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twin carb manifold
02GF74 - 7/4/06 at 10:56 AM

I have twin dellortos with manifold on a crossflow.

I know there is water going through the manifold and when measuring engine temp, the two centre ports are much warmer than the outer 2 due to the water flowing through them.

I am wondering what difference that makes to the carb set up - should the outer two carb ports in each carb be differently set up to the inner 2?

I am guessing that with the bonnet down and driving, the whole manifold will get to be the same temperature so maybe no messing is required?

DarrenW - 7/4/06 at 11:09 AM

id guess you cant really assess the temp difference until car has been driven for some time and the heat soak is evened out. I assuem you notice the difference after a few minutes running in the garage. Ive found 5 mins on the road warms the car up better than 15 / 20 mins in garage. Does that make sense?

02GF74 - 7/4/06 at 11:37 AM

Darren - I was koinda angling about what effect the heated carb has; i think it is to do with cold starting - getting the petrol to vapourise; byt yes, as you say, under driving condition, whcih is 99 % of the time, there will be minimal difference in temperature so I guess the answer is not to mess.

02GF74 - 7/4/06 at 11:38 AM

Darren - I was koinda angling about what effect the heated carb has; i think it is to do with cold starting - getting the petrol to vapourise; byt yes, as you say, under driving condition, whcih is 99 % of the time, there will be minimal difference in temperature so I guess the answer is not to mess.

oliwb - 7/4/06 at 11:43 AM

Think its supposed to give you more torque. But obviously it heats up the charge entering the engine which ultimately means a reduction in power. Oli.

02GF74 - 7/4/06 at 03:12 PM

quote:
Originally posted by oliwb
But obviously it heats up the charge entering the engine which ultimately means a reduction in power. Oli.


hmmm, not sure about that. If you do the sums, (& I haven't!s o may be talking ar5e) air is zooming in pretty quickly through the inlet manifold and it is also a poor conductor of heat; I'd be surprised to find that it has heated up much.

On the other hand, if any petrol droplets find themselves fallen on the bottom, the heated manifold would evaorate them.

DIY Si - 7/4/06 at 04:28 PM

Manifolds are heated to help prevent freezing in winter and to aid fuel economy. As you have observed, the warm manifold helps ensure all the fuel goes in as vapor. If it were always cold, you would see more power, but worse fuel figures. Never been overly sure about the theory behind this, as once you've been drivimg for more than about 10 mins, the engine bay is hot, as is the manifold. Culd be just to cover the majority of journeys joe public makes, ie 10-15 to work and back each day etc....
Also, I can't see how it would help cold starting, as the manifold will be cold until the engine warmed up the coolant anyway.