar, although considering it is 103 with SE tb I would have expected it to make more than an extra 2hp and 2tq but lets put that down to different dynos.

I will try the low cat pipe first as that will be cheaper than pulling the engine apart. I like winding it up but would like a tad more low down, although it wouldn't take much so fingers crossed the pop does it!

Thanks for sharing, you can never get too much information to these questions!!

 

From what I know about the 211 it is a late bloomer. The 2:1 might help a little on the lower end but I doubt your peak will shift with out a boost in compression.

 

I believe you're right, the physics of the thing suggest that it would be too fundamental a shift for a new exhaust to fix. To be fair the bike is pretty much perfect now for my riding style after I have fitted the new 50mm throttle body , so the low cat exhaust will be the icing on the cake until I decide to do the heads and cams.

 

I've got a 103 w/ 211 cams and mine comes to life around 2800 but gets to 2800 real fast.. Head work is the big thing with the 211.. Stock or less than 10-1 CR will make the cam feel a bit like a dog.. get the compression up with good port work and you'll like the cam.. At least I do.. Good luck..