Re: Fuel Enrichment Device

[Brad Sheridan <brads@mindspring.com>]

At 06:55 PM 1/14/98 -0800, you wrote:
>> 
>> I've been studying the Bentley manual, and the EC article on the Techtonics
>> Tuning CIS-E fuel enrichment device.  I'm more than 90% of the way into 
>> reverse engineering it.  (I'm an engineer by trade, so I feel qualified
>> in using such statements :-) )  What I've got left to learn is whether or
>> not the cold running enrichment is put on a duty cycle by the OX sensor
>> control module, which sends the signals to the control pressure regulator.
>> If it is, I believe that I can beat it by doing my own timed cycle, which
>> would reset the systems' duty cycle.  Well, I don't even know if it's 
>> going to be a problem yet.  I can you this though, the TT module doesn't
>> address it if it is an issue. 

The differential pressure regulator( I think thats the one you're talking
about) is controlled by a current, and you don't switch it off/on, but
rather give it varying current levels, in the mA range. I have some reverse
engineered data on the Autotech device someone else wrote up a few years
back. The Bentley I believe has some info as to what the current range is.
I think it can go from 120+ mA in cold start mode to around 15-20 mA at
full throttle to -40mA or so during closed throttle deceleration. 
Unfortunately, I have yet to posess either Autotechs or TT module, and so I
can't completely disassemble one to see what they're doing.
   Trying to rely on automotive journalists to explain how electronics work
can be quite futile, and I don't know that I'd rely on their description to
reverse engineer the device. I designed a fuel enrichment device for the
motorcycle market, and explained several times exactly how it works to both
people at work, as well as journalists, and whoever asked. But when I saw
an article describing the product, the description was so far off, I was
amazed. The journalists were getting their description of the products from
marketing people, both of whom felt they should modify my accurate
description of how the thing worked. But since neither had a clue about
electronics, the resulting product description had the product wired into
the wrong sensors, reading the wrong signals, and calculating the
enrichment incorrectly.
  The document I have detailing the reverse engineering of the Autotech
module appears to be written by someone who knows electronics, and from it
it appears that the Autotech module simply modified the DPR current at full
throttle. It did it in a very simple way. I had some ideas on how to
improve the design, I've just got too many electronics projects going on at
work to start up another one at home. But basically, instead of going to a
fixed enrichment current like the Autotech module, just add an adjustable
current source in parallel with the DPR wiring. This will allow your OXS
computer to still adjust for engine temp, and whatever else it adjusts for.
With the current source, you're just adding a set amount of current to the
signal from the OXS computer. You don't have to worry about feedback from
the oxygen sensor, since this enrichment only occurs at full throttle, when
the system goes into open loop mode. Run a pot from the current source
control to your dash, and you've got a very cool enrichment device.

Brad
>> 
>> I may just publish the specifications on my web site, whenever THAT becomes
>> a reality.

  If you have specs, feel free to email them to me, I'll add them to the
other info files I have on my site.

Brad


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