Better deal, or the best deal? At max torque rpm do we get maximum kms per litre than at any other rpm?

Then don't try those new things, they are surely gonna put down the mileage. You're getting one of the best mileage and that is due to the fact that you're actually "reaching top gear as soon as possible" according to the HH manual. Am I right?

best torque spot is better, but not the best. Better because speeds are fast enough for touring distances in short time still not causing strain to the engine nor to the rider..
For best mileage; think accelerator as a tap which controls fuel flow, less you open it, better mileage you get. (do this without lugging the engine)

For me best mileage is achieved when there is LEAST throttle for optimum speed range (45-55) alongwith RPM ranging 4000-5000 on highest gear. .
close to perfection but thats how it works out for me

Yup, that's right! I have been following such gear change pattern religiously for years...

for samarth and plasma bhai

what an awesome thread!! ..loved going through it!

Guys I have a few questions..please excuse me if they are irrelevant and be patient

1)Let us compare honda unicorn and yzf r15 2.0.What is the difference between the way they rev??..now on a honda i feel it very hard to rev to 5k rpm on a lower gear but where as on a r15..you can take it wee up higher..why is this??..Is it just because of the way engine has been manufactured??..stroke for uni is 57.8 while for r15 is 58.7..not much of a diff eh??..I just wanted to know why their behaviour is different.

2) Now , Lets compare a honda unicorn and a honda dazzler. uni reaches max torque which happens to be 12.75 Nm @5.5k rpm while dazzler reaches the same at 6500 rpm.So why is the reason and what is the advantage??..Just to have a better top end??

3) suppose if I want my uni to be tuned such a way that..it gives me ample torque even at low rpms and it gives its max torque at a higher rpm(say at around 7k rpm as opposed to 5.5k nw) , pretty much like the r15..can it be done??..for this what will I need to do??

Eagerly waiting for the reply

Still waiting for Samarth bro and others to throw some valuable info.

@ Sunny - Dude kindly post in black fonts which are easy to read. Post in red only if you want to show anger to someone.
By the way nice thread. Loved going through the technical discussion.

Regards,
Deepan

Alright bro

@fOrest Glad u liked it

1) Mostly it is because the way both engines have been manufactured are different. Even though the strokes may not be very different, other factors are very different, like the amount of valve lifts (due to different camshafts). But maybe other more knowledgeable people (Samarth?) can shed more light on this.

2) The Unicorn and Dazzler have the same engine but different characteristics, why? Because Dazzler has a high lift camshaft which means that in every cycle the valves are lifting higher and more fuel+air mix is being burnt. This directly results in a change in the torque curve and so the max torque spot moves to 6500rpm in dazzler. This btw also is why the HP is slightly higher at 14bhp in Dazzler. Why do this? Because by shifting the max torque spot to a higher RPM u can take advantage of the gearing of the bike. If the max torque comes in at low RPM, at higher RPMs the torque will fall to such low levels that in the top gear the bike will not pull much. If you shift the same torque figure up the RPM band then u can add an extra gear which will still allow you to pull the bike in high gear. Sure the low end torque will decrease but u can always cure that by adjusting gear ratios properly.
This is the reason why R15 has 6 gears, because its max torque comes in @7500rpm.
This is also the reason why some HeroHonda 125cc bikes had just 4 gears whereas Discover DTSi has 5 gears. There is not that much difference in the max torque, the difference is in the RPM that torque kicks in.
So for 2 bikes with identical torque value but different RPM spot for max torque, the bike where the RPM spot is higher will have a higher top speed and bike where max spot is lower will have lower top speed.

3) The simplest way to "get ample torque at low end" is to decrease the weight of the bike. In fact decrease the mass of the wheels as much as possible in particular. To shift the max torque spot up the RPM band will require stuff like high lift cam shafts and other changes to the engine components.

Hope what i wrote made sense. Please correct me if am wrong.

Question in bold

@sunny

Yes in R15 the absolute value of the torque is not very significant at RPM below 3500 but this is cured by gearing the bike to have an extra gear. So infact if you look at the gear ratios of R15 you will see that in R15 each gear has a slightly lesser pulling power than Dazzler (except 1st) but the final reduction is such that without a doubt R15 will be faster no matter what! In fact the huge difference between 1st and 2nd in Dazz means that u cannot use 2nd gear for traffic signal speeds, infact this bothers me since in my friends unicorn i could just be rolling and second gear will pull me, in dazzler if i do the same the engine knocks around, so i have to use half clutch and high RPM to launch in sec gear or ride in low speed or directly use 1st gear. This means lower mileage for me. Why have they done this? Precisely because low end of dazz is not good due to higher RPM spot of max torque. Compared to this the ratios of R15 are much better distributed, this means R15 not only accelerates better than dazzler in 1st gear, despite the gearing being better in dazzler for the other gears, the engine becomes much more usable for R15 for every other gear and presence of the final 6th gear means that the torque that the engine is producing at high RPM is still usable by the 6th gear and thus better top speed. The fact that R15 has a better ratio for first and none of the other gears than dazzler show the superiority of the engine components, quality and manufacturing of R15 engine and the resultant drastic difference in the 2 engine's torque curves. (And we thought Honda made great engines Baja better buck up!! :P )

Gear Ratios:

---------------Dazzler---- R15
1st------------ 3.076--- 2.833
2nd----------- 1.789--- 1.875
3rd------------ 1.304--- 1.364
4th------------ 1.090--- 1.143
5th------------ 0.937--- 0.957
6th ----------------------- 0.84

Again, as always, please correct me if am wrong.

I think you will find the answer about R15 in the above post regarding gear ratios. As far as Dazzler is concerned, I dont know for sure about an upper limit, I mean there must be but where is that upper limit I dont know.
The torque spot can definitely be shifted to more than 6500 by using better quality, low mass components and infact better components will improve the low end torque as well as is evident in R15. Everyone who gets their bike Joeled says they have a better lower end. Sure that is because of the free flow exhaust, but it is also because of the racing cam shafts, lighter pistons and thus an altered torque curve!

As far as the limit of an engine is concerned, have you seen the movie "The World's Fastest Indian" ? Its a must watch for every biker. Burt Munro took his 750CC 1955 Indian engine which did a top whack of 55mph and improved it till he achieved 203mph top speed, that's 316.68kmph..!! He was in his 68th year of life when he broke the speed record and his bike was a full 47 years old then! Limits? That is for you to decide my friend.

Burt Munro - Wikipedia, the free encyclopedia

thanks for the suggestion man! will surely watch it..am shooting some questions and opinions of mine..please correct me if I am wrong

how is "not having a significant torque at lower end cured by gearing the bike to have an extra gear" ??

how is the gear ratio related to pulling power??..I mean the gear ratios decide at which rpm your wheel rotates as to that of the engine?..So I suppose for a given engine rpm in 1st gear..r15 accelarates btr than unicorn provided they produce same torque!..and vice versa in other gears (with the same condition)..no??

Let us say that r15 has better lower end torque due to the make of the engine and stroke..so it can have better wheel rpm for a given engine rpm..since the gear ratios dont vary much between both..i feel for the amount of torque r15 produces..it can overcome the higher gear ratio factor and can outbeat dazz on any given gear..can this happen??

and cant we shift the max torque point to a higher rpm..maintaing the lower end torque..or even making it better??..isnt that possible??

Answers in red.