Serious Engine Knock less than 4000 miles brand new, done with Toyota

No idea how but it certainly would eliminate it as an issue.
Perhaps your engine is programmed and tuned differently there for that fuel?

 

Higher than 87 octane should NOT cause knocking. Higher octane fuel resist better from spontaneous combustion due to high temp created by high compression before top dead centre of the compression stroke. If anything it's less knocking. The Prius user manual recommends 87 octane OR HIGHER, not just 87 octane. Please read the manual carefully again.

However, using any fuel higher than 87 octane may not give you any mpg advanatage, except most gas brands claim better cleaning detergents with them. The fact that mwok's ICE still knocks once in a while in spite of using premium fuel indicates that the problem is something else.

I highly recommend people give their ICE a "blow" job once in a while by flooring the gas peddle to let the volume of gases blow away any carbon deposits, or else they'll accumulate to a point when the ICE violently knocks and shakes.

Give it a shot. Note to mwok, flooring the gas peddle of a well warmed-up engine WILL NOT damage it, so don't worry. On the other hand, it's been well known that idling the ICE for long periods of time DOES HURT it.

 

I suddenly remembered long time ago I asked my boss why he floored the gas paddle of his BMW every time before he turned it off. His answer was that flooring it blows the unburnt gunk away from inside the cylinders.

 

You can only buy 95 or 99 here.

 

Octane numbers are measured differently in different countries.

Higher octanes should not be harmful, but decrease MPG due to lower BTU content.

 

It was over the direct injection pump.

 

You beat me to it! lol

Flan, if you've ever been to France in your car you'll notice that a lot of stations will quote both octane numbers (US&Euro).

I believe the US standard unleaded fuel is about the same as our old 2 star (about 92/93 octane) then Premium at 95 and Super at 97. Whereas we just have Premium & Super.

But I could be wrong.

 

I know I am new here, but this thread has worn me out!

 

Hopefully in a good way?

You'll find this site a mine of information - whether that information is useful or not is debatable, and we like to debate.

 

flooring BMWs and "German tune up"

Sorry to go OT a bit... Must be a BMW or German car thing...

One of my former coworkers (who had a BMW and liked driving fast) every now and then referred to a "German tune up". For an idea of what I mean, I found this thread on one of these: 325i Top Speed Run - bimmerfest - BMW Forums. I'd never heard of a "German tune up" until I met him.

 

Re: flooring BMWs and "German tune up"

Thanks for the link. That's pretty much supported my theory. Like his last comment: "(By the way, I had 6 other opportunities to do the "German Tune-up". I'd say my engine is carbon-free)."

I don't think this applies only to Beamers though. It is a universal "problem" for all ICE. It's simple physics. Low air flow, things gor left behind. It's like us humans will cough violently if our air-paths are choked up with foreign objects or flem.

I've never heard of brand new cars having this problem untill I read it in this forum, though. I really think that the Prius' encouragement to it's driver to baby the gas peddle contributes largely to this.

Well, I don't think you'd need to go overboard with this "German tune up". Can we put it into neutral on the driveway and floor it for 10 seconds or so? Engineers in the forum, please advise. Thanks.

 

Re: flooring BMWs and "German tune up"

I don't recall in neutral that it's even possible to give throttle. In any case it's strongly advised to not put this car into neutral and then back into drive while driving. It can cause damage and, unlike above, I'm actually serious. I think it depends on speed, though; perhaps it's 42 mph or something (has something to do with one of the two motors). Putting it back into D above that speed causes one of the motors to over-rev.

Instead I'd just floor it from a stop if you do want to run the engine at full throttle for a bit.

 

What's even funnier...you get it into the dealer and the dealer DOES NOT hear anything!

You got to start with the dealer dude!

Happy Motoring,

Tom

 

The mechanics in the dealership are just... mechanics. They're not highly trained in engineering theories like our engineers in this forum. I doubt if they could really reason out every little nuisance of a car. They mostly go by the book, I guess, and ask you to replace parts instead of fixing them. It's easier for them and cost you a lot more money.

 

Re: flooring BMWs and "German tune up"

You can do that, but the engine won't run. The Prius is smart enough to realize that it makes no sense to open the throttle while the car is in neutral.

The only risk comes from a very special and unlikely situation. While in N, the ICE cannot change state. If it is off, it stays off. If you switch to N at low speed when the ICE is not running, you create the potential for damaging MG1 from overspeed. After switching to N, you need to coast down a very steep hill to gain highway speeds. At high speed, without the ICE turning, MG1 can be forced to spin too fast.

It's a very unlikely set of circumstances. In fact, I would say that you have to work at it to get there.

Tom

 

Anyway, if carbon deposits are the cause of random but seldom violent knocking, we can't blame the dealers not "hearing" it. Most (or was it all) of these knocking incidences reported here in the forum happen when cold starting the Prius. By the time you drive to the dealership the car is well warmed-up and of course it won't happen there.

I suspect that due to the colder temps these days the cylinders actually SHRUNK more in volumn overnight and that makes the top-dead-centre volumn even smaller with carbon deposits inside, and that's why these violent knocking happen mostly during cold starts. Once the ICE is warmed-up, the cylinders expand and the compression ratio is retored to normal again.

I also wonder if the Atkinson cycle has anything to do with this. Maybe the compression ratio of the Prius ICE was designed to the very limit of just before causing spontaneous combustion, and a little further reduction of the cylindrical volumn triggers fuel dieseling and knocking.

Maybe it's a design flaw/miss of Toyota's after all. Maybe they should have the variable valve timing adjusted according to real time cylinderical volumn (I don't know how it can be measured/calculated on the fly?) to compensate for this.

Anyways, should we be using some sort of carbon deposit cleaning additive in the fuel? Anyone has any good experience with these additives? Which brand?

 

Given there are at least 750,000 1.5L Prius, Atkinson cycle engines not counting the Ford versions, I would have expected reports from the early models. This seems unique to the ZVW30.

Right now, I'm trying to find some rate that looks to be less than 1/3d of those electing to enter data in the poll. Considering the 'brake pause' was detected by only half of the earlier poll takers, this looks to be relatively rare.

It might make sense to check some of the other 1.8L vehicle forums to see if they are seeing similar reports. If so, then we can start looking at the differences between the two engines. This may give us a clue.

Bob Wilson

 

Wow, it looks like somebody somehow recorded this normally rare event.

I only had it the one time despite starting the car many times since in much colder weather. For whatever reason, in some cases machinery/electronics do not always appear to get worse over time. I had another car that from day one would, every once in a while, make an awful sound when starting (timing chain tensioner?). The problem never got worse in the 100k I owned it. Also had a scrunch sound in tranny sometimes for many tens of thousands of miles, never worse. I've had a tv and a computer monitor both do weird things quite consistently (one didn't turn off easily and the other a pink screen sometimes) but after putting up with it for a while they self-correct and both have now been trouble free for at least two years.

 

I think this pretty much concludes that it's caused by fuel dieseling. The fuel explodes before top-dead-centre of the compression strokes making it sound like the pistons are physically hammering the cylinder tops. If it's mechanical fault it'll ever go away after warming up.

 

Yes people please enter into Bob's poll (I did), especially those who don't experience this knocking, otherwise we'll have the poll results skewed more towards knocking because I'm sure those having it will definitely enter the poll.

Maybe if you can also indicate your driving style in the poll, "babying" or "stepping on" the gas peddle?