wur controll pressure drops when i rev the engine
 

I have been struggling to get my arf#s in check .
so here's the down low.
i have a 3 way adjustable wur, the more i get on the throttle the more the car runs richer . i currently do not have the boost dump vacuum line connected and my afr#s still drop and keeps falling into the low tens under boost .

Here are my current #s
..My casual tooling around town not in boost afr is in the high 13s to mid 14s .
... Low boost starts at high 12s then instantly drops to mid 11s ...
... Full boost starts low 11 if I keep pulling the afr keeps falling into the low 10s.
.... I am assuming it will eventually bottom out if i keep on it long enough
The car has Noticeably a lot more torque and pull. then when i had the boost dump vacuum line connected and it would instantly bottom the afr gauge to 10..

The system fuel pressure is a 96psi at low rpm 98psi above 3000 rpm with or with out a load . The change in the system pressure corresponds with the charging voltage of the alternator more voltage more psi. 12 to13v 96 psi 14.2v 98psi

The wur control pressure drops when I rev the motor. without a load it drops from 48 psi at an idle to 42psi above 3500rpms .... What could be causing this drop in control pressure ? even a quick blip of the throttle the pressure dips to 42 ish .

i am reading the system pressure off the inlet side of the fd and the wur control pressure is reading off a tee on the head of the wur . i am running a single new Bosch 200 series fuel pump if i run both pumps my system pressure is over 125 psi . i have all new supply and return an6 fuel lines from the tank to the fd . everything in the fuel system is either new or rebuilt. so what am i doing wrong ? what is causing the control pressure to drop ?

Thanks in advance
Regards Ned

I have no cure for your fluctuating pressures but what stands out to me is the 48 psi warm pressure. On my car 48psi would be really rich, I usually run at 53 psi warm with about the same 13-14.5 afr's cruising.
Have you load checked your battery? Battery voltage will affect fuel pressure.
Good luck!

The early 3.0l turbos have a lower control pressure. the factory recommended setting is 2.6- 3 bar at operating temp . i am actually 3 psi over the factory recommended setting . but i have an i/c and sc cams and a k27 turbo .

Seems to me that the only way voltage may affect AFR would be insufficient heating of the WUR heating element, staying too cold and thus keeping the warm control pressure perpetually low as a result. Then on boost it's exacerbated. Seems logical...perhaps. What kind of voltage are you reading at the plug to the WUR?
One more thought: Are you running with the Lambda (O2 sensor and frequency valve) functioning? Perhaps part of that system (frequency valve??) is acting up.

The 76 is down and dirty no lambda no frequency valve. The dip in the pressure is instant. i don't think its voltage related . The pressure drops and rebounds in a second or two. like a knee jerk reaction it may not even be a factor in the running fat under boost . None the less it is worth looking into the voltage. I did tap my aar off the wur feed .
The running rich has been an issue before i added the aar. i actually tweaked it a little more this morning before leaving for work (49 psi ). i am running high 14 not under a load just cruising. When i start to get on it the afr drops to low 13 then upper 12 s in low boost and keeps falling when in full boost eventually mid tens after a 3 second pull. A 5 second pull puts me into low 10s . runs and drives really nice. im happy with the performance but it doesn't make sense i don't have the boost enrichment dump connected and the longer in boost the lower the afr will go .

Something not quite copacetic with the WUR. I don't have an adjustable WUR and don't entirely remember the inner workings of them. I don't recall if there is a separate diaphram responding to boost but it appears to be overreacting. You really don't need to be in the 10's when on boost.
Gotta be the WUR. If you had a spare stock one, slap it on and see what happens. Sorry not much help.

One thing that bugs me: Why is your system pressure so high when running both pumps? These 930 engines were designed to run with two pumps; pressure and capacity are two different things. Could there be some kind of delivery issue, perhaps related to regulated voltage as your rpms increase? Just brain storming....I'm still hung up on this voltage and psi relation which makes little sense.
Is this just a recent issue, coming out of the blue? And do you trust your AFR guage is reading accurately (most likely is). 02 sensors read residual oxygen content and with an excess of fuel it will consume more 02 than typical and read rich...well duh.
One option may be to run both pumps and adjust your system pressure with shims as needed at the fuel head. Don't mind me if I get way out in left field, just some brain ticklers.

I think of low voltage related to the fuel pump and not wur heating. If voltage at the fuel pump drops the system pressure and control pressure do also.

Yeah, I retract me earlier thought about the WUR heating element since his AFR's are good at cruising.

system fuel pressure is at a constant 96psi at 12.5v at an idle 98psi under a load 14.2v i have no fluctuation or bounce at all on the system pressure . i plan on relocating the sending unit from the system pressure on to the wur so i can monitor the control pressure while driving .

the car sat for 20 years before i got it replaced or rebuilt everything.
The higher the voltage the faster the pump spins. the faster it spins the more fuel it pushes. The pressure regulator in the fuel distributor is not dynamic. x inlet flow and pressure equally y outlet flow and pressure if inlet flow and pressure goes up so does the outlet. The fd is designed to bypass more fuel than it uses . ( this is how dale from flowtech explained it to me) .
The original pumps are no longer available. The pumps back in 76 had lower pressures and a lower volume . The new bosch 200 series pumps have a higher pressure and a higher volume . one pump can feed a 500hp motor so im told . as far as adjusting with shims, i actually had to remove all the shims to get the pressure under 100psi with just a single pump with both its 125psi . now you have me wondering if installing larger an6 lines from the tank to the fd and back less flow restriction could possibly be a factor.

the system pressure never drops . if any thing it goes up a psi or 2 was the engine accelerates.

This is the part that is confusing me because the boost enrichment ( fuel dump is a seperate diaphragm ) That is designed to lower the control pressure under boost (add more fuel) to stop the motor from leaning out. mine is not even connected so its not a factor if it was connected i could adjust it to compensate .
under boost without the ( fuel dump) connected by right the car should start to lean out .. but mine keeps getting richer the longer im in boost.
The reality is the car is running great i don't do 5+ second pulls at full boost im typically only in full boost for a second or two mid 11s afr . its just
bothering me why its doing this and why i cant figure it out . its going to be something stupid .

The next logical place to look is an air leak in the intake pathway. Most common would be the three o'rings...one at the turbo compressor, one at the top of the up pipe to the IC, and one at the throttle body/IC interface.

Your fuel distributor has already set up the correct amount of fuel based on air volume pushing the metering arm, but if any air were to later escape anywhere you would be too rich. Usually shows its ugly head when on boost when that pressure deforms a bad seal just enough to let air escape but not enough to cause running issues. You would see it in your AFR.

i probably need to get it on a dyno this way i can actually observe the motor while its under boost . i rechecked everything many times . i don't have the O-rings its all t bolt clamps and they are tight. i should probably pressure test my long neck ic that was used but looks' to be in great condition.

Have you ever tried a smoke test? This test showed me a problem area that I thought was fixed and allowed me to make a more permanent repair.

i have not, I thought about it but i don't think i could get the car in boost and introduce smoke while sitting in the driveway. i defiantly don't have a vacuum leak and the throttle body is is new old stock.

Smoke test may still work provided you apply 1 bar of air pressure along with the smoke. If you have a weak seal somewhere that only fails on boost, one would think that this would find it...mimicking boost pressure

any tips on how i could do that ?

Might want to search this forum. I've done it but once with the IC off. Entailed fabricating a plug for the throttle body, and disconnecting the airflow housing side of the rubber elbow, then rotating the elbow up enough to install a plug there as well. And of course plug the hose to the WG and the top of the up-pipe. With the IC off it gives you a little better view of hoses and such beneath it but won't tell you anything about the condition of o'rings for the up-pipe/IC or the TB/IC interfaces.

Or leave the IC on. Disconnect the elbow from the air flow housing, rotate it 90° and plug it with something like a PVC cap, disconnect the hose to the WG and attach a suitable hose there from which to pressurize the IC.