Discussion
I decated my 450 chim last year, It runs a little lumpy but very rich ( black soot all over rear of car )unless pushed hard when every thing is warm it is then very smooth. I have put off re-mapping as there has been talk of a new ECU available soon. I cannot remember which of the TVR related upgrade companies were advertising these. Any information gratefully accepted.
peter
peter
How right Daz is- I need to get a life methinks. Simply removing the catalysts should not make the car run rich, if you still have the same tune resistor under dash and it should have a white sleave on the resistor wire. Assuming you have not changed this, then something else is wrong with the system, like a faulty AFM, over high fuel pressure, misfire, or open circuit temp sender. If the tune resistor has been changed to the green one, then is likely the mapping is bad (ie its an unknown map), or the AFM CO trim is not set up.
The AFM setting will only alter the mixture if you are running a green tune resistor. You can set the value purely by setting a voltage on the side of the AFM, but its crude. A more precice way is to put a voltmeter across the black and white wires from one of the Lambda probes, and measure the voltage. If the cars running way to rich you should see 1- 1.3 volts (on a warm engine). You can then turn the screw adjustment on the side of the AFM- on mine its anticlockwise to weaken the mixture, and you should find the note of the idle changes, but it may take quite a few turns. (some are 20 turn pots) You should hit a point when the Lambda voltage suddly drops to 0 volts and the idle becomes rough as it becomes too lean, so then back it the other way until the idle is smooth after the lambda voltage has reached 1 volt, but no further, and this is as close as you can get to spot on. This is fractionly richer than the car runs on the catalyst tune, but gives a much better idle. This setting only sets the mixture up to around 2500 rpm, but if its wrong you will get sooty plugs and smoke at low speed. If you are running the white tune resistor, this has no effect, as the Lamda probes "should" be setting the mixture.
Or of course you could just wind the control until the idle is rough and then wind it back until it smooths out
Or of course you could just wind the control until the idle is rough and then wind it back until it smooths out
Edited by blitzracing on Wednesday 29th December 16:14
It's all on the V8D website I believe?
ETA: or even better contact Rob directly http://www.pistonheads.co.uk/gassing/profile.asp?m...
ETA: or even better contact Rob directly http://www.pistonheads.co.uk/gassing/profile.asp?m...
Edited by spend on Thursday 30th December 09:38
blitzracing said:
A more precice way is to put a voltmeter across the black and white wires from one of the Lambda probes, and measure the voltage. If the cars running way to rich you should see 1- 1.3 volts (on a warm engine).
I don't suppose there's a chart of lamda sensor voltage against lambda value anywhere?
Also, can I ask how you'd go about checking the air flow sensor?
There's nothing obviously wrong with it, but my decatted 500 is very thirsty for a light-ish car run at road speeds...
I spent a long time with a CO meter trying to accurately map the 1 - 1.3 voltage area of the lambda curve, but no two probes gave exactly the same results, plus the readings I got did not tally with what I expected, ( the switch point is supposed to be 14:35:1) so I think the CO meter was not stable or its difficult to effectively purge the system at idle (I think a rolling road would be a better idea) when you change the mixture but for what its worth theses where the readings, but please dont take them as gospel!:
.2v = 13.8:1
.4v = 13.77:1
.8v = 13.27:1
1.27v = 13:1
1.299v = 12.25:1
1.31= 11.891
It does show the the upper voltage change is very small for big AF ratio changes and the probes are not used by the ECU as a voltage reference, it just looks for a voltage change to know its hit Lambda 1.
Heres the AFM testing:
With thanks to Mark Adams of TornadoSystems.com
Note that you can drive without an airflow meter in case of emergency (i.e. airflow meter disconnected), because the system will drop into a default (limp-home) mode based on throttle opening.
Most airflow meter faults will cause the engine to run excessively rich. However if the airflow meter remains connected whilst defective then the vehicle will probably not run. In most cases the output from a defective airflow meter will be in the range 2.0-2.5 Volts, which is a viable value. This represents a moderate load and will cause heavy over-fuelling without setting a fault code.
Testing is performed in the following manner. Peel back the rubber boot on the airflow meter connector and leave it plugged in to the airflow meter. Set up the digital multimeter to read voltage. Insert the negative probe into the Red/Black wire (sensor ground), and the positive into the Blue/Green wire (Airflow signal).
Turn on the ignition, but do not start the engine. The meter should immediately indicate a reading of approximately 0.3-0.34 Volts. Most defective airflow meters will overshoot to 0.8 Volts or higher, and take at least 2 seconds to come down to the correct voltage.
Now start the engine, and the reading should rise to 1.6 Volts (3.5 Litre engine) to 1.75 Volts (5.0 Litre engine).
The next test is full load, and as with the fuel pressure test it will require use of a rolling road or a steep hill in the same manner. Under full load the voltage should rise to 4.45 Volts (3.5 Litre engine) to 4.95 Volts (5.0 Litre engine).
On this injection system, the idle CO mixture adjuster is provided on the airflow meter. It is located in a boss on the top of the airflow meter, pointing towards the engine. Leaving the multimeter negative probe in the Red/Black wire, move the positive probe to the Blue/Red wire.
Now turn on the ignition but do not start the engine. Observe the voltage. The normal adjustment range is between 0.0 and 3.6 Volts, with the higher Voltages producing higher idle CO values. There are approximately 20 turns of the adjuster screw to cover the entire range.
Annoyingly, the adjustment may be clockwise or anticlockwise to increase the value, and this varies from meter to meter! For this reason it is always preferable to have the multimeter connected in this manner when adjusting idle CO, so that you see can something is actually happening.
Typical Voltages that would be found at this point are between 0.9 to 1.4 Volts for non-catalyst cars. This Voltage is always factory pre-set to 1.8 Volts for catalyst vehicles. A value near to 3.5 Volts will generally produce an idle CO value of 9-10%. These Voltages may be used as safe initial values particularly if no CO measuring equipment is available.
.2v = 13.8:1
.4v = 13.77:1
.8v = 13.27:1
1.27v = 13:1
1.299v = 12.25:1
1.31= 11.891
It does show the the upper voltage change is very small for big AF ratio changes and the probes are not used by the ECU as a voltage reference, it just looks for a voltage change to know its hit Lambda 1.
Heres the AFM testing:
With thanks to Mark Adams of TornadoSystems.com
Note that you can drive without an airflow meter in case of emergency (i.e. airflow meter disconnected), because the system will drop into a default (limp-home) mode based on throttle opening.
Most airflow meter faults will cause the engine to run excessively rich. However if the airflow meter remains connected whilst defective then the vehicle will probably not run. In most cases the output from a defective airflow meter will be in the range 2.0-2.5 Volts, which is a viable value. This represents a moderate load and will cause heavy over-fuelling without setting a fault code.
Testing is performed in the following manner. Peel back the rubber boot on the airflow meter connector and leave it plugged in to the airflow meter. Set up the digital multimeter to read voltage. Insert the negative probe into the Red/Black wire (sensor ground), and the positive into the Blue/Green wire (Airflow signal).
Turn on the ignition, but do not start the engine. The meter should immediately indicate a reading of approximately 0.3-0.34 Volts. Most defective airflow meters will overshoot to 0.8 Volts or higher, and take at least 2 seconds to come down to the correct voltage.
Now start the engine, and the reading should rise to 1.6 Volts (3.5 Litre engine) to 1.75 Volts (5.0 Litre engine).
The next test is full load, and as with the fuel pressure test it will require use of a rolling road or a steep hill in the same manner. Under full load the voltage should rise to 4.45 Volts (3.5 Litre engine) to 4.95 Volts (5.0 Litre engine).
On this injection system, the idle CO mixture adjuster is provided on the airflow meter. It is located in a boss on the top of the airflow meter, pointing towards the engine. Leaving the multimeter negative probe in the Red/Black wire, move the positive probe to the Blue/Red wire.
Now turn on the ignition but do not start the engine. Observe the voltage. The normal adjustment range is between 0.0 and 3.6 Volts, with the higher Voltages producing higher idle CO values. There are approximately 20 turns of the adjuster screw to cover the entire range.
Annoyingly, the adjustment may be clockwise or anticlockwise to increase the value, and this varies from meter to meter! For this reason it is always preferable to have the multimeter connected in this manner when adjusting idle CO, so that you see can something is actually happening.
Typical Voltages that would be found at this point are between 0.9 to 1.4 Volts for non-catalyst cars. This Voltage is always factory pre-set to 1.8 Volts for catalyst vehicles. A value near to 3.5 Volts will generally produce an idle CO value of 9-10%. These Voltages may be used as safe initial values particularly if no CO measuring equipment is available.
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