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Topics - Kevin Wood

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106
LPG injectors such as the Valtek type 30 usually supplied with the Stag kits are designed to work with a wide range of engine power outputs and so a way to calibrate the rate of fuel delivery to suit the engine is required.

Fuel flow from an injector is controlled primarily by the time for which the ECU holds it open during the induction stroke of the engine and the pressure of LPG vapour with which it is supplied.

If the injector is delivering fuel too fast for the engine, it becomes impossible to achieve a short enough injection time to accurately control the mixture and the engine will idle poorly and emissions will suffer.

Conversely, an injector what is not able to flow fuel fast enough might end up open 100% of the time as the engine approaches maximum RPM at full throttle, and be unable to supply any more fuel. The engine may have a lean fuel mixture as a result and, at full throttle, this can cause burnt out valves and piston crown damage due to excessive combustion temperatures.

In order to calibrate the injectors to the requirements of the engine a small brass nozzle is fitted at the outlet of each injector valve. These nozzles should not be confused with the nozzles installed in the intake manifold to inject the fuel into the intake. The brass nozzles can be drilled out to various sizes and in so doing the rate of gas flow through the valve is set.

This can be regarded as a coarse adjustment of the fuel flow. Finer adjustments can be made by adjusting the pressure of the vapouriser output, and by adjusting the injector opening time by adjusting the map in the LPG ECU.

The nozzles are normally supplied with very small drillings and it is necessary to drill out the nozzles before installation to achieve sufficient fuel flow on all Omega engines.

The Stag manual contains a table of nozzle diameters against horsepower output per cylinder. In practice, it has been found that a 2.5mm nozzle diameter is a good starting point for a 2.5 or 2.6 V6 engine and, for all others, 2.8 - 3.0 mm works well.


107
Maintenance Guides / Battery, Charging and Starting diagnosis
« on: 03 November 2008, 14:54:59 »
Questions regarding battery, charging and starting problems are frequently asked here, expecially this time of year, and diagnosis is straightforward provided the correct approach is taken, so I thought a guide was in order for future reference:

From a practical point of view it is useful to know that the battery terminal voltage under various conditions can tell us almost everything we need to know about the state of the battery and charging system so accurately measuring the terminal voltage is key to fault finding in this area.

A cheap digital multimeter the like of which is available in Maplins or at most motor factors is the perfect tool for the job. Set it to a voltage range of around 20 volts DC if it has manual ranging, ensure that the test leads are inserted in the connectors marked "common" and "V" and connect them across the battery terminals, ideally with crocodile clips so you don't have to hold them conencted while you perform the tests. DO NOT connect a multimeter on the Amps range across a car battery, and make sure the test leads are not left in the "common" and "A" connectors.


Battery condition and charging circuit


Obviously the circumstances in which you find yourself with a starting or charging problem can vary, but in an ideal situation, when faced with a problem, I like to take the following sequence of actions to diagnose the fault:

1) Try to charge the battery, ideally using a mains powered battery charger for a couple of hours, to ensure it is likely to be fully charged.
2) Allow the battery to settle for perhaps 15 minutes after charging so the terminal voltage reflects its' true condition.
3) Measure the terminal voltage of the battery.
4) Apply some load (e.g. car headlights) and watch the terminal voltage for a minute or two.
5) Switch off all loads, start the engine, and, ideally, have someone watching the battery voltage while cranking the engine.
6) Measure the terminal voltage with engine at a normal idling speed.
7) Increase engine speed to a fast idle (2,000 RPM) and measure the voltage.
8) Add some electrical load (headlights, blower fan, heated rear window) and measure the voltage at idle speed.
9) Increase engine speed to a fast idle (2,000 RPM) and measure the voltage.
10) Check electrical connections to battery, starter and alternator and also all chassis ground connections in the engine bay for heat.


I interpret the readings taken above as follows:


3) Normal reading would be 12.5 - 12.8 volts indicating a healthy battery fully charged. Suspect battery if it has failed to reach and stabilise at this voltage after a charge.

4) Expect the voltage to drop to perhaps 12.2 - 12.5 volts due to internal resistance but to remain stable for a minute or two. If voltage continues to gradually decline below this level, and certainly if it reduces to 12.0 volts or below within a minute or two, and was previously fully charged, suspect battery.

5) While cranking, battery voltage will fall significantly. If it falls below 10 volts or so when battery was previously fully charged, I'd suspect the battery. If it's also cranking the engine rather slower than usual, it adds more weight to this diagnosis.

6) Expect 13.5 - 14.5 volts. Greater than 14.5 volts indicates battery is being overcharged (voltage regulator failed within alternator). If it's significantly greater than 15 volts do not drive the car until resolved as the battery could be damaged or even explode and other electrical accessories in the car may be destroyed.

7) If the voltage didn't make it to at least 14 volts when idling it should do now otherwise alternator suspect, or perhaps wiring from alternator to battery or chassis and engine block to battery negative terminal connections. Should remain under 14.5 volts, as before.

8) Expect perhaps 13.0 - 14.5 volts. voltage may well have dropped due to load on the alternator.

9) Expect 13.5 - 14.5 volts. Most of the drop with load in the previous step should recover at normal cruising RPM. If not, suspect alternator or wiring fault.

10) Electrical conductors may become slightly warm to touch with electrical load, but any conductors, or particularly crimped connections, that become hot to the touch have a high resistance (loose crimp perhaps?) and are reducing the effectiveness of the charging system. It doesn't take much voltage drop before the battery is not being adequately charged so rectify poor connections before they leave you stranded.

It may not be practical to perform the whole sequence above if you are stranded in a rainy layby. However, the battery terminal voltage will still give you some vital clues as to what's going on:

Engine stopped
No load: < 12.5 volts : Battery not fully charged or defective
Dropping to < 12 volts under load :  Battery flat or, most likely, defective

Engine Running:

< 13.8 volts: Battery not being charged adequately. Ideally expect to see 14.0-14.5 volts at cruising RPM with normal levels of electrical load



108
Maintenance Guides / How to fit line level outputs to a CCR2006
« on: 21 March 2007, 22:17:31 »
The CCR2006 stereo as fitted to many Omegas at the factory is quite a nice unit in many respects. The 4 CD changer is handy, the radio works nicely and it has nice integration with the MID to update the clock to RDS time. The steering wheel controls are very useful and it has decent support for connecting mobile phone car kits.

Unfortunately, whilst it sounds reasonable at low volumes I find that the power output is not quite good enough for  enthusiatic listening, especially at motorway speeds. In addition, the sound gets pretty harsh even at modest listening levels.

As with many car head units, the CCR2006 is let down by its' power amplifiers. Packing four channels of audio amplification into a DIN size case forces many compromises (although double din, the CCR2006 is built as two separate single DIN units, a radio/cassette and a CD changer bolted together). There is insufficient space for anything other than a couple of small chips to form the power amplifier, the unit is physically too small to dissipate the heat that is generated by more powerful amplifiers and, constrained by a supply voltage  of only 12-14 volts, the power output is limited to a theoretical maximum of 18 watts RMS per channel into 4 ohms with a bridged amplifier.

The solution to the power amplification issue is to use a good quality external power amplifier, of course. Less constrained by space, these have large heatsinks and good quality amplifiers, and have the space for additional power supply circuitry to step up the car battery voltage to a higher voltage, making much higher power levels possible. They also allow the head unit to run cooler.

Ideally amplifiers should be driven from "Line Level" outputs from the head unit, as this bypasses any deficiencies in the power output stage of the head unit. Unfortunately the CCR2006 doesn't have any line outputs available. Whilst it is possible to drive some amps directly from a speaker output, I was concerned that the CCR2006 power amplifiers would still degrade the sound and the amplifier I purchased on EBay didn't have speaker level inputs.

Some would say that a new head unit would be the best choice, and, indeed, it probably is the easiest option. However, there's a limit to how much I was prepared to spend for a line output and I like the way the CCR2006 integrates with the rest of the car and, most importantly, doesn't look anything special to the passer-by. Take away the nasty internal power amplifier and the performance of any CD player / Radio is adequate in a car environment as it's not exactly an environment suited to critical listening.

The following procedure describes how to fit Line Level outputs to the CCR2006. Note that it does require some dismantling of the unit and soldering small components. It should only be attempted by someone who is competent at working inside electronic devices.

109
The following table gives the expected air temperature at the face vents for an air conditioning system in satisfactory condition for various conditions of ambient temperature and humidity. The following conditions should be established in order to achieve a consistent measurement:

Engine running
Climate in Auto mode
Right and Left temperature : "LO" selected
Air distribution to face vents
Recirculation OFF
Front and Rear doors open
ECO mode OFF
Run engine for 15 minutes with bonnet closed
Increase engine speed to 1500 RPM for 5 minutes
All air vents open
Measure flow temperature at central face vents

All temperatures quoted in degrees Centigrade



Ambient TempHumidityFlow Temp
1550%5-10
2050%6-11
2090%9-14
2550%8-13
2580%11-16
3040%10-15
3070%15-20
3540%13-18
3570%19-24


110
The following plots, kindly provided by 2woody, show the effects on gearing of an Omega with the available diff and gearbox options:

















Plots are of road speed in MPH along the X axis against engine speed in RPM on the Y axis in the available gears.

111
Fuel Trim Malfunction codes (0170 and 0173) and Cat Efficiency problems (0420 and 0430) have been mentioned a few times recently, particularly with reference to LPG conversions. I've also chatted with a few members via PM who have been interested in what's behind it and the following explanation evolved, which I thought probably deserved to be available in public.

Fuel trim codes can be a common problem where an LPG system hasn't been tuned accurately or where another malfunction of the engine or associated systems has had an effect on the tuning of the engine. So, first things first. What is fuel trim?

The petrol engine ECU has a number of inputs to tell it about the engine operating conditions and from these inputs it looks up in a calibrated table (called the "MAP") how much fuel to inject into the engine. This results in the petrol injectors being opened for a precisely controlled length of time during each engine cycle called the "injector duration". Since the injectors flow petrol at a constant rate when open, the volume of fuel is directly controlled by the injector duration. This typically ranges from 3 milliseconds (0.003 seconds) at idle to perhaps 15 milliseconds at full load.

The above describes an "open loop" fuel injection system, of the type that were common before catalytic converters were mandatory. The map was calibrated for a given combination of engine, injector flow rate, induction and exhaust system, cam profile, etc. Provided none of this changed significantly the engine remained in a reasonable state of tune, with only the odd mixture adjustment required at MOT time to keep the emissions at idle within specification. Crucially, the ECU is operating "blind" in an open loop system. It delivers fuel to the engine, but has no idea if the fuel mixture turns out to be correct.

With the advent of 3 way catalytic converters the fuel mixture burnt by an engine became more crucial. A catalytic converter will only clean up the exhaust emissions successfully when there is a chemically correct mixture of fuel and air being burnt in the engine. This means tighter control of the fuel mixture. Lambda sensors are the mechanism by which this control is achieved. They give the ECU feedback on the actual mixture burning in the engine.

The most common type of Lambda sensor, and the type used on all Omegas, is termed a "narrow band" sensor. This is because it measures the fuel mixture over a very narrow operating region centred around the chemically correct mixture. Such a sensor can be viewed as indicating whether the mixture is "lean" (too little fuel) or "rich" (too much fuel) with respect to the chemically correct mixture. Basically, the petrol ECU will use the output of the lambda sensors to adjust the quantity of fuel injected (the injector duration) so that the lambda sensors are always at the point of switching between "lean" and "rich", so the average mixture is correct.

It does this by maintaining a variable called a "fuel trim" for each bank of the engine (on a V6 - just the one on a 4 pot). If the lambda sensor reads "lean" it will increment the fuel trim periodically. If it reads "rich" it will decrement it. The fuel value from the map is multiplied by the fuel trim before calculating the injector duration so the fuel trim has a negative feedback effect, adjusting the injector duration read from the fuel map to keep the mixture correct.

The fuel trim is used to compensate for variations between engines, fuels, injectors, etc. to ensure the mixture is always right for the catalytic converters. However, it has a maximum range based on how much trim would normally be expected. If the fuel trim exceeds a threshold programmed into the ECU, a fault code is stored and the EML comes on.

Many ECUs take this a stage further and store a "long term fuel trim" value based on the long term average of the fuel trim that is in use. This variable is often stored in non volatile memory so it is available from start-up before the Lambda sesnors have warmed up. It is also often applied to areas of the map where the closed loop correction is not active, for example at full throttle where the mixture is too rich for the Lambda sensors to provide useful feedback.

Many ECUs also store long term fuel trims in a so-called "block learn table" which effectively stores separate fuel trim values for different areas of the fuel map, as the fuel trim required when idling is often different to that in use when motorway cruising, for example.

Add LPG to the equation and the LPG ECU is watching the injector duration in use by the main ECU and using it to calculate the LPG injector duration required. The tuning of the LPG ECU relates these two durations, and also applies corrections for the temperature and pressure of the vapour being delivered to the engine so if, for example, the petrol ECU uses a 3ms injector duration, the LPG injector duration might be 5ms for the same amount of fuel. If this is done correctly the fuel trim remains roughly the same as on petrol and the main ECU is happy.

Now, let's say for a 3ms duration the LPG ECU only injects 90% of the fuel required, due to a fault in the LPG system or to bad calibration of the LPG system. The fuel trim is increased by the main ECU until the mixture is right. This will require a fuel trim of +10% to correct the situation. So, it is straightforward to see that, if the LPG ECU is not correctly tuned, the main ECU adds fuel trim to make the mixture correct again, and if that trim is too large, the EML comes on.

Incidentally, you can watch this process happening on a Tech 2 or, on later engines, using an OBDII compatible reader. It allows you to view the variables inside the ECU in real time.

112
Omega Electrical and Audio Help / Re: Bose By-Pass
« on: 08 November 2010, 11:28:19 »
You will need to change all the speakers for 4 ohm ones!.

You should be able to disconnect the Bose loom in the driver's footwell, install a loop-back connector from a non-bose car, remove the fuse for the Bose amp feed and that should be it.

Kevin

113
OK. I did it the obvious way on my Omega and it works nicely.

Here's the guide to recap:

http://www.omegaowners.com/forum/YaBB.pl?num=1279100997

One of the things I want to add to the Westfield is an intermittent wipe - it doesn't have one at all, let alone variable!

Anyway, I've been rersearching ways to do this and came across a VW part which implements variable intermittent wipe in quite a neat way.

This wiper delay timer "learns" the wiper interval in the following way:

It starts drizzling, so you flick the wipers once. It keeps drizzling so, when the screen is in need of another wipe, you flick it onto intermittent. The wiper delay timer sets itself to the time interval between your initial "flick" of the wipers and when you switched it to intermittent, and carries on using that interval thereafter.

So.. No need for a stalk with a variable setting and, the best part, this relay is pin compatible with the non-variable timer module already fitted in Omegas without variable intermittent!

The upgrade simply involves lifting the bonnet, pulling out the old timer module and plugging in the new one.

I should stress that I haven't tried this in an Omega as I've already changed the stalk on mine however I have obtained a timer module, tested it on the bench and I can't see any reason why this wouldn't work on an Omega. It behaves exactly as my old non-variable timer module except that you can set the time interval. 8-)

If anyone wants to try this, you will need the timer module which is VW part number 357 955 531. Also referred to on the net as the "99" relay as it often has a large number 99 printed on the case. This site suggests that there are some equivalent parts but I can't vouch for its' accuracy.http://wiki.seloc.org/a/Wiper_Variable_intermittent

I ordered one from ebay seller stevens_vw_dismantlers mid-afternoon yesterday and it was on the mat waiting this morning when i got up (OK, I had a lie-in). :y

I stress that I haven't tried this on an Omega but if someone would like to volunteer to try it out I will agree to buy back their relay if it doesn't work, such is my confidence that it will. Once it has been verified I will add the info to the guide.

Kevin

114
Omega Electrical and Audio Help / dndservices.co.uk
« on: 13 January 2010, 15:39:12 »
http://www.dndservices.co.uk/

Closed due to staff illness.  :(

Hope everything is OK, Dave.  :y

Kevin

115
Omega Electrical and Audio Help / Central locking motor
« on: 18 January 2008, 09:55:21 »
My driver's side central locking motor plays up occasionally. It seems to go through a phase of being lazy for a week or so at a time. It moves the button up but not quite far enough to unlock the door, so I have to nudge it round with the key to open the door.  

As I say, it'll d!ck me around for a week then work faultlessly for several months before playing up again.

I have to remove the door card at some point to change the speaker and I'm wondering whether to lube everything up or just change the C.L. motor.  :-/

Anyone know how much a motor is, what the normal failure mode is, and what my likelihood of success will be on just lubricating it?

Also, what's the best lubricant? White grease? Silicone? Something waterproof that doesn't go too thick in the cold, presumably?

Cheers,

Kevin

116
Hi there,

Just a quick one. Does anyone happen to know the location of the trailer bulb failure sensor (p39) on a facelift and which pins need to be bridged to enable the brake light output on the trailer pre-wiring connector in the boot?

Just fitted a tow bar and everything bar the brake lights is sorted.

Cheers,

Kevin
  

117
Omega Electrical and Audio Help / Alarm problems - post mortem
« on: 02 August 2007, 11:28:37 »
Rewind a couple of months and I had problems with my alarm going off. Normally about 15 minutes after parking and the trouble code pointed to the power sounder.

Anyway, it has been behaving itself of late but I had the scuttle cover off yesterday, saw the power sounder sitting there and wondered if it would be a good idea to investigate.  :-/

Decided to bite the bullet. Removed it and cut it open. Glad I did because both of the little rechargeable batteries in there had oozed acid all over the circuit board and it was a bit of a mess. Batteries were still working OK but it's clearly not well, and would have played up again, no doubt.

Not sure whether it can be salvaged. May just buy a new one as the chances of sealing it up properly are slim.

I may take some pics tonight if anyone's interested.

Kevin

118
Omega Electrical and Audio Help / Climate trouble code
« on: 30 July 2007, 19:04:35 »
Whilst checking for trouble codes related to my crank sensor failure I thought I'd have a look at the other systems. I found a trouble code 32 in the climate control.

Does anyone know what this means?

It was read with a cheapo Tech2 so I'm taking it with a pinch of salt, however, my air con is not performing that well despite apparently being charged and free of leaks. Just wondered if this is something I should investigate.

Any ideas?

Kevin

119
Hi All,

Still having hassles with my alarm. I'm thinking it would be good to know what sensor is setting it off. Bought a cheapo tech II cable but haven't got round to finding a PC that it'll run on reliably. Just wondering if it is worth trying to get it running to read the codes from the alarm?

Anyone tried this?

Also, does anyone know where the alarm horn and power sounder are on a facelift?

Cheers,

Kevin

120
Well, my CCR2006 is currently sitting on my desk playing CDs through a hi-fi amp using a proper line level output - and it doesn't sound bad.

Got bored tonight so I thought I'd investigate an alternative to driving my amp from speaker level outputs. Pulled the CCR2006 out, opened up the cover and the first chip I saw was a very popular volume and tone control chip. A quick google got me a data sheet which revealed on which pins the 4 outputs to the power amps emerged. A bit of soldering and I've got a pair of front outputs at line level emerging from the back of the box.

It hasn't been tested on the car yet but it looks good so far.

I took plenty of photos so I'll post up a step-by-step guide in due course if anyone's interested. It requires some delicate soldering but isn't that difficult.

I have a feeling line inputs might be on the cards too but that's for another evening.

Kevin

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