I don't know if they ever did it to TR6's, but certain Spitfire 1500
models had air rails attached to holes in the head that did pump air
into the intake side of the head, instead of the exhaust. So perhaps
everyone is correct!
Joe
Hugh Fader wrote:
>
> I had to re-read Tim's note. I think you are correct. It does pump air into
> the exhaust helping to combust unburnt hydrocarbons. Now, here's a new
> question. Does this increase exhaust backpressure? If so, there may be some
> efficiency lost from this.
>
> > -----Original Message-----
> > From: Eric Conrad [mailto:conrade2@msn.com]
> > Sent: Saturday, November 23, 2002 10:09 AM
> > To: Tim Hutchisen; Hugh Fader; 'Graham McMicken'; 'Triumphs'
> > Subject: RE: Emission Control
> >
> >
> > Tim, et al,
> > With all due respect, I have to take issue with your comments
> > regarding the
> > air pump. Having restored a '76 TR6 to as close to original
> > as possible, I
> > can confidently say that the air pump did not introduce fresh
> > air into the
> > cylinder. Rather, it introduced fresh air into the exhaust
> > manifold to
> > allow full burning of any fuel vapor or hydrocarbons escaping
> > the cylinder.
> > This is why the exhaust manifold temperatures of an engine
> > with an air pump
> > is much higher than those cars without the air pump.
> >
> > I have disabled my air pump by removing the belt and adding a
> > new (fresh)
> > check valve to keep the exhaust fumes from heading back
> > toward the emission
> > control equipment. The TR6 runs better, and a little leaner
> > (better gas
> > mileage) with the air pump disabled. Also, to address a
> > comment by Hugh
> > Fader, the fan belt running the air pump is a very short
> > belt. The beauty
> > is that it only runs the air pump, so removing it doesn't
> > affect any other
> > engine components.
> >
> > I will entertain comments counter to my feelings.
> >
> > Eric
> > '76 TR6 (CF52678U)
> >
> >
> > [tim hutchisen wrote:]
> > The air pump will _not_rob valuable horsepower a whole
> > lot. It's job is
> > to provide fresh air into the cylinder to help the burn of
> > hydrocarbons and
> > carbon monoxides. It helps in the efficiency of the flame
> > front inside the
> > cylinder. (Read: better fuel economy). It also reduces the temperature
> > inside the cylinder. So...
> > remove the air injection system if you want to:
> > 1.) pollute the atmosphere more 2.) get worse fuel economy
> > 3.) shorten the
> > life of your engine and 4.) create _more_drivability
> > problems due to rich
> > A/F mixture.
> >
> > <<snip>>
> >
> > Removing emissions systems usually result in an increase
> > of drivability
> > problems and decreased fuel economy as a whole. It is a false
> > perception
> > that these systems rob horsepower. It was the lower
> > compression ratios that
> > robbed the horsepower through the 70's, not the emission
> > systems. Lower
> > compression ratios were the easiest way to meet the strict
> > emission mandates
> > set in the decade of disco. The engineering had not caught up with the
> > mandates at the time in regards to cleaner running engines.
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