RE: [DML] CIS Fuel system tuning.

["John Hervey" <john@xxxxxxxxxxxxxxxx>]

I would like to say that if anyone is having trouble with their fuel
injection system not performing properly then call me in the evening and
tell me about it. 
I work with all the CIS FD's in Porsche, Lambo's, Merceded and DeLoreans and
others. 
It will run smooth and give good gas mileage as it was designed to do and no
I won't ask you to bring it in. 
Most of the problems are caused by improper care or not understanding CIS or
getting information from sources that don't understand it because it's not a
carburetor.
John Hervey
www.deloreanautoparts.com


 

-----Original Message-----
From: dmcnews@xxxxxxxxxxxxxxx [mailto:dmcnews@xxxxxxxxxxxxxxx] On Behalf Of
Bob Brandys
Sent: Wednesday, April 11, 2012 8:50 PM
To: dmcnews@xxxxxxxxxxxxxxx
Subject: [DML] Carburetor Tuning

In 1975 when catalytic convertors were first installed in cars virtually all
of them were carberated. 

Catalytic converters lasted for 50,000 miles by federal law with these
carberators. 

In the 1975 and later Quadrajet, there was an atmospheric compensator that
adjusted the idle circuit for atmospheric pressure. 

Other car manufacturer "computerized" carberators, with an idle air solenoid
that was connected by computer to an oxygen

sensor.   

Clearly, these carberators worked with catalytic convertors all the way
until the early 1980s.  

Carberators can be tuned to give almost equivalent mpg as fuel injection but
this must be set up using 
a dynamometer and an exhaust gas analyzer.  

I have a friend who set up his 501 camaro to get 21 mpg on the highway with
3.08 gearing and turbohydromatic. 

My dad had a carberatored 1980 Buick Century with V8 that 29 mpg on the
highway, with a 3 speed automatic NOT overdrive. 
It got this great mpg until about 149,000 when the timing chain slipped. 

What computerized fuel injection did is allow the fuel system to
automatically adjust for the variability of each engine and 
it induction system.  

Early automotive pollution research showed as much as 25% variation in air
flow on the same engines size production
engines at the same rpm.  It was not cost effective to individually adjust
carberator for this variation. 
But computerized fuel injection systems would do it automatically.   

Some of this individual engine variability has been reduced.  The best
engines still have about 5% variability.  e.g. the "better"
engines go into the corvettes. 

Computerized fuel injection can adjust for a lot of variable conditions, but
carberator can still function almost as well if properly tuned. 





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