EGT guage/probe question

[Juggy]

hey guys, I got an autometer EGT probe and guage, ran it in the car and was gettting really low readings....i think the probe was faulty because wires were frayed from trying to install/uninstall head (bad location for probe)

well i switched to another probe i had kicking around, i bought off another guy and i didnt some searching, its a PLX devices
PLX Devices R-500 EGT Probe Kit (K-Type) : BoostController.com LLC - America's Source for High quality turbo boost controllers and performance products - 877-836-6155- precision boost control - manual boost controllers, electronic boost controllers,

someone told me that different probes run off of different voltages so if im not running the right probe i will get faulty EGT readings.....is this true???

both the autometer and the PLX are K type.....but my egts went from 950 to over 1600 at WOT....im running cast pistons, only 5 psi at the moment but too afraid to keep giving it gas.....altho the A/F guage seems to have green lights still....I want 1500 EGTs i dont like popping pistons....

the car recently had a new top end installed ported/bigger everything.....it runs like poop on the stock cal, barely stays idle and has NO power...the 3 bar cal runs alot better but stalls......both cals still have the extreme EGT's.....

PLEASE HELP!!!! if the probe is the prob i will just find an autometer....where can u even buy just the autometer probe??

[detobias]

any K type probe should work with any K type meter

I *highly* doubt you are really running 1600F at 5 psi unless your timing (ignition or cam) is WAY off, or you are super lean ; 950 sounds much more reasonable ; I have never seen more than 1150 running ~13 psi (in cyl #1, 4" from exh port)

you could try putting the new probe in a pan of boiling water and see if it reads around 212

[jim34]

Wheres your probe mounted ? That makes a big difference the majority of people run the probe on #4 witch runs a little hotter than the rest since its the last to recieve coolant, my car runs around 850f at idle and 1475f at full throttle and I have not noticed any increase in temps going from 17-27 psi, retarding my ignition timing did increase the exhaust temp quite a bit just 4 degrees retard caused my idle temp to go up 100f.
But then again when I blew some pistons out last year before the wideband install and severe detonation from a fuel pump failure caused my egt readings to drop off to about 1300 so low readings arent necessarily good readings you want to find your sweet spot and tune from there. I would belive the 1600 reading more than the 950 because that just doesnt sound right depending on where the probe is mounted.

[Juggy]

im running the probe off #4, about an inch maybe little more, from the flange on the TU header.

never had a chance to check the plugs, car is parked for winter! head has to come off anyway because I have a leaking exhaust bolt in the head that isnt sealed

[Juggy]

Quote:

Originally Posted by detobias any K type probe should work with any K type meter I *highly* doubt you are really running 1600F at 5 psi unless your timing (ignition or cam) is WAY off, or you are super lean ; 950 sounds much more reasonable ; I have never seen more than 1150 running ~13 psi (in cyl #1, 4" from exh port) you could try putting the new probe in a pan of boiling water and see if it reads around 212

now that u think of it....i was running a FM ported exhaust at the time i was getting the lower EGTs...and the probe was near the turbo flange....now its a TU header with the new probe at cylinder 4 an inch or so away.....so the probe got alot closer.....

[phantomrt]

You can have all green lights at 14.0:1 air/fuel ratio. And thats not good. It is way too lean. You need to be in the low to mid 12:1 range and there is no way to determine that with.

Depending on the exact setup of the engine and location of the EGT probe, more fuel can cause a HIGHER exhaust gas temperature. Basing tuning decisions off of EGT readings is not an accurate tuning method at all.
At stoich on the interestate, my EGT's will nearly peg my 1600 degree guage, assuming it is accurate. I have my probe mounted at the collector of a stock exhaust manifold. Been running like that for 21,000 miles now.

[jim34]

Temps get way hotter at the collector and its much more difficult to find info or help from anyone who has done it that way.

[phantomrt]

How so? My brain tells me that it should read cooler than #4 but warmer than the other three. Just mixing exhaust gasses...?? If you take the flame from two torches and combine them, is the flame they now share hotter?

It is also difficult to find help from someone who has compared EGT readings with accurate air/fuel ratio readings.

According to the instructions that came with my autometer EGT guage, the probe is NOT supposed to be mounted upstream of the turbo. I decided against that part as do most other people...

[jim34]

Ive had the probe mounted in the collector and it does show much higher readings approximately 200f +, something about unburnt gases reigniting in the collector ?
I didnt have my wideband at that time though but I know others have agreed with my results even with other types of engines.
I would think that putting two torches together would inrease the temp a bit, just like having a bigger torch head allows you to cut through thicker material

[puppet]

Reason it reads higher is the sustained exhaust gas stream from all (4) cylinders.

[phantomrt]

I suppose... the exhaust flow is much more steady at the collector and doesn't really "cool off" in between cylinder fires. But aren't those kind of readings what you want instead?

The unburned gas thing is a very realistic scenario. You can install an EGT probe downstream of the turbo and you can get hotter EGT readings by running it richer because the gas continues to burn outside of the combustion chamber. But I do not know if the distance from the #4 runner and the collector is enough to make a significant difference.

[Juggy]

k am i reading this right? you guys are saying that i should have had the higher EGT readings with the FM exhuast manny since the probe was at the turbo flange where all the cylinders meet into one???

well my scenerio is opposite....they were lower there, now they are about 500deg hotter running off of #4

someone mentioned cam/ignition timing....well i installed the cam one whole tooth that i could, and advanced it...so thats like 8 degrees advanced?? i have an adjustable sprocket...i should have put it in stock location then moved it maybe 4 degrees with the cam gear instead....8 is way too much i lost some top end with the S3 cam...

[crazymadbastard]

what is your ignition timing at? Mine was at 0 for a bit and then it would shoot up really high(1600+ probe on #4). What is your idle vacuum?

Be very careful running that hot! Here are my results on #1:

[puppet]

Quote:

Originally Posted by Juggy k am i reading this right? you guys are saying that i should have had the higher EGT readings with the FM exhuast manny since the probe was at the turbo flange where all the cylinders meet into one??? well my scenerio is opposite....they were lower there, now they are about 500deg hotter running off of #4 someone mentioned cam/ignition timing....well i installed the cam one whole tooth that i could, and advanced it...so thats like 8 degrees advanced?? i have an adjustable sprocket...i should have put it in stock location then moved it maybe 4 degrees with the cam gear instead....8 is way too much i lost some top end with the S3 cam...

Now so that we can understand you correctly ... you got 500* difference, same probe/gauge, just from moving the probe location? If so, you have to wonder about an injector issue. It would be interesting (not practical though) to see what each cylinder read while making this same move.
A difference of 500* from what amounts to about 3" of probe travel doesn't add up.

BTW, nice piston cmb!! Detonation killed that one though ... not heat.

[crazymadbastard]

knock knock! I did have molten gobs hanging the exhaust valve open though. either way be safe 1600 is too high, verify timing and try to get a wideband. I did this damage without a copilot watching the wb and egt gauges.