WIERD- EGT wires disappearing!

[Eatoniashoprat]

Hi, I've recently started doing the wiring for my Ej20 turbo conversion. I've done this before with my van but I found something interesting this time that I thought I would share and see if anyone else has seen this.

The engine: 1989 JDM EJ20g turbo, first year for this engine, only came out in japan.

There was what looks like an EGT sensor right after the turbo. Its not an 02 sensor because that is in the up-pipe. Now, the interesting thing is that my diagram shows nothing of an EGT sensor. so I followed the wires coming from it and as far I can tell, they go nowhere! They go into a plug, and the plug that it goes to doesn't have those pins. This is also the case with one of the three temperature sensors on the upper coolant manifold, the single prong ones, it goes to an empty plug. So they installed an EGT sensor but didn't use it? What's the deal?

Am I making a mistake anywhere? I followed the wires several times. The only thing I can think of is maybe I'm connecting the wrong plugs, but there are no other plugs that match it. From my experience every plug on a subaru is different. Please correct me if I'm wrong.

Thanks for any help, or comments. My guess is I will find out more when I get down to the final stages of selecting which wires I need and which I don't, but its not looking like it right now.

Mike

[1303R]

could they be for a diagnostic plug in? so subaru garage can plug it in when servicing?

[Eatoniashoprat]

I think I've got it figured out, for the most part. I found out that the EGT sensor is only used for emissions and doesn't affect performance. its still not quite making sense why it doesn't go directly to the ecu like it should but I guess it has its own light in the dash so it could go through there first. At any rate, I'm going to take it out of the system since the ecu will be happy.

Mike

[beetle1303]

Mike, as u said it is confusing...
but how could an EGT sensor be used for emissions? im not saying that it can be used for performance either. not directly at least...maybe as a safety cut off to go into safe mode??if EGTs run really high?

From general theory, performance is affected by emissions and vice versa. The way to monitor that is through an O2 sensor often called lamda (λ=1=14.7 ideal mixture) and in an efi system the ecu is able to sense and alter fuel delivery and/or ignition timing...

another thing to consider is: was this engine propelling only one car or was used in other applications as well? sometimes in order to minimise production costs, they use the same parts through the whole range, or upgraded versions of the same engine are defined by simple to them changes but very confusing to us that we dont have all the application info about the product. just a thought

Chris

[Eatoniashoprat]

Originally Posted by beetle1303

Mike, as u said it is confusing...
but how could an EGT sensor be used for emissions? im not saying that it can be used for performance either. not directly at least...maybe as a safety cut off to go into safe mode??if EGTs run really high?

From general theory, performance is affected by emissions and vice versa. The way to monitor that is through an O2 sensor often called lamda (λ=1=14.7 ideal mixture) and in an efi system the ecu is able to sense and alter fuel delivery and/or ignition timing...

another thing to consider is: was this engine propelling only one car or was used in other applications as well? sometimes in order to minimise production costs, they use the same parts through the whole range, or upgraded versions of the same engine are defined by simple to them changes but very confusing to us that we dont have all the application info about the product. just a thought

Chris

EGT is directly related to emissions, the temperature of the exhaust is a direct correlation between if the engine is producing nitrogen oxides or sulphur oxides (I think its sulphur). Searching the nasioc.com site revealed that the EGT will only send a emission light on the cluster if exhaust temps go out of range, the ecu won't alter timing/air/fuel based on its reading, only the 02 sensor.

Emissions is tied to performance in a way, except it depends which kind of emissions you want to get rid of. When combustion temps are high (running close to ideal air/fuel) = lots of power, I think its the NOx that is produced, and when temps are low, I think its the SOx that is produced. As far as I know, the idea for emissions is to keep temps low so no NOx are produced and then reburn everything in the cat. These low temps mean a rich air/fuel mixture, meaning not the most power. (I'm definately on a tangent, and I've haven't taken a course on this in a while so the details might be slightly not correct)

Talking to other people with this engine they have the EGT sensor as well. From what I can guess, the wiring for the EGT must go through the gauge cluster first before going to the ecu, and I don't have the cluster. Either way its getting the cut.

[Bug@5speed(US)]

When I still had my subaru, it has a bung for the EGT sensor on the up-pipe as you mentioned..

After I swapped to my new exhaust and retuned the ecu, we omitted the EGT sensor and just plugged the bung as it would not be used.

I can't remember why the ecu did not really need it. But I do remember that we ran a small resistor across the plug to simulate some resistance that would have been provided by the EGT sensor.

One reason that the EGT sensor is removed is due to it failing and breaking, thus the potential for it to go into the turbo inlet and causing some serious failures..

Ran like this on the street and track for over 50K miles until I had some oil issues..

Plenty of posts on the subject on Nasioc or other sister forums..
VR
ALex

[Eatoniashoprat]

Originally Posted by Bug@5speed(US)

When I still had my subaru, it has a bung for the EGT sensor on the up-pipe as you mentioned..

After I swapped to my new exhaust and retuned the ecu, we omitted the EGT sensor and just plugged the bung as it would not be used.

I can't remember why the ecu did not really need it. But I do remember that we ran a small resistor across the plug to simulate some resistance that would have been provided by the EGT sensor.

One reason that the EGT sensor is removed is due to it failing and breaking, thus the potential for it to go into the turbo inlet and causing some serious failures..

Ran like this on the street and track for over 50K miles until I had some oil issues..

Plenty of posts on the subject on Nasioc or other sister forums..
VR
ALex

On mine the 02 sensor is in the up-pipe and the EGT is in the downpipe, its wierd I know.

[Bug@5speed(US)]

Eaton

That is weird.. Doesn't seem right but I then again I did not run a jdm motor in mine..

Do double check, again its seems not correct.
VR
A