[6pack] 3 carbs

[Robert Lang]

On Sat, 14 Jun 2008, Dale wrote:

> List
>
> A few of at our bi-weekly breakfast today were talking of gas economy
> for the stock TR6.
>
> Is there any advantage, from an economy stand point, to
> use the 1.5  carbs from the GT 6 on  a 3 carb manifold?
>
> Having the runners
> straighter and putting less and more precise amounts of fuel into each
> cylinder should help economy on a stock engine.
>
> What say you all?

I say no advantage. You'll also loose any top-end you might have dialed 
in.

Interestingly, a recent Classic Motorsports (maybe even THE latest) issue 
discusses that our cars are "over-carbed". I disagree, but that's because 
I like to disagree. But with a 1.75" carb you should be able to flow 
enough air into to the motor to get 175 HP or so (that's in the 130 cfm 
range). Of course then you have to get the air out - different problem.

But to your point, changing the carb size does not help fuel economy. What 
you need to do to get better fuel economy is to increase the volumetric 
efficiency. That means optimize the ignition timing and sprak control and 
stuff like that. It also means running a bit hotter coolant temps and 
stuff like that. You can also get some increase by working with vacuum 
advance, but to do that you need (most likely) a different distributor.

So, can it be done (get better fuel economy)? Yes, but you do it with 
tuning, not induction method (unless you switch to electronic fuel 
injection and engine management.)

> Dale

c ya,
rml
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