Kent engine : power and capacity

[eric]

If all the components are the same, same cam, pistons, head, carburators ... on a road goindg engine, what would be the expected power with a 1600, 1660, 1700, 1760 or perhaps a 1800 crossflow ?

 

A very theorical question but as everybody knows that a 1600 K supersport is 122HP

and a 1800 K supersport 140 HP, I have no idea with a Kent

 

 

 

 

 

eric

[CageyH]

I thought the 1.6k supersport was 132bhp

 

Only dead fish go with the flow....!

[Paul Richards]

as everybody knows that a 1600 K supersport is 122HP

And there was me thinking it was 132 bhp.

 

Paul Richards

Area Representative - L.A.D.S. (Lancashire and District Sevens)

LADS Website

Growing old is compulsory - Growing up is optional

[eric]

so if it is 132 200 cc give 8HP which is not a lot.

100 cc will give 4 HP and 50CC 2HP

 

and it is better not to rebore max but only the size needed

 

eric

[Paul Richards]

8bhp but what about torque? bhp is not the only thing.

 

Paul Richards

Area Representative - L.A.D.S. (Lancashire and District Sevens)

LADS Website

Growing old is compulsory - Growing up is optional

[CageyH]

Don't forget though - a bigger bore allows for bigger valves.

 

Only dead fish go with the flow....!

[eric]

I found a formula in a book :

 

Increase of power = Cubic efficiency x increase of capacity x 0.8

 

For a 110 HP Sprint Caterham, the cubic efficiency is : 110/ 1.6

If the increase of capacity is O.1 l

 

For a 1700, the increase of power would be in theory

(110/1.6) x 0.1 x 0.8 = 5.5 HP

 

eric

[eric]

A Supersprint which is 135 HP

 

is different from a sprint :

-increased capacity (1700)

-compression ratio raised by the use of a smaller combustion chamber from the 1300 pistons (not far from 10 but I don't know exactly)

- head (but I don't know if the valves are bigger)

- Cam a 234 instead of an A2

 

eric

[cskip]

My Sprint was 100bhp not 110bhp.

[eric]

due to a GT cam and not an A2

 

eric

[Stationary M25 Traveller]

 

So .... Same old story. .......... It's not just the size ....... It is what you do with it !!!!

[Roger King]

If you leave the spec identical and change nothing but the capacity there will be only a minimal increase in power as the engine gets bigger. But torque is a different matter and will increase significantly with capacity.

 

As a general rule, manufacturers who made varying capacity versions of the same engine (e.g. Crossflow, Kent) would fit a bigger cam to the larger versions. The extra torque of the larger engines would ensure that driveability was maintained, but the cam would allow the extra power to be produced.

[eric]

Thanks Roger

 

On the driveability side, can we say that a 1600 with a 234 could be compare with a 1720 or 1760 with a 244 ?

 

eric

[PAC]

My 1800 Xflow was measured at 175BHP, with 45's and a 264 cam.

It doesn't even think about going until 4.5k RPM! Drivability is not too bad, but only because the car is relatively light, compared to other Caterhams it's Cr@p.

I was told by a race engine builder that the holy grail is to divide the cc's by 10, and you get a rough estimate of the maximum possible power............

Probably a load of old carp but is about right for mine.

I'm sure I've heard of 200BHP Xflows tho

Edited to answer my own question: Probably 2.0L X-flows!!

P

 

Edited by - PAC on 29 Dec 2010 23:42:53

[eric]

I am used to think than after 100 HP / liter begins the hassles

 

So I do prefer 20HP less as a limit for my peace of mind

 

eric