S&S 475C bogging under 2k RPM

838 Views 20 Replies 11 Participants Last post by Gotham, 2 d ago

RGobsession

Discussion Starter · 4 d ago

Ok guys, I just installed the S&S 475 cam in my 21 RGS and I've been holding off on asking this question because I don't want to sound stupid and get flamed. Here goes. When taking off in first gear with the stock cam I recall it pulling hard right off idle without bogging. After the cam install it seems like I need to get the RPM's at least up to 2k before letting out the clutch or it will bog and begin to stall out. I believe that the concept of the 475 cam is it shifts the power curve to increase the mid and high range, so I'm guessing it leaves the low end lacking any power. And I noticed on the dyno that the tuning grid begins at 2k RPM. So, is it safe to say that the engine really doesn't make any power under 2K with a torque cam installed? BTW, I'm very pleased with the cam, the way that it sounds at idle, and the way it performs, just curious about this question. Ok, let me have it. LOL!

2021 RGS, S&S 475C, TTS tuner, K&N air filter, Tab 4.5 exhaust, stock head pipe - no cat

Reactions: 1

1 - 20 of 21 Posts

Violeiro

· #2 · 4 d ago

I think if you change your pipes to 4 you would get that back….

Sent from my iPhone using Tapatalk

Reactions: 3

RGobsession

Discussion Starter · #3 · 4 d ago

Violeiro said:
I think if you change your pipes to 4 you would get that back….

Sent from my iPhone using Tapatalk

Ok, so you think that more exhaust backpressure could reduce the bottom end lag? I currently have one Zombie baffle in the low side, and a louvered baffle in the high side. I could try running both sides louvered at first and see if that helps first.

Scott7d

· #4 · 4 d ago

The exhaust velocity (often misworded as back pressure) definitely slows down with the oversized mufflers affecting low end torque. The quality of the tune could also be an issue. As far as the sheet starting at 2000 RPM, that is just a common RPM range that tuners usually start the graph because people do not (or at least should not) realistically cruise under that range. Personally, I try to keep cruising RPM around 3000, but that's a separate discussion.

I've heard lots of people say the 475 just isn't a good low end cam. This is incorrect. In many of the instances it is due to what I just mentioned: poor exhaust combination and/or poor tune. I'm confident you can get that torque back, or even improved with the right exhaust combo and/or tuning resolution.

Reactions: 5

RGobsession

Discussion Starter · #5 · 4 d ago

Scott7d said:
The exhaust velocity (often misworded as back pressure) definitely slows down with the oversized mufflers affecting low end torque. The quality of the tune could also be an issue. As far as the sheet starting at 2000 RPM, that is just a common RPM range that tuners usually start the graph because people do not (or at least should not) realistically cruise under that range. Personally, I try to keep cruising RPM around 3000, but that's a separate discussion.

I've heard lots of people say the 475 just isn't a good low end cam. This is incorrect. In many of the instances it is due to what I just mentioned: poor exhaust combination and/or poor tune. I'm confident you can get that torque back, or even improved with the right exhaust combo and/or tuning resolution.

Thanks Scott, I appreciate your response to my question. I'm going to try a couple different exhaust options and see how that affects my low end torque.

Reactions: 3

NCPiper

· #6 · 4 d ago (Edited)

Can you explain that more?

I always thought the "exhaust velocity" that mattered happened before the mufflers and was more a function of the headpipe (2-1, 2-2, true dual, etc). The video below talks about this some starting at about 8:40.

And in the case stated by the OP it is a de-catted, stock pipe.

Scott7d said:
The exhaust velocity (often misworded as back pressure) definitely slows down with the oversized mufflers affecting low end torque.

Reactions: 1

Scott7d

· #7 · 4 d ago

NCPiper said:
Can you explain that more?

I always thought the "exhaust velocity" that mattered happened before the mufflers and was more a function of the headpipe (2-1, 2-2, true dual, etc). The video below talks about this some starting at about 8:40.

And in the case stated by the OP it is a de-catted, stock pipe.

I'll be honest. I don't know the full backstory behind it, I just try to absorb knowledge from my tuner and the experiences he's had with different combinations. The exhaust velocity is something he's mentioned to me a few times when it comes to the oversized mufflers. However, I do understand why oversized mufflers could slow down the velocity. Similar to the concept of blowing through a straw and blowing through the center cardboard roll of papers towels (lame comparison I know, couldn't think of anything else in the moment).

Even with a good aftermarket head pipe such as a 2-1-2 (or decatted stock unit which is actually fantastic), ovesized mufflers can still hinder the performance. And yep, it can be even worse with true duals.

Not in position to watch that video at this moment but I will ASAP. Always willing to learn and even admit if I'm wrong

Reactions: 5

Violeiro

· #8 · 4 d ago

Sent from my iPhone using Tapatalk

See less See more

Reactions: 5

18 Wicked Special

· #9 · 4 d ago

RGobsession said:
Thanks Scott, I appreciate your response to my question. I'm going to try a couple different exhaust options and see how that affects my low end torque.

Fwiw, I have the S&S 475 cam in combination with stock header decatted(for heat reasons), S&S 4" Grand National slip-on's and PV w/Fuel Moto tune. I have no lack of low end with a steady acceleration throughout the whole rpm range. The strong powerband occurs around 2800rpm and pulls like a freight train to redline.

I chose the these mufflers strictly for performance after reading so much about weak low end with any 4.5" slip-on muffler. An extreme example of poor back pressure would be drag pipes, great for WOT(wide open throttle) racing on a drag race but not for riding around town. If you've ever run them, you know the popping in the exhaust from a heavy deceleration due to no back pressure, where as a muffler helps exhaust pulses balance and scavenge exhaust gases out of the cylinder on the exhaust stroke.

I feel the 475 get's a bad rap from improper set-up. Yes, it's more sensitive to exhaust than other cams. But those other cams will yield differences in a tq/hp curve between different diameter mufflers, probably just not as dramatic.

See less See more

Reactions: 5

goblue90

· #10 · 4 d ago

RGobsession said:
Thanks Scott, I appreciate your response to my question. I'm going to try a couple different exhaust options and see how that affects my low end torque.

Did you get your bike dyno tuned after installing the cam? I highly recommend doing so even if you’re just using a canned tune or one provided by Fuel Moto. I installed my 475 cam and used a tune from FM, but then got my bike dyno tuned and my tuner was able to get an additional 4hp and 10 ftlbs of torque. My dyno graph is at the end of this video:

youtube.com

Dyno tuning Road Glide ST w/S&S 475 cam, Bassani Road Rage 3 exhaust and Feuling BA air cleaner.

#roadglidest #harleydavidson #sscycle #bassani #feulingparts #motorcycle #milwaukee8 #roadglidenation #roadglidespecial

youtube.com

Sent from my iPhone using Tapatalk

Reactions: 3

smitty901

· #11 · 4 d ago

RGobsession said:
Thanks Scott, I appreciate your response to my question. I'm going to try a couple different exhaust options and see how that affects my low end torque.

Give fuel moto a call or just look at the dyno sheets and CAM comparisons on their web sight . They list the exhaust.

S&S 475 is a CAM that wants to run the higher RPM. But you should not be seeing what you reported.
CAM, Exhaust and TUNE must work together . On theses bikes Exhaust is often what makes or breaks how it runs.

Reactions: 1

RGobsession

Discussion Starter · #12 · 4 d ago (Edited)

goblue90 said:
Did you get your bike dyno tuned after installing the cam? I highly recommend doing so even if you’re just using a canned tune or one provided by Fuel Moto. I installed my 475 cam and used a tune from FM, but then got my bike dyno tuned and my tuner was able to get an additional 4hp and 10 ftlbs of torque. My dyno graph is at the end of this video:

Dyno tuning Road Glide ST w/S&S 475 cam, Bassani Road Rage 3 exhaust and Feuling BA air cleaner.

#roadglidest #harleydavidson #sscycle #bassani #feulingparts #motorcycle #milwaukee8 #roadglidenation #roadglidespecial

youtube.com

Sent from my iPhone using Tapatalk

I had the bike professionally dyno tuned after I installed the cam. It made 112hp and 122 torque which seems to be average for the 475 cam. I've seen guys with alot more into there setup that get numbers similar to that. I agree that intake, cam and exhaust all need to work together to achieve the best results. I'm no expert on reading the dyno sheet so I'll attach it and let you guys look at it and give me you opinion. Also, i installed the cam myself so the first run is with the cam installed, but stock tuning. There is no stock cam run. Thanks!

See less See more

Reactions: 2

MORider

· #13 · 4 d ago

I won’t comment on the tech side. I will comment on your feeling stupid side. I have you beat, so relax.

I once asked where guys were get their mirrors for under the grips…..🙄.

aside from being called a dumbass, few other names that probably are common in the swamps of Florida (who knows), and being sent direction to the nearest TOYS R US. i was given my answer.

no stupid questions here.

Cheers Brothers!

Reactions: 2

S.McArthur

· #14 · 4 d ago

I had the same issue, had 475c, Fuel Moto header, Khrome Werks slip-ons, w/whatever came in the cans.
Damn thing felt like it was going to stall at stop signs etc., huge dip then a jerk and off we went; not smooth.
Installed the Louvered Baffles from KW, made it a little better, wasn't as prominent.
Swapped 2/1/2 exhaust to Fuel Moto RTX 2/1, made it much better. I'd say go to a 2/1 exhaust.

Swapped 475 for 22xe, made everything super duper bettererest.

Perhaps a better header will help as opposed to a big open non-cat header. Slap your stock mufflers on and see what that does, then you'll know what direction you need to go.
I have a couple videos of the RTX 2/1 w/475 if you want hear that setup, it sounds really good. I don't know how to post them here.

Reactions: 4

Zedbra

· #15 · 4 d ago

S.McArthur said:
I had the same issue, had 475c, Fuel Moto header, Khrome Werks slip-ons, w/whatever came in the cans.
Damn thing felt like it was going to stall at stop signs etc., huge dip then a jerk and off we went; not smooth.
Installed the Louvered Baffles from KW, made it a little better, wasn't as prominent.
Swapped 2/1/2 exhaust to Fuel Moto RTX 2/1, made it much better. I'd say go to a 2/1 exhaust.

Swapped 475 for 22xe, made everything super duper bettererest.

Perhaps a better will help as opposed to a big open non-cat header. Slap your stock mufflers on and see what that does, then you'll know what direction you need to go.
I have a couple videos of the RTX 2/1 w/475 if you want hear that setup, it sounds really good. I don't know how to post them here.

It is best to load them to Youtube, then supply the vid links here.

S.McArthur

· #16 · 4 d ago

Zedbra said:
It is best to load them to Youtube

I did it! My first video!

youtube.com

IMG 1336

Fuel Moto RTX 2/1 with S&S 475c

youtube.com

Reactions: 5

Zedbra

· #17 · 4 d ago

S.McArthur said:
I did it! My first video!

IMG 1336

Fuel Moto RTX 2/1 with S&S 475c

youtube.com

I just gave you your first 'like' on there, as well.

Sounds good.

Reactions: 1

RGobsession

Discussion Starter · #18 · 4 d ago

18 Wicked Special said:
Fwiw, I have the S&S 475 cam in combination with stock header decatted(for heat reasons), S&S 4" Grand National slip-on's and PV w/Fuel Moto tune. I have no lack of low end with a steady acceleration throughout the whole rpm range. The strong powerband occurs around 2800rpm and pulls like a freight train to redline.

I chose the these mufflers strictly for performance after reading so much about weak low end with any 4.5" slip-on muffler. An extreme example of poor back pressure would be drag pipes, great for WOT(wide open throttle) racing on a drag race but not for riding around town. If you've ever run them, you know the popping in the exhaust from a heavy deceleration due to no back pressure, where as a muffler helps exhaust pulses balance and scavenge exhaust gases out of the cylinder on the exhaust stroke.

I feel the 475 get's a bad rap from improper set-up. Yes, it's more sensitive to exhaust than other cams. But those other cams will yield differences in a tq/hp curve between different diameter mufflers, probably just not as dramatic.

Thanks for your explanation. That definitely makes sense and helps me understand what's going on with my current setup.

RGobsession

Discussion Starter · #19 · 4 d ago

S.McArthur said:
I had the same issue, had 475c, Fuel Moto header, Khrome Werks slip-ons, w/whatever came in the cans.
Damn thing felt like it was going to stall at stop signs etc., huge dip then a jerk and off we went; not smooth.
Installed the Louvered Baffles from KW, made it a little better, wasn't as prominent.
Swapped 2/1/2 exhaust to Fuel Moto RTX 2/1, made it much better. I'd say go to a 2/1 exhaust.

Swapped 475 for 22xe, made everything super duper bettererest.

Perhaps a better header will help as opposed to a big open non-cat header. Slap your stock mufflers on and see what that does, then you'll know what direction you need to go.
I have a couple videos of the RTX 2/1 w/475 if you want hear that setup, it sounds really good. I don't know how to post them here.

Thanks for your response and explanation. I'm glad to hear that I'm not alone with this issue and that there's options to get it resolved. Not sure which direction I'm going to go yet, but I'm taking it all in. BTW, I watched your video and your bike sounds great!

Reactions: 1

Scott7d

· #20 · 3 d ago

18 Wicked Special said:
Fwiw, I have the S&S 475 cam in combination with stock header decatted(for heat reasons), S&S 4" Grand National slip-on's and PV w/Fuel Moto tune. I have no lack of low end with a steady acceleration throughout the whole rpm range. The strong powerband occurs around 2800rpm and pulls like a freight train to redline.

S&S Grand Nationals are one of the most underrated performance mufflers out there. Especially with leaving the decibel reducers in. Those along with V&H Power Duals have been the best of the three combinations I've tried with my bike so far regarding performance. The D&D Billet Cat made better numbers on paper, but the S&S/V&H combo felt better at the throttle hand which matters more to me than dyno sheets. All of those systems I just mentioned rusted out and looked like shit in no time and my OCD couldn't handle it. None of the matte black stuff has held up for me.

My friend has a 114" with the 475 and Grand Nationals. He has absolutely no issues with low end and actually made better peak numbers than my 117 using the CR480.

Reactions: 3

1 - 20 of 21 Posts