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Ironic, the one item I know you and I are chasing to address, heat soak. The explanation makes plenty of sense. I have to look at my last datalog but the IAT were really hot. And my testing was early in the AM to avoid the midday heat.Lexus Update: So after checking out the couplers, I ended up replacing a couple of the couplers. <----- See what I did there haha. Long story short, it didnt fix the boost issue. If anything it made me really impressed how long they have held up. So no dice there...lol.
I did go to a larger Lexus meet up. There I spoke with a couple of other turbo Lexus owners, one of whom is pretty knowledgeable. I asked about my loss of boost and he brought up a good point. Extreme Heat.
Story time....gather around. When I was seeing 27/28 psi it was during the winter months. Looking back at the logs, it was 50 to 60 degrees during most of the pulls. Then I had issues with the throw out bearing which parked the car in March. Then I broke my leg, so I wasn't able to work on it. I didn't iron out all of the issues with the transmission until late July when I got the car back on the road. Going from 50 to 60 degrees in March evenings, to 100 to 110 degrees in summer month evenings makes a lot of sense.
It has been 100 to 110 degrees each time I have gone out and done these higher boost pulls. That could be my problem. Extreme heat = Less dense air to compress = less boost. Plus I am I think I might be on the limit of the current WG Spring. I know for a fact that this turbo is not out of air, or out of it's compressor map efficiency.
Well, I can have NONE of that. I have had this car at 27/28 psi and DAMN IT, I am going to use it. So today I am buying a heavier wastegate spring. Granted 98% of the time I drive the car on 17 psi (500 hp) but having the heavier spring and have being able to have the 27/28 psi at all times is the goal.
Even just from the photo, I can see they are very very clean. Burning nicely.Lexus Update: The plugs look great. I checked them out under a magnifying glass. No damage, straps are sandy/light tan in color. Porcelain inside is a light tan with a nice pencil ring pattern. There are no dark or silver specs anywhere on the plugs and in valley/near the base. Could probably get away with a couple of degrees of timing across the board. If I hadn't bought a new set of plugs, I would have zero issues putting these plugs back in.
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New plugs went in and I gapped them down to .018 which is down from .020 from the plugs I pulled. I did check the old plug gaps and they opened on average of .05 to .06 across the board. If I have problems at idle a .018, I will re-gap the new ones back to .020.
The pistons look great. No pits or anything out of the ordinary. They are actually a bit cleaner than before as well. Seems the alcowater is steam/chemically cleaning them lol.
All in all I will head over and schedule a dyno appointment for next week, and probably re-write a tune with a couple more degrees of timing added just in case......