[DML] Re: Carburator.

["endotex23" <endotex23@xxxxxxxxx>]

--- In dmcnews@xxxxxxxxxxxxxxx, "alex morgan" <mauibarber@xxxx> wrote:
> 
> 
> I live in hawaii where we have no smog or emissions check.  How
difficult is it to disconnect all emmissions from the Delorean?  Would
it still run correctly and if so how much additional horse power would
it get.<


Hmmm, depending on those trades winds to blow it away? It still goes
into the atmosphere you know and someone has to deal with it. Also, I
know of not a single state, emissions inspection or not, that legally
permits the removal of factory installed emissions equipment. That said...

The Lambda trim system is designed to dynamically control your mixture
to stoichiometric, 14.7 parts air to 1 part fuel. Also expressed as a
Lambda of 1. It's a trade off between good drivability, fuel economy,
and lowest emissions with lowest emissions being the priority of the
design. It's also there for one very other important reason: to supply
the catlayst with the narrow range of the three pollutant gas species
(along with a certain level of oxygen) it needs to operate correctly.

Note that this mixture is not one that provides best power, you need
to be richer for that. There are sevral ways to tune for best power.
One is to set your mixture up using a gas anaylzer or better still,
exhaust gas temperature. There are several ways to defeat the Lambda
system before doing so, some crude, some with technical finess. Either
way you need to also remove the converter because once mixture is set
to best power it will not only fail to function but will likely end up
being damaged. It'll help the engine breath better too. Also expect
lower fuel economy running best power. Fwiw, you won't gain all that
much but I suppose this car needs all the help it can get.

You could simply enbale your WOT throttle or Lambda thermal switch
input full time. Crude, open loop, and not exactly best power. Another
is to disconnect the O2 sensor and tweak primary mixture. Or
disconnect the power to the Lambda module and tweak primary mixture. 
Or disconnect the frequency valve and retune. All of these methods
will work but the one I prefer is to leave the Lambda operational and
change it's internal setpoint to introduce an offset that gives best
power. Closed loop control is then retained only now it's done at best
power instead of a Lambda of 1. 

You can do this one of two ways. You can open the Lambda and change
the calibration resistors or you can "fudge" the O2 sensor signal.
(You can also use a similiar method as a way to increase fuel economy
by running leaner, but only for highway driving. Anyone who tells you
running an engine a little lean at a constant low power setting will
damage it doesn't know what he's talking about).

No matter how you do it, for best power you're looking for about 12 to
13 for air/fuel ratio (about .80 to .90 Lambda). It differs depending
on combustion chamber design and other things so you'd need to do dyno
testing to get it exactly right but 12.5 to 13 is a good place to
start. If using a gas anyalzer shoot for about 3% CO as a start and go
from there. If using EGT tune for about 200 degrees F on the rich side
of peak EGT while under heavy load. Or you can use your (disconnected)
O2 sensor. Connect it to a high impedance millivolt meter and tune for
about 790-850 mv. Do not reconnect it when done. It'll need to be hot
and you'll need to be close to start with because the typical narrow
band O2 sensor's range is limited. A wide-band sensor would be better
for this and is a common, if not cheap, tuning tool.

In summary there are multiple ways to do what you want. It all depends
on how much you know and how far you're willing to go. You might
consider that you'll need to return the system to stock at some point
in the future. Increasing the engine's volumetric efficiency (short of
forced induction) will help too but it always require mixture tuning
afterwards. You can't make the engne breath better and not feed it
more fuel.

Finally, leave the Delorean's form of PCV intact because you'll still
need it. Also leave your fuel EVAP system intact as you won't gain
anything by removing it.

Greg










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