Not too shy to talk
From Christchurch NZ - Perth
Hi guys, I had my work mate translate the full-page article on the AY12 in Auto Technic Magazine 1982 volume 14 no.164 for us. I apologise if it has already been translated and posted but I hadn't come across it. Maybe somebody could add it to WIKI?
I found it a very interesting read as did my workmate because I am designing a LZ14 insired head for the A series. If anyone has some other old articles they want translated let me know.
Cross Flow function OHV A12 engine was once in the racing scene.
AY12 engine planed had started in 1972 with 76.8x70mm of bore and stroke and it had same capacity of AR12.
In those days of Race Regulation of J, Special Head cam was approved unless changing the placement of cam shaft(for example, OHV or OHC or DOHC).
So, Nissan employed the idea of A12 with OHV and cross flow function which was really difficult plan and only you can see this in A110 Alpine R
Offcourse this was first time for Nissan to do this challenge.
Although Nissan had enough knowledge and experience of OHC cross flow with G segment engine, with OHV AY12 which had push-rod aside, it made harder because of the port shape
and valve alignment limitation. As a result, AY12 didn't have enough power to win the races and had a short lifespan compared to AR12 engine.
The differences of AY12 from AR12 are below:
1. cross flow head
2. valve (length and capacity)
3. push-rod (length)
4. piston (cross flow type)
5. spark plug (10)
6. rocker arm
7. rocker shaft
8. intake manifold(Lucas Fuel Injection)
9. exhaust manifold(circle type)
12.distributor(AR had oval type)
The actual cars with AY12 started to run from Feb 1973.
The first impression of the engine was really good.
the wrap time in the test course was above average and it sounded like
ever famous Nissan the R380 race car.
In fact, the bench test marked more powerful than AR engine.
So the engineers expected this engine would have a significant impact on the race scene.
However, the power and response at high speed was never improved and
the double ignition system was added in May 1973.
Even though it said 'Double', Due to the lack of space at the head,
they just put one more spark plug in between rocker arms
and NGK developed special plugs for this to avoid oil leak from the cams.
From today's view, this is described as almost insane to have high-tension cables
going around the very next to the engine head where oil is pumped up and down.
With this 'Double' ignition system, specification of the engine was improved(especially fuel consumption) but to maintenance, it was worst.
At the end, the engine earned 140ps. However, because of the bad character of the engine, the plan was dismissed and AR12 became the mainstream of Nissan's racing engine development.
An illusion of AZ12 with 4 valve A-type engine
In 1975, an engineer, Mr.Ogikubo(or Place?), was developing LZ14 engine for
a 2 Litter Rally car or FP type car which would have been gone into PB210 Sunny.
With the strict restriction of the cylinder head height and valve angles, Ogikubo could not do what he wanted to do with LZ at all.
So, with his knowledge and experience, he decided to draw some final ultimate engine plan
as a engineer for his career.
This was totally just a plan on the paper and he did this for fun.
From today's point of view, it is a bit outdated and old-fashion but
using the efficient A-type engine block is interesting.
Makes us wonder what would be like if this engine would go against 3KR DOHC engine....
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Posted on: 2012/6/17 4:48