Bosch K-Jetronic System Questions Thread

[DeloreanJoshQ]

I have been studying the Bosch K-Jetronic Tech manual and have some questions....

-Is it possible to upgrade the Lambda sensor to a heated style?
-Why doesn't the Delorean have an auxilary-air device, or does it?
-Would some one please explain what the frequency valve does in laymen's terms?
-Are the Delorean fuel injectors "air-shrouded"? If not, why aren't they?
-How do you adjust the CO screw "by ear" vs. by hooking up wide band sensors?

[Bitsyncmaster]

You could probably upgrade to a heated O2 sensor and it may cure some hunting idle problems. Only change you would need is to provide the 12 volt power to the heater when the engine is running. Another more complicated option is to use a wideband sensor and controller.

The frequency valve adjusts the fuel mixture. It does this with the lambda ECU changing the amount of open and closed timing of the frequency valve. The lambda ECU reads the O2 sensor to hold the AFR at 14.7 (lambda at 1.00).

[DeloreanJoshQ]

-If you don't have any idle-hunting problems, would there be no noticable changes to performance or idle during warm-up?
-How exactly do you adjust primary pressure in the PPR and where do you find shims? For example, I read a thread on here where the A/F runs slightly lean after installing performance exhaust and adding a shim would help increase pressure...
-If the engine is running lean due to this performance part upgrade, why isn't it detected by the lambda sensor and adjusted through the lambda ECU to the frequency valve to adapt and richen automatically?
-Why are some people running "open-loop"? what A/F ratio is better for the Delorean? I would think that Lambda would make the car perform better by maintaining stoich....

[Bitsyncmaster]

The lambda ECU would try to adjust the AFR to 14.7. I've found with every thing adjusted, the lambda has a pretty wide range of adjustment. But I have not dyno tested so under a heavy load it may run out of adjustment. I would guess running higher primary pressure gives it a little more range. Most of the primary pressures I've checked on Ds run about 68 PSI. The specification says it should be 75 PSI +/- 5 PSI. I shimmed mine and it now runs 76 PSI. It took quite a large shim (0.030" I think). I have a large junk drawer of bolts, nuts and washers I've collected for 40 years and found some washers that worked.

Running open loop lets you adjust the AFR richer for more "pep". The richer mixture gives you very quick throttle response, smoother idle and probably more HP. You should increase your ignition advance a little to get the most out of a richer mixture.

I run a wideband in my car with a switch to select ECONOMY or POWER.

[DeloreanJoshQ]

The lambda ECU would try to adjust the AFR to 14.7. I've found with every thing adjusted, the lambda has a pretty wide range of adjustment. But I have not dyno tested so under a heavy load it may run out of adjustment. I would guess running higher primary pressure gives it a little more range. Most of the primary pressures I've checked on Ds run about 68 PSI. The specification says it should be 75 PSI +/- 5 PSI. I shimmed mine and it now runs 76 PSI. It took quite a large shim (0.030" I think). I have a large junk drawer of bolts, nuts and washers I've collected for 40 years and found some washers that worked.

Running open loop lets you adjust the AFR richer for more "pep". The richer mixture gives you very quick throttle response, smoother idle and probably more HP. You should increase your ignition advance a little to get the most out of a richer mixture.

I run a wideband in my car with a switch to select ECONOMY or POWER.

How do you add more washers?
When you say adjusting the AFR richer, you mean the CO adjustment screw?
Do you have details on the wideband in your car that you switch from economy or power?

thanks!

[content22207]

I have been studying the Bosch K-Jetronic Tech manual and have some questions....

-Why doesn't the Delorean have an auxilary-air device, or does it?

DeLoreans use CIS instead of an aux air valve (as do contemporaneous North American Volvo's)


-Would some one please explain what the frequency valve does in laymen's terms?

The frequency valve controls how much fuel goes into the lower fuel distributor chambers:
- More fuel in the lower chambers reduces the size of the upper chambers, reducing the amount of fuel metered for any given air flap/metering piston movement
- Less fuel in the lower chambers increase the size of the upper chambers, increasing the amount of fuel metered for any given air flap/metering piston movement

European fuel distributors do not have externally regulated lower chambers:
2952


-How do you adjust the CO screw "by ear" vs. by hooking up wide band sensors?

You listen to the way the engine idles, and you see how it behaves at throttle under load (drive the car).

Bill Robertson
#5939

[Bitsyncmaster]

How do you add more washers?
When you say adjusting the AFR richer, you mean the CO adjustment screw?
Do you have details on the wideband in your car that you switch from economy or power?

thanks!

You add the washers under the PPR spring so it gives the spring more pressure.

If your running open loop then you adjust the AFR with the CO adjustment screw. I'm running closed loop with a wideband so I adjust the AFR with the input signal into the lambda ECU.

[Farrar]

If memory serves, Bosch KE-Jetronic used an auxiliary air device; this system came about after DeLorean had ceased production.

Farrar

[content22207]

Aux Air Valves installed on PRV's respond to temperature alone. There is no way to open them for engine loads such as A/C or an automatic transmission torque converter. The situation is comparable to fast idle cams on our choke mechanisms.

Bill Robertson
#5939

[DCUK Martin]

-Is it possible to upgrade the Lambda sensor to a heated style?


Yes. You will need to power the heating element and "tell" the ECU to read it immediately.



-Why doesn't the Delorean have an auxilary-air device?


Because the Constant Idle System is more sophisticated and does a better job



-Would some one please explain what the frequency valve does in laymen's terms?


It's the actual valve which adjusts fuelling based on what the lambda system "sees" in the tailpipe.



-Are the Delorean fuel injectors "air-shrouded"? If not, why aren't they?


No, I don't think air shrouding provides a measurable benefit.



-How do you adjust the CO screw "by ear" vs. by hooking up wide band sensors?

Personally I use the way the frequency valve buzzes. Without the lambda system, the only way to do it, other than a wideband lambda, is with a CO meter (and no cat!)

[DeloreanJoshQ]

How do you test the warm up regulator? I am noticing during cold starts early in the morning the car has a slight miss at idle but once it warms up it is fine. Also, hot and warm starts are fine and it runs great at any temperature; it's just the cold miss at idle....


Thanks!

[elfking]

I managed to adjust my CO into good enough spec to pass smog and seems to run great from others here on the board. I just had to find a Multi-Meter which measured Duty Cycle...

http://dmctalk.org/showthread.php?481-Won-t-run-without-CPR%28WUR%29-and-CSI-plug-swapped/page2

Borrowing a multimeter that had the option was the hardest part...

[DMCMW Dave]

How do you test the warm up regulator?
Thanks!

With a KJet test fuel pressure meter. It's in the manual. You can buy the meter from places that sell BMW parts. (bavarian auto for one). I'm sure Dave B has one.

[Farrar]

Disconnect the wiring from the control pressure regulator. Connect a voltmeter across the electrical connectors and operate the starter briefly -- there should be a minimum of 11.5 volts. Connect an ohmmeter across the regulator heater element terminals -- the resistance should be between 16 and 22 ohms.

Farrar

[DMCMW Dave]

.......the resistance should be between 16 and 22 ohms.

Farrar

That tells you if the heater works, which is not particularly important (if the heater completely fails the car will run slightly rich for maybe 5-10 minutes longer than it would if the heater was there, depending on ambient).

It does not tell you if the regulator itself is running at the wrong pressure, which is the more common problem. You can really only see that with pressure gauges.

[Farrar]

I figured he just wanted to know if it was alive or dead.

Farrar

[DeloreanJoshQ]

Must the warm-up regulator be tested when completely cold or can it be tested at any engine temperature? (I have to drive 25 min to Dave Bauerle's shop to use the tester)

Thanks for all of the help!

[Bitsyncmaster]

Must the warm-up regulator be tested when completely cold or can it be tested at any engine temperature? (I have to drive 25 min to Dave Bauerle's shop to use the tester)

Thanks for all of the help!

When the engine is cold the control pressure reads about 20 to 25 PSI and starts moving higher within a few seconds of running. After 2 or 3 min. control pressure settles out about 50 PSI. That low control pressure is what makes the cold engine run rich. If your warmed up mixture setting is not properly adjusted to run the FV about 30 % duty cycle that setting can make the cold (before closed loop) run to rich or to lean.

So first thing would be check the mixture warmed up via a dwell or duty cycle reading of the FV. Then if you still have the problem you need to verify your control pressure as the engine warms up.

Have you checked the filter screen on the WUR yet?

[DMCMW Dave]

To really test the warm-up function it needs to be overnight cold. As (other) Dave mentioned it goes through the warm-up phase pretty quickly, and once the thermal switch has cut off the vacuum the throttle enrichment is done too.

Typically a bad WUR does not cause a cold miss, more often a huge fall-on-your face bog until the car warms up. (it feels a car with a carb missing the accelerator pump). I think you are probably chasing the wrong ghost on this one.

[DeloreanJoshQ]

To really test the warm-up function it needs to be overnight cold. As (other) Dave mentioned it goes through the warm-up phase pretty quickly, and once the thermal switch has cut off the vacuum the throttle enrichment is done too.

Typically a bad WUR does not cause a cold miss, more often a huge fall-on-your face bog until the car warms up. (it feels a car with a carb missing the accelerator pump). I think you are probably chasing the wrong ghost on this one.

Where should I start looking to find the problem?

[Bitsyncmaster]

How do you test the warm up regulator? I am noticing during cold starts early in the morning the car has a slight miss at idle but once it warms up it is fine. Also, hot and warm starts are fine and it runs great at any temperature; it's just the cold miss at idle....


Thanks!

How long do you note the miss? What spark plugs do you have?

[DeloreanJoshQ]

How long do you note the miss? What spark plugs do you have?

If I let it warm up at idle only, about 5-10 minutes
Otherwise, I don't notice it once I take off and start driving; I am guessing it probably takes the same amount of time to smooth out.

Regarding plugs, they are Mighty brand.