Variable resistor (adjustable)

[The Mechanic]

Many of you GSer's may have seen a thread about fitting a resistor into the ECU circuit to produce a change in the fuel /air ratio.

I used to own (sometime ago now I hasten to add) a Toyota MR2 Mk1, this delightful little roller skate stuck to the road like sh and one t to a blanket, went like hot poop and best of all had fitted courtesy of Mr. Toyota an adjustable (variable) resistor housed in a neat little housing with an access hole for a screwdriver blade to alter the mixture from lean to rich to suite your driving/altitude/mood etc. It was sited on the rear of the engine bay bulkhead, its size is a very bike friendly 30 mm x 15 mm and the wires are in a neat little plastic loom sheath.

The same engine control system was fited to the Toyota Corolla(?) GTI 1.6 now some of these things will have made it to the scrap yard by now and I'm sure that there is someone out there in GS land clever enough to wire one of these dinky little resistor housings into the ECU loom of a GS. Hey presto adjustability for about a fiver.

NB Lambda etc altered/removed etc.

Possibly Radio Shack can supply a similar device cheaply to but not quite as weather proof.

Ideas and comments before I set up shop flogging my own alternative to the Dyno-Clusion people. Hey I could call it The Powertech #1

 

[Steve]

Ideas and comments before I set up shop flogging my own alternative to the Dyno-Clusion people. Hey I could call it The Powertech #1

If it works, and costs less than a tenner, including set-up, I'll take one...

 

[Rob Farmer]

Any idea on the resistor value?

 

[Rob Farmer]

Mechanic,

If you have a technical spec for the lamba probe I can source weather proof variable resistors for £2 to £3 each. The operating range of the resistor would have to match the probes; but there are always ways round this.

 

[Rob Farmer]

Just done a bit of research on Lamba sensors...this is taken from my source:

(quote)
The exhaust gas oxygen sensor (EGO or O2), or lambda sensor, is the key sensor in the engine fuel control feedback loop. The computer uses the O2 sensor's input to balance the fuel mixture, leaning the mixture when the sensor reads rich and richening the mixture when the sensor reads lean.

Lambda sensors produces a voltage signal that recognises the amount of unburned oxygen in the exhaust. An oxygen sensor is essentially a battery that generates its own voltage. When hot (at least 250 degrees c.), the zirconium dioxide element in the sensor's tip produces a voltage that varies according to the amount of oxygen in the exhaust compared to the ambient oxygen level in the outside air. The greater the difference, the higher the sensor's output voltage.

Sensor output ranges from 0.2 volts (lean) to 0.8 volts (rich). A perfectly balanced or "stoichiometric" fuel mixture of 14.7 parts of air to 1 part of fuel gives an average reading of around .45 volts.

The lambda sensor's output voltage doesn't remain constant, however. It flip-flops back and forth from rich to lean. Every time the voltage reverses itself and goes from high to low or vice versa, it's called a "cross count." A good O2 sensor on a injection system should fluctuate from rich to lean about 1 per second. If the number of cross counts is lower than this, it tells you the O2 sensor is getting sluggish and needs to be replaced.

Most lambda sensors will cycle from rich to lean in about 50 to 100 milliseconds, and from lean to rich in 75 to 150 milliseconds. This is referred to as the "transition" time. If the O2 sensor is taking significantly longer to reverse readings, this too is an indication that it is getting sluggish and may need to be replaced.

Observing the sensor's waveform on a scope is a good way to see whether or not it is slowing down with age. If the sensor becomes sluggish, it can create hesitation problems during sudden acceleration.

(end quote)

So...

It would be a bit more difficult than just putting a potentiometer into the circuit. I can easily produce a circuit that gives an output of 0.2 to 0.8 volts and is set by an adjustable potentiometer on the handlebars...but who is going to test it? I've got an 1100 so theres no probe on mine. If you want to give it a go just let me know.

 

[Rob Farmer]

A bit more research show that some Vauxhauls are fitted with Titania Oxygen Sensors, these sensors vary there resistance according to the air mixture; low resistance (less than 1000 ohms) when the mixture is rich to high resistance (over 20,000 ohms) when the mixture is lean.

I presume that this is the sensor type fitted to the older Toyotas, allowing them to have a simple potentiometer installed to adjust the mixture.

Interesting to see that the life expectancy of a Lamba probe (any type) is only 30,000 to 50,000 miles and can be considerably less if subjected to contamination.

 

[Panzer Patrol]

Good discussion guys but, the way I see it, the moronic system runs with two settings. Open loop and closed loop. The car systems may be very different.

Closed loop is for tickover and very light throttle openings.

Open loop is where it follows a pre-determined map on the chip.

So at tickover the lambda sensor comes into play and adjusts the mixture. As soon as you open the throttle it trips into closed loop and the lambda sensor is ignored. The engine then follows the mapping on the chip for fuel at that throttle setting.

If I am right, then it follows on that any form of adjuster on the closed loop side will only affect tickover and very light throttle openings. The gizmo on the car may have been to fine tune tickover. In other words give a manual adjustment for atmospheric pressure (if you live up in the mountains or down on the coast).


What do you think

 

[Rob Farmer]

Panzer,

Do you know for sure that it runs open loop above tickover? from the previous discussions I've seen it appears to be just an assumption. I don't know enough about engine management systems to be able to say that they do or do not.
I was searching around for books and documentation on the Motronic system, but it seems very scarce. A Lamba probe seems a lot of trouble and expense to go to just to get a lean mixture at tickover when they could have stuck with the 1100s 'Pot' and just set it lean.
The Motronic has a pressure sensor inside that compensates for atmospheric pressure and this has an influence on the system, so why not the Lamba?

 

[Rob Farmer]

I've been on Amazon.co.uk.

Motronic Engine Management: Engine Management for Spark-Ignition Engines : Technical Instruction : Edition 94/95

Availability: we are currently unable to offer this title. It may be out of stock with the publisher or out of print. If you would like to purchase this title, we recommend that you occasionally check this page to see if it has become available.




Edition: Paperback


More Product Details


--------------------------------------------------------------------------------


Product Details:


Paperback (1 January, 1999)
Publisher: Robert Bentley; ISBN: 0837604710
Category(ies): Reference & Languages

Amazon.co.uk Sales Rank: 406,687

Does anybody have this book and want to sell it to me? or know where I can get it.

 

[Steve]

I've been on Amazon.co.uk.

Motronic Engine Management: Engine Management for Spark-Ignition Engines : Technical Instruction : Edition 94/95

The US site says 3 - 5 weeks, but it's probably still not available.

It's no longer listed by the publishers either....

www.bentleypublishers.com

 

[The Mechanic]

Injection info

Due to my job I have in my collection and at my disposal from other colleagues resources, most of the Bosch publications on Motronic et al; plus a great many other manufacturers technical instruction and introductory publications. Unfortunately I have to abide by a copyright license so I can't just put things out to the public or closed forums, but I'll see what I can do from another angle.

As I've said in the past, I have to teach this stuff at all levels of competency for a living, that is why from time to time you will see my two pennies worth shoved in on this site.


It would be entirely possible to trick the ECU, the Lambda sensor signal and the air temp sensor by the use of various resistors however; the ECU has still got the same fuelling map (chip) and when it reaches the limit of that map in either scale (lean or rich) it can make no further control adjustments. The Techclusion and the Power Commander provide different fuelling maps with/without ignition maps as well. They may well interrupt the injection signal and the Lambda signal voltage but I believe the Power commander is more refined and accurate (personal belief).

A company who I'm sure some of you may have heard of called 'Superchips' actually interrogate the fuel and ignition chip(s) and then reprogramme them to provide a better map (this map is a 3 dimensional graph). By putting more reference points onto the map or by altering the existing reference points more power, or economy or whatever is required can be extracted from a particular engine. The ECU works like any other computer and obviously these maps are in reality binary numbers or look-up tables. In effect the ECU has now a bigger choice of/range of adjustments.

By running an engine hooked up to the necessary kit and being able to acces the binary read-out, just by knocking off a number from one line and observing the effect and then changing that number may mean the engine stops, increases revs or whatever but this is what goes on I'm told. As the ECU on the BMW is sealed then the Techclusion etc is the most effective way of obtaining the desired result. Buy an Aprilia Racing and it comes with a different chip for the race can fitment. Buy a Ducati and the same thing applies.

When the warranty period expires for my bike (03 1150GS Blue...so its faster than a silver or graphitan etc) I'll be buggering about with all sorts of gizzmos. Until then I happy to read everyone else's reports.

Spoke yesterday to man with very busy Dyno, who fits Remus cans and Y piece to lots (lots?) of BMW's says the 1150 GS should be perfectly alright without any further mods. Just watch the response to that comment.

 

[Steve]

Re: Injection info

Spoke yesterday to man with very busy Dyno, who fits Remus cans and Y piece to lots (lots?) of BMW's says the 1150 GS should be perfectly alright without any further mods. Just watch the response to that comment.

Well, that's what I'd always been led to believe as well. Steve Rose of RiDE mag fitted the Y and race can, then had it dyno'd. According to him, or rather the dyno, the fuelling was supposedly perfect.

 

[Panzer Patrol]

Hi Rob,

The point I made was just my assumption (the way I see it) I made the assumption from the various bits of research I have made on the subject, but I DONT KNOW FOR CERTAIN. Thats why I ended the post with what do you think? Someone out there must be able to nail this one.

Mechanic seems to be a very knowledgeable guy in this area so, Mechanic, does the moronic run like this?????

Closed loop is for tickover and very light throttle openings.

Open loop is where it follows a pre-determined map on the chip.

So at tickover the lambda sensor comes into play and adjusts the mixture. As soon as you open the throttle it trips into closed loop and the lambda sensor is ignored. The engine then follows the mapping on the chip for fuel at that throttle setting.

Excellent thread

 

[simonm]

Re: Injection info

Due to my job I have in my collection and at my disposal from other colleagues resources, most of the Bosch publications on Motronic et al; plus a great many other manufacturers technical instruction and introductory publications.

Top quality thread.
Across the pond on advrider there are people who would sell their granny for that info
See here and also here

Simon

 

[Dave Barrett]

Still here on the sidelines

Although I've not posted for ages, I still look on the BB from time to time, and felt that I had to comment on this one.

As Rob Farmer posted, the Lambda sensor informs the ECU (Electronic Control Unit) about the level of Oxygen in the exhaust, by sending it either a self-generated voltage signal (Zirconia type) or by modifying a voltage sent to it from the ECU (Titania type).

The whole concept is based on the fact that if the air/fuel ratio is lean, there will be too much Oxygen in the resulting exhaust gas, procucing a low (or high, depending on the system) Lambda sensor voltage to the ECU. When this happens, the ECU makes the air/fuel ratio richer. Following this action, the resultant exhaust gas has zero Oxygen content, therefore the Lambda sensor sends a High (or low) voltage signal back. Consequently, the ECU make the air/fuel ratio leaner and the whole proces starts again.

The above process is the Closed loop system, i.e. the loop between the Lambda Sensor signal and the resulting fuel mixture is always being controlled by the ECU. This system is fine for normal operation, but under certain circumstances works against you.

The best example is under hard acceleration. When you whack the throttle open, air flow is suddenly increased and the correct response should be to inject as much fuel as possible to provide the necessary power.

If the system were to run in closed loop in this example, the resulting high fuel injected would be interpreted as a rich mixture and the ECM response would be to reduce the amount of fuel being injected......not exactly what we want.

The same situation applies when the engine is cold. Everyone knows that the mixture should be rich (even though the days of chokes are over for fuel injected vehicles) for starting and cold running. Once again, if the ECU listened to the Lambda sensor, it would be trying to lean out the mixture all the time and the engine would not start or run when cold.

Therefore, under starting, cold running, full (or high opening) throttle, deleleration or very high temperatures, the system will run in open loop - open loop meaning that the Lambda sensor is ignored and the ECU controlls fuelling from its inbuilt map, which will be based on (depending on the system), throttle sensor, water tem,perature, engine speed etc.

So, Panzer Patrol, yes, Closed loop is for tickover, but only when the engine is warm, and for very light to medium throttle openings (if the same as every other system,both car and bike).

Open loop is where it follows a pre-determined map on the chip.

Although adding a resistor would modify the value, it would not modify the switching or the point where the system switched from closed to open loop or vice-versa. Additionally, if the Lambda sensor voltage is outside the threshold voltage for too long (which is what a resistor would potentially do), a fault would be logged in the ECU and the system may go into fail-safe, triggering the engine warning light and maybe (I'm not sure about the BMW system) even reducing the power during fail-safe operation.

Put it this way, I wouldn't put a resistor on my bike.....

 

[Rob Farmer]

Well that was a pretty steep learning curve wasn't it? Good stuff guys especially Dave and Mechanic. It was apparent as soon as I looked into the Lamba probe that a potentiometer or Voltage source was never going to be an option for replacing it. Mind you I'm pleased to see my 1100 has got one for me to play with.

 

[Panzer Patrol]

Hi Dave,

Outstanding....super response and explanation. I had a feeling that this was the case but could never pin it down. You have supplied the definitive answer and I am sure there is a lot more than me very grateful for the input.

Cheers matey

 

[The Mechanic]

Open and shut case.

Dave Barrett, you have saved me alot of typing. What you missed and I'm sure it was not intentional is the MAP sensor (manifold absolute pressure sensor).

Under reasonable brisk acceleration there would be too much air and not enough fuel supplied to the engine and this would produce a flat spot or hesitaion. The MAP (if working correctly) reads manifold vaccum (or lack of it) and then opens up the fuel pressure regulator a bit more. As an example the regulated fuel line pressure could be 30 psi for normal modes of operation, but under acceleration the regulator allows say for example the pressure to rise to that of the fuel pump (in my example) 42 psi.
The net result of this pressure rise is to produce the richer mixture needed to prevent flat spots.

Its this device that most of the spotty oiks in XR3 and GSI Astras change first because they can induce richer running across the rev range of their soon to be junked car.

This is a probable way to get over the weak mixture that nearly every one assumes their GS has. Catalytic convertor and other bits junked modded etc. Just make the FI pump deliver a little more squirt to the injectors.

At the risk of being pulled up by other members, I have to say that this is one practical demo that I do and it works very well thank you. especially as the pump is running through a pressure guage and the MAP is hooked up to a vac guage.

See you when me warranties up.

My 1150 GS is blue so its dam quick anyway.

 

[The Mechanic]

Addendum

Oops, I might have misled some of you sorry. Of course the Map feeds info to the ECU in terms of engine load via vacuum The ECU then modifies the ignition and fuelling (injection pulse width--how long the injector is held open) to suit the load i.e. steep hill and driver still in too high a gear (engine slogging away) with throttle pedal floored.

The fuel pressure regulator is vacuum controlled and as soon as the manifold depression disappears (as in acceleration) the regulator opens up and allows more fuel pressure through which equates to more fuel being injected despite the pulse width.

Hope that was ok.

 

[(RIP) Kaister]

Dont know if you've seen this site before - i think its aimed mainly at american kids - but it tends to explain things in reasonably plain english.

http://auto.howstuffworks.com/fuel-injection.htm

Phil