airfilter box

Post by **rein** » Mon Dec 03, 2007 4:42 am

Hi all,

I have noticed that the 948 airfilter box gives better airflow than the later 1098 model ones. The car pulls up a particular hill in fourh gear and with the 1098 airfilter box I need to change down to third gear. It is also possible that the 948 box is able to draw in cooler air I suppose?
Cheers,

Rein

Post by **simmitc** » Mon Dec 03, 2007 6:31 pm

With the 1098 filter it is supposed to be rotated so that the intake is over the exhaust in winter (warm air) and away from the exhaust in summer for cooler air.

Post by **rayofleamington** » Tue Dec 04, 2007 11:19 pm

Are you sure it is the air filter maing the difference and not just one running rich/lean and the other running with the right amount of fuel?

Post by **RogerRust** » Wed Dec 05, 2007 6:34 am

It takes the same filter element so I can't work out why. Perhaps you had an air leak with one. As Ray suggests it's likley to be the mixture. Or you could well be right and its temperature related.

Post by **rein** » Wed Dec 05, 2007 9:37 pm

Rich/lean: I don't see any difference when I look at the plugs in both situations.
Perhaps the difference is to small?
I know that the 1098 box has got a summer and winter position, but when set in summer position, the inlet is still close to the exhaust manifold. I therefore figured that the 948 box is drawing in cooler air than the 1098 box.
I also noticed that the carburettor opening on the 1098 box is not perfectly aligned with the opening of the carburettor. It may loose some airflow in that area. (Especially when I remember parts in the David Vizard book on the airflow at a carburettor opening). And does the 90 degrease angled connection on the 948 box accelerates the air because it gradually goes from a larger diameter to a smaller one to match the carb opening?
I know there is much more to it, but the fact remains that by simply changing from the 1098 box to the 948 box I don't have to change to third gear on this particulary incline.
And I did repeat this experiment several times.

Rein