Experiments: Overall Gear Ratios with Formulas for speed->rpm conversion | Ideal Fuel Efficiency RPM of sp125

Hi, after riding the bike for about a year, as an efficiency enthusiast (for the sake of it), here are some observations I have taken using data from the user manual and from the inbuilt instantaneous mileage digital meter by actual experimental trials. Couldn't find something even similar for this or any other bike, so im doing it myself.

The goals were to:

1) Get the formula (and values) enough to convert speed to RPM.

2) Identify the speeds in each gear where torque and power peaks.

3) Identify the potentially ideal efficiency points of rpm (and the req speeds to hold constant in each gear) of the engine.

‐----------------------------------------------------------------

1) Firstly, below are the specific gear ratios for each gear:

1st: 3.454

2nd: 1.933

3rd: 1.315

4th: 1.095

5th. 0.933

Primary reduction ratio: 3.421

Final reduction ratio: 2.928

Here are the overall gear ratios for each gear (primary reduction ratio × specific gear ratio x final reduction ratio): -

1st: 34.597640352

2nd: 19.362257904

3rd: 13.17194472

4th: 10.96827336

5th: 9.345569904

* Speed in kmph should be converted to m/s by multiplying by (5/18), then multiply by 60 to get in units of m/min .

Now the rear tyre dimensions is given as 100/80-18 which means 18 inch rim diameter and for the remaining height it's 2 x (thickness of wheel heightwise).

Here it is 80% of the given 100 (as given by 2nd and 1st number in the notation) which is 80mm. 

(Yes it's in milli metres and can vary based on air pressure and wear and tear, slightly changing equation)

=> Total diameter after conversions = 0.6172 metres. 

Now we can use circumference in the formula.

Therefore,

RPM at given speed = (speed in kmph * (5/18) * 60 * total gear ratio for the given gear) / (pi*0.6172)

Peak RPM for torque: 6000 RPM

Peak RPM for power: 7500 RPM

2) By using above formula,

Speeds at each gear at which max torque is acheived sp125: -

1st: 20.177

2nd: 36.0515

3rd: 52.997

4th: 63.6453

5th: 74.6963

Speeds in each gear at which max power acheived at each gear sp125: -

1st: 25.221

2nd: 45.067

3rd: 66.2468

4th: 79.5567

5th: 93.37048

3) Caution: This section has data from real world experiments rather than calculations using purely formula due to the lack of relevant data. So the values are subject to change due to various factors like bike condition, winds, throttle sensitivity, road smoothness , weight load, etc.

Note: Also see the important "Edits" at the end of this post.

So in this case, there is a big flaw in the instantaneous mileage meter. It cant display above 99.99kmpl, which sounds ok but usually it's readings are much higher than actual mileage but it can be decently reliably used for relatively checking instantaneous mileage for our case.

3rd , 4th, 5th gears are out of the question since the peak values easily cross 99.99 so we can't find the peak value using this meter. First gear has so much torque, when I tried finding difference, the difference in fuel eff. readings between each rpm is so less that its arguably less than the error margin of this exp, so it's of barely any use.

Due to this, finally 2nd gear is the best to check as the instantaneous mileage reading at constant speed can't cross 99.99 kmpl.

Here is the summary of observations: -

* Only close to 20 kmph vaguely , the green eco indicator turned on after holding throttle constantly at each speed at 2nd gear.

* At 8 kmph 2nd gear (the lowest speed after leaving clutch fully but without giving any throttle) is actually NOT the most efficient rpm contrary to common opinions. It couldn't even touch 60 kmpl I think, mostly aroumd 55-60 kmpl at best.

* For a fun fact sake, I tried 3rd gear resting rpm at approx 12 kmph, it struggles, so it only reached like 68.4 - 71 kmpl or so in same as above point's conditions. (But this is not our goal, we need to find the ideal rpm in 2nd gear so in 5th gear we can cruise in the speed which we calculate later)

* In the rpms where I consistently easily got green eco indicator in 2nd gear were from very vaguely close to 20 kmph upto 26 kmph (constant speed for all trials). So it was clear compared to other speeds the best point lies around this region.

* Tried riding in extremely unrealistic constant speed in each of these speeds of this range in 2nd gear. Around 21 to 23 kmph showed good reading around 71kmpl approx (depends on how constant and how long you hold it).

Similarly for 21 kmph and below speeds , they were also quite economical but it was clear the efficiency point isn't below 21kmph 2nd gear, coz the rpm should be high enough for the engine to have enough torque for the load for maximum combustion efficiency. High rpms have high internal friction and poor valve timings wasting fuel so definitely not higher than the said range.

* Finally when I thought there isn't a single clear rpm point which exists, at around 25kmph 2nd gear I noticed in ALL my trials I got better readings relative to other speeds when relatively comparing readings in different trials. So I tried to see if it were a fluke or not.

* Tried on center stand to nullify road's effects : (these values are only from 1 trial)

66-68kmpl is usually coming for 23-24 kmph
Something around 21.5 kmph is coming around 72-74 kmpl
only at 25.5 kmph at 2nd gear it gives 80-82 kmpl mileage.

I can conclude that after several trials in real roads, around 26 kmph 2nd gear gave slightly higher inst. mileage and in extremely unrealistic constant speed touched 80+ kmpl (usually 74-77 kmpl) , the only speed which reached the mark without leaving the throttle to "artificially" temporarily increase the number. 

But when I convert from 2nd to 5th gear, the error range can become bigger , so officially range is 25.5 to 26.99 kmph at 2nd gear .

Therefore, here is the final list of speeds at each gear to acheive peak efficiency rpm :- (Note: can vary by previously stated conditions, see edits at end of this post)

1st gear: (15 kmph) 14.2708453966 to 15.1047104806 kmph

2nd gear: (26 kmph) 25.5 to 26.99 kmph

3rd gear: (38 kmph) 37.4840304183 to 39.6742737643 kmph

4th gear: (46 kmph) 45.0150684932 to 47.6453607306 kmph

5th gear: (55 kmph) 52.8311897106 to 55.9181886388 kmph

Final ideal rpm range: 4243.93907423 to 4491.91825935 rpm

OR

Around 4410.36805753 rpm avg (26.5 kmph 2nd gear)

Around 73.5% of peak torque rpm.

==================================

Edit: immediately after I gave 3rd service, the mileage numbers have slightly changed, but the 21 to 27 kmph at 2nd gear range is still better than other speeds, but the peak I said at 25...Well the mileage at that point isn't "peaking" higher than the others now😅

Will investigate further...

Edit 2: Finally, after 1 round of testing in centre stand, this time fresh after 3rd service engine oil, 26 kmph came as the topper. This is after engine is pretty heated too. So if you didn't understand Edit 1 properly, ill give context: Previously I said rpm ideal efficiency range comes when driving around 24.75 to 26 kmph in 2nd gear. But I'm getting slightly changed readings after new engine oil 3rd service (25.75 to 26.99 kmph at 2nd gear)

So do note it can be anywhere in these 2 ranges based on engine oil's age and how hot it is right now. 

Review Of Honda sp125 BS6 OBD2

 Hey there, this is a review of my new bike after riding it for almost 50km (inside city, but will update this incase i find other things worth telling here). Here are the pros and cons (points are ordered in descending order of important / significance to me):

PROS: -

• Excellent mileage (though initial mileage was lower but I'm not sure if it was because of engine break-in period or I adapted to drive optimally. Initially avg mileage was around 50kmpl it came for a load of 100kg on bike. Then as I tried to drive it economically by early gear shifting and constant speeds, it gives 53-57 kmpl for now with instantaneous mileage going very high sometimes)
• Power Delivery is pretty good for a 125cc, which is expected for a brand new bike, but still I'm pretty satisfied in this. As long as you upshift late power delivery is definitely not bad.
• Digital display with - Trip A,B meters, avg mileage, instantaneous mileage, range (only appears when fuel isn't full), with Eco indicator just as reference to teach rider to drive at constant speed at lower rpm.
• Quick and Clean Silent Start - The start of the bike is very silent and easy , you dont hear a starter motor or anything as it doesnt have one exactly like other bikes (uses some magnetic stuff to spin it directly apparently) WARNING: Engine sound will only be silent when you buy or immediately after services. Later it creates a sound so not very silent but silent enough.
• General Look, seating etc - Has a look of a stylish commuter vehicle which has a sport vibe in some angles, but generally nothing bad to say. It also has a chain guard to avoid mud getting stuck on chain. Seating was ok though I've heard in other reviews it was mentioned to be hard, but I feel its fine, atleast the "fatigue" level seems reasonable when driving it for me. Also, the rear wheel width which has improved in bs6 phase 2 does have some good effect on confidence so that's another plus point.
  But I dont know if its for my size, but sometimes i felt the tank being so wide, i get some muscle cramp like pain when sitting, it rarely happens though, but not in bikes with thinner tanks.

CONS: -

• Confidence while driving with pillion is pretty low. Due to its light dry weight, this is the case,the back wheel from bs6 obd2 thankfully has a wider Tyre than older version , but still I feel it clearly.

• False Neutrals and Incomplete Gear Shifting - Suddenly while gear shifting, the gear doesn't fall and we have to press twice most of the time. Worst thing is sometimes it doesn't fall at all!!! Took a few seconds after I slowed down the bike, and pressed it by slowly "feeling" the gears, then it worked. This happens occasionally but can be very irritating. So just see about that (asked in 1st service, so have few others, they have tried but only slight improvement)
  
  Edit: When you drive for long you get the touch of how to not make it fall in false neutral, and it gets better with time also.

• Breaks could be stronger - Yes this has CBS built in it, but (if you didn't know) it works only for back / foot pedal brake, but front brakes neither have CBS nor are strong. So when travelling I have to slightly be cautious since I cant brake very fast. Its good for regular breaking but sudden breaking...not exactly.
  Though I bypass this by conciously using BOTH normal braking along with engine breaking simuntaneously, and this works good enough. NEVER go for drum brake variant. breaking will become useless then.
  
  
• Back Tyre Ridges are deep but their shape is such that mud gets splashed on underside parts of the rear of the bike, especially bad even if you go on slightly wet roads. So keeping this bike clean in even slightly wet roads is not easy at all when driving in muddy regions.

• Build Quality does feel slightly low for some structural things, but also more important things like indicator lights. Yes, the kerb weight is low but some things they shouldn't do tradeoff to reduce weight and also reduce cost like this.

Overall, I would still go for the bike even though current on-road price with "good to have" extra fittings like engine guards,etc (like 7 things or so) costed 1.17L in 2023 . Besides, honda gives 3+7 years warranty! (on mostly the engine ONLY)

General notes: 
Important not to rev engine too much or lug the engine too much initially in break-in period after buying (not recommended other times also, but mainly initially after buying) for proper calibration of engine in terms of friction between parts, etc. So one of the things you can control is gear shifting...

Too early shifting, Engine lugging, Late shifting and high rpm is bad for mileage and heating, reducing life of some vulnerable parts slightly. (Though it is controversially suggested redlining is good for the general engine (search "italian tune up" in google), anyways do it conservatively only.)

A NEW BLOG!!!

 Hey there, I have started a new blog for releasing good quality chord sheets with very good specifications, exclusively for Christian Hymns. The reason is Christian Hymns are played strictly according to a given sheet music, even if it was'nt made for a piano or organ to play in church (sometimes they are actually just SATB sheet music, not for playing). So, instead they could use this website for a couple of hand picked songs which (I felt) were a mix of well known, slightly overplayed and/or "original chords are too basic".

mjgchords.blogspot.com

Hope you atleast visit the blog, give it a go, comment down below and Share the blog. Your kindness is much appreciated!

I CAN'T BELIEVE that I have to put up a post FOR THIS...

 When I say they are an On spot piano compositions, people seem to just ignore those first 2 words and judge it like any other piano compositions and commenting about the audio quality.

Link To My Spotify Artist Profile (Please do check it out if you haven't)

Firstly no one sets up good audio equipment and gets ready for a recording session when literally minutes or seconds ago, I was never planning to do any recording. I always record stuff for safety and suddenly try random improvisations when suddenly I just start and go with the flow.

This isn't something you can reproduce again. Once I stop playing even for a moment, its gone (90% of the time).

Secondly, how anyone with an IQ greater than 73 could even think a composition made in literally milliseconds or a few seconds (yes, that's the time within which I have to come up with the next set of notes to play, optimistically speaking that is) could be perfect, without mistakes, excellent production quality, plagiarism (seriously...I don't even know what I'm gonna play so how can I avoid it entirely).

I hope the people reading this just ensure you treat normal compositions and compositions made on the spot differently.

Thank You.

Also if you want to hear those compositions, use the link: Piano Solos - Spotify Playlist

If you want to check out my overall profile, use this link to see my google knowledge panel: Matthew Jonathan G - Google Knowledge Panel

Also Note: I have decided to release even my cover songs on such platforms!!! Some of them might not be available in your region but many might be. So do give them a listen with headphones!

When someone forgot to switch of the Church Service Recording after service...My piano improvisation performance was recorded

This is simply a improvisation which I was doing after service which happened to be recorded without my knowledge. It's a pretty good one for something like compilation of improvisations except everything is sorta on spot (and some real songs here and there occasionally too).

I lost the youtube video among hundreds of live streams which literally have the same thumbnail and similar looking titles, but finally i found it, so i decided its best i put it here.

https://youtu.be/n0yN0Ux66hg?t=5714

Edit: In a similar fashion, here are more of the same (that is if any occur after I post this):
https://youtu.be/B60ZJUxff6g?t=5507

DONT forget to use volume boosters to hear these, as the sound is recorded from other mics far away from organ, which also means "disturbances" are bound to be heard.

Any Kind Of Guy - Cover (v .o .i .c .e + MIDI)

Hey there, as stated in the previous post, since I'm converting my YT channel to OAC, I'm moving the videos irrelevant to it here.

Try Harder (Original) - A .c .a .p .e .l .l .a Version (Trial)

Hey there, as stated in the previous post, since I'm converting my YT channel to OAC, I'm moving the videos irrelevant to it here.

Nobody Can Save Me Now - A .c .a .pella Cover

Hey there, as stated in the previous post, since I'm converting my YT channel to OAC, I'm moving the videos irrelevant to it here.

 

The Prayer - Piano and V .o .c .a .l Cover (in F .r .e .n .c .h)

 Hey there, as stated in the previous post, since I'm converting my YT channel to OAC, I'm moving the videos irrelevant to it here.

Digital Organ Covers (more videos obtained from my Youtube Channel)

Hey there! As stated in the previous post, since I'm converting my YT channel to OAC, I'm moving the videos irrelevant to it here.

Three Fold Amen / Lord Keep Us Safe This Night

Morning Has Broken - Organ and Piano