I've never had car with a turbo engine and not familiar with turbo noise aside from test driving multiple brands. Recently purchased 2022 NX 350 F Sport (non-hybrid) and noticed gargling noise in the low rev range (1500-2500 RPM) when not driving aggressively in standard/eco mode. I do hear hissing noise when I step on it, but this gargling noise bothers me. Can someone tell me if this is normal or I should take it to the dealer. Car has only 400 miles on it. Thanks

 

"Turbo gargle".

I test drove an F and a non-F a couple of weeks ago and noticed the same thing - it's probably normal for this vehicle, although it's definitely not what I would expect from a Lexus.

 

I've driven two NX350s with the 2.4 t engine. We are leasing one and we've also had a loaner. Both of them exhibit engine knock (the gargling or clattering you describe) at certain rpm under load. If you rev the engine at a stand still it won't knock. It only knocks under load. At first I thought it was low octane fuel. I pumped some 100 octane racing fuel into it and the noise was still there. This makes me think it might be the variable valve timing actuator. This tends to be a problem area for a lot of Toyota engines. I'm going to report it to the dealership and see if they'll take a look. If you want to do some DIY troubleshooting, you can see if you can disconnect the variable valve timing solenoids (one at a time for intake and exhaust). Then take the car for a drive and see if either one of those solves the problem. Keep in mind this engine has an 11:1 compression ratio, so we may just have to except engine knock...even though you'd think the 100 octane racing fuel would not knock even with 11:1 compression ratio...but who knows. Good luck.

 

Ours does the same thing. Makes me think it's a RAV4. Funny that they're putting this buzzy thing in the new RX's.

 

350 and same thing as well. I didn't know how to describe it , but you nailed it ( gargling). I thought ill tell the dealer next visit in a 1000 km. ( normally i listen to high music so i don't notice it.) .

 

Given that we all seem to be hearing the same thing I'm guessing this is normal. Undesirable, but normal.

 

I don't understand the problem with the lexus turbo. Thet are going to use the same engine in the 2023 RX 500h. Not all turbo's sound bad!. My current turbo has a sound enhancer from factory; a lot of people have disconnected it, not me. My car sounds great pos and gurgle when you get on it a let off gas and runs like a bat out of hell. ,,,then I have hte NX for luxury and quiet sereness

YMMV,
MidCow3

 

This is going to be long, but I think it's the reason you hear the "gargling" noise. Anyway, here goes. Toyota and Lexus use a dual fuel injector setup. A direct injector and a port injector. Most manufacturers only have the direct injector on their turbo engines. Toyota uses the port injector primarily to clean the back of the intake valves and prevent carbon buildup. Carbon buildup is a common problem for direct injection engines.

Direct injection came along a while back but one of the benefits was that it allowed manufacturers to increase the compression ratio without introducing engine knock (the gargling noise). The 2.4 t engine in our NX is a good example of this. It has an 11:1 compression ratio.

Here's where things get interesting. Before manufacturers were required to fit all vehicles with an "auto engine start/stop" feature, Toyota programed their direct injection cars to only switch over to port fuel injection when their cars were idling at a stand still. Now that "auto engine start/stop" turns off the engine when the vehicle is at a stand still, I'm betting that Toyota/Lexus has reprogrammed their cars to switch over to port fuel injection when the cars are moving, possibly during low or negative boost conditions.

This is why you don't hear the "gargling" when the boost is on. You only hear it when the boost gauge is around zero or below (engine under vacuum). Feel free to test this theory. Switch your Driver Information Display to the boost gauge. Watch the gauge as you modulate the throttle. I bet that you won't hear the gargling sound when the boost gauge is at 7.5 psi or above. You will only hear the "gargle" under low to negative boost conditions. Although, engine RPM might also be a factor. I haven't tested this yet...

If I'm right, Toyota/Lexus needs to address this problem with an engine management software update. This "gargling" is engine knock, either pre-ignition or post-ignition detonation. Neither condition is good for the engine. To be clear, the engine is not suppose to run this way. It's possible that it's a much bigger problem in states that only have 91 octane premium gas. Many states have 93 octane and I'm betting the cars did their endurance testing using the higher octane gas. Now, the problem still occurs to some degree even with octane up to 100, so, octane booster and 93 octane are not going to eliminate the problem. They may reduce it to some degree.

What I'd like to see happen, is a reprogramming of the engine management software. Specifically, if you disengage the "auto engine start/stop" feature (button on center console), the engine switches over to port fuel injection only when the vehicle is at a stand still. At all other times, only the direct fuel injectors are active. This way, you can prioritize reliability if you want to (prevent carbon buildup on intake valves) or you can prioritize refinement if you want to (eliminate engine knock/gargle).

Now...whether Toyota/Lexus will look into this or not is the big question...

 

A very nice analysis and write-up, though I got a little lost near the end (my fault, not yours).
Bottom line question: I routinely disengage auto start/stop as soon as I get into the vehicle. By doing so, am I hurting the long-term health of the engine? (I have not heard or sensed any engine knock.)

 

No, the engine start/stop is only meant to save gas. It likely has minimal effect on gas consumption. It's mainly a gimmick. As far as engine knock, you probably are hearing it, it just doesn't sound like gargling to you. To me, it sounds like an extra layer of clatter on top of the engine's normal mechanical noise. It's not necessarily noticeable unless you know what you're listening for. If you are using 93 octane, you will probably not hear it as much as those using 91 octane. One way to check for it is this: try accelerating up a hill at low RPM. To do this, put your car in manual mode. Then as you take off, force it into 2nd gear (short shift) before it would normally shift up to 2nd. Then, give it a lot of gas. I'm pretty sure you'll hear engine knock. What you're going for is low RPM, low boost, heavy throttle pressure. It's especially noticeable in the 2-3K RPM range. Good luck.