Spider exhaust

[Joe Martin Cantrell <agiyo@domain.elided>]

Date: Sat, 5 Oct 2002 09:00:38 -0500
From: "Greg McNair" <gmcnair@domain.elided>
Subject: Spider driving experiences (and smelling like exhaust)
Is it just me, or after a day's worth of driving do you other spider owners
also smell like car exhaust? Is there a way to direct airflow from the rear
of this car so that it doesn't push the exhaust back into the cabin?
Obviously, good straight fast driving should be the cure, but unfortunately
there are people ahead who insist on using brakes on the interstate.

Greg,
What model is your Spider?
What sort of exhaust outlet does it have, up turned, or down?
Are there any exhaust leaks?
Does it have any oil leaks, from the engine or driveline, which may be 
putting oil on the header pipe?  Are all the grommets in place and tight in 
your firewall?
Are your shift lever boots in place?
Emergency brake boot intact?
Is the trunk seal in good shape?
Does the car smoke?

I'd guess you probably have a Kamm tail Spider; the slipstream eddies 
behind the car are widely suspected to suck fumes back toward the 
cockpit.  This was addressed by the factory's fitting the donkey d*ck 
exhaust tips which directed gases down toward the pavement.  They also drag 
the ground more than others, and don't look very good to most people.  I 
don't know of any after market rear mufflers which have downturned 
pipes.  The popular replacement pipes are almost all too short, and 
discharge gas right into the square tail's eddy, but they look good and 
don't drag as much.

I'm not sure when Alfa went to the neater looking upswept exhaust tips, but 
I wonder if the rubber ducky tails of the '80s cars might not be at least 
partly to disperse and block exhaust gas dumped there by the upswept tips.

I have procrastinated for years about putting wind tunnel style tufts 
around the tails of several Alfas and photographing them at speed, to get a 
better idea of exactly where that air is going.  Might be time to do it.

You imply, though, that you smell the exhaust more when you slow down, 
which might indicate you are getting oil smoke from a point further 
forward, perhaps from one or more of the other sources I listed 
above.  I've seen exhaust in the cockpit from all of them, and believe the 
Kamm tail's been blamed for more problems than it caused.  A slight oil 
leak from the cam cover, working its way onto the header pipes, or a head 
gasket O-ring leaking onto the 2 into 1 collector, can make very stinky 
smoke which will work its way into the cockpit through any of the orifices 
I mentioned, and doubtless several others.  Likewise, the common small 
cracks where the exhaust pipe joins the mufflers can cause obnoxious---or 
noxious---smells.

I'd check the header side of the engine and look around under the car, to 
see if there may be oil getting onto your exhaust.

Cheers,
Joe
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