Got this from a customer showing what can be done to the 114 engine and still run the STOCK exhaust with the Cats installed. Customer was after better performance but did not want the noise and wanted to see what we could do still running the Stock headpipe with Cats in place and a pair of SE Slip-on mufflers. Here is a list of the final parts used in this 117 build.

HighFlow Air Cleaner Kit
SE 64 mm ThrottleBody and manifold
5.5g/s Injectors
SE CNC Cylinder Heads
4.075" bore 11:1 Pistons
TTS 200 Camshaft
Stock Headpipe with Cats
SE Slip-on Mufflers
Tuned with Mastertune

 

That's pretty impressive with the cats still in it!

 

VERY interesting!

I am really interested in knowing how far a Fat Bob can be pushed, while retaining the stock head pipe. It is a signature piece of the M8 Fat Bob's look, and I really like the 2-1-2 with the big mufflers.

I figured it should be at least good for 120/120, as that's what the SE Stage IV advertises and they say it's with the stock head pipe and Street Cannons, and the SE tuner.

I am content with, but not bowled over by, the Harley Stage II, 100 HP/120 tq. I think I would probably be thrilled with 130/130 or above.

Looks like you got extremely close to that with this build.

Now that you have done a build and tuned for the stock exhaust, do you think it would be able to support a good solid 130/130 or more, maybe by using something like a 124 piston/cylinder kit and a TTS 150 or 200?

What do you think would be the upper limit of what the stock exhaust and some Grand Nationals mufflers could be?

 

I love the look of the exhaust system on the Fat Bob. I'd like to have it on my Breakout, but after looking it over the headers don't give enough clearance for the 240 rear. Shame, as it would have looked great and not messed with my warranty.

 

 

Very nice!

Are those all HD parts apart from the camshaft? i.e. is it a standard HD Stage IV kit but with a different cam and proper tune?

 

 

That's what I was wondering as well.

Peak numbers are in line with the Harley Stage IV, but the torque curve is so massively improved it's not even funny. If that was what the Harley Stage IV offered, I would have gone with it on day one.

 

In the HD catalog the Stage IV results are with the SE Full High Flow exhaust installed on a Touring model. You should expect lower results on a Softail due to Twin Balancers in the engine and the fact that there is NO High Flow exhaust from HD for it, only slip-ons. The results are what they are in the customer testing but it is also inline with what we have done ourselves. I can tell you that had the dyno been run in 6th gear instead of 5th the Torque would have been higher and a slight increase in Peak Hp numbers. We typically see about 4 - 6 increase in Torque by running in 6th gear along with 1 - 2 HP increase. I can also tell you that when we have run the SE-515 cam then installed the TTS 200 in the same bike just with a retune the 515 will show slightly higher HP above 5500 RPM by about 2 HP. The 200 will kick it's *** everywhere else. It your looking for that higher RPM Hp then the TTS 250 would be the cam for you.

I've attached the TTS 250 cam in a Touring bike build, if that what your looking for. This is another customer build (in a Touring bike) that sent the results to us.

 

The Harley catalog has separate charts for touring M8s and Softail M8s, and on the touring M8 it definitely lists it as using the high flow exhaust for Stage IV. But for the Softails, it shows the chart results as having been obtained with Street Cannons.

I think that even though the peak numbers are only a little higher with your build, the quality of power looks infinitely better with yours. I specifically chose not to get Stage IV because of the lousy torque curve, it shows even less torque down low than a stock bike does. Your cam and tune change that dramatically, resulting in what looks like a pretty much perfect combination of strong usable torque and good high-RPM horsepower.

Strong torque is the most important factor to me, and I would sacrifice ultimate HP to get that torque. Your build shows that we may not have to sacrifice, and the stock exhaust header is capable of supporting ~125 HP and ~130 tq.
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How much of that is due to the cam and tune, and how much to the SE parts? Have you done a Fat Bob 114 with Street Cannons and just the TTS200?