Weber manifold for Xflow?

[Blatman]

What happens when you blow air across the top of a milk bottle?

Er....it makes a funny noise.........if you then drink some of the milk, the pitch of the noise goes down a bit..........oh, I get it........it's not my gearbox whining at all...............      

[Man with no name]

……what’s on the other side of that bonnet of your’s Mr. B?

[Graham.J]

.....Graham, love the shagtastic clamshells, baby.

You can have them if you want, i despise the things, eugh.

They're standing against the wall in my garage at the moment, I'm waiting for my WSCC membership to come through so I can advertise them.

[Blatman]

……what’s on the other side of that bonnet of your’s Mr. B?

Nothing but gorgeous lime green gel coat............or someones back garden, and some trees.............    

We've had the discussion about whether having a hole or not is better. There is obviously a power increase when you can get cooler air into the inlets, although whether this is something you can actually discern is another matter.

Also, all the temperature readings ever done place the temperature sensor somewhere in the air filter/trumpet area. To get an optimal reading, you need to measure the temperature of the air/fuel mix that actually gets detonated. I'm betting that the atomised petrol reduces the air temp quite significantly before it explodes..........

FWIW, my green car has a sister car, which, as far as the engine is concerned, is identical, with the exception of the inlets. My car has injection and no hole in the bonnet. The sister car has 45's, and a hole in the bonnet. On the rollers, they were within 5bhp of each other, IIRC, although I never got to compare the torque spread across the rev range. I'll bet there was b******* all in it though. My map doesn't, as far as I know, have a temperature correction algorithm, so even if the air was colder, the engine management would know that it was, or care that it was, so it wouldn't alter the fuelling to make the best of it..........

All of which doesn't escape the fact that MarkJ is almost certainly going to have to cut some sort of hole in his bonnet.........

[MarkJ]

b*******...

[MikeR]

Is it only the first trumpet that gets affected by the vacum?

If it is, would placing a curved bit of ali in the front of the forward facing filter to stop the air flow rushing in have any benefitial effect?

[stu999]

Possibly Mike. But the only real way of finding out is hours testing aerodynamics.....

The ideal situation is for the trumpets to be sucking from airflow that is as still and calm as possible. Hence the reason a lot of well designed performance cars/bikes have huge airboxes feeding the carbs or throttle bodies. Remember, on a rolling road, the car may be doing silly speeds on the rollers, but it is nigh on impossible to send the equivalent wind speed past the trumpets or air filters to see what difference it *may* make.....

The new Demon Thieves catalogue has a range of  air intakes which 'box up' the trumpets, with a single large air intake. But I am sure something similar wouldnt be too difficult to make....

[chazpowerslide]

Blatman is correct in saying that the atomisation of the fuel in the intake will reduce the inlet charge temperature to drop quiet significantly. I would never run side-draught Webers without the trumpet as it helps strengthen the pressure at the main venturi by smoothing the airflow in that area.

You want at least 35mm between the mouth of the trumpet and the inside of the filter cover so as not to restrict airflow into the carbs. I'd run the longest trumpet/largest filter setup as was practically possible and not worry too much about the vacuume affect described. I think I'd rather have what's best for the engines requirments in terms of trumpets and filters and cut the engine cover if nessasary.

Chaz.