What affects acceleration??

[NewbRider15]

Ok so i'm 16 and new to biking, and the engine (know some of the basics, i'll be putting an old ajs together in the holidays so i get a jist of how an engine works and how to put one together) and wondered what affects the acceleration of a bike. I know weight and more flammable fuel has an effect, but engine wise what is it?
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Now on - 1986 Kawasaki ZL400 Eliminator (33bhp restricted)
Own - 2009 Huatian HT50QT-25 Scooter

[NewbRider15]

i mean... ok say you wanted to make your bike get to 60mph quicker than it usually does, how would you modify the engine to do that?
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Now on - 1986 Kawasaki ZL400 Eliminator (33bhp restricted)
Own - 2009 Huatian HT50QT-25 Scooter

[P.]

[DrDonnyBrago]

I think the more flammable fuel comment was a bodged up comment about the octane rating of fuel used? If it was, then unless your engine requires a higher octane fuel you wont get more power - higher octane fuels just prevent predetonation knocks in high compression engines, any potential "power increases" in normal engines are negligible.


As you are 16 forgive me if I assume you ride a automatic ped; if so then adjusting roller weights can give you more top speed at the expense of acceleration and vice versa.

Engine wise it is a combination of factors:

Fuel amount (i.e. larger carb jets, larger displacement)
air amount (i.e. larger carb sizes, forced induction and displacement)
combustion efficiency
compression
gearing
etc
etc
etc

If you ride a 2 stroke ped then they are usually restricted - removing the restriction should make it faster but it will also no longer be a moped; at 16 if you derestricted it you'd be riding it illegally.

[NewbRider15]

oh yeah i see how that would work, but i mean like the cc of the engine would count towards it aswell wouldn't it?
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Now on - 1986 Kawasaki ZL400 Eliminator (33bhp restricted)
Own - 2009 Huatian HT50QT-25 Scooter

[Kickstart]

Hi

Acceleration is down to weight and thrust. Less weight you have or the more thrust you have then the more acceleration you will have (although when things get silly, more weight and a choice of where to put it will help enough with control to overcome the slight loss in theoretical acceleration from having more weight).

Thrust is down to torque and gearing. Produce the same torque at higher rpm and you can use lower gearing, giving you more thrust. Most engines have the torque dropping off fairly early in the rev range, but while changing up gets you a bit more engine torque you likely lose it due to the higher gearing you now have.

Different fuels (at least road fuels) make virtually no difference to the power / torque of an engine (power is just torque x rpm). The exception to this is an engine with a turbocharger or supercharger AND with the ability to adjust the level of boost and the ignition timing depending on feedback from a knock sensor which can take advantage of higher octane fuel.

While different fuels burn at different rates (which affects the octane rating, slower burning fuel is a cheap way to make it more knock resistant) and have different energy contents by volume, these are within a fairly tight range for any road fuel. To get an engine to run you need a certain amount of fuel for the amount of air you have got. There is a bit of leeway here where a slightly richer mixture (ie slightly more fuel for air) will give a bit more power, but most engines are set up like this already and making the mixture even richer won't gain you anything.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[NewbRider15]

Thanks guys, it helped a lot cheers. No i'm not altering my ped, i'll probably break it. i was just curious. Thanks fo the info.
____________________
Now on - 1986 Kawasaki ZL400 Eliminator (33bhp restricted)
Own - 2009 Huatian HT50QT-25 Scooter

[bickeroony]

malossi 80cc kit, rollers and carbs

get like 50-60mph then

[DrDonnyBrago]

[The Artist]