Indian Scout - Cruising RPM

Discussion in 'Indian Scout Performance' started by EPOCH6, Mar 5, 2018.

  1. EPOCH6

    EPOCH6 Well-Known Member

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    Found myself reeled into this discussion on the other forum, figured I'd bring it over here as well.

    A big part of what makes the modern Indian Scout an exciting motorcycle is the unusual performance characteristics of its engine when compared to most other v-twin cruisers. Being a liquid cooled, dual overhead cam, short stroke engine means it was designed to rev high and maintain consistent torque across a wide rev range. This is a departure from traditional American cruiser design. Most Harley-Davidsons and many of the Japanese competitor models that have appeared over the years were air cooled, overhead valve, long stroke, push-rod engines designed to make peak torque at a relaxed cruising RPM. For example, the Harley-Davidson Fat Boy makes its peak torque at 3000 RPM. The Indian Scouts make their peak torque between 5500 and 6000 RPM, twice as high in the rev range, and are still over 2000 RPM away from their upper redline of 8300 RPM.

    For most cruiser riders, that is a very different power band than what they are used to, and it's difficult to adjust when transitioning from a traditional cruiser to a sportier creature like the Scout. Since a lot of Scout owners did transition from traditional overhead valve cruisers, a lot of them are riding the Scout the same way they rode their previous bikes. While this is not immediately problematic, as the Scout's power band does begin around 2500 RPM, and it will ride smoothly at that RPM, it does mean that the Scout is at a higher risk of being "lugged" than other cruisers, which may lead to premature engine failure for some riders.

    This post is an effort to explain why it is beneficial and safe to ride the Scout higher in the rev range than most typical v-twin cruiser style motorcycles.

    The primary reason that we ought to avoid cruising at an RPM of 2500 is that it is right on the edge of "lugging" the engine. If you're cruising in the 2500 RPM to 3000 RPM range all it takes to accidentally fall below 2500 RPM is letting off the throttle for a second or two. Once the engine RPM falls below 2500 it is no longer running within its power band and it has to work harder to carry its load. It probably won't stall, but it will require more throttle than usual to climb back into the power band. This isn't an immediate problem, but over the life of the bike, if this is something that happens every time it is ridden, it will shorten the life of the engine.

    The easiest way to imagine what "lugging the engine" feels like is to compare it to riding a geared bicycle. If you're pedaling along at a low speed with the bike in a high gear and you try to accelerate quickly it's going to require much more leg strength to get the bike moving than it would if you were in a lower gear. You'll sweat, your legs will get sore, and you'll become exhausted very quickly. The same thing is happening to an engine when it tries to take off from below its power band.

    More specifically:

    - Combustion chamber temperatures rise (risk of overheating parts)
    - Timing accuracy decreases causing uneven combustion (risk of engine knocking/pinging/"piston slap")
    - Piston slap causes cylinder wall and piston ring damage
    - Piston slap ripples excess forces throughout the bottom end and power train
    - Cylinder wall and piston ring damage causes oil burning
    - Oil burning causes loss of lubrication and carbon buildup
    - Carbon buildup further decreases engine efficiency and increases heat causing all of the above

    Cruising higher up in the rev range allows you more leniency to let off on the throttle without accidentally falling below the power band and lugging the engine when throttle is re-applied.

    The dyno chart below from Fuel Moto shows the torque curve of the stock Scout 69 engine. You can clearly see that the torque curve dives downward below 2500 RPM. The dyno runs will never measure as low as 2000 RPM because it is inefficient and harmful to run the engine that low for the reasons stated above, the same applies in the opposite direction when revving the engine above 8000 RPM (which is why the ECU is programmed with a rev limiter, preventing that from ever happening).

    A comfortable cruising RPM for the Scout engine is a number of your choice between the green lines below. The lower that number, the higher the risk of falling below the power band during deceleration. The higher that number, the higher the amount of vibration in the foot pegs and eventually the handlebars, but the engine will not care. It's up to the rider to choose a cruising RPM that balances comfort, risk of lugging, and accessible power. For some that will be 3000 - 4000 RPM, for some it will be 4000 to 5000 RPM. The engine will be happy and safe at any of those numbers, but it will not be happy below 2500 RPM.

    [​IMG]
    The curve is almost identical for the Scout 60 up until a little over 6000 RPM where the factory ECU configuration causes it to dive. With a PVCX Scout 60 tune the higher end of the torque curve is restored and very closely matches the curve above (in shape, not peak torque).

    I apologize for the wall of text but it has to be shared. I fear that there are a lot of Scout owners out there used to low revving air cooled pushrod cruiser engines that simply don't know how different the Scout engine is. Knowing the difference and why it must be ridden differently to maximize the life of the engine will cause the owners less grief in the long run and will improve the quality of the second hand Scouts out there in the used market.
     
  2. Alpal

    Alpal Gold Member
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    Another excellent write up Epoch6, thanks heaps, very worthwhile. Interestingly it made me rethink how I ride my Scout. From memory, ( because I'm not riding at the moment and done little since the accident,) around town I ride in fourth and the revs are about 2300 rpm. I get there quick but settle back to that 2300 rpm range. Reading your article has me rethinking that and the first thing I will do when back on two wheels is drop down one more gear and see where the revs take me. I imagine 2400 to 2600 rpm.
    Ok, now there has to be someone out there whose dying for a ride! Quick! Jump on your Scout and go out to check my figures! Third gear at 30 MPH. COME BACK AND TELL US THE REV RANGE.

    Out on the open highway I cruise at about 70 MPH which puts the revs at about 3700 to 3750 RPM. I would not know what the bike revs to when I WOT to overtake traffic but the speedo does flick up to 100 MPH when I do. I suppose whoever goes out on the test above could check that too. Rpm at 100 mph. Don't get caught now!
    Alpal
     
  3. Scouts Honour

    Scouts Honour Well-Known Member

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    Hi there @EPOCH6, This info is very useful. Coming from an XVS 1100 Yamaha Virago and being a driver of heavy diesel vehicles I have always operated in the lower rev range which also suited my cruiser style of riding. Had a few issues with this when I first purchased my Scout as I was unaware it was such a high performance engine. I emailed Shane at Wellington Motor Cycles from where I purchased my Scout (RED) and he took the shop demo out for a ride to get a handle on the best speeds for which gears and recommended I Increase my rev range and no problems since then. I now keep in second around town and don't move up to third until I'm over 60 - 65 kms, have settled into 3000 - 4500 rev range which suits the bike ok. Still not used to having so much power though and I struggle to rev her over 6000 RPM. Thanks for your post which makes me feel I'm doing the right thing with my Scout, Cheers, Scouts Honour.
     
  4. fumbles

    fumbles New Member

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    Interesting- It feels great to chill in higher rpm's- the rider's guide says to shift at what looks at 2500 ish rpms. So I'm a bit confused (novice rider and have only had my 60 for just over a month-4k miles ish) about which is the proper way? Shifting with higher rpm's has me hitting the shifts every time as well versus accidentally starting to shift a little early and lugging or it doesn't stick and I have to hit it again. Attached is the chart:
     

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  5. Warlock

    Warlock This space for rent.
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    I'll defer to the Scout folks...I'm just gonna say welcome. Please post up an intro so we can get to know ya.
     
  6. fumbles

    fumbles New Member

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    It’s a good topic to question. It feels great with higher rpms and has zip to it as it peaks. I have a performance intake I installed but I doubt that affects shifting much.


    Hi! I joined after I googled powerband and what not for a scout. My knowledge is noob level for riding but I’m technical so no issues learning and trying.

    I’m a new rider in Austin. Have a pearl white 2017 Scout 60-have had it since mid April. It’s wonderful.
     
  7. EPOCH6

    EPOCH6 Well-Known Member

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    @fumbles

    The owner's manual is a strange place for every motorcycle, the Scout included.

    Some of us believe they're written with a minimum risk sort of strategy. Maximize fuel economy and maximize safety (minimize lawsuits). Logically, this makes the most sense.

    Some other's believe they're written to slightly increase engine wear to slightly increase dealership service profits. Conspiratorial? Yes. But there are some things in the manual that make you wonder. Oil changes in 16,000 km (10,000 mile) intervals? Valve lash checks at 32,000 km (20,000 miles)? Shift points at ~2500 RPM when all dyno charts prove clearly with data that 2000 RPM is below the power band of the engine?

    I'd love it if there were a Polaris or SwissAuto engineer available on the board to clarify it all to us but that doesn't seem to be happening anywhere online, with Indian or any other brand.

    At the end of the day most of us just do our own thing, monitor other rider's experiences on the forums, and hope that our bike lasts.

    What we do know for sure is that the dyno charts above are accurate, they've been replicated countless times by countless dyno shops since the Scout came out, and they are the best tool we have for determining how to achieve the performance we want out of our Scouts (which of course depends on what you want out of your Scout).

    The general amateur common sense rule for maximizing acceleration is to keep your RPM as close to peak torque as possible for as long as possible. On the Scout peak torque is at 5500 RPM. The approximate distance between most gears, in RPM, seems to be around ~500 RPM. So shifting around or just before 6000 RPM should drop you close to peak torque in each gear. If you're aiming to win traffic light drag races, that should be good enough. If you're aiming to win professional drag races, things get more complicated. To calculate the exact optimal shift points (for max acceleration) of any vehicle you will need some good dyno data (torque/hp vs. RPM), your transmission's gear ratios, your tire specs, and maybe some other variables.

    The interesting and lovely thing about the Scout is that it's power curve more or less has two peak torque curves, one near 3500 RPM and one near 5500 RPM.

    [​IMG]
    For that reason there are two ways that I ride my Scout, depending on my situation.

    If I'm commuting, roaming aimlessly, or just trying to get somewhere I usually shift around 3750 RPM and ride the torque curve between 3000 and 3500 RPM. Not only do you great acceleration that way, you get better fuel economy than you would shifting at 6000 RPM.

    However, when someody pulls up to me at a stop light and revs their engine, I'm going to rev that sucker up to 6000 RPM, sacrifice some fuel, and ride the much flatter peak torque curve between 5000 RPM and 6500 RPM.

    As far as engine wear goes, the Scouts up until this point have proven to be pretty tough bikes. The only incident I can remember, from the forums, is the following thread on the other board where the user rev'd his Scout up to redline in 1st and then slammed it into 2nd (there is no reason to do this other than to see what happens, and now we know).

    Tranny went BANG
     
    #7 EPOCH6, May 31, 2018
    Last edited: May 31, 2018
  8. Scouts Honour

    Scouts Honour Well-Known Member

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    Welcome from New Zealand
     
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  9. fumbles

    fumbles New Member

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    @EPOCH6 thanks! That explanation really helps a lot.
     
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  10. Zipperhead Frankenberry

    Zipperhead Frankenberry Bronze Member

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    3rd gear 30MPH is 2500 Rs. 4th/45=2600 Rs. Those are my "around town" gears. Just remembered to look at the Rs today. Maybe this weekend I'll remember to check the Rs at 100. ;)
     
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  11. JayFL459

    JayFL459 Silver Member
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    Simply Put Basically kept my RPM around 3,000 cruising give or take 500 RPM .. Usually shifted around 4,000 unless Traffic was in the way .. :)
     
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  12. SweetSwing

    SweetSwing New Member

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    @EPOCH6 Thanks a bunch. Having it been a couple decades since my last bike owned. (Harley Sportster & Suzuki 600 Enduro). I just got into a 2018 Scout a month ago. Thus far I love the bike and many of those who I have met seem to like it as well. You still do not see many of them around. But back to the point. I have been riding it like it was a Standard V-Twin and occasionally getting the lugging. I have brought my RPM's up to 4500 a few time and likely over when I watch it but my fear was blowing the engine. As it turns out I SHOULD be running my bike over 3K at cruising speeds. I will make it a point to monitor this going forward until it becomes second nature...
     
  13. Alpal

    Alpal Gold Member
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    Give it heaps Buddy,......it's a bullet proof engine which I had out to 6500 rpm the other day overtaking a car,.....what great fun the Scout is to drop down a gear or two and WOT down the road. I do the same as Zipper, 3rd around town, that's about 2500,..... Any lower in the revs and you lugging the engine which it does not need or like. On the highway I'm usually around 65 to 75 mph which is 3750 ish to 4200 ish?? Love my Scout!
    Alpal
     
  14. PileOParts

    PileOParts Bronze Member

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    Here's a good standard for any engine, taught to me by the dealer who sold me my first real motorcycle, a very peaky Yamaha 305 two-cycle. "Keep a happy engine." That means throttle response. If you crack the throttle open and nothing happens, if you don't feel a surge or at least a flinch forward, gear down. If it feels mushy or "dead," gear down, until there's a lively, "happy" response from the engine. I believe this applies to any small engine of any type or characteristic. Subjective and seat-of-the-pants, but anyone deserving of a good motorcycle can understand this and practice it. .
     
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  15. Hugh Jorgan

    Hugh Jorgan Well-Known Member

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    We have had this very discussion at bike nights at the local Indian dealership. The head mechanic at the shop said to run it at 3500-3700 rpm. He said the bikes are happy at this rpm range. I run Stage 2 on a Springfield. 4th Gear is up to 70 mph, 5th is 70-90 mph. I rarely use 6th gear. He said you are not doing yourself any favors running the rpm below 3000.
     
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  16. Alpal

    Alpal Gold Member
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    Agreed,......
     
  17. ButterSmooth

    ButterSmooth New Member

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    Part of the 'cruising RPM' concern are the words 'cruising' and 'lugging'. You can cruise at fairly low and pleasant RPMs, but the instant you try to accelerate, you are lugging the engine and putting more stress on it than necessary. You can feel the engine complain. Cruise low if you want, but downshift before applying power. Watch the tach in your car with an automatic transmission and you'll be surprised how low they keep the revs. When you step on the gas, it will downshift (multiple times) BEFORE applying power. The argument against this approach on a motorcycle is that you may need instant acceleration for safety. Like cruise control, the low rev and downshift method should only be used in low stress driving environments.
     
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  18. SweetSwing

    SweetSwing New Member

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    I have been monitoring my RPM's since reading an earlier post. I have been running it in the 3K to 4K range with the exception in 1st gear. That seems to not lug the engine when gassing it up at 2500. I will continue to monitor until it becomes second nature. Thanks for the info.
     
  19. Alpal

    Alpal Gold Member
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    I do watch my revs when out and do not run the engine below approx 2500 revs in a 30 mph zone. Lugging is not a problem for me out on the highway as I'm doing 3750 to roughly 4200 rpm most of the time,.....
    Alpal
     
  20. PileOParts

    PileOParts Bronze Member

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    My RM pulls happily up to about half-throttle from about 1700, though if I'm in a hurry it takes 2000 up. I'm sure Scouts need more RPMs.
     

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