bruthaboost

I'm piecing together the rest of my "turbo kit" and dayam I'm getting nickle and dimed to death on fittings and such. Anyhow I've arrived at purchasing an egt and have read the archives on such. However, I'm considering just buying the gauge and making my own probe. At work we have lots of different gauge k type thermocouples lieing around and 316 stainless fittings. I'm wondering if it's a reasonable idea to fab my own probe up and save the dollars toward the DIY wideband O2. Is there anything else to these probes/gauges besides the thermocouple wire and the fittings?

Feedback.

G

Actually, there is. There's a driver for the probe, and a translator of sorts. The probe is either given voltage or ground (sometimes a frequency), and the driver interpets the resistance the probe is sending in relation to heat, the translator circuit sends a current or voltage signal to the gauge.....

For quick and easy, you could measure the resistance of the probe at different known temperatures and make a linear graph and use the resistance measurement to get temps, cheap and useable, just not pretty or easy to interpret (without practice).

Arturbo

A thermistor??

art

G

I don't understand... Are you asking me if I am referring to a thermistor? I think thermistors, thermocouples are the same. Please clarify....

BlackOutSi

OK here goes.. Here's how the EGT works on military planes (since i work on that system) You have Alumel and Chromel, which are fused at the thermocouple. When heated, they make a very small voltage (millivolts). You amplify that at the guage and you get your reading. Here's a Mr. Wizard science experiment for ya: Get a Nickel and a penny, put spit between them(to conduct electricity), and hold them together with multimeter leads while heating them up with a lighter. You'll see a few millivolts as they get hot.

Another idea if you're trying to save $$ is to look at private aircraft guages. They are usually a 2" diameter guage, with a square outside edge so you can screw it into the plane's dash. Just dremel off the square portion, and it'll fit in a normal pod. You can get them for around $80 guage and probe... Just a thought

rjardy

hey black out , you must be a c-130 machanic!!! i used to be stationed there!! at little rock!!!

BlackOutSi

Yup

BlackOutSi

OK, I found a decent guage for ya! Westach Guage=$39.95...Sender=~$30...
http://www.aircraftspruce.com/main.html

I looked at others, but Westach seems the best buy.. I have a friend with one and it works great. The others are as follows:

UMA- cheap and self contained, which means no backlighting, no wiring, but may have a bit of lag. $38, probe included
Sky flight- Kinda cool, it's a digital display with a preset alarm for overtemp. Would look kinda cool on the dash. $135, probe not included.
VDO- Nice, includes probe for $130
The rest are kinda pricey..

marklamond

Until i got my Autometer EGT gauge (out of stock) i used a cheapo multimeter that supported "K" type probes. It allowed readings in either C or F, and was very accurate, and the readout was digital of course. The probe i used was the Autometer one.

Arturbo

Yes, I was just asking if you were refering to a thermistor. But they are the same. I was trying to sound smart, which Im really not...

art

EE_Chris

Lets go ahead and clarify, shall we: Thermistors and Thermocouples are different. Operation of a Thermocouple has already been stated by BlackOutSi....so good to go there.

However, a thermistor is just a resistor that varies its resistance with temperature. You can have negative and positive temp coefficient (sp?) thermistors...so that when temp goes up...the thermistors resistance will either go up or go down, depending on which version you have.

The ECT and IAT are examples of thermistors used on a Honda. And just to note...these are the SAME sensor. They give the same output for the same temp (roughly). So when your car is cold, you could measure there respective inputs and they should be the same...a little sanity check if you will.

bruthaboost

Thanks for all the info fellas. My question has been answered. Yeah I forgot about calibration . I'll just go and buy one.

G

You are smart, you're tha "Art of turbo", saved me alot of time, hehehe. You are the poop!

Hybrid

yeah I have a link at home about the airplane EGT's which is the way I'm going I think. I mean for like 80USD you can get the probe and gauge. the gauge I seen was alread round on the egdes and 2".

I'll post it up when I get home to see what yees all thinks about it.

It has to be accurate if its approved by the transportation safety board, and not over priced like Greddy or Blitz etc....