superkart vs F3 , where is the cross over

I have read that UK Superkarts are quick on a full road track but I only saw them live this weekend and yes, VERY quick.

A superkart is basicaly  a normal kart with a full nose cone, side pods and a small rear wing. They have either a 250c two stroke twin or 450cc four stroke single and  90 bhp or so.

The trick is they only weigh 200kg including driver and a less then half the width and height of a typical track sports car. The CG without driver must be no more than 200mm off the track instead of about 400mm on a normal car.

On the 3 mile Snetterton circuit thy are under 5 seconds slower than an F3 car and quicker than most other cars there.That is due to having a 450bhp/ton loaded power to weight ratio and about one quarter the frontal area. 

By contrast an F3 car had 200 bhp and weighed 565kg with driver for about 350bhp/ton. 

It would be easy to add another engine for about 25kg and with a solid axle synchronisng is not an issue: twin engined kart are nothing new.

That would give 180 bhp and around 800 bhp/ton. 

Now the usual rules of power vs lap time would suggest  such a kart would be as quick as the F3 car BUT would that really be true?  Is it possible to scale up a kart's power while keeping it the same size and gain so much lap speed?

I seem to recall that the outright lap record for the Brands Hatch Indy track was held by a 250cc superkart for many years.  

You mention being slower than a F3 at Snetterton, but I suspect this relates to a kart - with a driver sitting upright in the wind - having the aerodynamics of a brick.  On a long fast straight, they will run out of steam long before a streamlined formula car.  Also they have almost no downforce which matters in fast corners, whereas the small size of a kart allows a much faster line through slow corners.  So somewhere like Brands, the kart has more advantages but on more open tracks, it is disadvantaged more. 

I have read that UK Superkarts are quick on a full road track but I only saw them live this weekend and yes, VERY quick.

 

A superkart is basicaly  a normal kart with a full nose cone, side pods and a small rear wing. They have either a 250c two stroke twin or 450cc four stroke single and  90 bhp or so.

 

The trick is they only weigh 200kg including driver and a less then half the width and height of a typical track sports car. The CG without driver must be no more than 200mm off the track instead of about 400mm on a normal car.

 

On the 3 mile Snetterton circuit thy are under 5 seconds slower than an F3 car and quicker than most other cars there.That is due to having a 450bhp/ton loaded power to weight ratio and about one quarter the frontal area. 

 

By contrast an F3 car had 200 bhp and weighed 565kg with driver for about 350bhp/ton. 

 

It would be easy to add another engine for about 25kg and with a solid axle synchronisng is not an issue: twin engined kart are nothing new.

 

That would give 180 bhp and around 800 bhp/ton. 

 

Now the usual rules of power vs lap time would suggest  such a kart would be as quick as the F3 car BUT would that really be true?  Is it possible to scale up a kart's power while keeping it the same size and gain so much lap speed?

I would think it's more down to available grip in the cornenrs and not speed off the corner/straight line speed. Put some proper aero on the kart and tyre 20% wider and I think you would probably get your 5 seconds.

This is pretty much the conundrum that "special" builders in the 1930s were trying to work out in the 1930s. A GN chassis with chain drive shares characteristics with a kart.

If you increase mass with a second engine at the back, you change weight distribution and weight transfer. There is not a lot at the front end that you can use to put the right grip there.

If you increase tyre width, with solid axles, you may actually reduce tyre contact area.

A son once upon a time ran a twin engine kart (2 times 100cc) very competively.  The twins were fractionally quicker than the the 100cc singles but not by as much as you might ecpect.  I drove it several times under practice conditions and truly did not like it compared to a 100cc single with a top class engine. 

The single was fast responding to steering inputs and mid-corner throttle changes.  The twin was terribly quick in a straight line but a veritable pig in cornering ability.  The lovely balance of the single was completely lost and a point and squirt driving style needed to be adopted for the twin.

.

I also drove F3 once upon a time so can compare in relative terms,  There is nothing in driving a twin kart that is transferable to any formula class and I personally do not recommend trying to get any real racing experience with a twin.  If you want to progress a motor racing career go directly from gearless kart singles to any formula class from F Ford or upwards as one can afford.  Anything else is a waste of time and money resources.

Of course, if you have  no aspirations beyond karting, dabble in anything to your hearts delight.  My recommendation is to stop at something like Rotax 125cc racing for best use of time and money.

Regards

Here on a track we know.

1:40 laps

Here on a track we know.

 

 

1:40 laps

 

What is an F3 lap time?

Just looked it up 1:32.271 was the lap record in 2017, have Karts improved much in 5 years?

Edited by 7MGTEsup, 09 May 2019 - 15:28.

What is an F3 lap time?

 

Just looked it up 1:32.271 was the lap record in 2017, have Karts improved much in 5 years?

I would think not, it is fast but the F3 will beat them at Hockenheim.

They should support F1 at Monaco   OK, too dangerous but surely a chance at being close to an F1 car there.

Long,long ago Road and Track magazine held a competition to see what vehicle was quickest around a skidpan test circle. Despite various racecars turning up it was won by the "Gkart". This was basically a standard kart with sheet of plywood  fixed under it plus skirts and a fan evacuating the sealed underbody area. It was similar in concept to the Chapparal 2J "sucker car" and was IIRC brought along by some of the GM engineers who worked on the 2J. With its downforce independent of speed it was well suited to low speed circle work and won comfortably.

Actually if you think about it there is great similarity between Karts and F1 cars since the adoption of 13" wheels in F1 as both rely on the tyre sidewall flexing to provide most of ride movement.