K-jetronic systems.A little more in depth.LARGE!
Verfasst: 12. Okt 2005, 01:56As i know that..this stuff is more or less black art to most people..
I´ll try n explain the basis of the K/KE-jet(as they´re based on the same principle)to let you all in what goes where and why...
First of all.
NO engine in the world..can stand on its own without spark,so..before TOUCHING ANYTHING fuel...ALWAYS check tune of spark first.
That said..
The "K" series injections are really mechanical by design.
Even so the KE units in our 16 valve cars.
Fuel gets injected over mechanically controlled injectors.However,the injectors per se does NOT control the amount of
fuel delivered as its modern day era electronically controlled counterpart.
THe K series injector basically controls spray pattern,and that´s it.
Within the injector there is sort of a pressure valve that keeps fuel from going the wrong way.
The control pressure normaly hoovers around 3bar+ mark.
Fuel gets drawn from the fuel tank of the car.
Either,by a prepump within the tank,or by simple means of gravity.
No matter how,the fuel is fed to the main pump.The main pumps of K series injections are normaly referenced at 5 bars of pressure,
and what´s more it is one of the more powerful pumps of the injection era to this day.
The K series pumps used on our cars will suffice for a stand alone EFI system that is normaly referenced at or around 3 bars
to in excess of 500 horsepower on the 10mm fuel lines in the car-just to give you an idea.
In close proximity of the pump there´s an accumulator.
This accumulators purpose is simply to even out the pressure pulses induced to the pressure side of the system by the pump.
Accumulators are normaly an item that either works or they don´t.
The accumulator per se is simply a spring(pressure)loaded chamber that has a rubber diaphragm as a separator,and when the accumulator
is at fault...one will notice it leaking.Fuel..so be aware.
Thereafter the fuel reaches an ample filter.
Filter is speced in microns,and the K system unit i´d go on record and say is even more delicate than its current crop electric
counterpart.
Reason..is that the orifices found within the K series injections are VERY acute and fairly small(On some models down to 16/100mm)
After the filter,the fuel is shoved towards the main metering unit.
It reaches the metering unit-which on the 16V by definition is the aluminium part ontop of the main metering housing.
The one that sports in our case 4 steel hardlines running from it to each injector.
The metering units main parts are;
Lower housing.
Upper housing.
Plunch and metering cylinder.
Also found within the housing parameters are the system fuel pressure valve,and inside the lower housing part load setting valves.
The fuel reaches the lower housing first.
Via a set of drillings between the chambers,each and every "channel" is reached by fuel-that eventually reaches each and every injector.
That means..that the fuel for respective cylinder is divided already at this stage.
The fuel rushes onwards(towards the center of the unit) to reach the metering cylinder.
THIS...THIS...is where the K series injections are known to be of extreme accuracy.
The metering cylinder openings are cut to minute tolerances on an electronic bridgeport for the lack of better description.
For those of you that are engineers..you know what this means,and the so called Ra..is down to extreme decimals.
Reason..is really calibration.
Each and every opening has the form of an elongated slot.See picture
And as the plunch within the metering cylinder moves up and down per movement of the fabled "flap" in the intake system,more or less
of each elongated slot will be free of obstruction for the fuel to pass.See picture.
That means..that the higher the "flap" in the intake by mechanical control lifts the plunch,the more fuel mass can trickle through
each slot for each cylinder-rendering more fuel towards the injectors.
As genius as it´s simple..
This ALSO means...that the amount of fuel that reaches the injectors are met here.Right at the metering cylinder.More..on this later tho..
Here...the saga could really have been to an end weren´t it for the mere fact of that an engines vaccum(sub atmosphere really)
fluctuates to say the least.(It pulses)
That would mean...
That the pressure excerted on the "flap" in the intake tract that really controls it all by a mechanical arm...
would start to swerge by its own motion,and the more it would-the more such movement it would induce.
Ergo.
We need some way to control the PLUNCH movement.
Enter...counterpressure.
By excerting counterpressure ONTOP of the plunch..we can keep the plunch from letting the pressure from the "flap" make it jump all over
the place.
The device...is to the english speaking crowd know as an EHA(Electro hydraulic activator) for the KE guys and a WUR
(varm up regulator) for the K guys.
They both..basically do the same thing.
By simple means of electronics,or in the case of the K system a bimetallic spring,the counterpressure is varied dependant on primarily
temperature.
In the case of the KE units..the counterpressure is also dependant of load-amongst other things.(this is what all those sensors
try and keep track of)
That said..
From a practical standpoint?
What can,and from time to time NEEDS,to be adressed?
Well,most have at one time or another surely seen the CO adjustment.
The little 3mm allen(insex) that control where the plunger will be set to rest,and that as such controls the ENTIRE fuel amount
-or more to the point how much relative lift we´ll get out of the plunch in its cylinder.
Apart from that tho...what can be done?
The adjustment of counterpressure...
In the case of the KE units this is set at the little black "thingy" that´s on the drivers side of the main metering unit.
It´s easy to recognize as it has a 2 point electric connector leading to it.
The current over those two wires is what it controlled by all the other electronics and pickups all around the engine bay.
None the less...there is a static setting made to the EHA as well.
The EHA is fastened to the metering housing by two stainless torx headed bolts(Tx 25 or 30 if memory serves me)
When you unbolt the EHA and flip it over you´ll see a brass screw on its backside.
This,is simply a plug because underneath there´s the static set screw for the EHA.
That set screw..is individualy set to each EHA,and..the point is that altho sensitive..they´ve been set with enviromental control in mind
Ie;there´s power to be had by playing around with it a little.
NB!Be VERY anal about using a screwdriver that really FITS in the screws slot.The screw is made out of brass,and easily distorts
if the wrong size is used.NB!
Set screw is a 2mm allen(insex)
Any and all FIRST adjustment is done by turning the screw CLOCKWISE as this will REDUCE counterpressure.
1/4 of a turn is plenty.
NB!!!After each and EVERY adjustment of the EHA the basis CO setting HAS to be reset.NB!
Per OEM Mercedes specs..shoot for the 1% CO level-or at least thereabouts.
What will this induce behaviourwise on the engine then?
Mainly the reduced counterpressure will let the engine to a more heavy duty acceleration enrichment,and hand on heart..
What is it these cars REALLY lacks in comparison with a modern day era engine?
It is my findings tho that you seldom need to turn the setscrew in by more than half a turn on ANY engine.
Alright.
That little trick right there might be all good and well,but what if you need fuel for a hotrodded engine?
Well..basically you need to
1/Crank the system pressure up.
You do this by shimming the pressure valve within the lower part of the metering housing.See picture.
The OEM recomendation is for approx 5,5 bar.
The truth is that a KE-jet with a couple a yrs of use ALWAYS respond well to even higher system pressures.
Main reason is that it´ll clean up the spray pattern at the same time as delivering more fuel.
In other words..don´t be afraid to increase system pressure in excess of 6 bar even on a stocker.
I´ve more often than not..touched down around 6-6,5 bars to get older systems to work as intended.
System pressure valve;
2/The lesser the counterpressure(again play around with the EHA-but to a larger degree),the more the fuel-TO A CERTAIN LIMIT!
Sooner or later..you´ll hit the wall for how much fuel those slots in the cylinder can pass(Slots btw are either 16/100 of a
mm wide for the 1600cc era engines,and 2/10s of a mm for the 2-2,5 liter ones.
This "wall" is normally seen at or around the 230-235hp mark for the "large" K series metering cylinders.
In other words,the metering cylinder needs to be adressed.
There ARE those -apart from Bosch gmbh-that claims to have had success at modifying the cylinder slots.I am sure as hell
not one of them.
I for one have run slots that look like damn mushrooms back when the K series where the only thing we had to work with.(Turbo cars)
We got them to deliver power alright,but the problem was that we could NEVER get the counterpressure to balance to an extent
that we by todays standards would view it as tolerable.In other words it was OUR findings that modifications like that made
the car more or less undriveable.
In other words..the housing per se can deliver the air alright..but..if you´re into tuning per the stock idea i´d use an ad on controller
a´la the old microdynamics PIC 5 or similar for the needed extra fuel.
Heavily modified K-jet housing for turbo Porsche,to flow more air as it was indeed needed.
Alright.
On to what might be of much use for the average Joe whos KE unit has broken down then.
What are the things to check?
Problem;
1/No matter WHAT you need to do..you HAVE to have some sort of digital multimeter around(DMM).
Without it...any further fault diagnosis is pointless.
If fuel economy is out the door...start by checking the resistance values of the temp sensor.
This if found at the front of the engine in the thermostat housing.
It is normally green to the colour,and has TWO connection towers.
Values..can easily be looked up in any manual.
2/AFTER having checked that,check and adjust CO level per specs against a CO machine.
3/If that doesn´t help-check the EHA for correct resistance.
If not..you need a new unit,and what´s more..sorry guys-but it´s 16V specific.
In other words..you´re out some serious cash.
Problem;
Hesitation.
The engine..will not take the gas when you use the throttle.
K.
First thing-again-is to check the CTS(coolant temperature sensor)
If that checks out,the next thing is a little more involved.
On the opposing side of the EHA on the metering hosuing there´s a rectangular little black plastic thingy.
This..is the airflow mass meter.
Its innards are basically a mechanicaly-by an arm-variable resistor.
What one does..is to flip the lid of the connector open(this takes a little patience and some SMALL tools),
to be able to measure the output voltage.
THere are three poles.
One..is the drive voltage
One is ground.
..and the last one is output voltage for the EHA control unit by the battery.
Dismantle the airfilter box.
Turn the ignition on.
Measure the output voltage with the engine TURNED OFF.
By spec you´re to depress the flap until the upper surface of it is in line with the lowest part of the air cone
on the housing.
If memory serves me there+s supposed to be something like 0,6 volts at that stage.
SLOWLY depress the flap with your hand.
If you at ANY stage see the voltage disappear or drop...that there sensor is kaputt.
A..replacement is in order,and again...hard cash..
I guess you by now see where i´m going with all of this..
A KE-jet unit that is giving you trouble can easily put you in the poor house.
So..if and when it starts to give you REAL trouble..just give the idea of an aftermarket stand alone
injection system some thought at least..
What´s worse..is that even if you DO invest hard earned cash into the KE jet..it´ll sooner or later kick right
back at you again..
An EFI..can easily be remedied by the mere use of your own lap top..over and over..
Likewise you will NEVER get a KE or K jet to have the amount of adjustment points an EFI has.
Not in a million years.
That said..
If..you happen to be amongst those that need help-apart from understanding what i´ve written above..
Let me know.
However..seing that YOUR KE-jet system by now is reaching at LEAST 15 yrs of age..don´t be surprised if
i sound a little like..."just toss it out of there and install an EFI already" kind a guy
Jesper
I´ll try n explain the basis of the K/KE-jet(as they´re based on the same principle)to let you all in what goes where and why...
First of all.
NO engine in the world..can stand on its own without spark,so..before TOUCHING ANYTHING fuel...ALWAYS check tune of spark first.
That said..
The "K" series injections are really mechanical by design.
Even so the KE units in our 16 valve cars.
Fuel gets injected over mechanically controlled injectors.However,the injectors per se does NOT control the amount of
fuel delivered as its modern day era electronically controlled counterpart.
THe K series injector basically controls spray pattern,and that´s it.
Within the injector there is sort of a pressure valve that keeps fuel from going the wrong way.
The control pressure normaly hoovers around 3bar+ mark.
Fuel gets drawn from the fuel tank of the car.
Either,by a prepump within the tank,or by simple means of gravity.
No matter how,the fuel is fed to the main pump.The main pumps of K series injections are normaly referenced at 5 bars of pressure,
and what´s more it is one of the more powerful pumps of the injection era to this day.
The K series pumps used on our cars will suffice for a stand alone EFI system that is normaly referenced at or around 3 bars
to in excess of 500 horsepower on the 10mm fuel lines in the car-just to give you an idea.
In close proximity of the pump there´s an accumulator.
This accumulators purpose is simply to even out the pressure pulses induced to the pressure side of the system by the pump.
Accumulators are normaly an item that either works or they don´t.
The accumulator per se is simply a spring(pressure)loaded chamber that has a rubber diaphragm as a separator,and when the accumulator
is at fault...one will notice it leaking.Fuel..so be aware.
Thereafter the fuel reaches an ample filter.
Filter is speced in microns,and the K system unit i´d go on record and say is even more delicate than its current crop electric
counterpart.
Reason..is that the orifices found within the K series injections are VERY acute and fairly small(On some models down to 16/100mm)
After the filter,the fuel is shoved towards the main metering unit.
It reaches the metering unit-which on the 16V by definition is the aluminium part ontop of the main metering housing.
The one that sports in our case 4 steel hardlines running from it to each injector.
The metering units main parts are;
Lower housing.
Upper housing.
Plunch and metering cylinder.
Also found within the housing parameters are the system fuel pressure valve,and inside the lower housing part load setting valves.
The fuel reaches the lower housing first.
Via a set of drillings between the chambers,each and every "channel" is reached by fuel-that eventually reaches each and every injector.
That means..that the fuel for respective cylinder is divided already at this stage.
The fuel rushes onwards(towards the center of the unit) to reach the metering cylinder.
THIS...THIS...is where the K series injections are known to be of extreme accuracy.
The metering cylinder openings are cut to minute tolerances on an electronic bridgeport for the lack of better description.
For those of you that are engineers..you know what this means,and the so called Ra..is down to extreme decimals.
Reason..is really calibration.
Each and every opening has the form of an elongated slot.See picture
And as the plunch within the metering cylinder moves up and down per movement of the fabled "flap" in the intake system,more or less
of each elongated slot will be free of obstruction for the fuel to pass.See picture.
That means..that the higher the "flap" in the intake by mechanical control lifts the plunch,the more fuel mass can trickle through
each slot for each cylinder-rendering more fuel towards the injectors.
As genius as it´s simple..
This ALSO means...that the amount of fuel that reaches the injectors are met here.Right at the metering cylinder.More..on this later tho..
Here...the saga could really have been to an end weren´t it for the mere fact of that an engines vaccum(sub atmosphere really)
fluctuates to say the least.(It pulses)
That would mean...
That the pressure excerted on the "flap" in the intake tract that really controls it all by a mechanical arm...
would start to swerge by its own motion,and the more it would-the more such movement it would induce.
Ergo.
We need some way to control the PLUNCH movement.
Enter...counterpressure.
By excerting counterpressure ONTOP of the plunch..we can keep the plunch from letting the pressure from the "flap" make it jump all over
the place.
The device...is to the english speaking crowd know as an EHA(Electro hydraulic activator) for the KE guys and a WUR
(varm up regulator) for the K guys.
They both..basically do the same thing.
By simple means of electronics,or in the case of the K system a bimetallic spring,the counterpressure is varied dependant on primarily
temperature.
In the case of the KE units..the counterpressure is also dependant of load-amongst other things.(this is what all those sensors
try and keep track of)
That said..
From a practical standpoint?
What can,and from time to time NEEDS,to be adressed?
Well,most have at one time or another surely seen the CO adjustment.
The little 3mm allen(insex) that control where the plunger will be set to rest,and that as such controls the ENTIRE fuel amount
-or more to the point how much relative lift we´ll get out of the plunch in its cylinder.
Apart from that tho...what can be done?
The adjustment of counterpressure...
In the case of the KE units this is set at the little black "thingy" that´s on the drivers side of the main metering unit.
It´s easy to recognize as it has a 2 point electric connector leading to it.
The current over those two wires is what it controlled by all the other electronics and pickups all around the engine bay.
None the less...there is a static setting made to the EHA as well.
The EHA is fastened to the metering housing by two stainless torx headed bolts(Tx 25 or 30 if memory serves me)
When you unbolt the EHA and flip it over you´ll see a brass screw on its backside.
This,is simply a plug because underneath there´s the static set screw for the EHA.
That set screw..is individualy set to each EHA,and..the point is that altho sensitive..they´ve been set with enviromental control in mind
Ie;there´s power to be had by playing around with it a little.
NB!Be VERY anal about using a screwdriver that really FITS in the screws slot.The screw is made out of brass,and easily distorts
if the wrong size is used.NB!
Set screw is a 2mm allen(insex)
Any and all FIRST adjustment is done by turning the screw CLOCKWISE as this will REDUCE counterpressure.
1/4 of a turn is plenty.
NB!!!After each and EVERY adjustment of the EHA the basis CO setting HAS to be reset.NB!
Per OEM Mercedes specs..shoot for the 1% CO level-or at least thereabouts.
What will this induce behaviourwise on the engine then?
Mainly the reduced counterpressure will let the engine to a more heavy duty acceleration enrichment,and hand on heart..
What is it these cars REALLY lacks in comparison with a modern day era engine?
It is my findings tho that you seldom need to turn the setscrew in by more than half a turn on ANY engine.
Alright.
That little trick right there might be all good and well,but what if you need fuel for a hotrodded engine?
Well..basically you need to
1/Crank the system pressure up.
You do this by shimming the pressure valve within the lower part of the metering housing.See picture.
The OEM recomendation is for approx 5,5 bar.
The truth is that a KE-jet with a couple a yrs of use ALWAYS respond well to even higher system pressures.
Main reason is that it´ll clean up the spray pattern at the same time as delivering more fuel.
In other words..don´t be afraid to increase system pressure in excess of 6 bar even on a stocker.
I´ve more often than not..touched down around 6-6,5 bars to get older systems to work as intended.
System pressure valve;
2/The lesser the counterpressure(again play around with the EHA-but to a larger degree),the more the fuel-TO A CERTAIN LIMIT!
Sooner or later..you´ll hit the wall for how much fuel those slots in the cylinder can pass(Slots btw are either 16/100 of a
mm wide for the 1600cc era engines,and 2/10s of a mm for the 2-2,5 liter ones.
This "wall" is normally seen at or around the 230-235hp mark for the "large" K series metering cylinders.
In other words,the metering cylinder needs to be adressed.
There ARE those -apart from Bosch gmbh-that claims to have had success at modifying the cylinder slots.I am sure as hell
not one of them.
I for one have run slots that look like damn mushrooms back when the K series where the only thing we had to work with.(Turbo cars)
We got them to deliver power alright,but the problem was that we could NEVER get the counterpressure to balance to an extent
that we by todays standards would view it as tolerable.In other words it was OUR findings that modifications like that made
the car more or less undriveable.
In other words..the housing per se can deliver the air alright..but..if you´re into tuning per the stock idea i´d use an ad on controller
a´la the old microdynamics PIC 5 or similar for the needed extra fuel.
Heavily modified K-jet housing for turbo Porsche,to flow more air as it was indeed needed.
Alright.
On to what might be of much use for the average Joe whos KE unit has broken down then.
What are the things to check?
Problem;
1/No matter WHAT you need to do..you HAVE to have some sort of digital multimeter around(DMM).
Without it...any further fault diagnosis is pointless.
If fuel economy is out the door...start by checking the resistance values of the temp sensor.
This if found at the front of the engine in the thermostat housing.
It is normally green to the colour,and has TWO connection towers.
Values..can easily be looked up in any manual.
2/AFTER having checked that,check and adjust CO level per specs against a CO machine.
3/If that doesn´t help-check the EHA for correct resistance.
If not..you need a new unit,and what´s more..sorry guys-but it´s 16V specific.
In other words..you´re out some serious cash.
Problem;
Hesitation.
The engine..will not take the gas when you use the throttle.
K.
First thing-again-is to check the CTS(coolant temperature sensor)
If that checks out,the next thing is a little more involved.
On the opposing side of the EHA on the metering hosuing there´s a rectangular little black plastic thingy.
This..is the airflow mass meter.
Its innards are basically a mechanicaly-by an arm-variable resistor.
What one does..is to flip the lid of the connector open(this takes a little patience and some SMALL tools),
to be able to measure the output voltage.
THere are three poles.
One..is the drive voltage
One is ground.
..and the last one is output voltage for the EHA control unit by the battery.
Dismantle the airfilter box.
Turn the ignition on.
Measure the output voltage with the engine TURNED OFF.
By spec you´re to depress the flap until the upper surface of it is in line with the lowest part of the air cone
on the housing.
If memory serves me there+s supposed to be something like 0,6 volts at that stage.
SLOWLY depress the flap with your hand.
If you at ANY stage see the voltage disappear or drop...that there sensor is kaputt.
A..replacement is in order,and again...hard cash..
I guess you by now see where i´m going with all of this..
A KE-jet unit that is giving you trouble can easily put you in the poor house.
So..if and when it starts to give you REAL trouble..just give the idea of an aftermarket stand alone
injection system some thought at least..
What´s worse..is that even if you DO invest hard earned cash into the KE jet..it´ll sooner or later kick right
back at you again..
An EFI..can easily be remedied by the mere use of your own lap top..over and over..
Likewise you will NEVER get a KE or K jet to have the amount of adjustment points an EFI has.
Not in a million years.
That said..
If..you happen to be amongst those that need help-apart from understanding what i´ve written above..
Let me know.
However..seing that YOUR KE-jet system by now is reaching at LEAST 15 yrs of age..don´t be surprised if
i sound a little like..."just toss it out of there and install an EFI already" kind a guy
Jesper
?
..
bei all der anfettung bleibt aber wieder eine frage: regelt die lambdasonde nicht dagegen und kompensiert einen teil der anfettung? gut.. bei vollgas hat sie auch keine einflussmöglichkeit mehr, das darf man auch nicht vergessen..
)........wahrscheinlich gibt es noch mehr Gründe, bin nicht der Spezialist, hab mich nur in Selbstversuchen geübt 
Immer die ursprüngliche Grundstellung des Stellgliedes im Auge behalten, damit man notfalls auf Nullstellung zurück kann 
