performance of a 250 4 stroke

**Monsterbishi** · 20th February 2005, 21:27

Originally Posted by John

but hes trying to say cars are better than bikes for racing and I resent that.

There's nothing to resent, you certainly can't argue the clear fact that cars have better brakes, and more traction than bikes, and unless conditions are perfect for the bike, a car will out-corner it as well.

We all enjoy what we enjoy, it's rather shallow of you to resent someone else because of your own biased opinion.

**FEINT** · 20th February 2005, 21:40

Originally Posted by Monsterbishi

99% of 4wd turbo cars do a factory 14 second 1/4...

99% of "FACTORY" 4WD TURBO cars may be able to do a 14 second 1/4 mile. But they are in the HIGHER END of cars, where as 250's are just the beginning of the bikes. Higher end meaning compared to the 2.0L, 1.6L etc... We are talking about stock standard here.

**John** · 20th February 2005, 21:41

Originally Posted by Monsterbishi

There's nothing to resent, you certainly can't argue the clear fact that cars have better brakes, and more traction than bikes, and unless conditions are perfect for the bike, a car will out-corner it as well.

We all enjoy what we enjoy, it's rather shallow of you to resent someone else because of your own biased opinion.

yes, but I'm a spitefull wee man, I am not allowed to resent anything - although you can spoon feed everyone your own biased crap so shove it, see now I'm upset and NOW I'm being biased, BIASED TO CRAP.

And it all started with me saying that you can beat most cars off the intersection (unless all your cool cars, have the wastegate draging and are civics cool man your a real dude) i.e lights, then you made it the quarter mile, then your car came into it then you said turbo 4wheel drives, then you started stabing other people, I dont care what you like I like both - always have liked them, but if you want to propagate yourself for purpose of your 'superiour' car tuning and other 'stuff' then why do you havto complicate crap, why not say - I have a car, it is fast cool huh, STOP TRYING TO MAKE YOURSELF BIGGER THAN YOU ARE.

I'm 5'6 and have a fucken small dick and I dont find a need to make myself better than someone else.

**Timber020** · 20th February 2005, 22:26

A 250 4 stroke is food to any half decent car. On road surface the car has you on the brakes and around the corners, which just leaves you only winning on the straight lines.
It takes alot more skill and effort for a bike rider to ride to the limit of his tyres in a corner and takes very little to throw him. Recovery of composure of a bike once its gone to far is very tough and injury rates from any bin while going at full noise is huge.
From the start your average performance car is inherently more stable, has better grip and composure on the picks and through the bends and even if they stuff up a bit the chances are they will be able to reel the cage back into line. Esp if its a 4wd.

**NordieBoy** · 20th February 2005, 23:15

Originally Posted by vtec

My quartermile times are as follows.
Honda Prelude 14.86 @152k/hr
Honda CBR250RR 14.3 @ 147k/hr
and I hadn't dragged the other two.

My Nordie did 14.1 @ 147k/hr and just beat a Suzuki Goose (worked dr350 single with a skinny bugger riding).
Was also just beating a stock KDX 200.
Dunno what my 250 would do but I think you'd have to use a calander to time it (geared to max speed of 100kph or so).

**TwoSeven** · 21st February 2005, 12:57

Lets do the math for a cbr250RR

Taking the claim that the prelude does 14.86@152 and comparing that to a cbr250rr (standard as measured on the dyno).

Said bike has a 72km/hr 1st gear, 102km/hr 2nd gear, 128km/hr 3rd gear and 152km/hr 4th gear. So to hit the preludes speed of 152km/hr you'd have to change to 4th gear on the CBR and rev it out.

Normally riding this bike you short shift 2nd and 4th if you were doing a max speed run (and please dont try it unless on the track), but if you just short 2nd and hold 4th out to 17500rpm, you'll beat that car - still with another gear to go (its 6 speed, but the speed limiter can be hit in 5th).

In fact I would expect to see a standing quarter time with a speed of about 176km/hr if everything was done properly.

You can do the math for what the time should be. Since 1/4 mile is only 400 meters, 176km/hr is 48.8 m/s so means you could in theory do it in 8.18 seconds (although not from a standing start).

There are factors that add to this time.

One such factor is the 0-100km/hr time. The critical time is 4.2 seconds - times under this are normally theoretical calculations as this is the point where the rear tire will start to spin (it means the driving force will be greater than traction allows for) - its a subjective measurement as its based on normal road tires and road bikes - luckily the 250 has a time greater than that (its a little over 5 seconds) so it wont spin its tires.

This also means that it will be in 2nd gear at the time its hit 100kph, so you can add 0.5 seconds for a gear change to that.

However, I happen to know from testing the bike that its maximum acceleration can't be done at more than 12.5k rpm in 1st and 2nd due to the fact that the bike will wheelie, meaning you lose time and speed. In fact, being forced to limit the revs means you lose 30km/hr off of each gear so a rough calculation means about 36.39 m/s or a 400m time of 10.99s.

As I said before, its about 0.5 for each gear change and you have to allow for throttle pickup, so thats about 1.5 seconds (3 changes) so a time of 12.49 would be good.

So a 12-14 standing 1/4 time is pretty respectible for said little bike.

Out of interest the cbr600F2 will do that speed in 2nd gear at 15,000 rpm and I happen to know that its 0-100 time was given at about 4.8s. Racing starts are done at 10.5k rpm (which lifts the wheel in the air by about 1m) so you literally short 1st into 2nd straight away, then rev it out. Since there are 3 less gear changes involved, it should be closer to 11.5 seconds. A quick google around shows people claiming elevens and twelves - so the math is in the ballpark (although I know not correct).

One day i'll get round to working out the buggering around facter and see how much of a percentage of the 1/4 mile time it actually works out to. At a guess, 152km/hr is 9.47s for 400m, so 14.3-9.47 = 4.6s used up in acceleration and buggering around.

**k14** · 21st February 2005, 13:54

you're not going to get anywhere near 176kph on a 400m run. if i remember correctly hoon was just doing over 150 on his zxr400 and he was doing 12.9's. i think 140 to 150 is a better bet.

**Coyote** · 21st February 2005, 17:07

Originally Posted by TwoSeven

Lets do the math for a cbr250RR

Taking the claim that the prelude does 14.86@152 and comparing that to a cbr250rr (standard as measured on the dyno).

Said bike has a 72km/hr 1st gear, 102km/hr 2nd gear, 128km/hr 3rd gear and 152km/hr 4th gear. So to hit the preludes speed of 152km/hr you'd have to change to 4th gear on the CBR and rev it out.

Normally riding this bike you short shift 2nd and 4th if you were doing a max speed run (and please dont try it unless on the track), but if you just short 2nd and hold 4th yaady daady da, so on, so forth

I'm going to have to find some of that out for myself

**TwoSeven** · 21st February 2005, 19:33

Do it safely on the next track day

**Teflon** · 21st February 2005, 21:08

Originally Posted by Monsterbishi

There's nothing to resent, you certainly can't argue the clear fact that cars have better brakes, and more traction than bikes, and unless conditions are perfect for the bike, a car will out-corner it as well.

We all enjoy what we enjoy, it's rather shallow of you to resent someone else because of your own biased opinion.

I've heard that before too.

Road cars carry alot of mass, so logic tells me a 160kg bike will corner faster than a 1 1/2 ton car.

**Atomic** · 21st February 2005, 21:14

Originally Posted by Teflon

I've heard that before too.

Road cars carry alot of mass, so logic tells me a 160kg bike will corner faster than a 1 1/2 ton car.

Remember that while the bike has about 10mm or so of each tyre contacting the tarmac the car has anything from 800mm to a meter or more.....thats a hell of alot more grip.

**Fluffy Cat** · 21st February 2005, 21:21

More tyre more grip yeah and nah car weight bike weight?.Yeh the car will have more grip but there are some more variables weight suspension etc.Anyway you guys have the wrong 250.You need some thing with more power like an NSR 250 sp or any of the 2 strokes.The 4 stroke 250s are just play bikes.If you don't belive catch me at the next tracktime or a practice session at Puke.FC....

**Monsterbishi** · 22nd February 2005, 08:19

Originally Posted by Teflon

Road cars carry alot of mass, so logic tells me a 160kg bike will corner faster than a 1 1/2 ton car.

Mass/Weight are relative to traction, as has already been posted, I just measured the contact patch on my YZF, about 7cm all up, at 300kg's including Rider(Yes, I'm a big bugger), that's 42.85kg/cm - compared to my Mirage, with very cheap street 195/60/15's - which have 44cm all up, car is 1240kg including me which makes 28.18kg/cm, to achieve the same ratio, I'd need to add another 650-ish kilo's to the equation.

**Atomic** · 22nd February 2005, 17:14

Originally Posted by Monsterbishi

Mass/Weight are relative to traction, as has already been posted, I just measured the contact patch on my YZF, about 7cm all up, at 300kg's including Rider(Yes, I'm a big bugger), that's 42.85kg/cm - compared to my Mirage, with very cheap street 195/60/15's - which have 44cm all up, car is 1240kg including me which makes 28.18kg/cm, to achieve the same ratio, I'd need to add another 650-ish kilo's to the equation.

I wouldnt think your bike would have 70mm when cornering!?
The contact width would be bugger all when your at the tyres limit.....after all
we are comparing cornering performance so you would need to base this on
a bikes tyre contact area at full lean. More like 10mm id guess.

Excuse the mm, being a chipie I find CM just looks wrong!! Cant help but add the extra 0.