V-Twin to Inline-Four or Inline-Four to V-Twin??? - Sportbike Forum: Sportbike Motorcycle Forums
View Poll Results: Which transition is easiest?
Inline-Four to V-Twin. 10 52.63%
V-Twin to Inline-Four. 6 31.58%
There's not much difference. 3 15.79%
Voters: 19. You may not vote on this poll

 
LinkBack Thread Tools Display Modes
post #1 of 7 (permalink) Old 04-20-2002, 10:17 AM Thread Starter
 
Join Date: May 2001
Posts: 4,528
V-Twin to Inline-Four or Inline-Four to V-Twin???

I need help settling a heated debate... Do you think that it's easier making the transition from an Inline-Four to a V-Twin or from a V-Twin to an Inline-Four? (This question only applies to sportbikes.)

I thought this was a fairly innocent question so I brought it up last night while I was out at the bar w/ some buddies. About 5 minutes later we had half the guys in the bar arguing with eachother.

What do you think???


Last edited by slaintedan; 04-20-2002 at 10:25 AM.
slaintedan is offline  
Sponsored Links
Advertisement
 
post #2 of 7 (permalink) Old 04-20-2002, 12:48 PM
 
Join Date: Jun 2000
Posts: 5,474
In-line to a twin is easier I would guess for street riding. For race bikes it really depends on the person and their style.
RCjohn is offline  
post #3 of 7 (permalink) Old 04-20-2002, 04:50 PM
 
Join Date: Apr 2001
Posts: 48
I agree with RCjohn

you have to keep momentum better with a 4 and think about shifts more. Twins you just put it in gear and go.

I liken it to changing from a 2-stroke motocross bike to a 500 4-stroke single. The 2-stroke is a little faster but it's harder to keep on boil, while the 500 all you have to worry about is dialing the right amount of twist with your right hand.
fasthrc is offline  
 
post #4 of 7 (permalink) Old 04-20-2002, 05:16 PM
Registered User
 
DataDan's Avatar
 
Join Date: Mar 2002
Location: California Central Coast
Posts: 298
Which inline four and which V-twin?

I don't think there's anything inherent in the engine configurations that makes one or the other more difficult to ride. However, examples of each can exhibit vastly different torque characteristics, and that's the interesting question to me.

I find that 600 fours (talking about the four Japanese sportbikes here) require the most attention. Let revs drop below 7K or so, and torque falls off into an abyss. An unsuspecting rider who's not watching the tach might find himself without the power to get out of a jam.

Liter fours, OTOH, are wonderful. The 929, for example, has bags of torque from 4K, and even below that. I haven't ridden an R1, 9R, or GSXR1K, but on paper they seem just as good.

Twins, likewise, vary considerably. The Hawk GT, SV650, and air-cooled Ducati 750s produce torque similarly to the liter fours (though, obviously, not nearly as much)--over a nice, even band that extends into the low end of the rev range.

Though I haven't ridden one of the Superbike twins (RC51, 916/996/998, Mille R), they seem much less user-friendly than the all-around twins. The torque curves peak high in the rev range and fall off considerably if revs drop below 5K. The Motorcyclist "Hard numbers" page reveals that these supposedly "torquey" motors don't even match the 600s in a 60-80 roll-on (e.g., 4.12 for the F4i, 4.94 for the RC51).
DataDan is offline  
post #5 of 7 (permalink) Old 04-21-2002, 11:38 AM Thread Starter
 
Join Date: May 2001
Posts: 4,528
DataDan,
The information you've posted regarding the 60-80 roll-on times of the F4i versus the RC51 raises a new question...

1) Can't one make the argument that the gearing on an F4i, which makes considerably less torque than an RC51, may perhaps allow a slightly quicker roll on from 60-80mph without downshift because of the point in the torque curve the F4i is at versus the RC51? Basically, if the F4i is at 9k rpm and the RC51 is at 4k rpm while traveling 60mph the F4i may be within the optimal portion of its torque curve, while the RC51 may be at the bottom end of its torque curve? (note: I used the 9kRPM and 4kRPM numbers purely for conversation's sake. I do not know them to be accurate)

John,
I'd like to hear what you have to say regarding this comparison 'cause, coincidentally enough, I'm considering making the jump from an F4i to a 2002 RC51.

Thanks,
Dan
slaintedan is offline  
post #6 of 7 (permalink) Old 04-22-2002, 07:38 PM
Registered User
 
DataDan's Avatar
 
Join Date: Mar 2002
Location: California Central Coast
Posts: 298
Quote:
Originally posted by slaintedan
1) Can't one make the argument that the gearing on an F4i, which makes considerably less torque than an RC51, may perhaps allow a slightly quicker roll on from 60-80mph without downshift because of the point in the torque curve the F4i is at versus the RC51? Basically, if the F4i is at 9k rpm and the RC51 is at 4k rpm while traveling 60mph the F4i may be within the optimal portion of its torque curve, while the RC51 may be at the bottom end of its torque curve? (note: I used the 9kRPM and 4kRPM numbers purely for conversation's sake. I do not know them to be accurate)
Good point. If the RC51 is "overgeared" compared to the F4i, that alone would put it at a disadvantage. I don't know whether that's true or not, though, because I don't know what the gearing really is.

But from info available, we can make a cocktail-napkin calculation. The RC51 has a top speed of 165mph and the F4i 155 (MCN). Assuming optimal gearing (top speed = power peak), the 60-80 roll-on would take the RC51 from 36% of peak power revs to 48% and the F4i from 39% to 52%.

Checking the dyno charts, that range corresponds on the RC51 to a range from 42% to 56% of peak torque revs and on the F41 from 48% to 63%. Part of that difference is due to the assumed taller gearing for the RC51 and part to the fact that the F4i has a slightly less peaky torque peak. The 600's maximum torque hits at 18% below maximum power while the twin's is at 14% below maximum power.

If anyone has real data (e.g., mph/1000RPM for the two bikes), we could find a more definitive answer.
DataDan is offline  
post #7 of 7 (permalink) Old 04-23-2002, 09:56 AM Thread Starter
 
Join Date: May 2001
Posts: 4,528
Quote:
Originally posted by DataDan

Good point. If the RC51 is "overgeared" compared to the F4i, that alone would put it at a disadvantage. I don't know whether that's true or not, though, because I don't know what the gearing really is.

But from info available, we can make a cocktail-napkin calculation. The RC51 has a top speed of 165mph and the F4i 155 (MCN). Assuming optimal gearing (top speed = power peak), the 60-80 roll-on would take the RC51 from 36% of peak power revs to 48% and the F4i from 39% to 52%.

Checking the dyno charts, that range corresponds on the RC51 to a range from 42% to 56% of peak torque revs and on the F41 from 48% to 63%. Part of that difference is due to the assumed taller gearing for the RC51 and part to the fact that the F4i has a slightly less peaky torque peak. The 600's maximum torque hits at 18% below maximum power while the twin's is at 14% below maximum power.

If anyone has real data (e.g., mph/1000RPM for the two bikes), we could find a more definitive answer.
Your "cocktail napkin calculations" could explain the .8 second difference in the roll-on times of the 2 bikes. However, as you said, "real data" would definitely enable "a more definitive answer."

I'm curious to see the 80-100 roll-on times of the 2 bikes. Do you have that data?
slaintedan is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Sportbike Forum: Sportbike Motorcycle Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome