Alex Posted May 22, 2002 Share Posted May 22, 2002 Pin 43 or 45 on the ECU (I forget which) is the intake air temp sensor...where exactly is this positioned in the engine bay? Also what sort of temperature could I expect it to record during weather which is a cool 15degC and dry, with a K&N induction whilst cruising on the motorway? I ask as I'm i've connected my SBC-id to this signal and the throttle position (and soon the O2 sensor) but I have to configure it. But in order to config it I need to know what I should be getting. Cheers Alex H Quote Link to comment Share on other sites More sharing options...
badtoy Posted May 22, 2002 Share Posted May 22, 2002 on the nato/uk specs the intake air temp sensor is in the maf. if you install a vpc instead of the maf there is a resistor which give the ecu one and same value every time. I think it is about 30 degrees. remember the more colder intake air value you give to the ecu, the ecu will raise the fuel the more hot air value you give to the ecu the ecu will reduce the fuel. but on a uk spec car you have to reduce fuel by an s-afc anyway. I think thats the point why hks give a standard value for the ecu of about 30 degrees. hope this helps. markus Quote Link to comment Share on other sites More sharing options...
Alex Posted May 22, 2002 Author Share Posted May 22, 2002 What's the voltage range on it? So is it then mounted in the intake manifold? Is it pre or post turbo's? Sorry, a bit confused Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted May 22, 2002 Share Posted May 22, 2002 On a UK spec it is in the MAF, so that's pre-turbo's. Voltage range on the UK spec is :- 20degC 0.5 - 3.4v 60degC 0.2 - 1.0v This would be measured on pin 45 of the ECU. HTH Quote Link to comment Share on other sites More sharing options...
Alex Posted May 27, 2002 Author Share Posted May 27, 2002 Ok, I've played with this for a couple of days and somethings not right!!! The Blitz unit shows a decrease in temp as it gets hotter in the engine bay...I start the journey at 27degC (when its more like 20degC) and end it on about 11degC!!! Could someone explain this please, I assume the voltage drops the hotter the sensor gets...so how can I get the damn thinh to read it properly. There is a high and low voltage setting but the high isn't allowed to go below the low (understandable really) and therefore read the signal the right way round. Any ideas or am I just not going to get it to work. Cheers Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted May 27, 2002 Share Posted May 27, 2002 Maybe the SBC-id can't handle inversely proportional inputs. It could be as simple as that. The boys at Blitz not expecting it to be hooked up to voltages that start high and decrease. Only way arround it would be to use an op-amp and feed the signal into the inverting input and then take the output and feed that to you SBC-id. Quote Link to comment Share on other sites More sharing options...
Digsy Posted May 27, 2002 Share Posted May 27, 2002 What is the temperature sensing element? Thermocouple, platinum resistance, or thermistor (or other)? Seems odd that Alex's unit is looking for a voltage / temp relationship that works in the opposite sense to the one that his air temp sensor is putting out... Thermocouple - creates voltage proportional to temperature. Platimun resistance - resistance increases proportionally with temp. Thermistor - resistance decreases proportionally with temp. If the output voltage is dropping relative to earth, could you measure it relative to a 12V source without blowing anything up? *Disclaimer. Please don't try that until someone has confirmed it. I don't even know what an SBC-id is! Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted May 27, 2002 Share Posted May 27, 2002 Originally posted by Darren Blake If the output voltage is dropping relative to earth, could you measure it relative to a 12V source without blowing anything up? *Disclaimer. Please don't try that until someone has confirmed it. I don't even know what an SBC-id is! Errr wouldn't want to try that one out without checking and double checking. Chances are the unit has a common earth anyway. As for the measuring device i'm not sure what is on the jap spec, but on the UK\US cars it is all part of the hot wire sensor. Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted May 28, 2002 Share Posted May 28, 2002 It might be simpler if you tell us what the Blitz units expects as a voltage range? OR is this configurable? as Darren says Thermocouple - creates voltage proportional to temperature. Platimun resistance - resistance increases proportionally with temp. Thermistor - resistance decreases proportionally with temp. (although you can get them increasing as well) I've got K-Type Thermocouples and Thermistors. and I've actually got a bag full of BOSCH water/air temp sensors. Maybe fitting an external Air Temp sensor would be better, as you can choose exactly what you want. But you do need to know what the Blitz unit requires. BE careful mixing sensor types, as your Blitz unit may be actively powering the sensor and measuring a resistance differential (Thermistor) or it could be passively sensing a change in voltage by amplification (Thermocouple). Over the bank holiday I plan to fit sensors to my car and plumb into my new product and display temps from all over the car. If feasible I'll take a look at the stock sensors. I've also got a Fluke temperature meter which I plan on using to calibrate it all. (although the purists out there will realise it's all deterministic anyway, it just makes me feel better knowing another instrument measures the same thats all) Regards Pete ps. I must start writing shorter replies...... Quote Link to comment Share on other sites More sharing options...
Alex Posted May 28, 2002 Author Share Posted May 28, 2002 The harness comes with another earth cable on it so the entire unit is earthed twice. All it is, is a plug with 4 wires. 3 data and 1 earth. The three "data" wires passively read the voltage on the line and report it on the configurable display. I chose to tap the throttle position sensor (which I've now calibrated and works fine) The Intake air temp sensor (where ever and whatever it is) And I'll finish off with the OXY1 sensor. ECU pins 43, 45 and 71. The Blitz has a two values you have to calibrate. Low voltage and high voltage. Low's min is obviously 0.00 and high's max is 16.00. The high voltage has to be greater than the low one, if you try and do it, it just ignores you and goes back the previous setting. Can anyone please find out what type of temp sensor it is. and if I need to reverse the signal where can I get an OP-AMP from? Maplins? Cheers Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted May 28, 2002 Share Posted May 28, 2002 Op-amp's are readily available from the likes of Maplin, but it's not just a case of buying an op-amp and feeding the signal in and getting the inverted one out. You need to add some additional components, the most important being a feedback resistor. Also need to select the correct type of op-amp for your application. Anybody remember what value the resistor should be for unity gain ? Something that Pete would be better of helping with as my hands-on days are oh so far behind me, unfortunately. Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted May 28, 2002 Share Posted May 28, 2002 Anybody remember what value the resistor should be for unity gain ? Gain for an inverting type amplifier = Rf/Rin Where Rf is the feedback resistor and Rin is the input resistor. You want Rin to match the impendance of the device you are sensing, normally quite high like 10kOhms or something. The feedback for unit gain therefore has to be the same. The circuit is more complicated as you require 0v to become 12V or something and 12V to become 0V. An inverting amplifier will try to make 0V = 0V and 12V = -12V which isn't quite what you want. Now the op amp cannot generate -12V if it doesn't have a -12V supply rail and it's not what you want anyway. So you'd also need to bias it as well to add 12V. It's getting fiddly now. As has been mentioned before its not just a case of buying one off the shelf to do the job. The op-amp is a semiconductor device that will need correct power supplies, resistors, probably capacitors for some form of noise immunity and a circuit board (VERO-board) to solder it all onto. Then a box to put it all in, plus wire of course. You can buy all the bits from Maplin and solder together as a DIY project. Regards Pete Quote Link to comment Share on other sites More sharing options...
Adam W Posted May 28, 2002 Share Posted May 28, 2002 Wouldn't it be a LOT easier to buy a temp sensor which provides the "correct" scal of output voltage? ie one that is proportional to temperature, rather than inversely proportional? Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted May 28, 2002 Share Posted May 28, 2002 I've got most sensors and they are easily available from places like Farnell. However most, if not all, sensors require some form of signal conditioning, power to drive them etc etc and I think the Blitz unit just displays units from low to high according to a changing voltage input. The sensor on it's own will not give you any voltage output at all. And although Thermocouples generate voltage this is about 40uV per degree C so obviously won't be much good on it's own. It might be possible to just attach a new sensor to 12V via a resistor and measure the potential divider circuit, using a thermistor (resitance) sensor. Sorry I cannot help on the stock sensor front as I've never looked at it properly. Regards Pete Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted May 28, 2002 Share Posted May 28, 2002 Probably, but then you have to get it into the intake somehow. Anybody know how this is done normally ? Are sensors drilled and tapped into the rigid sections ? Quote Link to comment Share on other sites More sharing options...
Digsy Posted May 28, 2002 Share Posted May 28, 2002 Originally posted by TRL Performance And although Thermocouples generate voltage this is about 40uV per degree C so obviously won't be much good on it's own. And mounting that beaker of pure melting ice for the cold junction in the engine bay it is going to be a pain. Sorry. Not being helpful now. Martin, most of the temp sensors I have seen have a tapered thread which screws into a rigid part of the intake system, usually upstream of the throttle body. I have seen some in plastic systems that have a bayonet style attachment. I'm going to stick my neck out and say that the ones I've seen are thermistors... Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted May 28, 2002 Share Posted May 28, 2002 And mounting that beaker of pure melting ice for the cold junction in the engine bay it is going to be a pain. The cold junction is actually in the drivers compartment in the measuring instrument, it's the hot junction that's in the engine bay. But I'm being pedantic now Instead of Pure ICE you normally have another temp sensor (like a thermistor) on the printed circuit board of the unit to detect the actual COLD JN TEMP and then compensate for 0degreeC Regards Pete ps. still no help for Alex though. pps. for those who care. The COLD Jn is the free terminating ends of the wires from the sensor and the HOT Jn is the point at which the dissimilar metals of a thermocouple are joined. (and the bit that you place into the medium to be measured. It does NOT relate to the actual temperature of each end. ppps. Will I ever shut up ?? Quote Link to comment Share on other sites More sharing options...
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