k4nnon Posted November 30, 2023 Report Share Posted November 30, 2023 Alright link fam, I have a in depth question here bout individual cylinder EGTs. Hoping someone can shed some light on this for me. OK, So I just installed individual egt sensors in the exhaust runners of my fully built evo 9. Egt sensors are placed exactly 2 inches from the end of the cylinder exhaust ports. Depths of all sensors are the same at about 10mm of tip extended into the runners. I know and understand that the cylinders will never be the same temp and probably average 20-50*F at any given time with a spread of 100* or more between cylinders/runners. Now with 0 trim to any cylinders, iv noticed that my cylinders 2 and 3 are awesome and run right in line with eachother at only a difference of about 10*of eachother. My cylinders 1 and 4 seem a little different and I assume its due to the outer runners having a little harder angle on them coming off of the head. They follow similar patterns as 2 and 3 but are reading about 50-70* cooler than the others and my cylinder 4 seems to run an average of about 100* or more cooler then the others. Now,, all of this is with normal driving to work or out and about, no full throttle stuff yet. Iv noticed that if I let my car sit and idle that my cylinder 4 will sit like 200-250* cooler then the others and its confusing me because the others are within 50* or so of eachother. Heres where it really starts confusing me, If I pull fuel away from cylinder 4 at idle the temp doesnt change much. But if I add fuel to cylinder 4, the temp will increase slightly. Adding more fuel on top will increase the temp slightly some more, to a point, and then egt on cylinder 4 doesnt rise anymore. I have also noticed that adding fuel to cylinder 4 also smooths out the idle slightly. Question is, why would adding fuel to a cylinder at idle increase the egt? And is there a sweet spot to this? kinda like injector spray timing, should I add fuel to the cylinder until the egt peaks and starts coming back down or should I just leave it at 0 trim where my egts are drastically cooler then the other cylinders? What about the smoother idle with added fuel to cylinder 4? If the engine idle seems smoother then thats a plus right? See what I mean by confusing. If anyone has any input on this please let me know what you think. I know EGT tuning less then 5k and out of boost is mostly useless but if I can make the car run better, im gonna try. Thanks everyone! Quote Link to comment Share on other sites More sharing options...
JMP Posted December 1, 2023 Report Share Posted December 1, 2023 are the exhaust ports different lengths from the valves? I generally try to install the sensors with same difference from the valves which can mean different lengths from the head flange depending on the engine. I don't have an answer for your fueling at idle as the cars I've got EGT on are circuit cars and the readings are used to help trim the top end of things Quote Link to comment Share on other sites More sharing options...
k4nnon Posted December 1, 2023 Author Report Share Posted December 1, 2023 @JMP Hey thanks for the response! I believe the exhaust ports are as close to identical to eachother as possible, and sensors are as close to the same distance and depth as I could make them. Im probably being too picky with this because I logged another full cold start full warm up cycle again later in the day and I had better results. My paired cylinders 1 and 4 still read about 80* cooler then my other paired cylinders 2 and 3, but are within about 20* of eachother. My cylinders 2 and 3 are also close within about 20 degrees of eachother. So I feel this is probably not worth trying to make better. Durring the road test there was a larger high low spread between paired cylinders but both pairs stayed within 50* of eachother. I think these are fine results and I will proceed with more fine tuning into the power curve now. Thanks again for the response! Pics for reference to placement. https://drive.google.com/drive/folders/1vCdK0dcf-e1trjPDdsWoatiVo4tss9UE?usp=sharing Quote Link to comment Share on other sites More sharing options...
k4nnon Posted December 1, 2023 Author Report Share Posted December 1, 2023 Also the logs for the warmup and road test for anyone wanting to view.. https://drive.google.com/drive/folders/1fFhGordB8L6PUbTOF4wy3vvB_RKhiEO_?usp=sharing Quote Link to comment Share on other sites More sharing options...
Adamw Posted December 2, 2023 Report Share Posted December 2, 2023 Peak egt is close to stoichiometric, egt drops as you go richer or leaner than Stoich. So it sounds like your #4 cylinder is significantly leaner than the others at idle. Not unusual with large injectors operating in their non-linear region. k4nnon 1 Quote Link to comment Share on other sites More sharing options...
k4nnon Posted December 5, 2023 Author Report Share Posted December 5, 2023 Thanks @Adamw for the post. That makes sense, I was thinking because of the large injectors and trying to have them control such small quantities is probably some inconsistencies between cylinders. I actually played with my sensor depths and found out that the difference in temp vs depth is like 50* or more per 1mm. Some very small tweaking in the depths and I was able to get my egt values all within about 15* of each other. Im plenty happy with that. Moving into some wide open logging soon. Thanks again for the reply. Quote Link to comment Share on other sites More sharing options...
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