Homebrew Fuel Enrichment Device

[Miles Lott <milos@insync.net>]

Well, firstly, my car is an 8V.  Sorry if I dipped into a 16V
discussion.  However, on the 8V there is a CPR and a frequency
valve(DPR, EHA, whatever).  I was speaking of the frequency valve and its
reaction to the thermo switch.  I was in error that the WOT switch
does the same thing as shorting the thermo switch.  But doing
so has a similar effect. 

It pretty much shuts off the frequency valve, allowing for the maximum
fuel pressure in the lines, based on the action of the fuel pump, distr,
injectors, and the state of the CPR (temp sensitive). If this is done at
idle, the idle will raise noticeably.  This is the condition at below 68
degrees at the thermo switch.  It is only a switch, so a variable control
on its terminals will have questionable results.  The perceived HP gain is
beneficial enough at low RPM, IMHO, despite their claim to a loss in HP.

I may be dreaming, but I seem to remember connecting a scope to the wiring
at the frequency valve back in 1995.  It seems that its duty cycle is
controlled by what is known as a variable duty-cycle square wave
oscillator.  This would make current variances in the wiring to it less
of an intelligent way to do the mod.  What you need is to be able to 
vary the duty cycle of a 12V square wave to it.

The aforementioned mod of shorting the thermo switch is a low tech, yet
effective way of acheiving similar results with the stock control module.
You have less control, but risk little insofar as damage to the control
unit and other parts. ***** (I mean by using a homebrew method - I make no
claims as to the fitness of Autotech or TT's mods.) *****

Yeah, the kick was adjusting the CO screw for a 50/50 duty cycle square
wave ;)

On Thu, 15 Jan 1998, Etrik wrote:

> Miles Lott wrote:
> > 
> > If you short the contacts of the temp sensor, you duplicate exactly what
> > the WOT switch does.  As I remember, it puts an 80 % duty cycle on the
> > fuel pressure return valve, so that fuel pressure is near the maximum the
> > system can manage.  I have this for warming up the engine, and it does
> > make a nice boost switch, too;)
> > 
> >
> 
> Is the fuel pressure reture valve different form the DPR?  Cause that
> would
> not really make sense, is you car CIS?  If all the WOT switch does is 
> short the leads, then what use is the TT moduel?  I am no expert on
> BOSCH F/I so I may be wrong.
> 
> Etrik
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