Honda Car Forum

I'm new to these engines and don't understand the full function of the 4th
valve in this head.

Initially I thought it was an Aux. intake valve but notice that it is next
to the exhaust valve.

My Chilton manual doesn't provide any help..

May seem like a dumb question but it's got me stumped. Once I have an
understanding of this question, I'm sure I'm going to have a few more before
I get this nice little car ('85 CRX) running properly.

Thanks,

Steve

Chilton's 1984-1995 Civic/CRX/[blah blah] manual, Chapter 3, under "Engine
Mechanical, Engine Design":

"On the 1984-88 models, Honda decided to improve engine breathing by
replacing the single large main intake valve with a pair of smaller ones.
This allows a much greater total intake valve area than a single valve and
it also permits intake valve timing to be staggered slightly. This gave
Honda engineers a unique opportunity to design air swirl into the combustion
process. Such swirl (turbulence in the combustion chamber) not only tends to
reduce engine knock but improves combustion speed and therefore engine
efficiency, especially at low speeds. These engines retain the auxiliary
intake valve on the exhaust side of the head.

All of the 1988 and later Honda engines have substituted fuel injection for
carburetion, and the CVCC system is no more. In the interest of good fuel
efficiency, increased power and low emissions, the two intake valves were
retained."

This text is also available free at www.autozone.com .

"Steve" <estevew@hctc.com> wrote
> I'm new to these engines and don't understand the full function of the 4th
> valve in this head.
>
> Initially I thought it was an Aux. intake valve but notice that it is next
> to the exhaust valve.
>
> My Chilton manual doesn't provide any help..
>
> May seem like a dumb question but it's got me stumped. Once I have an
> understanding of this question, I'm sure I'm going to have a few more
before
> I get this nice little car ('85 CRX) running properly.
>
> Thanks,
>
> Steve
>
>

"Elle" <elle_navorski@nospam.earthlink.net> wrote in message
news:s0ZUe.8877$Wd7.704@newsread1.news.pas.earthli nk.net...
These engines retain the auxiliary
> intake valve on the exhaust side of the head.
>

Thanks for the informative reply. Let me make sure I understand this
correctly; there are 2 standard intake valves on the intake manifold side of
the head and the aux. intake valve on the exhaust manifold side. Does this
mean there is an intake passage going across the head??

The Long Story:

Since I haven't found a need (yet) to pull the head off, I'm amaze and
puzzled by this complexity.

This whole car is new to me and only has 67,000 original miles, been garaged
all it's 20 yr. Really well maintained.

I was told it had a timing belt failure and possible valve damage. I bought
it with this assumption but soon found that the timing belt was fine and the
cam timing was exactly where it should be. I did cold compression tests and
found #3 was only 90# while the other three were 170-185#. I replace the
(missing) plugs and it started right up but rev'ed high (3500) for about a
minute. Finally idled down and ran smooth after warm up.

Initial road test were so-so. I did warm compression tests and found all
four cylinders were between 170-185#.

More extensive road test presented problems when the throttle was opened
more than half (before AT kick down). There was significant loss of power
and popping back through the carburetor. Part of this problem was traced to
broken vacuum hose (#28)coming off the throttle venturi. Repair of this
resolved the popping back and initially the car ran great on a 30+ mile road
trip. On return, while coming up a hill, as I depressed the throttle, the
engine lost power, like it was running out of gas. Briefly I could pull the
hill in second but when ever it shifted into 3rd gear, there was no power
again.

I still have a problem with it rev'ing high when first started and until it
is warmed up. Also runs ruff until warmed up.

Sorry this has been so long. Just though I would slip the whole story in
here.

Thanks,

Steve

Steve wrote:
> I still have a problem with it rev'ing high when first started and until it
> is warmed up. Also runs ruff until warmed up.

theres a bunch of preventative maintenance stuff that should probably be
done regardless... but might help resolve the problems also.

coolant change w/ orange prestone dexcool/distilled water(50/50)
new OEM honda thermostat
new OEM honda plug wires
new ND or NGK spark plugs
new OEM honda rotor
new OEM honda distributor cap.

other stuff...
brake fluid flush
AT flush/refill with honda ATF

any car thats been sitting 20 years likely has major degredation to all
the fluids

I finally found the Chilton reference that Elle provided and now have a
somewhat better understanding of the Aux. Intake Valve function.

Before I dive into the carb or do a valve job, I think I will revisit the
vacuum hose "jumble".. I am greatful that (i appears) no one else has messed
with these and if I trace and replace them one by one, as necassary, I may
eventual correct the problem. (Hoses are cheaper than an unnecassary valve
job.)

BTW. I opened the cover on one of those the two vacuum control "Black
Boxes".. Amazing at what is/was involve prior to fuel injection/computers.
Needless to say, I didn't tamper with any components in these boxes.

Steve

"Steve" <estevew@hctc.com> wrote
> "Elle" <elle_navorski@nospam.earthlink.net> wrote
> > These engines retain the auxiliary
> > intake valve on the exhaust side of the head.
> >
>
> Thanks for the informative reply. Let me make sure I understand this
> correctly; there are 2 standard intake valves on the intake manifold side
of
> the head and the aux. intake valve on the exhaust manifold side. Does this
> mean there is an intake passage going across the head??

I'd like to get some clarifications from you:

The subject line of your post says "EW1 12 valve SOHC."

Does your engine actucally have "EW1" stamped on it?

How many valves (both intake and exhaust) per cylinder have you actually
counted under the valve cover?

"Elle" <elle_navorski@nospam.earthlink.net> wrote in message
news:773Ve.1162$LS5.509@newsread3.news.pas.earthli nk.net...
> "Steve" <estevew@hctc.com> wrote
>> "Elle" <elle_navorski@nospam.earthlink.net> wrote
>
> I'd like to get some clarifications from you:
>
> The subject line of your post says "EW1 12 valve SOHC."
>
> Does your engine actucally have "EW1" stamped on it?
>

The engine number/designation is: EW1-2015401

Door label plate indicates MFG date of 1/85.

It is really a carborated engine. Some part house books reflect it should be
FI but it's carboratated.

> How many valves (both intake and exhaust) per cylinder have you actually
> counted under the valve cover?
>
It has a engine valve cover imprinted with 12VOHC.
However, the head has two (2) intake valves and one (1) exhaust valve and a
much smaller Aux valve. The Aux valve is next to the exhaust valve.

The carburetor is a three barrel. Primary, secondary and an Aux barrel,
about the size of my little finger. I haven't really explored all of this,
but will in the next day or so.

I did another test drive today. About 60 miles. Mostly on the flat and as
long as I didn't advance the throttle into the "dead zone", it ran great and
smooth. I think I'm noticing the "dead zone" is when the secondary throttle
begins to open and before it kicks down the AT to 2nd gear. When it is in
2nd, it will only rev to about 3000 rpm.

Not sure if I should look for fuel or vacuum problems.

Steve

"Steve" <estevew@hctc.com> wrote
> "Elle" <elle_navorski@nospam.earthlink.net> wrote
> > "Steve" <estevew@hctc.com> wrote
> >> "Elle" <elle_navorski@nospam.earthlink.net> wrote
> >
> > I'd like to get some clarifications from you:
> >
> > The subject line of your post says "EW1 12 valve SOHC."
> >
> > Does your engine actucally have "EW1" stamped on it?
> >
>
> The engine number/designation is: EW1-2015401
>
> Door label plate indicates MFG date of 1/85.
>
> It is really a carborated engine. Some part house books reflect it should
be
> FI but it's carboratated.

Well, the carbureted part is well-documentd; what threw me off was whether
it had 12 or 16 valves. Evidently the number of valves has thrown others off
in the past, and it's not easy to clear up using drawings and online Honda
parts sites... unless one knows exactly what to look for. Naturally the aux
int valve has its own exclusive listing at the two parts sites I use. For
example, see it at www.slhonda.com 's parts site, under simply engine, blah
blah, "Auxiliary Valve."

> > How many valves (both intake and exhaust) per cylinder have you actually
> > counted under the valve cover?
> >
> It has a engine valve cover imprinted with 12VOHC.
> However, the head has two (2) intake valves and one (1) exhaust valve and
a
> much smaller Aux valve. The Aux valve is next to the exhaust valve.
>
> The carburetor is a three barrel. Primary, secondary and an Aux barrel,
> about the size of my little finger. I haven't really explored all of this,
> but will in the next day or so.

I think the above straightens things out; I trust you get it all now, too.
In summary:

Your vocabulary is dead-on here. The little valve next to the exhaust valve
is indeed Thee "auxiliary intake valve." From my reading on the net, it's so
small that it's customary to disregard it in the valve count and categorize
this as a 12-valve engine. That aux barrel of the carburetor must go with
the aux intake valve, etc.

Maybe you already looked at the full Chilton's entry on this (just above the
paragraphs I first noted). If not, it provides some clarification:
---
The [1983 and earlier] CVCC engine is unique in that its cylinder head is
equipped with three valves per cylinder, instead of the usual two. This
design employs the usual intake and exhaust valves, and beside each intake
valve is an auxiliary intake valve which is much smaller than its
counterpart. This auxiliary intake valve has its own separate precombustion
chamber (adjacent to the main chamber with a crossover passage), its own
intake manifold passages and carburetor circuit.

Briefly, the CVCC engine operates as follows: at the beginning of the intake
stroke, a small but very rich mixture is inducted into the precombustion
chamber, while next door in the main combustion chamber, a large but very
lean mixture is inducted. (A rich mixture has a high proportion of fuel in
the air/fuel ratio, while a lean mixture has a low proportion of fuel.) At
the end of the compression stroke, ignition occurs. The spark plug, located
in the precombustion chamber, easily ignites the rich auxiliary mixture and
this ignition spreads out into the main combustion chamber, where the large
lean mixture is ignited. This two-stage combustion process allows the engine
to operate efficiently with a much leaner overall air/fuel ratio. So,
whereas the 1975 and later non-CVCC engines require a belt-driven air
injection system to control pollutants, the CVCC engines accomplish this
internally and gets better gas mileage to boot.

On the 1984-88 models, Honda decided to improve engine breathing by
replacing the single large main intake valve with a pair of smaller ones.
This allows a much greater total intake valve area than a single valve and
it also permits intake valve timing to be staggered slightly. This gave
Honda engineers a unique opportunity to design air swirl into the combustion
process. Such swirl (turbulence in the combustion chamber) not only tends to
reduce engine knock but improves combustion speed and therefore engine
efficiency, especially at low speeds. These engines retain the auxiliary
intake valve on the exhaust side of the head.
---

I couldn't find drawings of this crossover passage and carburetor circuit
(mentioned above) for the little "aux intake valve." But all else that you
described now seems dead-on consistent with the Chilton's entry. Maybe it
will give you some ideas...

> I did another test drive today. About 60 miles. Mostly on the flat and as
> long as I didn't advance the throttle into the "dead zone", it ran great
and
> smooth. I think I'm noticing the "dead zone" is when the secondary
throttle
> begins to open and before it kicks down the AT to 2nd gear. When it is in
> 2nd, it will only rev to about 3000 rpm.
>
> Not sure if I should look for fuel or vacuum problems.

Sorry; this part is beyond my experience. I'd be probing as you are, but
probably more novice-like (I messed with a carburetor for just a few hours,
total, in my life). I'd start with a good carburetor cleaning, and using
Chilton's as my guide for its adjustment, disassembly, and so forth, which I
bet you already noticed...

Thanks for all the comments and explaination of this CVCC.

I will look around for more information on the Honda web sites.

Steve