I've been wondering if it would be possible to use the built in Ambient temperature sensor display as an ACT gauge. I need to measure the output from the ambient temperature sensor's thermistor, to see how many volts are output for a specific temperature. Then I could wire in thermistor wire under the silcon hose just before the throttle body and put a toggle switch in to select either outside temperature or ACT!

The service manual doesn't say anything about the A/D scaling values, so it's not going to be a fool proof reading, but I'm sure it would give a good indication of ACT.

http://ken-gilbert.com/wrx/STi_Manua...y%20System.pdf

http://ken-gilbert.com/wrx/STi_Manua...%20Display.pdf

Does anyone know where this sensor's installed? Has anyone else done this? I'm sure you'll probably say buy a stand alone gauge, but where from?

Cheers

Anders

 

Anders,
The sensor is just in front of the radiator (on a newage car).
Two problems I can see. The document describes how the temp is ignored when the car is moving less than 10 KMH.
If you want to monitor ACT when stationary then you'll be scuppered.
The other thing I've noticed from Ecutek delta dash runs is that the response rate of the temp changes is pretty slow. This may be down to the "custom ecu" logging at a slow interval or perhaps a long averaging period is used.
This won't be much use if you are looking at rapidly increasing temps for WOT.

As for a standalone guage then I'm using a SPA dual guage, with boost pressure and ACT using a type K probe mounted directly in the silicon hose.

Nick

 

I wasn't too bothered about the < 10kmh values being ignored - I'm having one of Harvey's FMIC's fitted soon, so heat soak will be less of an issue. If I boot it from a low speed, it will probably fly past 10kmh before the display has the chance to update.

I take your point about the update interval. What would be an acceptable level? When Harvey took me for a spin in his Wagon, his ACT gauge was up to 50C in a short blast from second to fourth gear - probably around 10 to 12 seconds.

I had a look at the SPA gauges the other night when I found them on Google. I don't doubt their quality, but the £450 price tag is what made me look in to this.

Where do you buy your k probes from?

Cheers

Anders

 

A dual SPA gauge is IRO £130. K probe is £10 (Ebay) and a voltage convertor is about £50 (DIY).
SPA sell their own K probe and convertor but for silly money.

I thik the SPA will sample readings every 0.1 secs but you can apply an averaging period to smooth readings out. I think my ACT gauge is set at 0.5 secs.
Nick