Tuning idle speed circuit

["checksix3" <jetjock11@xxxx>]

Johh, permit me to give you change back for your 2 cents. 

Where is the slight correction? Everything Martin stated is correct. 
While what you state is true, it's only valid during warmup. 
It's hard to have WOT enrichment without CPR enrichment? That's 
exactly how it's done after warmup. Control pressure is maxed and 
stays at that value. On a stock D there is no vacuum supplied to the 
CPR (and no acceleration enrichment) after warm up. And as Martin 
states, the ignition advance is disconnected during warm up. These 
vacuum sources are swapped when the thermo valve changes state at 
appx 130F. Quoting from the manual does not impy an understanding of 
how the CPR operates. The CPR is pretty much dead weight after 
warmup, seving only as a static regulator to keep control pressure at 
it's maximum regulated valve. Listen to Martin and H. McElcraft, they 
seem to understand the details of how this stuff actually works.

As for the delay valve, it's speced at 10 seconds but fwiw, I've 
never seen one take that long to bleed down.

I've removed my CPR and use a digital controller that performs both 
warmup and acceleration enrichment by PWM. It also permits full 
manual mixture management, allowing tuning by EGT. This improves 
highway fuel mileage and allows tuning for either best power or best 
economy during steady state cruise conditions. (Anyone knowledgable 
about operating piston powered aircraft engines will be familar with 
these techniques.) 

It switches back to an auto mode when it senses load changes. The 
stock CPR does not allow mitxure control after warmup, leaving it to 
the FV for emissions and to the airflow sensor geometry for 
acelleration. The facts are that mixture tuning can be done by 
manipulating either control pressure or FV duty cycle. If you do it 
with CP you need to fix the FV duty cycle during that time or the 
Lambda will attempt to correct your "mistake". 

After all, the Lambda system does not provide true stoichiometric 
combustion...it's shifted slightly to the rich side of peak EGT. Full 
control via the FV is a better way, leaving a static control pressure 
to provide plunger damping and to set the range the FV will operate 
around. (Controlling both at first provides a wide lattitude for 
experimentation if you've seriously modified the engine in any way.)

EGT monitoring (or by feedback loop) replaces the O2 sensor signal 
during this time but you'd better have a way to switch it back duirng 
load changes. For long highway drives over flat terrain you can't 
beat this system. You can even run slightly lean of peak as long as 
the induction air distribution is fairly decent, as it is in the 
stock D. An added benefit is that it keeps your pistons and valves 
very clean.


----original message----
From: John Hervey

>>Martin, Slight correction. Our WUR are equipped with a dual spring 
set up. When the throttle valve is open further at full load, the 
pressure in the intake manifold increases....>snip<

-----Original Message-----
From: Martin Gutkowski<<

>>The vacuum enrichment on the DeLorean's CPR is only active under 
warm-up conditions, at which time the distributor vacuum is 
disconnected. As the CPR vac is removed, it is placed on the 
distributor (so to speak). Martin<<