hybrid450

Hey there,

I have a second thread on a knocking issue, which is rather unrelated to this one, because this one happened much earlier and of course I also cannot find anything on the internet about such a thing, so here it is:

My GS450h (2008) was running fine since I bought it this year, I could drive with no issues with really high speeds for long periods of time, even hitting the speedometer edge a few times while on the same ride. I have to point out that my unit has electronically limited speed limit to 260km/h (250/h via GPS). There were no issues at all even with longer driving with speed ~200km/h. After some time I decided to change my timing chain due to its mileage, all of that done professionally with OEM parts at trusted workshop, everything was running same good as before. After some more time, I had to change my hybrid battery pack due to the old one failing already, so sadly that was another big cost for me - I got a battery from a 2020 Lexus so it's like new, and the car was running even better because the car could run much longer on electric mode than before, and I could see the whole green battery much more often. So far all good, I took some rides, normal and sportier ones and all was good until...:

Case #1:
Some time after, I was on a road driving normally around 120/h, after around 5 minutes on the road, I pressed the gas pedal 100% and here's the issue, the car simply didn't pass the 220/h. It seemed totally like a speed limiter engaged BUT with a sensible push, like you slightly pressed on the brake (which of course I did not). Just FYI, during a normal speed limiter at 260/h on speedometer, you simply continue to drive normally with a constant max. speed but there's no any "push" or anything, you can only see the kWh gauge dropping down.

Case #2:
After around month since case 1, there were no problems meanwhile, even on higher speeds, then once I was on a speedway I tried to floor the gas pedal again, from around 180/h, it went smoothly with no hesitation to 250/h. Same road, 5 minutes later, I do it again, and boom - the car backed off at 220/h. This is the time I wanted to check if it wasn't just my "feeling" or mistake, so 1 minute later I try again - 220/h max, again - 220/h max, every time a small push is felt when reaching the "limit".

Case #3:
Some time later, again car was driving fine, no issues reaching 230-250 speeds with full throttle, then once on a road it happens again, but this time, I floor it from around 180/h and it stopped at 240/h, which was different from all previous times when it happened ~220/h. The feeling was the same, though.

Few facts:
- engine coolant temperature was at all times showing 1/2 gauge
- I did not try to stop and restart the engine and immediately try again, maybe that would "reset" something and allow me to cross the temporary limit
- once it happens, the car drives totally fine, there are no any errors, the power does not change, the engine sound is all okay, no errors on dashboard
- it happened only once to cut out at ~240/h, all the others (around 6 times total, from which 3 were checked in a row) were ~220/h
- 80% of the trials were with the gas floored, and the rest was with around 80% gas pedal press
- before the timing chain change and battery pack change (and other smaller things), the car never cut out at a lower speed than the electronically limited 260/h on speedo
- driving with the max. speed was also possible without issues even for some time without releasing the gas and there weren't any cut outs, now I was afraid to try that.
- the outside temperature was similar in all cases so I doubt it matters
- sometimes I tried to floor the car from a few speeds, like 150+, 160+, 200+, and I could not replicate the cut off.

What I have not tried due to being afraid of is: trying NOT to release the gas pedal when the "limit" is hit. At all times it occurred, I automatically released the pedal as I did not want to overheat anything or cause any trouble to the engine cause I don't know what's the cause of the cut off. Maybe if I kept holding the pedal, something would happen, maybe not, but I preferred not to try it yet.

What I monitored on Techstream while driving normally and with higher speeds is:
- Motor Temp MG1 and MG2: one of them sometimes went over 100 degrees C with the car floored, and during normal drive they stayed around 80-95 degrees
- Inverter Temp MG1 and MG2: highest I reached on MG1 was 96, on MG2 it was 57 on higher load, both around 50-60 on normal drive
- Engine coolant: almost never passed 90 degrees and once it did it was for a few seconds only and around 92 deg
- Converter Temperature: ~ 50 deg almost all time even on high load
- T/M Oil Temperature (AT temperature I guess): 81 deg was the highest value I got

Sadly, the above parameters are all from the trials when the "limit" wasn't there, with speeds from 160 to 250 without issues, I could not replicate the "limit" on the go when I was connected to Techstream to check the parameters at the moment of cut out.

Concluding... I think the temperatures are normal, even with some hitting ~100 when car is under high load, so I am not sure if that would be the case of overheating. I also know that there is some kind of "hybrid system overheat" error on the dash when the battery is overheated, which never happened to me. The engine works at all times normally if we speak of its power. I have no idea what might be the cause of the faster "speed limiter" happening randomly. I thought that some ECU might be putting on some emergency trigger to avoid overheating something, but I think it would show some error in Techstream, and there's nothing even after it happened a few times in a row.

Does anyone of you have an idea what happens, suggestion on what else to check or maybe someone had something similar on their Lexus?

Lwerewolf

MGs (the electric motors) hover around 100 celsius.

Inverter temps... try getting the car to 125, decelerating to 65 and then flooring... if you want to see your inverter MG2 temps spike to 125+ and your car will throttle... actually, don't do that, you might blow your inverter. More here: https://openinverter.org/forum/viewtopic.php?f=14&t=776

ATF temp - 80-ish sounds normal. https://lexus-europe.epc-data.com/gs...ne/1603/16491/ - cooled/warmed by the engine's coolant

Get this:
http://hybridassistant.blogspot.com/
...and a good compatible adapter. The app can export logs in .csv

Other than that...
https://club-lexus.ru/forum/viewtopi...=0&per_page=15
Might want to read through this.

hybrid450

So you are saying that Inverter temps should not cross ~120? Then, in my case of driving nothing should happen where I rarely floor the car from lower speeds such as 60/h, but it happens from time to time and nothing happened luckily. And flooring from ~160 to 230 got me around 100+ degrees. I quickly read through that Russian thread and it looks like cleaning the radiators helped the guy at the end, but his problem looks a little bit different because he could not speed over ~130/h, while for me it happened almost every time at same speed of ~220/h, and like I said, sometimes I could not pass that speed, and the other times I could normally reach the max. speed even with full throttle and no issues.

Good to hear the ATF and MG's temps are normal. I'll try to connect the hybridassistant app to my OBD adapter as soon as I get my car back, but I will not floor it until my knocking issue is solved or known. Any specific things I should watch out for in there?

I heard that the inverter may even blow up and I saw some pictures of it blown up, could you tell me which temperatures in Techstream relate to that inverter which is under the hood connected with these orange cables? Is is the "converter" temperature, or the inverter consists of "Inverter MG1" and MG2 inside that box?

The whole situation might be dangerous considering someone tailing you at that speed - and sometimes it happens - and suddenly the engine/whatever cuts down the power and you slow down unexpectedly without the brake lights... you know what I mean. It has never happened to me for 2 years while I had GS430 earlier, and like I said in GS450h it hasn't happened before at all, and now it happened from time to time and I had no idea what the hell was happening, but I wasn't connected to techstream or anything to check the temps when it actually happened.

Lwerewolf

If you look at hybridassistant clips, inverter temps should barely swing at all - whether it's the mg1/2 powerstage or the buck/boost converter. If you floor it from <100 (say, 60) and you feel lack of power until 110-ish, MG2 is probably still in high gear. The car typically throttles power output to maintain temperatures at 125, but if it's too far gone, temperatures might spike too quickly = POP, lights, no power (or just an "inverter performance" code and limp mode, if you're lucky). Read the openinverter thread for more details, if you want. Theory is thermal solder cracking - not an issue on ls600h/rx450h/4th gen gs450h/etc. - models with double-sided cooling on IGBTs. I'm waiting for an ls600h inverter right now, it might be compatible with our vehicles... if so - that issue is solved.

If somebody's tailing you at those speeds, he should have way bigger issues than your power going out.
https://www.bussgeldkatalog.org/abst...FanMtAodpwkAcw

The whole idea about hybridassistant for those cases is that you can review the logs later - in excel/calc/whatever you're using to navigate .csv files easily.

EDIT:
I thought the guy in the russian club lexus forum had a similar issue like yours - "dies off" at high speeds. Regardless, you might want to take a look over there - plenty more documented issues with regards to the harsher operating conditions (fuel, air, road quality, some people withholding maintenance, lots of fake oils... etc, etc - really shows what's robust and what needs attention).

hybrid450

I'll definitely check the data with the assistant if it works with my OBD adapter and if my car runs fine. I'm little scared to try flooring it from 60/h for testing, but if I recall correctly, I had no issues when floored from ~60 to ~130 a few times since I bought the car, and the second "gear" got engaged pretty quickly with a slight ~1sec or less power loss but that'd be normal due to the gear change and looking at the others acceleration videos from this car.

Except for the temperatures of the hybrid systems, do you think of any other component that would cause such situations at random times? Any sensors, maybe something with the timing chain or whatever that would sometimes "block" higher speeds before the speed limiter?

Lwerewolf

Anything can happen, you're pushing the car - even if it's relatively more reliable than its competitors from other makes. There is a reason why airliners don't take off at full power

60-130 with gear shift is not a problem. Loading MG2 while it's sub-5000rpm seems to cause temperature spikes - MG2 is around 2500rpm at 50kph when in 2nd gear. If it makes the gear shift at 120 (~105kph, ~65mph for US/JDM-spec cars with the 3.769 final ratio diff, EU/Global has 3.266), then you were obviously in 1st gear up until then. The dowshift occurs when dropping to 55kph at the earliest - potentially at even lower speeds if you're in S-mode and engine braking at the time.

hybrid450

I know it can be anything, I just thought you might have any other idea what can cause this, because no one in the internet mentions a similar problem, except for inverters blowing up or this Russian thread you mentioned but IMO it was a little different case, but worth trying to clean the radiators too.

So generally it should be fine to floor only when MG2 is in the second gear, right? What about flooring from around 10/h or from traffic lights? Is it also dangerous or MG2 will handle that properly in such cases? Of course it's very rare case, at least for me, but sometimes I wanna "go crazy" and not blow anything up

Just FYI, on all the cases where the "blocking" occurred, I did not floor the car on speeds lower than 100, it was more something like 140/150+. About the downshift, I can sometimes feel it when cruising in "D", especially when driving on a hill up or slightly pressing the brake when driving off hill, but I don't think of it as an issue because I guess that if the "gear up" is sensible when speeding, then the "gear down" can also be felt sometimes.

Lwerewolf

Log and you'll see. In my case - I get throttling in non-cold weather and the circumstances I mentioned (high gear and low speeds). Haven't had issues from a standstill - beyond the lack of traction.

2nd gear = high gear = "highway" gear or whatever. 1st gear = low gear.

https://slideplayer.com/slide/14432904/ - same transmission, motor, etc - the mg2 power increase is probably on the inverter-side.

Downshift - I really have to misbehave to notice it - giving it gas right as it downshifts, etc. Upshifts - noticeable, depending on how much you're flooring the car.

hybrid450

By "throttling" do you mean you are getting a cut out and cannot cross a certain speed on the mentioned conditions? If so, at what speed are you blocked? From a standstill I also get traction issues but that's kinda normal with such amount of power and RWD, unless you got really good tires and weather conditions.

About up-shifting I totally agree, although I almost always feel the downshift when e.g. driving off the highway cruising up the hill with slightly pressed gas, but in normal driving it's very rare to feel it so I didn't worry about it.

Lwerewolf

It's a power output throttle - 150kw at worst (summer weather).

Traction might've been a bit better if the car had a torsen, but... they learned their lesson with the IS-F 2010 update... and still didn't apply it to the 450h f-sport :P

hybrid450

FYI, speed cutting problem solved, it was due to the failing fuel pump in the tank. Replaced with a used one and the car hasn't cut the revs since then, even when near the reserve. I don't drive so hard with nearly empty tank, but I floored it many times when fuel was like 2/5 full and it didn't do any speed cutting, only at the real speed limiter (250km/h GPS speed) so all good.