Temp gauge pin-out 2004 Busa in Smart car ForTwo

smarterbusa

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I'm 74 and this is all new to me and not sure how to ask questions to all ....I just finished fitting a Hayabusa to a 2003 Smart car
fitted with a 2 stage turbo and using a AEM Infinity 508 ECU....all is working well just my temp gauge dosent work and just want to know what wires or colors are used for the temp gauge.
hope someone can help me.
Cheers Tony

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Hi
Thanks for this info.....but still no wiring to temp gauge....where does it get get the signal from??
Black/ Blue wire Pin 51 is the signal wire from the Coolant Temp Sensor to the ECU, and the Black/Brown wire Pin 54 AND Pin 21 which is sensor ground shared with most other sensors, the atmospheric pressure, TPS, Tip over sensor, air intake temp, Airbox Pressure
 
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If your not sure how it works, it is simply a Thermistor, which changes resistance with temperature, As coolant temp goes up, resistance goes down, The ECU measures this resistance to ground change and calculates
voltage drop, and determines the coolant temp. It does not need a 3rd wire for a signal reference like a MAP sensor or TPS due to the properties of a temperature based resistor or better known as a thermistor
File:Old JIS Symbol of Thermistor.svg - Wikimedia Commons
 
Thanks...much appreciated...I connected the Busa ECU and all works well..I then cut the data wire B/Gr
and the temp gauge dropped to Cold....thought I was on a winner here...then connected the AEM 508 ECU and temp gauge went to Hot as before....I'm told it cant be done as the AEM 506 ECU is designed for the Busa and the 508 is for a V8 as I use the other bank of 4 to take my secondary injectors that cut in after boost.
Below is a pic of the dash I built with the Busa instruments.....I'm a fussy bugger...and would love to get it working rather than having a stand alone gauge.
Cheers TJ

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That looks like very cool setup! Do you have any videos of it running or driving around?
 
Not just yet... only when first startup before it was in the car.....its no slug...its on 4lbs boost at the moment and limited to 9000rpm with 235hp....sorting a few bugs out as still running in....should be over 300hp soon.
 
Check the configuration in the AEM for your coolant sensor, sounds like the the resistance on the sensor isn't matched to the AEM. It is the same as a 2000-2007 Honda S2000, which should be easy to configure using that.
 
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