bhp, rpm an torque.

[muhuha]

Just would like a little information on all three of these, i know torque is power (punch) and bigger cylinders have more of it because they have a bigger bang. Rpm obviously how high is revs but bhp at certain rpms, why does bhp come into the matter, i mean a 70cc is going to produce the same amount of tourque as each other but rev differently producing different bhp's? But you can get 50cc engines with 15bhp and 70cc with 9bhp so whats more powerful? and how can you feel the difference when riding?

 

[tiba_karotsu]

Just would like a little information on all three of these, i know torque is power (punch) and bigger cylinders have more of it because they have a bigger bang. Rpm obviously how high is revs but bhp at certain rpms, why does bhp come into the matter, i mean a 70cc is going to produce the same amount of tourque as each other but rev differently producing different bhp's? But you can get 50cc engines with 15bhp and 70cc with 9bhp so whats more powerful? and how can you feel the difference when riding?

hp is the result of torque measured against rpm, if you produce a linear torque curve which extends over a wide range & measure it at different rpm's you can get the hp output of the engine.

getting 15hp from a 50cc engine is just as difficult as getting 20hp from a 70cc, it will need very high levels of tuning & setup time before you get anywhere near those figures.

i don't know why you are so obsessed with getting a 50cc kit, to me it isn't really practical to run a 50cc race cilinder on the street, it would need to rev much higher in order to make hp & stock ports of 50cc race cilinders like MHR & Evo have quite mild port timings.

if you are asking which is more powerful a 50cc with 15hp & 70cc with 15hp of course both will be the same as hp is concerned but the difference is the torque, the 70cc would have much more torque at lower rpms where it is more accessible for street use, a 70cc would outlast a 50cc b'coz the former will only make power when it revs.

torque is what makes your scooter accelerate & not hp, with that big & heavy italjet dragster scooter you need all the torque you can get.

 

[muhuha]

NO i was using 50cc as a example to see what the difference is, so whats going to produce more bottom torque a hi or low revving 70cc kit? Also you remember that ebay kit i showed you and your using the piston in your corsa? I take it the build quality is ok then but you said the cylinder head is a hemi cylinder, what does this mean and how can a engine not product squish?

 

[Areomyst]

NO i was using 50cc as a example to see what the difference is, so whats going to produce more bottom torque a hi or low revving 70cc kit? Also you remember that ebay kit i showed you and your using the piston in your corsa? I take it the build quality is ok then but you said the cylinder head is a hemi cylinder, what does this mean and how can a engine not product squish?

Typically, hemi style combustion chambers are domed with the piston at the top and center of the head. They do not include a squish band worth mentioning. There are very many 2 strokes out there that have this kind of head, but more power and efficiency can be found in the more modern cylinder head designs that include a squish band to direct the gasses at the edge of the cylinder toward the center of the combustion chamber.

Squish is generally a 2 stroke term. All engines (that I can think of) displace air, and create compression, not squish. "Squish clearance" is the distance between the piston and the squish band of your cylinder head... this needs to be measured and adjusted for optimal performance on most scooter cylinder kits.

Here's a link that might help you understand the relation of horsepower, torque, etc: http://www.howstuffworks.com/horsepower.htm

Hope this helps.

~Josh

 

[Ben]

Also 1HP is eauivelant to if a person can pull 70kg 1m up in 1sec. Well , this is what my teacher told me @ my last school...

 

[muhuha]

think im learning here, so if i want to get my drags front wheel up i need torque and right setup but then if i want top end power its got to produce a high rpm and create power and to make the bike accelerate i need hp?

Will any low revving 70's be able to get my wheel up, looking at 3 alu kits, stage 6 sport-1ring
airsal racing-2ring
motoforce racing-1ring

or x-tech by pm https://www.pmtuning.co.uk/index2.htm

By looking at the heads are they hemi-cylinders? and then if i were to put a small gakset on creating more compression and more power right?

btw using laser x-pro n std crank and not changing, i found my 50cc stage6 didnt really like my pipe got high rpms but it only allowed to have a tiny bit of proper power where it flew and belt slipped and all but then that stopped and went as usual

 

[Big B NRG]

HP is a combination of (RPM * Torque) / constant.

The smaller the displacement (Torque) the more RPM it needs to get the same HP.

A 70cc cylinder that makes 9 HP, doesn't do that much RPM. But still makes 9 HP because of it's torque.

It's the same with the 180cc engines, they do 7k RPM, but have 20-21 hp, because of the torque.

 

[muhuha]

ahh well how i used to think that was if you got a engine running its the force its takes to stop it, ie torquey is hard to stop because of the power but then so is the high revvin because its moving quickly and got momentum.

AH i gt another question, port timings and exhausts why wont some exhausts work with some cylinders. Now as another example when i was running that racing 50cc pipe as above i has a tiny gap where the bike hit some really good power, it flew and the belt slipped everywhere but then it stopped and acceleration was normal. How can you match pipes with cylinders, the pipe i used was a alser x-pro i mean being a 70cc pipe wouldnt it produce lots of power witht he 50's kit. Any using with my standard 50cc it doesnt have a peak power gap but accelerated a bit better throughout.