Re: Some details of the 2AZ-FE engine

Steve wrote:
> C. E. White wrote:
>> "Steve" <no@[EMAIL PROTECTED]
> wrote in message 
>> news:AM6dnZjsFev_EhrVnZ2dnUVZ_vednZ2d@[EMAIL PROTECTED]
>>
>>> ****ms-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
>>
>> 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.
>>
> 
> 
> 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 ****ft 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.