[flaco]

So I'm still looking for a 1100 engine... mine is still laying around in pieces...

What's the preferred aftermarket pistons? JE, Wiseco or? I see JE has big-bore kits, I'd love to go 3mm+ = 1216cc.

However I fear that new compression ratio (13:1) will be too much for street gas. Anyone knows if 13 will work on street gas? And how about heating? Will I need an extra oil cooler?

Wiseco makes the same pistons (3mm+ bore) but with compression ratio of only 12. That sounds better I guess...

But if 13 works, why not?

Also, I got confused about sprocket sizes. A bigger rear sprocket will make the bike accelerate faster right? And I will lose a bit top speed, right?

I drove a factory modded 93' honda cbr900rr, and there is no gsxr1100 that can keep up with it. I was amazed to see it in front, and even more when I drove it. It 'only' had different cams (part numbers???) and a different crank to clutch conversion ratio (longer actually, you could get ~70mph in first gear!!!). Wouldn't the longer ratio make the bike poor at acceleration???

flaco
90' gsxr1100 without engine...

 

[somejeffguy]

Originally posted by flaco:
Also, I got confused about sprocket sizes. A bigger rear sprocket will make the bike accelerate faster right?

<font size="2" face="Verdana, Arial">short answer is, not necessarily.

gearing is a form of mechanical advantage. when you lower the gearing (make the rear sprocket larger and/or the front sprocket smaller), what you are really doing is multiplying the torque to the rear wheel. this implies that the tangental force the rear tire imparts to the ground is also greater, since torque about an axis is equal to the mathematical product of the radius and the tangental force, and we assume the radius stays constant. it also implies that the angular acceleration of the rear wheel is also increased, since torque is also the mathematical product of the moment of inertia of the rear wheel/tire assembly and angular acceleration, and we assume the moment of inertia stays constant.

so this should mean we are guaranteed to get quicker forwards acceleration, right? wrong.

the problem is, when you use mechanical advantage, there is always a tradeoff involved. i.e., you don't get something for nothing.

in the case of gearing, you are sacrificing rear wheel rpm's for greater torque. in other words, with lower gearing, the rear wheel turns less for a single revolution of the countershaft.

the net result is, you don't get greater acceleration everywhere on a mph-to-mph basis.

we can guarantee that the bike will rev through the gears quicker with shorter gearing. but this doesn't mean that the bike is accelerating quicker.

And I will lose a bit top speed, right?

<font size="2" face="Verdana, Arial">again, not necessarily. for any given engine/aerodynamic configuration, there is an 'ideal' gearing that will give you maximum top speed. gear the bike/car any shorter or taller than this ideal gearing, and you will go slower.

I drove a factory modded 93' honda cbr900rr, and there is no gsxr1100 that can keep up with it. I was amazed to see it in front, and even more when I drove it. It 'only' had different cams (part numbers???) and a different crank to clutch conversion ratio (longer actually, you could get ~70mph in first gear!!!). Wouldn't the longer ratio make the bike poor at acceleration???

<font size="2" face="Verdana, Arial">don't forget power to weight ratio.

also, on a light, short wheelbase bike like the 900rr, taller gearing may very well give you quicker forwards acceleration because the bike doesn't want to flip over as easily. more of the power is used to get you moving forward rather than trying to flip the bike over.

 

[gsxr1216]

I'd like to see that 900rr out run my gixxer

good write up by the way!!!

[ 12-17-2002, 12:25 PM: Message edited by: gsxr1216 ]

 

[Yosh]

Jeff. I think that is more then he was looking for.

Flaco I'm at a mile high so with 12.7:1 ratio I run pump premium. But lets say phoenix I have to run racing fuel. More air (lower altitude is heavier denser air) isn't more compression ratio just more total pressure increasing the chance for pre detonation.

[ 12-17-2002, 12:37 PM: Message edited by: Yosh ]