I have been awaiting confirmation of this theory from an independant source, and as they have now confirmed the original info, I thought I would share it with the rest of the membership.
There appears to be a problem with the crankshaft design in the 1ZZ engine that causes it to resonate at approx 4,000 rpm *THIS IS A KNOWN AND MEASURABLE FACT*
*Now the theory begins* - this vibration is then transmitted to the pistons which causes them to wear the cylinder bores unevenly. The theory is borne out in a number of non-roadster 1ZZ engine failures that have occured within Europe (all that do NOT use pre-cats) where oil consumption is extremely high due to uneven cylinder bore wear.
The one common factor is 4,000 rpm coincides with their local speed limits when in top gear and also helps to explain a drop in (although not complete abscence of) failures of engines in post face-lift roadsters as they now have a 6th gear which shifts the engine rpm away from 4,000 at normal cruising speed.
If this is correct (and I have no reason to doubt either of my sources), then we can expect to see a lot more engine failures before Toyota finally admit to the problem. It also means that whilst gutting the pre-cats may help reduce the problem by removing the potential source of debris entering the engine (which it is fairly certain DOES occur although not proven), it is not guaranteed to save your engines life. Only time will tell.
Hi Steve;
Hmmm, sounds plausible, what speed does 4000 RPM equate to with the 5 Speed ??
PeterC
For my 1zz, 4000 rpm is about 75-77 mph.
So what we should do is cruise around at under 4k revs and cane the nuts off it at any other time s:twisted: :twisted: s:twisted:
So anything under VVTi zone is OK then? I sense a sudden increase in MPG if this is provem s:D :D s:D
Quote from: "SteveJ"There appears to be a problem with the crankshaft design in the 1ZZ engine that causes it to resonate at approx 4,000 rpm
Do you have any knowledge about this matter in 3ZZ/4ZZ...?
4000 rpm is about 100mph in 6th on my car. I reckon my engine might break soon s:lol: :lol: s:lol: s:roll: :roll: s:roll:
While I was present for the discussions with one of your sources and seeculated that the rest of your post was correct, are you now saying we have definative data to back up the fact that motorway speed limits for the appropriate gearing in different countries equates to 4000rpm.
please share.
I'm also curious as to your second confirmed source.
While I concure with teh speculative theory, I'd want a little more specific ref teh "proof" before confering it factual status.
The theory sounds plausible. Is the center frequency of resonance precisely 4000RPM? I imagine the bandwidth would be rather small, maybe +/- 100RPM. If this were true, something might show up on a dyno of an well-worn engine that has bores getting out of spec.
Very interesting - thanks.
FWIW I find that 5th at 70mph is ~ 3200rpm
I am very interested! This may benifit my case as well.
I have a habit borne of several years of reading theoretical posts. Namely, I never believe anything until its been measured.
Toyota et al spend thousands of hours in design, analysis and development of new engines, and thousands more in NVH anlysis, eradicating any such resonance from their engines. If anything they engineer any resonant speeds into areas that the engine is unlikley to ever reach, not right in the middle of the rev range. Also, were such a fundamental design problem to exist, it would be a relatively straightforward fix to "re-tune" the resonant speed by altering some aspect of the cranks counterwieghts, or even the flywheel mass. Still, the idea is not without some merit, and is a fairly easy one to prove or disprove.
I have an SKF Microlog vibration analysis tool here at work, which, when plugged into a tachograph input will allow me to generate a vibration vs. engine speed graph. It'll also pinpoint any resonant speeds, the magnitudes of the vibrations, and the direction of movement. It'll also print out handy graphs which can then be published here. Let me finish the job I'm currently on, which believe it or not, involves balancing the rotating parts of internal combustion engines, and the avoidance of resonant frequencies in rotating equipment... Hence the suddenly very useful tool...
More data when the current job is over and done with. I'd anticipate having vibration analysis graphs here by the end of December.
Grant you have access to some very nice tools.
s:D :D s:D
Interesting that this resonance problem occurs around the same rpm for the valve timing change.
Nothing to add to this, I just thought it coincidental s:) :) s:)
Quote from: "markiii"Grant you have access to some very nice tools.
s:D :D s:D
When you work with engines this big, you need them... s:wink: :wink: s:wink:
(http://www.spydermagazine.com/files/GSBturbine.jpg)
s:o :o s:o How cool is to have GSB onboard? s:D :D s:D
Side note: I work on a US Navy base where they do depot level maintenance of aircraft, among many other things. It is one of the few remaining Naval Air Depot facilities to survive several rounds of facilty closings. I'm right across the street from the main hangar and hear jet engine noise all day. A common bumper sticker is "Jet Blast: The Sound of Freedom"
Quote from: "Hanslow"Interesting that this resonance problem occurs around the same rpm for the valve timing change.
Valve timing change occurs from idle to rev limit s;) ;) s;)
(that's why it's called variable)
Yes, but there is a definite difference around 4.2k revs, which almost coincides just before the peak torque arrives - according to the scientific diagram in my brochure.
Oh, and can one of those engines fit in an MR2?
I have always noticed an extra kick of power at 4k so assumed there was a profile change or something.
Quote from: "mrsmr2"Oh, and can one of those engines fit in an MR2?
s:D :D s:D Not liklely I'm afraid... The rotor alone weighs someting like 160tonnes, and its about 60ft long, ao you're MR2 would be a bit back heavy... As for fuel? Phenomenaly thirsty, but then it does knock out the equivalent of about 340
thousand bhp
Quote from: "GSB"s:D :D s:D Not liklely I'm afraid... The rotor alone weighs someting like 160tonnes, and its about 60ft long, ao you're MR2 would be a bit back heavy... As for fuel? Phenomenaly thirsty, but then it does knock out the equivalent of about 340 thousand bhp
The question is, in that picture.. which one's you? Because I can't see anyone with big spiky red hair and a big pink nose s:lol: :lol: s:lol:
Anyway, vaguely back on topic - if the theory turns out to be correct then it would be very worrying - essentially all our engines are doomed to fail sooner or later (depending how long we spend cruising on the motorway, basically). s:( :( s:( (My glass is half empty, sorry s;) ;) s;) )
But then if it is true, as Grant says, we could move the point of resonance by switching flywheels (never a bad idea anyway s;) ;) s;) ) potentially to somewhere less damaging.
I seem to recall one of the big Japanese tuners also sells special crank pulleys with liquid harmonic dampeners that can be 'tuned' - but that's getting a tad expensive then s:) :) s:)
Anybody want to buy a never used lightweight crank pulley? s:lol: :lol: s:lol: I actually bought one from someone on SC because it was a good deal.
Quote from: "mrsmr2"Yes, but there is a definite difference around 4.2k revs, which almost coincides just before the peak torque arrives - according to the scientific diagram in my brochure.
There's a difference in power, but there's not difference in VVT-i behaviour s;) ;) s;)
(someone who knows something about engines once tried to explain to me that every engine has a bump in power at certain rpm, which is related to bore and stroke and tons of other stuff, but I really didn't get half of it s:oops: :oops: s:oops: )
Quote from: "Tem"Quote from: "Hanslow"Interesting that this resonance problem occurs around the same rpm for the valve timing change.
Valve timing change occurs from idle to rev limit s;) ;) s;)
(that's why it's called variable)
I dont know where this mis-conception comes from, but VVT-i is an on-off switch - the only reason it is called 'variable' is because there is a
change in the valve timing. The 'i' bit is because the timing change occurs at different points in the rev range depending on the current demands on the engine.
Take a look at the workshop manual for the engine - the valve control mechanism is controlled by an on/off solonoid - there are absolutely NO analogue devices present in the control system.
Now if it were called :-
C onstantly
V ariable
V alve
T iming with
I nteligence
we would be talking a whole different ball game.
Quote from: "SteveJ"Take a look at the workshop manual for the engine - the valve control mechanism is controlled by an on/off solonoid - there are absolutely NO analogue devices present in the control system.
Yes, it's an on/off switch, but it's controlled by a PWM output s;) ;) s;)
More about PWM, first hit from Google:
m http://www.embedded.com/story/OEG20010821S0096 (http://www.embedded.com/story/OEG20010821S0096) m
Quote from: "SteveJ"There appears to be a problem with the crankshaft design in the 1ZZ engine that causes it to resonate at approx 4,000 rpm *THIS IS A KNOWN AND MEASURABLE FACT*
*Now the theory begins* - this vibration is then transmitted to the pistons which causes them to wear the cylinder bores unevenly. The theory is borne out in a number of non-roadster 1ZZ engine failures that have occured within Europe (all that do NOT use pre-cats) where oil consumption is extremely high due to uneven cylinder bore wear.
It makes sense and coincides with the explanation I got when my engine blew... Could this be the "unknown reason" for the "sudden oil starvation" which caused a rod to break, opening a hole in the cylinder wall? As I said on my first post, "I was cruising at about 100Mph"...
http://www.mr2roc.org/forum/viewtopic.php?p=65630#65630
Well, I just had a read of a few results from googling "toyota vvti explained" and looks like Tem is right and I'm wrong (not a first s;) ;) s;) ).
I thought that the VVTi operated more like a variable cam in that it had one or two different profiles but it doesn't. I've learnt something today s8) 8) s8)
All we need now is for Tem to sift through his memories and remember all this bore and stroke guff because I'd like to know why my engine seems to open up around 4k revs s;) ;) s;)
This could turn out rather interesting if there is a more widespread problem across VVTi engines in general. Would the resonance be transmitted down the manifold and aid the breakup of the precats as well? Could be that the broken pre-cats are a sympton of prolonged driving in the resonance band? Be interesting to know what happens to the engine internals in this resonance band too.
Quote from: "Hanslow"All we need now is for Tem to sift through his memories and remember all this bore and stroke guff because I'd like to know why my engine seems to open up around 4k revs s;) ;) s;)
that's because your engine has reached peak torque, so of course its going to feel like the car is pulling harder
But if it's reached peak torque at 4k, shouldn't the torque then decrease as the revs increase? Or is it flat from 4k to around 6k as mine seems to go a bit mental from 4-6k?
Quote from: "Hanslow"But if it's reached peak torque at 4k, shouldn't the torque then decrease as the revs increase? Or is it flat from 4k to around 6k as mine seems to go a bit mental from 4-6k?
I seem to remember a dyno chart showing the torque being absolutely (near as damnit) flat between 4 and 6k - fairly sure it was a chart Tem posted, but I could be imagining that bit..
Quote from: "Hanslow"All we need now is for Tem to sift through his memories and remember all this bore and stroke guff because I'd like to know why my engine seems to open up around 4k revs s;) ;) s;)
It was more of a "didn't understand it" than "forgot it" s:oops: :oops: s:oops:
Quote from: "aaronjb"I seem to remember a dyno chart showing the torque being absolutely (near as damnit) flat between 4 and 6k - fairly sure it was a chart Tem posted, but I could be imagining that bit..
This one?
m http://koti.mbnet.fi/temmeke/tmp/dyno.jpg (http://koti.mbnet.fi/temmeke/tmp/dyno.jpg) m
(dyno of my stock engine about 6 months before it blew)
Quote from: "Tem"This one?
m http://koti.mbnet.fi/temmeke/tmp/dyno.jpg (http://koti.mbnet.fi/temmeke/tmp/dyno.jpg) m
(dyno of my stock engine about 6 months before it blew)
That looks familiar, so maybe that is the one I was thinking of, yep s:) :) s:)
Aaah, that would explain a lot. Thanks guys s;) ;) s;) s8) 8) s8)
I'll get back to trying to understand things I'm a bit more familiar with s:oops: :oops: s:oops:
I don't know what I was thinking (dyno idea). After further thought, I don't think a problem (wear caused by vibration) would show up on a dyno at RPM that caused the wear. It would have to be a small thing that took a long time to do damage, so you wouldn't hear or feel it at any one time unless you had sensitive equipment. Awaiting GSB's test results.
Quote from: "Beanie"Awaiting GSB's test results.
Me too, with great interest. I share his scepticism.
Quote from: "Andy S"Quote from: "Beanie"Awaiting GSB's test results.
Me too, with great interest. I share his scepticism.
As do I. If only so it means I didn't spend a whole saturday beating up my exhaust. s:wink: :wink: s:wink:
What I have heard (from DaSpyda/Don on SC), to the best of my recollection, is that Toyota had some sort of miscommunication between two groups of engineers and this resulted in inappropriate rings, which they later fixed (change went into 2003 and later cars). COULD SOMEONE VERIFY?
If rings wear too much and/or warp due to running lean or anything else that causes excess heat, oil will get by the rings.
The engine employs valve overlap for emissions reasons. Sport Compact Car speculated that this was what caused some NISSAN engines to have catastrophic failures. I can't recall if they have something like precats.
Hot oil on precat material (ceramic and ?) could cause them to deteriorate. THIS COULD BE TESTED.
(continued)
Ceramic particles could get drawn into engine due to valve overlap. Ceramic is hard and could score cylinder walls, causing further oil to get by rings. At the very least, precats getting clogged precedes serious engine problems. There would be more heat in that area as well as increased backpressure due to clogging of precats/main cat.
I have not read of any cat-astrophic problems on 2003 and up engines, which would give some weight to the idea that the original problem was the rings. Perhaps there is another possible cause of failures, so I shouldn't say THE original problem. It could be that removing precats would be unnecessary on 2003 and up engines. It could also be that the amount of wear in cylinders would "never" cause a catastrophic problem if nobody had precats.
The mystery continues.
Quote from: "Beanie"What I have heard (from DaSpyda/Don on SC), to the best of my recollection, is that Toyota had some sort of miscommunication between two groups of engineers and this resulted in inappropriate rings, which they later fixed (change went into 2003 and later cars). COULD SOMEONE VERIFY?
MR Mikes September 2003 2 had an engine failure s:? :? s:?
I was under the impression that better oil control rings were fitted to the pistons of all 2002 roadsters onwards!?!
See GSB excellent post here! (http://www.mr2roc.org/forum/viewtopic.php?t=4807) s:wink: :wink: s:wink:
Well, so much for the rings being the magic bullet. An '03? That stinks.
Quote from: "heathstimpson"Quote from: "Beanie"What I have heard (from DaSpyda/Don on SC), to the best of my recollection, is that Toyota had some sort of miscommunication between two groups of engineers and this resulted in inappropriate rings, which they later fixed (change went into 2003 and later cars). COULD SOMEONE VERIFY?
MR Mikes September 2003 2 had an engine failure s:? :? s:?
The engine never failed..per se. The pre-cats were changed, and the VVTI mechanism seemingly wasn't operating, which was a result of the car consuming Oil. I still subscribe to Mark and Steve's initial theory on the fuel rail.
I just went through the sticky topic on spyderchat and came up with the following numbers (with a few possible mistakes)
2000 model year: 32 reported cases
2001 model year: 22
2002 model year: 2
Both of the 2002 people said the build date was in late 2001.
One person with a 2003 car had a main cat replaced, but not the engine.
No cat-astrophies for 2003 or 2004
So it could be the rings, right?
I just did this.
(http://www.spydermagazine.com/files/engine_failures_in_miles.jpg)
Quote from: "Beanie"I just did this.
(http://www.spydermagazine.com/files/engine_failures_in_miles.jpg)
Some low mileages there s:shock: :shock: s:shock: s:? :? s:?
Quote from: "Beanie"I just did this.
m http://www.spydermagazine.com/files/eng ... _miles.jpg (http://www.spydermagazine.com/files/engine_failures_in_miles.jpg) m
How do we read this...? At first I thought the X-scale is tmiles and Y-scale blown engines, but that would equal to several thousand blown engines and there's no such info I suppose...?
If Y-scale is tmiles, how can there be several bars for 40tmiles...
I'm confused s:? :? s:?
Edit: Uh...nevermind...X-scale is individual cases and Y-scale their mileage, right? s:oops: :oops: s:oops:
Right on the last sentence. Sorry for the confusion.
Quote from: "SteveJ"Quote from: "Tem"Quote from: "Hanslow"Interesting that this resonance problem occurs around the same rpm for the valve timing change.
Valve timing change occurs from idle to rev limit s;) ;) s;)
(that's why it's called variable)
I dont know where this mis-conception comes from, but VVT-i is an on-off switch - the only reason it is called 'variable' is because there is a change in the valve timing. The 'i' bit is because the timing change occurs at different points in the rev range depending on the current demands on the engine.
Take a look at the workshop manual for the engine - the valve control mechanism is controlled by an on/off solonoid - there are absolutely NO analogue devices present in the control system.
Now if it were called :-
C onstantly
V ariable
V alve
T iming with
I nteligence
we would be talking a whole different ball game.
Mmmmmmmhhhh.... I don't think so. The VVT-i is a
Variable Valve Timing - intelligent system. OK, there's no analogue ECU (it's digital) but it controls the valve openning and closing position (advance, retard, hold). This position is variable (not just on/off)...
Just to quote some explanations (from Toyota's "New Car Features"):
QuoteThe camshaft timing oil control valve selects the path to the VVT-i controller according to the advance, retard or hold signal from the engine ECU.
In proportion to engine speed, intake air volume, throttle position and water temperature, the engine ECU calculates an optimal valve timing under each driving condition and control the camshaft timing oil control valve. In addition, engine ECU uses signal from the camshaft position sensor and the crankshaft position sensor to detect the actual valve timing, thus performing the feedback control to achieve the target valve timing.
I think you are getting a bit confused with the VVT
L-i system where you actually have two intake camshafts (like in Honda's VTEC) instead of just the one. With that system, the engine
switches to the high-rev high-volume intake mode. I believe this happens above 6000rpm on the 2ZZ-GE engine.
I am a little bit sceptical about the claim that the engine could suffer excessive wear from a resonant frequency in the crankshaft. Although this is something common in light aircraft engines (that run at constant rpm's for long periods of time), I doubt the harmonic frequency quality would be low enough (spread wide enough) to be damaging the engine. (Engine rpm's in a car are hardly perfectly steady, even on a motorway.) Besides, it's something easy to fix and I cannot see how the engineers at Toyota could have missed something that simple.
I believe that many engine failures nowadays are due to oil starvation (low oil levels) which has been aggravated by the extended service intervals (and many people who don't check and top up the oil regularly enough)... I also heard of many cases in the US (where manual gearboxes are a bit of a novelty) where engines were destroyed (or had serious valve damage) by accidently overreving the engine (putting in 3rd instead of 5th or 2nd instead of 4th, etc... s:? :? s:? )
Quote from: "phat"I also heard of many cases in the US (where manual gearboxes are a bit of a novelty) where engines were destroyed (or had serious valve damage) by accidently overreving the engine (putting in 3rd instead of 5th or 2nd instead of 4th, etc... s:? :? s:? )
that's been a problem with mainly the 2zz-ge, 6-speed equipped vehicles......as far as i know, this has not been a major issue with the mr2......(but then again, i primarily associate with enthusiasts)
the biggest question i have is with the model year trends - this problem as been almost exclusively associated with earlier cars.....the failures have not been tied to mileage, so we can sort of scratch that off....this lends credence to the various theories that say this is reulting from a manufacturing defect, but...and this is a big
but we've seen numerous
replacement engines fail as well (in some cases, owners losing two or three engines on the same car)....if this was a manuf. defect, and the problem has been fixed, wouldn't it be safe to assume that these replacement motors are also free of defect?
i guess what i'm asking is - though we haven't seen many motors pop on '03 or '04s, why are replacement motors built "after the 'fix'" going boom?
kev
There's definitely a few design issues in the earlier MR2s. I noticed that the lattice structure in the pre-cats (or warm-up cats) fitted on the earlier models ('00-'01) is definitely finer and more fragile than that fitted on later models. So I reckon they are more likely to desintegrate and cause engine failure.
IIRC many of the cases of new replacement engines failing shortly after being installed could be attributed to a blocked exhaust line (i.e. pre-cat debris blocking the entrance of the main cat, causing massive back pressure and quickly warping and damaging the new engine.)
If the first engine was damaged (e.g. because of letting the engine run out of oil), it is possible that the pre-cats got shot too. So if the engine is rebuilt (or replaced) but the exhaust line isn't cleared, this could explain why a new engine breaks shortly after being fitted.
I've always taken care of my car (an '01 model), always used the best oils and checked the oil level, etc. Despite all that, the pre-cats were toast after less than 30000m. I was less than impressed!
'53 plate 18k miles - left hand precat was showing serious signs of degradation so I dont think the pre-cats have been redesigned (or if they have it hasnt done the trick)
Car continued to 39K before I sold it without any problems (except BIG lumps of the LH precat missing by that point), but I did stay away from 4K rpm