6 replies to this topic

[Dusky]

Hi guys!

 

Im studying for my mid term finals atm.

So I have nothing better to do than thinking about cars , and today carb's in particular! ;)

 

I've read a few things lately :

 

- on twin carbs, each port only see's one carb

- With a single carb, there is only 1 cylinder breathing through the carb

-A twin 1 1/2 can be used between 65 and 110 bhp

- a single 1.75 is good from around 80 to 115 bhp.

 

Now,why is a twin 1.5 aroun the same as a single 1.75 when you take the 'each cylinder see's one carb/ breaths 'alone' ' in consideration?

Is there that big of a flow through the balancing pipe? ( I think not as I've heard a lot of racers just cut it up?)

Or are twins not that good and should you, if you want peformance, use twin's in the same size as the single?

 

OR should I just stop reading on the internet and concentrate on my finals?

 

thanks in advance, sorry for all these questions but I'm just curious by nature :)

 

cheers

[mingy]

I for one cannot answer your question but, i am sure if you emailed SU Burlen they will give you an explanation.... good luck.

[nicklouse]

First thing you need to ask yourself is this where is the info from. For what type of engine?

[Dusky]

First thing you need to ask yourself is this where is the info from. For what type of engine?

Elaborate. For me it would be an a series weekend toy. For someone else reading this thread it could be an everyday car. And for another guy it migh tbe his racer.

[timmy850]

I'd say there is enough flow from the opposite side carb to make a difference. Otherwise twin HS2 carbs would make no extra power than a single. From the graph:

Single HS2: 25 to 40hp

Twin HS2: 35 to 75hp (or roughly double)

 

You've not got your figures right in the top too, reading the graph it says 

-A twin 1 1/2 can be used between 65 and 110 bhp

- a single HIF 1.75 is good from around 40 to 100 bhp.

-A single 1 1/2 is 30 to 65hp

So twin 1.5 carbs flow significantly more than one 1.75. They also do roughly double what a single 1.5 carb does. 

 

I've got twin Cooper S carbs with the original type airbox for my car. Not because I want ultimate performance, but because I like the look and they'll be sufficient for the power I want to make (they made 75hp in the Cooper S)

[Dusky]

Makes me wonder why the maniflow manifold makes the balance tube that small?

[Dusky]

bumpy