Technical measurements

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Postby Murray Betts

Some measurements on the Cappuccino that might be useful for those of a "fiddling" nature :wink:

Postby Murray Betts » Wed Jun 11, 2003 13:18

This is the calibration curve for my MAP sensor. I have checked one other SCORE member's and it was as near identical as measurement allowed. I'm not certain, but suspect the max output is limited to 5volts (supply voltage) which would mean that the MAP sensor would "hit the end stop" at about 1.25Bar boost (above that you'd be running at fixed fuel flow).
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Postby Murray Betts » Wed Jun 11, 2003 13:27

This shows the workshop manual curve for the AIT (air intake temperature) and ECT (engine coolant temperature) sensors, an I've put on the curve a few measurement points from my car. Again another SCORE member's car was checked and agreed well. Basically if the sensor agrees with the curve at the hot end and the cold end (which you can do without removing the sensors from the engine) it'll be OK in the middle also. To check, simply remove the connector and check the resistance between the two sensor pins. You'll need something to check the sensor temperature (multi-meter and thermocouple, or thermometer)
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Postby Murray Betts » Sat Jun 14, 2003 19:21

I wanted to see if my aircon was working within spec; I thought it wasn't as effective as it used to be.
This shows the centre fascia vent temperature as a function of time with the engine idling. You can see how the temp pulls down when the aircon is first switched on, and then the temp cycles up and down as the system alternately clutches the compressor in/out.
These temperatures show my system is within spec according to the Workshop manual.
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Postby Murray Betts » Sat Jun 14, 2003 19:26

This was a check at higher ambient temp.
At idle the system couldn't get the aircon out temp down quickly enough to overcome the high ambient (incidentally this was outside my garage with the roof off, so it was working against the atmoshere!)
Also I ran the fan at different speeds, and ran the engine at different speeds. Interestingly you can see the cycling temp range doesn't change significantly; putting the fan onto high just makes the system clutch in/out more frequently as more cold air is demanded.
At these temps the system is still within spec. However I suspect a re-gas is probably about due (never been done since the car was new!).
Notice at the start, I put the thermocouple from ambient air into the vent, and the temp increased. This is because when the car is stationary, the air going into the cabin intake at the base of the screen gets heated from the engine bay and bonnet; on the move you'd get a few more degrees of "chill".
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Postby Murray Betts » Thu Dec 04, 2003 23:40

This shows the injector pulsewidth measured after a cold start from about 10degC, unassisted (foot off throttle).
You can see the afterstart enrichment lasts for about 10sec, the engine then runs on the basic map fuelling corresponding to the temperatures for another 10sec or so, and then the warm up begins to take effect.
I have not yet measured the pulsewidths at other temperatures, so I cannot at this stage say how much afterstart fuelling you get when colder, for example, nor whether it ramps off at different rates.
If you are experiencing afterstart stalling/stumbling, you may be able to relate it to a certain fuelling phase from this plot.
I'm not sure exactly what happened at the 105-110sec range where the P/W does a couple of dips; it could be the feedback starting and coming under closed loop control, it's the right sort of timescale and the P/W seems pretty constant after that time.
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Postby Murray Betts » Thu Sep 14, 2006 18:51

some accel figures for a variety of cars
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