16 replies to this topic

[mini-man14]

Hey guys,

 

If you have a KAD 16V twin cam engine with 120 or 140bhp engine and the whole car would weight 650kg what would be top speed and accelerations??

 

Any ideas please :)

 

Regards, Jure

 

[Badboytunes]

Depends on a few things, such as gear ratios and final drive ratio....

[Richie83]

What colour would you paint the engine?

[Dusky]

What colour would you paint the engine?

VHT burnt copper, looks great imo ( some pics in the engine bay styling thread,last page)

[Tamworthbay]

It all depends on what you gear it for, it's impossible to determine top speed and acceleration without knowing a lot more about the build. A far better way to look at it is to work out what you want it to be good for and build a car to suit. A car with good acceleration will lose out on top speed so could be a pain on motorways, but you might want it as a B road blaster so would be happy to sacrifice top end for better acceleration. Only you can answer those questions.

[KernowCooper]

Check the revs per 1000rpm against mph and that will show what speeds each diff gives and decide what spec your engine will be on Cams and peak power / torque is and decide what you intend using the car for, you could have a low ratio diff, massive acceleration  and 85-90mph.

 

Attached Files

•  Mini Rev Per 1000.png   15.85K   10 downloads

[MJWarren]

I have 150bhp kad 16 valve in my sprint car on 10 inch wheels, top speed is limited by revs 8000rpm is about 114mph.

0-60 never recorded but I'd say under 5 secs as a guess

Car weighs less than 600kg

[Spider]

Try one of the various on line calculators / estimators

 

eg

 

http://www.tciauto.c...ng-calculators/

 

http://johnmaherraci...rip-calculator/

[Ethel]

If this is for bragging rights, purely theoretical, then you should also put the competition through the online estimator. In the real world gearing will determine how effectively you can use the engine's power curve & make a big difference.

 

You should be able to get a more accurate top speed from the drag coefficient, front area and bhp at the wheels. Though you'd need to get the final drive ratio right to make the maximum.

 

If it was that simple building and racing real cars wouldn't be as interesting.

[nicklouse]

the same reply as last time you asked this.

 

it depends on more things than you are asking.

 

my 120hp (non KAD) will do a max of 160KMH and do Zero to 100KPH in about 6 seconds. A KAD engine using the same gear ratios would do about the same.

[Dusky]

Gearing is the compromise between acceleration and top speed..

 

My dad's race mini (118BHP) has a limited top of about 116 KM/h ( FDR is very high, can't remember how high, but higher than a 4.1 atleast) @ 8500K rpm ( limited).

 

My mini ( hoping for a good 60 BHP) 's top speed is higher than 120km/h ( haven't properly tested it ) but takes longer to get there...

[MJWarren]

the same reply as last time you asked this.
 
it depends on more things than you are asking.
 
my 120hp (non KAD) will do a max of 160KMH and do Zero to 100KPH in about 6 seconds. A KAD engine using the same gear ratios would do about the same.

Don't agree with that, the characteristics of the 2 engines are completely different

[nicklouse]

the same reply as last time you asked this.
 
it depends on more things than you are asking.
 
my 120hp (non KAD) will do a max of 160KMH and do Zero to 100KPH in about 6 seconds. A KAD engine using the same gear ratios would do about the same.

Don't agree with that, the characteristics of the 2 engines are completely different

Which has nothing to do with the mechanics. Ok saying that both engines would send a car to about the same 0-60 is maybe a bit fanciful.( as there are so many variables other than the engine) but top speed is a mechanical relationship to the engine revs. If the have the same max rpm then top speed is the same.
Yes how they get there can and will be different.

A KAD road spec motor doing 120 will be a easier to drive to max speed rather than a 120bhp race engine and the time taken to get to the max speed will be different but the max speed will be the same if the max RPM is the same.

So back to the OP your question means nothing.

It all comes down to the gearbox and FD.

Do want acceleration or top speed?

We tend to look at what we want from the car and then build to that.

[ajmount88]

 

 

the same reply as last time you asked this.
 
it depends on more things than you are asking.
 
my 120hp (non KAD) will do a max of 160KMH and do Zero to 100KPH in about 6 seconds. A KAD engine using the same gear ratios would do about the same.

Don't agree with that, the characteristics of the 2 engines are completely different

Which has nothing to do with the mechanics. Ok saying that both engines would send a car to about the same 0-60 is maybe a bit fanciful.( as there are so many variables other than the engine) but top speed is a mechanical relationship to the engine revs. If the have the same max rpm then top speed is the same.
Yes how they get there can and will be different.

 

That depends on whether the car is limited purely by the maximum rpm of the engine, or whether it is limited by whether it can produce enough power to overcome the road load at a given speed.

 

If you're top speed is limited by available power (there's some rpm headroom at top speed), then top speed will vary depending on the rpm at which the engine produces peak power, rather than the max engine rpm, and gear ratios will not have such a great effect on top speed, only by shifting the road speed at which you reach peak power. If, however, the gearing is shorter, then you will be limited by the maximum engine rpm, and changing the ratio will give a proportional increase in top speed.

 

I agree though, that just having the same peak power won't give a very accurate indication of 0-60 times, as this depends on the whole of the engine's torque curve, not just the peak power value.

[Cooperman]

If an A-Series is used there is a lot of real-world experience to draw upon in estimating performance.

With a hybrid power plant there are so many variables that it is difficult to make any meaningful off-the-cuff  'guesstimate'.

The mass of the vehicle has little bearing on maximum speed. That is a factor of drag coefficient v maximum power v overall gearing.

For optimum maximum speed it needs to be geared so that the maximum power is produced at the point of maximum speed. The possible maximum speed can be established from the drag coefficient, remembering that the drag increases approximately as the square of the speed ignoring certain road effects.

So a graph can be plotted using known data which can start at the max speed of an 850 with 34 bhp at 72 mph. Then the 998 Cooper had 55 bhp and topped out at 86 mph. The 1275 'S' had 75 bhp and topped out at 96 mph. All those figures are approximate, but the graph can be smoothed out between those points.

From that graph, put in the bhp of a hybrid and you can read off the theoretical maximum speed.

That is the speed at which the hybrid engine should be at maximum power. So then you have the max speed and revs for that speed and from that the ideal final drive ratio can be calculated in top gear with a 1:1 top gear ratio. It is usually not possible to get exactly the correct ratio, but you can get close.

Calculating the acceleration is more complicated.