DCOE/DHLA Ver. Efi

[Greg Hermann]

>
>"The last carburettors Dell'Orto produced were the unique "tri-jet" DHLA45's
>for Lotus, which as well as an idle and main circuit, has a power jet
>circuit for extra enrichment at high revs. This system was also fitted to
>the Lotus Esprit Turbo carburettors, which can hold up to 30-PSI boost
>pressure."
>
>Copied from http://www.racecar.co.uk/dellorto/cars.htm

The concept of having a "power" circuit in a DCOE/DHLA type carb was not
unique to the DHLA45 Lotus carbys.

In a DCOE,  there are two separate and distinct high speed/high load
enrichment functions:

The pump jets act as a high speed enrichment bleed. How much fuel you get
from them is controlled by the size of the pump jets, and when it comes in
and the shape of the delivery curve is controlled by the size of the chokes
in concert with the mass of the weights above the ball check valves in the
pump circuit.

The area of the passages in the auxiliary venturii acts in concert with the
throttle butterfly position to dampen the intake pulses to the main jet
wells--thus at wide open throttle, when the pulses are not damped by the
throttle butterflies, a smaller aux venturi passageway damps the pulses
more than a large one. More damping gives a leaner mixture. Thus, the A/F
ratio at WOT can be adjusted vs. the A/F mixture from the main circuit at
part throttle.

Moral--

There's a _LOT_ more to tuning DCOE's than meets the eye (or than the
average club racer knows) !!

Greg



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