Some details of the 2AZ-FE engine

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.

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.... :-(

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.

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

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

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.

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

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

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.

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.

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

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.

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

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.

On Fri, 01 Aug 2008 11:58:47 -0500, Steve snipped-for-privacy@spam.thanks 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