Some details of the 2AZ-FE engine

We all do that. The internet seems to induce a kind of Adult ADD - we go too fast when reading and responding...

Reply to
Leftie
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Advanced? Its an average modern v6. Apart from VVT, there's not a damn thing to distinguish it from any other (and most others have VVT these days, so even that's not distinguishing- some have VVT and cylinder deactivation).

And if the hear really were iron, then it would be exactly as advanced as the 1962 die-cast aluminum block/iron head slant-6.

Reply to
Steve

Shims-in-a-bucket cam followers for valve adjustment is positively stone-age (the last car I had so-equipped was a '78 Plymouth Horizon with the VW-based SOHC 4). Rocker-tip mounted hydraulic lash adjusters that are common now don't carry enough mass penalty to worry about and are commonly used in engines with 7500+ RPM redlines. That said, I never had to adjust the valves on that VW engine either. Everything else about it sucked, but the valves never needed adjustment! ;P

Reply to
Steve

Numerous modern engines from Toyota and Nissan do not use hydraulic lash adjustment. The most modern Camry V-6 does have hydraulic lash adjusters, the older Camry V-6 and 4 cylinders do not. The engines without hydralic lash adjustment do require routine valve clearance checking (if not actual adjustment). I think this requirment is widely ignored. Interesting, Fords, newest V-6 also does not have hydraulic valve adjustment - I guess they have learned from Toyota.

Ed

Reply to
C. E. White

Similar combination to the '62 Chrysler 225 slant-6 (aluminum block version). Cost and manufacturing considerations necessitated the use of a common iron head on both the die-cast aluminum block and the simultaneously-produced iron block version of the 225. The aluminum 225, unlike the first iteration of the Vega engine, did have cylinder liners. Both were, as you noted, open-deck designs with free-standing cylinder bores.

Later, the notorious Cadillac HT-4100 4.1L v8 of the 80s used cast iron heads on an aluminum block also. The failure of the 4100 really doesn't say anything bad about iron heads on aluminum blocks, per se. The slant-6 had relatively little trouble, although people who build them today for restoration (and occasional racing- the bare block can be hauled around one-handed!) note that it doesn't have a lot of margin for high cylinder pressures and doesn't take well to much boost or any detonation. But the stock ones held up just fine, and there are a surprising number out there still running around (sometimes with the owner completely unaware that its an aluminum engine). But conceptually, it really is a little backwards to build a light aluminum block and then penalize it with a pig of an iron head. If you need iron, it makes more sense to use it in the BLOCK where the extra strength is most needed, and that's why there are so many iron block/aluminum head engines still in production. And looking back to the first poster quoted above, I can't think of ANY iron block/aluminum head engine that proved to be a "fatal combination." I know a lot of people believed it was going to be awful when they first started appearing in the 70s, but in practice it worked just fine with the correct choice of head gasket material to allow for the differential expansion. Heck, my wife's iron block/aluminum head Chrysler 3.5 has 260,000 miles and has never had the heads off (or anything deeper in than the intake plenum gasket, for that matter).

My memory of the Vega's problems pretty much agrees with yours- the main flaw was the lack of rigidity of the block itself, allowing the cylinders to "go egg shaped" with the slightest overheating (or even normal spirited/agressive driving), resulting in huge oil consumption and of course power loss.

Reply to
Steve

Dumb statement.

V-configuration pushrod engines can be significantly more compact than OHC designs because the cam is tucked between the banks rather than having a cam hanging out over the bank making the "V" both taller and wider. Plus the cam timing wanders less because the chain is shorter. And when there are other engine architecture considerations that make it unnecessary to wind them tighter than 6000 RPM, overhead cams don't have any advantage. That's why so many pushrod engines, ranging from pedestrian GM v8s and v6 to the Corvette ZO-6 and Chrysler SRT-8 Hemis are still being designed and built.

Reply to
Steve

Probably a cost-of-production decision, IMO. rocker tip mounted hydraulic lash adjusters are so tiny they don't add any appreciable mass to the valvetrain, are almost impossible to "pump up" (I did a quick calculation a while back that indicates it would require over 700 PSI of oil pressure to "pump up" a lifter against valve spring pressure), and keep the valve timing events right on spec over the life of the engine.

Don't forget, Toyota is learning from GM too. Learning how to live on the laurels of the past and cut corners in the present. And how to introduce a gas-guzzling pig of a truck just in the nick of time for $4/gallon gas, leading to idling a shift at the new plant that builds it in about 1 year of operation. That's gotta hurt. And that doesn't even count the front suspension and brake recalls.... :-(

Reply to
Steve

Actually, the reason to go to mechanical lash is not for high speed valvetrain control but rather to reduce engine friction. The hydraulic lash adjusters exert a significant amount of force on the cam base circle, increasing mechanical friction. This IS both measureable and does contribute to fuel savings. If you examine the base circle of the came you can even see the lobe is narrower and flairs out to a wider surface (Ford Zetec).

With modern oils and their additive packages, the need for frequent lash adjustment is very rare. Most will make it thought the mandatory 100k emissions durability requirements with no adjustment.

Reply to
Dyno

I guess I'm just to stupid for my shirt. How is increasing the amount of necessary routine maintenance as well as increasing the cost of operation a step forward?

Jack

Reply to
Retired VIP

The unfortunate problem is that most people don't do proper maintenance on their vehicles. As a consequence, manufacturers design cars to avoid the need for that maintenance because, given the poor treatment of the average owner, the car will last longer as a result.

This means hydraulic lifters, but it also means sealed chassis components that don't need regular greasing with every oil change but which fail before 80,000 miles is up. It means "sealed for life" transmissions, where that life is about half what it should be.

This is what the market demands, and it's what is best for the average car owner today. Sadly it's not what is best for folks who actually intend on taking good care of their vehicles, but those people are in a small minority and probably always have been.

--scott

Reply to
Scott Dorsey

There are two problems with hydraulic lifters: they are more expensive to build and, more to the point for us, they tend to fail long before the rest of the engine. Who wants to have to spend $1k on new lifters on a car with 150k miles on it? The shim & bucket type setup rarely needs adjustment when properly designed (and it is as used by Toyota and Volvo in their older engines) and it doesn't fail. I've had two cars and one motorcycle suffer from hydraulic lifter failure. I'd much rather have the valves adjusted every 5 years or so.

Reply to
Leftie

That would be a lot more palatable explanation if not for two factors:

1) Lash adjusters (unlike hydraulic lifters) are generally located at the valve-stem end of the follower. They're about the diameter of a valve stem, not a lifter. Therefore, the plunger inside them is about the diameter of a valve stem, not order-of 5/8 inch like a lifter. Taking the oil pressure and multiplying it by the surface area of the lash adjuster plunger produces a TINY number. When lift begins the valves in the lash adjuster close and the entrained oil is incompressible so they don't collapse, but the BASE CIRCLE pressure is solely due to engine oil pressure multiplied by plunger area, and is miniscule. 2) With roller followers cam followers, adding base circle pressure doesn't increase friction much at all. That's one big reason they're used- far far lower friction than flat lifters from base circle all the way to full lift. And of course they can follow a lobe profile with a much sharper ramp rate so that you can get long duration without excessive overlap.

No argument there, but I still think eliminating auto lash adjusters is more cost-driven than engineering-driven. And I don't even disagree that its a good idea to go ahead and save that money IF the engine can run

200k miles without opening the overhead, as we've come to expect from cars with hydro lifters or hydro lash adjusters.
Reply to
Steve

They FAIL before the rest of the engine? Hardly. Ask any mechanic how many hydraulic lifters or lash adjusters he's had to replace because the lifter or adjuster ITSELF was a root cause of a problem in the last 10 years and I'll bet you can count the average answer on 1 hand, and if you probe further you'll find that those were typically in badly neglected sludged-up engines.

Reply to
Steve

Here here! Eliminating the dipstick on automatic transmissions has to be the single most unnecessarily STUPID thing car makers have done in the last 50 years. Maybe since the dawn of the automobile.

Reply to
Steve

Ok, I'll grant that hydraulic lifters are more expensive to build but 'they tend to fail long before the rest of the engine'? Maybe for people who don't change their oil but in over 35 years of car ownership, I've NEVER had hydraulic lifters fail. I have heard a lot of cars with solid lifters clicking and clacking down the road sounding like an old Singer sewing machine and punching holes in their rocker arms.

This would seem to me to be another example of why bean-counters should be kept in a locked room. They should never be allowed to attend management meetings or review mechanical drawings.

Jack

Reply to
Retired VIP

My engines were not "badly neglected". The motorcycle was given full synthetic oil. The two Mazda engines may have had poorly designed oil passages, but I've also heard from other people abut lifters failing. Think of all the "stuck lifter" stories out there, and you may realize that it isn't just bad maintainance causing it to happen.

Reply to
Leftie

Why? All my current cars still have dip sticks on the transmission, but there never seems to be any change in the level. I think eliminating dipsticks was a safety measure more than anything else - I remember reading that a significant number of transmissions were damaged because either they were over filled (people don't follow the instructions for using them) or the wrong lubricant was added tot he transmission through the dip stick hole (wrong ATF or just the wrong stuff - like engine oil). How may car owners ever use the automatic transmission dip stick?

Ed

Reply to
C. E. White

All of them with half a brain.

How often do you actually add ENGINE oil? I never need to between changes, but I still CHECK it weekly. Same with the transmission fluid. The whole idea of maintenance is to CATCH a potential problem before it becomes costly. Eliminating the transmission dipstick pretty much guarantees a low-fluid failure will ultimately destroy the transmission, be it at 10,000 miles or 200,000 miles.

Reply to
Steve

On Fri, 01 Aug 2008 11:58:47 -0500, Steve wrote:

Hard to imagine not having a trans dipstick. Might as well tell this story, even if it's about my U of I engineer son. He had a Hyudai something or other. Saw it a couple times and it looked and sounded decent enough. He drove it almost every weekend from Champagne to Chicago and back. He bought it used, and had a couple grand in it. One Friday he calls me from his mom's house saying his check oil light is coming on, but the dipstick shows normal. He said he had an oil change a few weeks ago at a fast change place, checked the oil after that and has been checking it at least every week. I told him he might have bad mains, bad oil pump, or a bad sender, and to get it to my mechanic to have it checked out. But it was the weekend and he had to get back to school. Sunday evening a daughter is visiting me, driving the son's Hyundai because her car is down. I walked her out to the Hyandai when she had to get back so the son could take off for school. I chatted with her a bit before she pulled out, and the Hyandai didn't sound bad. Didn't see or smell oil burning. No drips on the driveway. Something told me to check the oil, just out of habit, but she was in a hurry and I pushed it aside. Next morning she calls to say the car broke down on him on the way to school. Engine shot. The tow truck driver found it dry of oil. Turns out my son had been checking the trans dipstick the whole time. Saw his mistake when the tow driver pulled the right dipstick. Can't tell you how bad I felt in not checking the oil when it was in my driveway, but I really never thought for a second my "smart" kid couldn't check his own oil. He's a successful engineer now, but still doesn't give a crap about cars. He does know how to pick the right dipstick though.

--Vic

Reply to
Vic Smith

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