# K-Jetronic and Air Density?



## xero (Jan 5, 2003)

Is there some sort of mechanism that allows basic K-Jetronic to allow for different air densities? At first I figured the plate would take care of that, but that's actually backwards to what the metering plate would do, hot air would move the plate more, thus injecting more fuel.
same with higher altitudes, air is less dense, so it'd require less fuel.
or is this one of the reasons why they use the lambda sensor?
I'm all confused now


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## antichristonwheels (Jun 14, 2001)

*Re: K-Jetronic and Air Density? (xero)*

you are thinking too much. CIS like many fuel systems does not compensate for air pressure or temp and it works quite well. with the o2 sensor there is compensation under closed loop conditions. I have used every version and I would still prefer CIS basic over all the others


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## epjetta (Sep 19, 2006)

*Re: K-Jetronic and Air Density? (xero)*

it pulls past an air flow plate. denser air lifts it more than thin air. it automatically compensates.


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## VDub2625 (Jan 4, 2003)

*Re: K-Jetronic and Air Density? (epjetta)*

There is actually an altitude sensor available in Europe. All US cars have the wiring for it but it's never hooked up. The 3 pin connector right by the ECU.
It has 3 pins, and of those, 2 are shared with the air flow potentiometer. I figure it's just a variable resistor that modifies what the ECU sees from the throttle pot.


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## EuroKid83 (Jan 26, 2005)

*Re: K-Jetronic and Air Density? (xero)*


_Quote, originally posted by *xero* »_Is there some sort of mechanism that allows basic K-Jetronic to allow for different air densities?

I would have to think because colder air is more dense (containing more oxygen) the O2 sensor would detect higher oxygen content in the exhaust during closed loop mode and compensate accordingly. If there's more oxygen going into the engine the fuel system will add more fuel to keep the A/F ratio in check. During WOT acceleration K-Lambda switches into open loop with a fixed duty cycle of 70% so any benefit of denser air will not be seen.


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## ABA Scirocco (May 30, 2001)

*Re: K-Jetronic and Air Density? (EuroKid83)*


_Quote, originally posted by *EuroKid83* »_
I would have to think because colder air is more dense (containing more oxygen) the O2 sensor would detect higher oxygen content in the exhaust 

The OP was asking about basic K-jet, IOW, there is no O2 sensor. But you're sort on the right track, cold air is denser so it exerts more force to the air metering plate causing it to move more thus (hopefully) providing the appropriate enrichment.


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## wclark (Mar 28, 2001)

*Re: K-Jetronic and Air Density? (xero)*

On the K-Jet, altitude compensation is done with thesame part as is used to cold start enrichment and extreme cold outside air enrichment...the WUR or control pressure regulator.
Thre is an aneroid chamber at the bottom of the regulator that acts to increase control pressure as atmospheric pressure decreases.
In cold temps and with a cold engine a bimetal arm in the WUR pushes against the valve spring which decreases the control pressure to richen the engine. That arm also has an electrical coil around it to warm it up faster than the warming engine block would and begin to lean the engine.


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## xero (Jan 5, 2003)

*Re: K-Jetronic and Air Density? (wclark)*


_Quote, originally posted by *wclark* »_Thre is an aneroid chamber at the bottom of the regulator that acts to increase control pressure as atmospheric pressure decreases.

excellent, I didn't see anything about that in the bosch manual, but maybe that's cause it doesn't specifically say anything about altitude.
http://****************.com/smile/emthup.gif


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## ABA Scirocco (May 30, 2001)

*Re: K-Jetronic and Air Density? (wclark)*


_Quote, originally posted by *wclark* »_There is an aneroid chamber at the bottom of the regulator that acts to increase control pressure as atmospheric pressure decreases.


I've disassembled a few CPRs, some have that but most do not. The diagram below shows the typical set-up.


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## chois (May 12, 2000)

The flapper is a mass air flow sensor. Mass of air is what is pertinent to fueling requirements. It thus automatically compensates for air density. Part of the simple beauty of the system.


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## EuroKid83 (Jan 26, 2005)

*Re: K-Jetronic and Air Density? (ABA Scirocco)*


_Quote, originally posted by *ABA Scirocco* »_
The OP was asking about basic K-jet, IOW, there is no O2 sensor. But you're sort on the right track, cold air is denser so it exerts more force to the air metering plate causing it to move more thus (hopefully) providing the appropriate enrichment.

Yeah there is no O2 sensor in CIS basic, basic K-Jetronic doesn't exist. The first version of CIS is called CIS basic, K-Jetronic came after CIS basic and is often referred to as K-Lambda. Denser/colder air is not going to lift the sensor plate any more than warm air does because its mass does not change. Air is air whether it's hot or cold. I could be wrong but I have no means of measuring the mass of air at different temperatures. Also because control pressure remains constant, the sensor plate is only gona lift so much depending on the volume of air flowing through it regardless of it's density.


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## ktm841 (Jan 4, 2008)

*Re: K-Jetronic and Air Density? (EuroKid83)*


_Quote, originally posted by *EuroKid83* »_
Yeah there is no O2 sensor in CIS basic, basic K-Jetronic doesn't exist. The first version of CIS is called CIS basic, K-Jetronic came after CIS basic and is often referred to as K-Lambda. Denser/colder air is not going to lift the sensor plate any more than warm air does because its mass does not change. Air is air whether it's hot or cold. I could be wrong but I have no means of measuring the mass of air at different temperatures. Also because control pressure remains constant, the sensor plate is only gona lift so much depending on the volume of air flowing through it regardless of it's density.

im not so sure that is true but i may be wrong. k-jetronic = basic cis. ke-jetronic = cis-e. and k-jetronic lambda was in between, basically k-jetronic with an 02 sensor.


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## VDub2625 (Jan 4, 2003)

*Re: K-Jetronic and Air Density? (ktm841)*

I always figured the K meant O2 sensor, and E meant electronic, so there was Jetronic, K-Jetronic, and KE-Jetronic.


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## turbinepowered (Mar 19, 2007)

*Re: K-Jetronic and Air Density? (VDub2625)*

L and E are oxygen sensor versions. K-Jetronic/CIS, KL-Jetronic/CIS-Lambda, KE-Jetronic/CIS-E. I've also seen CIS referred to as "K-Basic" and the lambda version as "K-Lambda."


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## EuroKid83 (Jan 26, 2005)

*Re: K-Jetronic and Air Density? (ktm841)*


_Quote, originally posted by *ktm841* »_
im not so sure that is true but i may be wrong. k-jetronic = basic cis. ke-jetronic = cis-e. and k-jetronic lambda was in between, basically k-jetronic with an 02 sensor. 

No K-Jetronic is CIS with lambda PERIOD. First there was CIS (which may or may not have been referred to as jetronic I'll have to check) then came K-Jetronic then KE-Jetronic and its variants. I've read/own enough books about CIS to know this for a fact. As the times and emissions standards changed Bosch integrated a oxygen sensor, frequency valve, and control unit to keep the AFR in check. With CIS-E they pretty much left everything from K-Lambda but they replaced the WUR with a coolant temp sensor and replaced the FV with the DPR. KE-Motronic was the most advanced version of CIS integrating both fuel and igniton timing maps. 


_Modified by EuroKid83 at 8:34 PM 3-5-2008_


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## VDub2625 (Jan 4, 2003)

*Re: K-Jetronic and Air Density? (EuroKid83)*

So an electronic control unit only exists with an oxygen sensor,.. and that ECU is called "Jetronic". That's weird, becuase the A2 bentley calls it jetronic even if it's an 8v without an OXS (like in the Canadian MZ engine).


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## ktm841 (Jan 4, 2008)

*Re: K-Jetronic and Air Density? (EuroKid83)*


_Quote, originally posted by *EuroKid83* »_
No K-Jetronic is CIS with lambda PERIOD. First there was CIS (which may or may not have been referred to as jetronic I'll have to check) then came K-Jetronic then KE-Jetronic and its variants. I've read/own enough books about CIS to know this for a fact. As the times and emissions standards changed Bosch integrated a oxygen sensor, frequency valve, and control unit to keep the AFR in check. With CIS-E they pretty much left everything from K-Lambda but they replaced the WUR with a coolant temp sensor and replaced the FV with the DPR. KE-Motronic was the most advanced version of CIS integrating both fuel and igniton timing maps. 

_Modified by EuroKid83 at 8:34 PM 3-5-2008_

well there is a k-jetronic version that used no o2 sensor. aka cis. at the same time, (i think) or at least roughly the same time, there was k-jetronic with lambda. aka cis and then later comes ke-jetronic. aka cis-e. 

_Quote, originally posted by *VDub2625* »_
So an electronic control unit only exists with an oxygen sensor,.. and that ECU is called "Jetronic". That's weird, becuase the A2 bentley calls it jetronic even if it's an 8v without an OXS (like in the Canadian MZ engine).


well there are like 10 versions of jetronic and i think the manual just calls pretty much all of them jetronic. and yeah its the name of the computer but also all the other components that go along with it


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## VDub2625 (Jan 4, 2003)

*Re: K-Jetronic and Air Density? (ktm841)*

There is one electronic component common to all the systems: the ignition controller. Don't know if that's VW or Bosch though.


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## DTDSasquatch (Aug 26, 2004)

*Re: K-Jetronic and Air Density? (EuroKid83)*


_Quote, originally posted by *EuroKid83* »_
No K-Jetronic is CIS with lambda PERIOD. First there was CIS (which may or may not have been referred to as jetronic I'll have to check) then came K-Jetronic then KE-Jetronic and its variants. I've read/own enough books about CIS to know this for a fact. As the times and emissions standards changed Bosch integrated a oxygen sensor, frequency valve, and control unit to keep the AFR in check. With CIS-E they pretty much left everything from K-Lambda but they replaced the WUR with a coolant temp sensor and replaced the FV with the DPR. KE-Motronic was the most advanced version of CIS integrating both fuel and igniton timing maps. 

_Modified by EuroKid83 at 8:34 PM 3-5-2008_

I think you read wrong. Have you read _How to Tune and Modify Bosch Fuel Injection_ by Ben Watson?
http://books.google.com/books?...P1,M1
K-Jetronic = CIS "basic"
K-Jetronic with Lambda = CIS + O2 sensor circuit
KE-Jetronic = CIS-E


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## DTDSasquatch (Aug 26, 2004)

*Re: K-Jetronic and Air Density? (DTDSasquatch)*


_Quote, originally posted by *DTDSasquatch* »_K-Jetronic = CIS "basic"
K-Jetronic with Lambda = CIS + O2 sensor circuit
KE-Jetronic = CIS-E

By the way, the "K" stands for "Kontinuierliche" which means "continuous".


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## ABA Scirocco (May 30, 2001)

*Re: K-Jetronic and Air Density? (DTDSasquatch)*

Copied from wikipedia.

_Quote »_
Jetronic is a trade name for a type of fuel injection technology marketed by Bosch from the 1960s forward.
K-Jetronic (1974-c.1988)
Mechanical fuel injection. The 'K' stands for 'Kontinuierlich', the German word for continuous. This is different from pulsed injection systems in that the fuel flows continuously from all injectors, whilst the fuel pump pressurises the fuel up to approximately 5 bar (72.5 psi). The air that is taken in is also weighted to determine the amount of fuel to inject. Commonly called 'CIS' (Continuous Injection System) in the USA. This system has no Lambda loop or lambda control. K-Jetronic was installed into a number of VAG, Ferrari and Ford cars.

K-Jetronic (Lambda)
A variant of K-Jetronic with closed-loop lambda control. Was developed to comply with Californian exhaust emission regulations, and later replaced by KE-Jetronic.

KE-Jetronic (c.1985-1993)
Electronically controlled mechanical fuel injection. The ECU may be either analog or digital, and the system may or may not have closed-loop lambda control. Commonly known as 'CIS-E' in the USA. The later KE3 (CIS-E III) variant features knock sensing capabilities.


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## EuroKid83 (Jan 26, 2005)

*Re: K-Jetronic and Air Density? (DTDSasquatch)*


_Quote, originally posted by *DTDSasquatch* »_
I think you read wrong. Have you read _How to Tune and Modify Bosch Fuel Injection_ by Ben Watson?

Yes I have that book, Looks like I'm gona have to refresh my memory a bit.


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## mdunman (Jul 29, 2008)

*Re: K-Jetronic and Air Density? (epjetta)*

hello, i have a 83 rabbit. suspension done, engine has be balanced and blueprinted, head ported and polished, and a 280 advertised duration with 0.440 lift. intake ported. 10.5 compression. header. the fuel injection appears to be stock? so, what is the scoop on megasquirt? thank you for your time.
best regards,
michael dunman


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## mdunman (Jul 29, 2008)

*Re: K-Jetronic and Air Density? (epjetta)*

also wanted to ask about the altitude sensor. would you recommend that it be added on american cars? i live in florida. thank you.
best regards, 
mike dunman


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## Dave926 (Mar 30, 2005)

*Re: K-Jetronic and Air Density? (VDub2625)*


_Quote, originally posted by *VDub2625* »_There is actually an altitude sensor available in Europe. All US cars have the wiring for it but it's never hooked up. The 3 pin connector right by the ECU.
It has 3 pins, and of those, 2 are shared with the air flow potentiometer. I figure it's just a variable resistor that modifies what the ECU sees from the throttle pot.

no ****...i always wondered what that was for


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