CIS/WUR Help

[ZEGM]

Just got an 87 930 and the fuel mileage is awful. Installed a pressure gage between FD and WUR regulator and got the following values:

Outside Temperature for all test were 23C (73.4F) Lambda disconnected

1. System Pressure 6.8 Bar (98.6 psi)
2. COLD Warm Up Regulator 3.3 Bar (48.p psi)
3. WARM (Electrical Connection only) 4.8 Bar (69.6 psi)

Questions
1. This is not what I expected as wouldn't this make is LEAN?
2. Can a bad Fuel Pressure Regulator allow too much pressure?
3. How much is a new Bosch (Not Porsche Branded Bosch) regulator go for if needed?
4. CIS Flow Tech can rebuild it but there is a 7 - 9 week lead time, any other companies out there that do this work?

The car actually runs fairly well and starts right up. Mileage is AWFUL 9 mpg.
Any and all help would be fantastic!

[356911930]

Is that 9mpg highway or spirited driving.

Rahl

[ZEGM]

Rahl,

It is a mix, I would consider it a normal day of driving. Not on the track stuff.

[908/930]

The numbers I have written down are

system pressure 7.0 bar 105psi
CP warm 3.75 bar 55psi

My cars WUR that I checked years ago cold 28psi, warm (2min) 45psi hot (4min) 55psi. I see what you are saying, higher pressure one would expect lean, fuel distributor problem?

Did you check fuel delivery amount from the pumps?

[Bucketlist]

Maybe the experts will chime in but in my experience your cold CP is too high at 3.3 bar (48psi). Mine likes about 2.3 (33psi) and your warm CP is way too high at 4.8 (69psi). Mine likes about 3.65 (53psi). It might run a few minutes cold but would go lean and die. Do you have an air fuel meter hooked up? It should show something between 12 -14 once you get it running.
Look at your testing equipment and procedures before buying a bunch of parts, sometimes its just the learning curve on these old cars.
Fuel mileage? This is a Porsche.....I've never worried about fuel mileage.

[krasuskyp]

my understanding is yes higher pressures translate into leaner conditions

there's no FPR in these per se, it's controlled via adjustment shims in the fuel head pintle

I've never gotten great mileage in mine, typically use 10 for gas range calcs and aren't far off (it can get to 11-12 occasionally, and I track every tank) 9 does seem low

def hook up a EG sniffer or better yet install an AFR gauge as you'll want one anyway to own monitor and diagnose and enjoy these cars - what's it tell us?

car runs / boosts well otherwise?

congrats & welcome btw - also btw... pics are obligatory here 8 )

[Alan L]

Your numbers should be like 908/930. System pressure can be a bit lower than 7 bar tho.
Yes, the high pressures make it lean. Surprising it actually runs OK.
I see no advantage trying to lean it out for gas mileage - it is either running at optimum or not.
I would get the WUR numbers in spec then see what the problems are.
Alan

[pkabush]

Agreed. Get a AFR gauge and tune your CIS components to spec. If your worried about mileage stay off the boost. Where’s the fun in that though. I’m with Paul. I figure if I’m getting better than 11 mpg I’m not on the loud pedal
In all seriousness, our cars are capable of pretty decent fuel mileage. Especially considering the age and performance capabilities. But only if driven lightly.
And yes, we need pix

[T77911S]

hi CP makes it lean out....but....if you adjust the mixture screw you are back to "normal" AFRs.
i have played with different CPs to both extremes and always after resetting the mixture it drove the same and i had the same AFR's
what the non-factory CP does change is at what RPM does rich-lean-rich happen.
that is off idle rich to lean for cruise to higher RPM richness.
now given the 930 AFM appears to be like a straight cone with no "steps" in it like the 911 AFM i could see at what RPM this would happen.

[Alan L]

I think there is some sort of profile in the 930 cone - to allow some progression? Been a while since I looked - but thought there was something there.
Alan

[ZEGM]

Guys I was concerned that the poor mileage was a symptom of running too rich. But the Control Pressure shows it should be running lean. Now the Lambda is disconnected for this test, but I am wondering if it is compensating somehow, actually allowing it to run richer?

The question in my mind is can a "Broken/Worn out" Control Pressure Regulator cause pressures this high?

So, the test was done correctly but NO I didn't not get a calibration sticker for the fuel pressure gauge. I really like the idea of measuring the AFR. What good kits are out there that someone can recommend?

The car has about 95k miles on it but unfortunately it has been sitting in a Dealer/Museum for the last 10 years with an occasional ride around the block.

Thank you all for your inputs!

[RarlyL8]

it has been sitting in a Dealer/Museum for the last 10 years with an occasional ride around the block.

This is the problem.
Likely there are deposits everywhere which can manifest in many ways. Old rotten fuel loses octane rating causing poor running as well. I would suggest a complete cleaning of the fuel system. If that doesn't fix the problem then time to look at the individual components. I stock rebuilt -145 FD and -153 WUR should you need that service.

[ZEGM]

car runs / boosts well otherwise?

congrats & welcome btw - also btw... pics are obligatory here 8 )[/QUOTE]

The car seems to run pretty well but I have no Baseline to compare it too. I can say that our 2014 BMW X5 35D (diesel) is slightly faster to 60mph.

[flightlead404]

Originally Posted by ZEGM

Guys I was concerned that the poor mileage was a symptom of running too rich. But the Control Pressure shows it should be running lean. Now the Lambda is disconnected for this test, but I am wondering if it is compensating somehow, actually allowing it to run richer?

The question in my mind is can a "Broken/Worn out" Control Pressure Regulator cause pressures this high?

So, the test was done correctly but NO I didn't not get a calibration sticker for the fuel pressure gauge. I really like the idea of measuring the AFR. What good kits are out there that someone can recommend?

The car has about 95k miles on it but unfortunately it has been sitting in a Dealer/Museum for the last 10 years with an occasional ride around the block.

Thank you all for your inputs!

If lambda is all disconnected it could have been enrichened to compensate?

If you are comfortable with where the AFR is, go out and get hard on it for a while and get some of those deposits blown off.

You s/b able to hear any detonation starting and a little det is not horrible. Its pre-ignition that will melt your pistons right away, if you get off the pedal when you hear/feel det its ok.

Modern cars in highway cruise are on the edge of det all the time.

[ZEGM]

I am ready to purchase an AFR kit, can someone provide me with some suggestions? Would love to be able to see real time data in the driver's seat.

[908/930]

Innovate Motorsports and AEM both make them. I installed a AEM AFR gauge into the location for the clock, but have not finished the install of the sensor so cant report on function yet. I have a stand alone Innovate LM2 that works pretty well.

[Chris_chch]

I'll put in a vote for the innovate SCG-1. Covers off a few things all in 1 package. Most helpful if you have the ability to put a lighter spring in your wastetgate.

https://www.innovatemotorsports.com/products/scg1.php

[patina]

Originally Posted by ZEGM

I am ready to purchase an AFR kit, can someone provide me with some suggestions? Would love to be able to see real time data in the driver's seat.

In my opinion the Innovate kits are higher quality than the AEM equivalents. The wiring/connectors/gauge itself just seems better built.

[Bucketlist]

Originally Posted by Chris_chch

I'll put in a vote for the innovate SCG-1. Covers off a few things all in 1 package. Most helpful if you have the ability to put a lighter spring in your wastetgate.

https://www.innovatemotorsports.com/products/scg1.php

I've been using Innovate for years with both the LM2 that will record A/F to an sd card, and also Boost(map) RPM, etc after some fabrication. I also run the digital gauge in the dash to keep an eye on. The new gauge that Chris mentions above sounds like a real improvement and worth checking into.

[MZ3 SBC]

a ruptured diaphram in the WUR will make it run pig ritch...Pershaps he dealer raised control pressure to combat - but likely not gonna fix a leaking diaphram which isnot hard to break.

I suspect you have a stock air box and hose between the WUR bleeder and airbox? if you disconnect that hose- youi may see it leaking?