Radio88

I drive with my window down, and this brought to my ear, a mild detonation in my motor when mildly throttling up after it engages 2nd gear and third-and also when going up hills. Something you'll NEVER hear with the windows up.
I use nothing but Chevron or 76 premium 91 octane in my 4RX. Period.
Sure enough, while searching around the manual, on page 684 it states: "you may occasionally notice a light knocking for a short time while accelerating or driving uphill. This is normal and there is no need for concern."
Pinging/knocking/detonation are all a pet peeve of mine I hate it. I know what it can do to a piston over time. I am all about making my vehicles last a long time. I realize Lexus' stellar reputation for reliability, and am trusting that they aren't lying when they say "no need for concern".
To me, even mild pinging can start some internal damage over years and miles of one point being nagged by preignition hammers blows.
Talk me out of this.
By the way- is it true that our 3.5 v6 is an "Atkinson Cycle" engine? I do know that direct injection has detonation as a side effect.

aznkorboi

I didn't understand half of what you said.

I had a toyota engine that did some crazy misfires and misshifts. Lasted me 12 years plus.

Don't be a worry wart.

Curryolla

I read the same thing and did a double take. But, I'd be concerned if the pinging was continuous or if I got a check engine light. As for the Atkinson Cycle part, the answer is yes and no.

The RX 450h runs in the Atkinson Cycle all the time. The RX 350 has VVT-iW. Basically, it can hold open the intake cam mid-way to enable running in sort of a Atkinson Cycle at lower RPM. At higher RPM, it runs in the Otto Cycle. In addition, it has D-4S which involves both port and direct injection depending on the engine load required.

Radio88

First, no need for name calling, I'm just trying to get info. Second, I think I text pretty well, in plain English. I don't know how you read it. In simplified text, I am concerned that my RX pings a little when grabbing second and third gears with mild throttle; and when climbing hills. This is with 91 octane.

I appreciate the info. So it's Atkinson Cycle part-time. Maybe it's the direct injection and a lean map for economy that causes the ping.
Nobody else has heard any pinging in their RXs?

frubalup

No pinging on my 350 F Sport. But I run on 87 octane. I've heard of some actually having a better experience after reverting back to 87 octane rather than using the 91 but no personal experience.

Radio88

Were they experiencing engine knock too? Where did you hear that?

NateJG

I understood all of what you clearly said.

I've been looking for more details on the Otto-Atkinson Cycle feature (teasers like: http://gas2.org/2014/03/06/lexus-rc-...-cycle-engine/ - and was a bit sad to NOT read that the 4-Gen RX got the dual fuel injection (port and direct) of the version in the GS*.

Being able to control the valve train to achieve Atkinson Cycle surely allows the engine designer to let the engine also run in Otto Cycle as well (I'm wondering if they've already been doing that with the 3rd Gen RX 450h's).

You're probably as amused as I with the fuel discussions like "...my engine runs just fine on regular despite the prescribed Premium because the knock sensor causes the computer to retard the timing..." - and also wondering just how far on-the-edge of adjustment the engines can tolerate.

I'd be annoyed by being able to hear ANY pinging - let alone any sustained pinging; and in my engine-building years, I NEVER heard pinging at full throttle - rather only at part-throttle - which further amuses me when I read comments like "...I never floor it, so I don't need Premium...".

At least your engine isn't Prescribed Premium; and/but the fact that you're hearing ping while running it would cause me to do more research as well.

Please post your findings.

Radio88

Thanks Nate I appreciate that. I noticed today that it doesn't ping in sport mode, which makes me think the fuel is mapped to be richer in that mode, which then leads me to think that ECO and normal are mapped too lean? Regardless, I will tell Lexus at the 1st service. Sounds like I'm the lone ranger with this one.

frubalup

Sorry it was unrelated to the engine knock but about the hesitation and vibration problem. I tried doing a search for it again to find the post but couldn't seem to find it for some reason. Guess it doesn't quite help your situation anyhow.

ggebhardt

Hard to miss it: https://www.clublexus.com/forums/rx-...vibration.html

AL13NV8D3R

Are you guys sure you are not hearing the Direct Injection fuel rails pumping. Over at the 4GS forums we had a discussion about diesel like noise when at idle and while mild accelerating. It turns out that its just a byproduct of Direct Injection. Some members even wondered if their 4GS was pinging or knocking.

JDR76

The 4RX did get the dual injection system (D-4S). The ES does not have it.

Radio88

At the risk of appearing like I have no life, when I get time I am going to try and find a windless spot within the engine bay to mount my digital camera and get a sound recording of this thing. I doubt I'll pick it up through all the other racket in there like the valve train and such, but maybe it's worth a try.

ggebhardt

I am betting if your camera/recorder is on the "other side" of the sound insulation it will over load the recorder. It has got to be loud in there.

NateJG

Correct. I meant GS (and IS).

Thanks