D-Jetro and L-Jetro

[Remix-]

Could someone please explain what the differences are between the two in the case of a L/D Jetro ECU configuration.

Thank you

[SteveL]

Could someone please explain what the differences are between the two..

Do you mean Bosch D-Jetronic vs L-Jetronic injection systems ??

D-Jetronic uses a MAP sensor to detect engine load and injectors are batch fired once per engine cycle (ie once per 2 engine revs) to give the fuel required for the next combustion cycle. Flow rate of injectors are therefore quite large. This system is found mainly on European cars of the early 70's (eg Volvo, Mercedes). Probably the first mass produced EFI system....but all analogue.

L-Jetronic uses an air flow metre (AFM), almost invariably the flap type. Injectors are batch fired twice per engine cycle (ie once per engine rev) each firing giving half the amount of fuel for the next combustion cycle. The L-Jet system is much more common than the D-Jet and pretty much the main stay of EFI systems up until the mid 80's or so when full digital systems started to take off (L-Jet is still analogue). Later versions used oxy sensors and had a form of error code read out.

A bit of trivia - 'D' is the first letter of the German word for pressure, while 'L' is the first letter of the German word for air (I think).

Hope that helps and was what you were after (there are other detail differences) - if not, sorry to waste your time

[R32-GTS]

I dont think hes talking about that somehow.

[IMACUL8]

Never the less very interesting read.

Dan

[foznice]

just a couple of questions...

Whats the map sensor, and engine mapping eg how does it work... etc etc (i know it's a noob question but I haven't read about it anywhere):

Injectors are batch fired twice per engine cycle (ie once per engine rev) each firing giving half the amount of fuel for the next combustion cycle.

what do you mean by batch fired? I guess it dosn't have anything to do with the individual cylinders firing because if cylinders fire twice per engine cycle that would make them 2stroke engines right?

[Cake]

i think that pretty much answer's the question

map = d-jetro

afm = l-jetro

[SteveL]

Whats the map sensor, and engine mapping eg how does it work... etc etc (i know it's a noob question but I haven't read about it anywhere):

MAP = Manifold Absolute Pressure sensor. In simple terms it measures vaccuum or pressure (from the turbo) in the inlet manifold - it's a measure of engine load. From this the ECU works out how long to fire the injectors to give the correct air-fuel ratio (well along with some other stuff...eg engine temp).

what do you mean by batch fired?

It means the injector are all fired together.

[SteveL]

Could someone please explain what the differences are between the two in the case of a L/D Jetro ECU configuration.

You've edited your OP but still haven't made it clear what it is your talking about. Clearly not what I was trying to explain.

[dangerous_daveo]

Maybe he means PFC?

[Remix-]

Basically I have heard that the HKS Fconv pro ECU can be used with either D-Jetro or L-Jetro setups. I want to know the differences between the two in detail

Cheers

[Remix-]

i think that pretty much answer's the question

map = d-jetro

afm = l-jetro

Cheers!

[Sydneykid]

Basically I have heard that the HKS Fconv pro ECU can be used with either D-Jetro or L-Jetro setups. I want to know the differences between the two in detail

Cheers

I have never heard that terminology used together, "Jetro" is a term used by Apexi and obviously the term "FCon" is HKS. A HKS FCon can be used for AFM or MAP, most I have seen use MAP. Most cars that arrive with Fcon have them removed as they are unknown here (except for one place in Sydney). Plus they need specialist software (and interface) to tune via a laptop. They don't have a Commander like Apexi Power FC.

If you intend to get the car tuned once and never make any other mods, then you could stick with the FCon. But it is risky, what happens if its tuned on a warm day and it doesn't run right on the first cold day, or in high humidity, or in traffic with aircon on a 40 degree day. What happens if BP or Shell come out with 100 octane? What happens if you have to change something because it fails? Or want to take advantage of that cheap pairs of cam you always wanted?

[discopotato03]

Bosch Automotive Electrical / Electronic systems manual (5/87) states -

Bosch K-Jetronic . Pure mechanical continuous injection system .

Bosch KE-Jetronic with electronic controls for extra functions and flexibility .

Bosch LE-Jetronic . Multi point electronic solenoid port fuel injection with vane or

flap type airflow sensing .

Bosch LU-Jetronic . As above with Lamda closed loop control (oxygen sensor) for

countries with strict emissions legislation ie USA .

Bosch L3-Jetronic . As above with ECU on air fow sensor (reduces cost of looms

and no ECU in passenger compartment) . Digital .

Bosch LH-Jetronic . Similar to last 3 but with hot wire air mass meter which

measures air mass inducted by the engine . The result of

measurement is thus independent of the air density which is

dependant upon temperature and pressure .

Bosch Motronic . this system combines both ignition and injection systems and

controls both electronically .

This covers the early Bosch injection systems .

Many feel that EFI load sensing via a hotwire mass airflow sensor gives a more accurate idea as to how much air an engine is breathing . Some prefer Manifold Absolue Pressure sensing but its a measure of pressure rather than airflow . Doing it this way requires complex temperature corrections as air temperature is directly related to air density . The way I see it to achieve a set air fuel ratio say 14.7 to 1 we need to mix 14.7 units of air by mass to one unit of fuel by mass . Another drama is competition type induction systems with one throttle per cylinder such as the GTR or GTiR etc . Getting a suitable pressure signal at low revs and not much more than small throttle openings is difficult .

To air pressure , its easy to use atmospheric pressure as a base line but lucky for us its not zero . Air pressure is generally measured in PSI-A (absolute) or PSI-G (gauge) . PSI absolute means zero is a total vacuum and anything above is positive pressure regardless of atmospheric pressure . PSI gauge assumes atmospheric pressure at sea level is ZERO , most compound boost gauges read like this . So these gauges read above and below atmospheric pressure . I find it hard to see the logic in a negative or below zero pressure but obviously once upon a time the powers that be though otherwise .

Cheers A .

[SteveL]

This covers the early Bosch injection systems .

It's missing D-jetronic.....

But none of this is relevant.

[discopotato03]

Just for laughs did a search on D-Jetronic , was developed in the early 1960's and the first form of OEM EFI using some Bendix technology . The speed density system it used was very different to the Delco ones in Vomit Doors and Camiras . It had a flip flop style switching system incorporated into its soft ball sized MAP unit and fired its injectors in groups of two . The distributor had a couple of sets of points in its base as well just to confuse things . It was used in some early Mercedes Benzes Porsches and Type Three Dack Dacks (V Dubs) and other things no doubt .

I doubt very much if AP Engineering copied anything off D-Jetronic to develop D-Jetro .

Cheers A .

[SteveL]

I doubt very much if AP Engineering copied anything off D-Jetronic to develop D-Jetro

No-one is suggesting they did.....as I said it's not relevant.

If you want to be accurate about D-Jet, it was first used on experimental cars in 1959 but didn't see line production until 1967 when it appeared on VW Type III 1600 passenger cars manufactured for the US market. It was an attempt by VW to meet ever more stringent emission standards (yes, even back then). It actually exceeded expectations plus gave improved fuel consumption and driveability.

I have a copy of the research paper by the then Chieff Engineer of automotive products at Robert Bosch describing system development, etc

FWIW I fitted the D-Jet system from a Volvo 164E to a C210 Skyline running an L28 in the late seventies. It ran reliably and well for a few years until I got an R30. Certainly a vast improvement over the carb'd crap available at the time.

This is getting waaaay OT.

Sorry to gtr90 for hijacking the thread.