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Im having trouble finding the best spot for my EGT and need some help. So I am planning on using a cast iron log turbo manifold (for lack of space) and I am getting a lot of different answers on where to put the egt sensor. I originally didn't want to tap and weld a bung in the manifold that could compromise the structural integrity or exhaust flow, but many people as well as maxxecu customer support are telling me that putting the Egt bung post-turbo (in the down pipe), would make the sensor useless to use in tuning or temp monitoring. Is this true? Does the egt HAVE to be pre-turbo to get accurate or useable results?
Since my ecu can utilize an egt sensor, I would really like to use everything I have available to me since this will be my first attempt at tuning the car by myself. Also, I am using e85 for this build, so many people are also telling me that I will be fine not using an egt sensor at all. Not really sure what to do, but if it could be utilized in any way from inside the downpipe, I would be most interested in leaving it there with the Wideband. Engine is a 2jz ge-t by the way. And please let me know of any questions, comments, concerns, or advice you have. Thanks
The turbo, in the process of doing work to generate boost, is extracting heat energy from the exhaust. This can lead to a temperature differential across the turbine wheel inlet and outlet of a couple of hundred degrees under boost. This doesn't give you an ideal representation of what the combustion temperatures in the cylinder/s are, which is the primary reason for using an EGT probe.
Without seeing the design of the exhaust manifold that you are using, if you are using a single probe to read all of the sensors, then you would try and mount to probe after the final collector to give an overall EGT reading. Try and avoid mounting the probe in the collector as these tend to be the hottest part of an exhaust system.
If you have the probe and the ECU supports it without sacrificing another sensor, then I would run the probe, even if you are using E85. Too much information is not enough.
I see, thanks for the reply Stephen. I actually can't seem to attach any photos to my message right now, but here's the link for the manifold online so you can get a look at it. https://shopfigs.com/v5/B597 (Its the Treadstone 2jz-ge log manifold if the link doesn't work). I would like to hear your thoughts based off the design of this one, and see if its even worth tapping into. Maybe separating the banks with 2 egt sensors a little ways before the collector would be best, so they don't get heat soaked from the turbo? Thanks
EGTs aren't the primary tuning aid, that's more lambda and ignition on a dyno', but where the EGT peak IS important is at the turbine wheel, as the materials used have maximum safe operating temperatures and, if too hot, it can actually result in turbine failure. Different turbo' manufacturers use different alloys, some will tolerate more than others, so there's no set value to work to.
That looks like one of the better 'log' designs, and if I were to use an EGT probe, I'd place it in the centre of the 'collector' region, to get an average. best would be one in each runner, close to the flange.
It's going to be tricky to do a true 'EGT per cylinder' install on that manifold due to the log-style. I don't think you're going to be able to locate the EGT close enough to the header flange for it to not be potentially affected by flow in the main log and hence the reading really can't be relied upon. If you want EGT on this manifold I'd be inclined to add a single sensor pre collector and be done with it. While I'm always of the opinion that more data is better, the reality is that I usually only fitted individual EGT on very high output drag engines where I really wanted to ensure I wasn't seeing cylinder to cylinder variations. For mild to moderate tuned engines it's uncommon to incorporate any EGT at all in most applications so anything would be a bonus.
Thanks for the help guys. If my only option is a single probe below the collector, then I don't believe I can utilize an egt quite yet with this manifold. The turbo flange (bottom) side does not have the angle for a sensor to be positioned there, it would come in contact with the head. And placing it below the collector in the middle of the wastegate (top) side would both come in contact with the overhead intake, and could cause potential structural damage or cracking from how very thin the manifold material is in that one spot. Sad.
I have found another log style and the fabricator said he wouldn't mind adding egt to it, but it is not available right now. So I will stick with this one for now and try to keep boost pressure and temps minimal. Thanks again