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1800 pistons in a 1600?
Posted 26 February 2004 - 02:00 AM
EDIT: If I can't do this, how hard and which how much machining would it take to fit EA81T heads on an EA71?
Posted 26 February 2004 - 02:10 AM
from my comparisons, ea71 heads will line up at the combustion chambers, but the boly holes are closer. it almost looks you can slot the holes, if it wnt hurt the integrity of the heads
i also noticed that the ea71 heads have a smaller combustion chamber
Posted 26 February 2004 - 03:33 PM
Posted 26 February 2004 - 08:17 PM
for that matter, how do you intend on getting F/I stuff on a ea71? last time I checked, the ea81 and ea71 manifold length is slightly different... but like miles said, the fat case later modles might be the right size
Posted 26 February 2004 - 08:24 PM
Posted 26 February 2004 - 08:53 PM
so i would go with the lower compression, rather than lower boost. simple physics. there was a topic about this, try searching compression+volume+turbo and see if you can find it
Posted 27 February 2004 - 12:24 AM
Posted 27 February 2004 - 04:00 AM
>>>>>>>sidenote about the heads, the fat case 85+hatch motor heads have the same valves as the ea81, 83 and 84, and my comparisond prove that ea81T valves are the same size as ea81
Posted 27 February 2004 - 03:13 PM
The turbo unit is an exhaust gas drive air pump.
You could call it a compressor of sort.
It pumps air into the engine and in doing so
increases the air pressure in the turbo's tract,
which includes the intake manifold and ultimately
the combustion chamber.
In doing so it increases the DENSITY of the air.
Now DENSITY in simple PHYSICS terms, is defined
by the mass divided by the VOLUME.
The VOLUME DOES NOT CHANGE.
(unless some one has somehow "INVENTED" the variable displacement Subaru engine,
hey they are in developement.)
Repeat, there is no VOLUME change.
Simple math then tells us that the MASS
of air pumped in must increase.
Back to our simple PHYSICS.
Combustion is defined as rapid OXIDATION.
To "oxidize" something we need, yep you guessed it, oxygen.
Since air is made up of approx. 21 % 02, when we increase the mass of air entering,
we also increase the MASS of 02.
Add fuel and burn it rapidly. SIMPLE PHYSICS, ....
but now we find swirl factors, next thing you know
the head to block junction comes in to play as a "squish zone".
The spark plug position and ignition spark timing along with the head design all
must be examined when considering the flame front
PROPAGATION, but this is all just SIMPLE PHYSICS.
The higher compression a car starts with the higher
efficiency on and off boost.
Deal with the simple physics and have a more drive able car when not blowing the snot out of it.
And a more power car when you do.
But remember it's just simple physics.
>>>>>>>>side note on modifying the intake manifold,
as you now doubt know
the EA81T head is a single port intake.
The multiport fuel injection engines
have the injector positioned to fire on the back of the intake valve.
Thus the bosses on an EA81T head and the placement
of the injectors on the intake on an EA82T
(which is a twin port intake)
Just something to consider if you choose the manifold mounted injector that was suggested.
Must be something with the simple physics once again??
Posted 28 February 2004 - 05:51 PM
Why? Well, the EA71 has a shorter stroke and thus will rev up quicker than an EA81. I believe that this would be a nice quality for a turbo engine. As a bonus, this engine would likely get better gas mileage too.
Miles, you're just a little off about the "fat case" engines. There were actually 3 major versions of the EA71 in the USA. The '70s version has the funky external water pump. The "fat case" models look much more like an EA81. I believe that these were introduced in 1980 with the EA81, but they may have actually shown up in '78 or '79 (I'm not at home right now, so I'm working from memory). In 1984, a third EA71 variation appeared. These late models use the same bellhousing shape as the EA81, as well as the same valves. I've heard that there was yet another version available overseas that had hydraulic lifters.
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