SimonB Posted May 15, 2005 Share Posted May 15, 2005 Just got round to wiring the 2nd analogue input of my E01 to the intake air temp on the ECU (figured I might as well!). Only trouble is I have the voltages for the US/UK air temp sensor in the MAF but not the Jspec IAT voltages, and they are definitely not the same. Has anyone got the voltage ranges for the sensors on a Jspec, particularly the intake air temp? It would be in the factory repair manual. Maybe someone with a standalone ECU has the info? Can't find it anywhere. Quote Link to comment Share on other sites More sharing options...
SimonB Posted May 30, 2005 Author Share Posted May 30, 2005 Just thought I'd answer my own question here . It looks like the Jspec IS the same as the UK/US spec, I just got the voltages the wrong way round so thought it was different. The voltages are: 0.5V = 80C 3.4V = 0C Quote Link to comment Share on other sites More sharing options...
eyefi Posted May 31, 2005 Share Posted May 31, 2005 stupid Quote Link to comment Share on other sites More sharing options...
Guest Usmann A Posted May 31, 2005 Share Posted May 31, 2005 LOL, temp sensors work like NTC devicies, the EMS sends a 5 volts to the sensor, then dependant on the temperature of the filament inside, it affects its resistance and thus its voltage back to the ecu. Its normally, temp up= lower resistance = bigger Voltage back to the ECU. HTH Quote Link to comment Share on other sites More sharing options...
SimonB Posted May 31, 2005 Author Share Posted May 31, 2005 Its normally, temp up= lower resistance = bigger Voltage back to the ECU. HTH That's what I thought originally, but it's not the case. temp up = higher resistance = lower voltage in this case. Quote Link to comment Share on other sites More sharing options...
Guest Usmann A Posted May 31, 2005 Share Posted May 31, 2005 yea, agreed. thus why I said normally ... Quote Link to comment Share on other sites More sharing options...
TLicense Posted May 31, 2005 Share Posted May 31, 2005 huh? I thought resistance always dropped with temp. Hence why you need very cold temps to superconduct. At least that's what I was taught when I designed superconducting magnets. Thanks anyway though for doing that simon. I think the AEM guys would be interested in this info as there is no calibration for the stock J-spec sensor, and most people buy the GM IAT and use that. Quote Link to comment Share on other sites More sharing options...
Ian C Posted May 31, 2005 Share Posted May 31, 2005 Some things have resistance drop with heat, but don't ask me to name any of them. Chocolate? Haha. -Ian Quote Link to comment Share on other sites More sharing options...
Digsy Posted May 31, 2005 Share Posted May 31, 2005 MAT sensors are normally thermistors, which are semiconductors and therefore don't obey the normal rule that resistance drops with temperature. In fact I think you can get thermistors whose resistances rise or fall with temperature increase. Quote Link to comment Share on other sites More sharing options...
Ian C Posted May 31, 2005 Share Posted May 31, 2005 Right, Digsy, that is THE most offputting avatar I've ever seen, get rid of it before I boot you out of the tech section... -Ian Quote Link to comment Share on other sites More sharing options...
Guest Usmann A Posted June 1, 2005 Share Posted June 1, 2005 Digsy,I agree, that is my thinking, but then again not all EFI systems use, NTCs for thier AIT. Majority do ... Must be a PTC(positive temperature coefficint) sensor instead, I can kind of see why they would do this, as the MAF system in basic terms is kind of similar principle ... ie, platinum wire kept at constant temp, and air passing cools it, and affects resistance=voltage to ECU, etc, so on. Quote Link to comment Share on other sites More sharing options...
SimonB Posted June 1, 2005 Author Share Posted June 1, 2005 Having had a look at that link I posted up a couple of days ago the sensor itself is a normal thermistor that has high resistance when cold and low when hot. The sensor is connected in series to a fixed value resistor. the ECU supplies +5V to the circuit and measures the change in voltage between the fixed value resistor and the sensor. Here. Anyway, the values I posted up aren't quite right - they came from the repair manual and seem to to max and min values or something. The doc in the link has a graph which is much more like it, and I've found another link with resistances which can be converted to voltages. I'll post up when I have some more accurate figures. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted June 1, 2005 Share Posted June 1, 2005 That's what I thought originally, but it's not the case. temp up = higher resistance = lower voltage in this case. Other way around unless my AVO is seriously on the blink Quote Link to comment Share on other sites More sharing options...
Guest Usmann A Posted June 1, 2005 Share Posted June 1, 2005 Right, so its basically a NTC then. here is the GM IAT resistance values .. 100C 185 70C 450 40C 1.8K 20C 3.4K 0C 7.5K -20C 25.0K -40C 100.7K Quote Link to comment Share on other sites More sharing options...
Wez Posted June 1, 2005 Share Posted June 1, 2005 I am using the AEM with stock AIT sensor and this is what my calibration graph looks like. Quote Link to comment Share on other sites More sharing options...
Guest Usmann A Posted June 1, 2005 Share Posted June 1, 2005 wa la .. Quote Link to comment Share on other sites More sharing options...
ihavenone Posted December 22, 2005 Share Posted December 22, 2005 This might seem like a stupid question (been Supra owner for 3 weeks and don't know the engine) but where is the IAT lcoated? Quote Link to comment Share on other sites More sharing options...
Ian C Posted December 22, 2005 Share Posted December 22, 2005 In the intake plenum, one of the fittings on the engine side, near the throttle body. I can't post pictures at work -Ian Quote Link to comment Share on other sites More sharing options...
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