92 Civic VX VTEC-E

Need people's expertise here. I have a 92 VX with the VTEC-E. I'm having
problems with something I have yet to discover. My question is ... In my
quest for the search of my problem, is there a way to manually activate the
VTEC to always be on. Right now, The VTEC-E is set to activate at about
2500-3000RPM. My problem is that below these RPM, I get very low performance
but as soon as I hit 3000RPM, the VTEC or whatever kicks in very hard to
scream down the road. So I'm basically tring to see if it's the VTEC not
properly engaging itself or if it is something else. If I unplug the VTEC
spool valve or the pressure swith, don't remember which, I pretty much solve
my problem but have no VTEC above 3000RPM.
Any Ideas on how to activate VTEC? Do I need to ground the Spool valve or
the pressure switch?
Thanks
Frank

 

Some service manuals call it a spool valve, other a solenoid valve, I
guess spool valve is a poor translation from Japanese, a solenoid is, in
effect, a spool of wire. I'll refer to at is the VTEC Solenoid Valve

The VTEC Solenoid Valve is always grounded, it is turned on by applying
voltage to the single pin connector. The service manual is somewhat
confused on the issue, in the wiring diagram it shows the wire from the
ECU to the VTEC Solenoid valve being ORN/WHT. It then connects to the
engine wire harness where it changes color to GRN/YEL. Now, in the
troubleshooting section it say to apply battery voltage to the GRN/WHT
terminal to open up the VTEC Solenoid valve. My interpretation is that
you should remove the 1-pin connector from the VTEC Solenoid Valve and
apply battery voltage directly to the pin on valve.

I would be cautious about this. Under normal operation, VTEC will not
engage unless the engine is warm and the oil pressure is sufficient. I
would pull a wire from the VTEC Solenoid valve into the cabin and either
have lighter plug type connector on it or some sort of switch to +12V.
That way you can engage it while driving and make sure the engine is
warmed up before doing so.

Sounds to me like VTEC is slow to disengage in your engine. I don't know
if there is a port to release oil pressure when VTEC is disengaging, or
if it is just expected to leak down. In either case, If you are close to
doing an oil change, you could try using the thinnest oil recommended
for your engine (or even spring for a full synthetic) and see if it
helps.

 

3k is /way/ too low for the vtec cam. fixed cams are a compromise based
on extensive research to map an engine's volumetric efficiency. having
two sets of cams [vtec] allows a broader effective power band [two bands
with an area of overlap between them]. the lower cam set works well up
to 5k and is relatively torquey. the vtec is much more powerful /at
high revs/ but lacks low end and is narrower. on real high tune
engines, the power band can be as little as 1k rpm. trying to stick
with the majority of rpms on the vtec cam achieves nothing but emissions
problems and premature wear of the cam. notice how there's two sets of
lobes for the low rev cam profile and only one for the vtec? that means
greater load bearing area and therefore lower wear rate for the region
in which a road engine spends the majority of its life.

bottom line - if this car's a daily driver, don't monkey with the vtec.
anything below 4k is absolutely pointless. if you want this car for
the track, don't bother with the vtec at all - you shouldn't be pulling
at much less than 6k anywhere on the circuit so you may as well just go
straight to a single profile cam with a high rev power band.

 

jim beam wrote:

Jim, the OP has VTEC-E (D15Z1). The proper shift-over point on that
engine is between 2500 RPM and 3000 RPM depending on load.

 

I got to do what you mention, connect 12V via a switch and with that I was
able to recreate my symptoms. Driving with VTEC off is smooth all the way to
about 4500-5000rpm at which point I have not much power left. That's o.k.
However, activating the VTEC at 2500rpm almost stall the engine at first but
it picks right up after 3500rpm and accelerates fast to 6000+rpm.. If
activating at 5000rpm, almost feels like a common VTEC found in civic SI.
So the VTEC solenoid valve is probably not my problem. Maybe the pressure
switch is, or maybe a clogged solenoid valve filter. If I activate the VTEC
at cold, it reduces engine speed.(Does engine have high pressure when cold
idling?) When warm, no effect at idle(Is there little if no pressure when
idling warm?). Thus, since my hesitations or loss of power occurred at
around 2500rpm but than kicked in power at 3000rpm, I would presume I might
have a pressure related problem. Like you said, I'm probably having a VTEC
engaging trouble. Pressure might be too little at 2500-rpm to activate VTEC
but high enough at 3000=rpm. What do you think of this? Would you have any
other suggestions or probable solutions? anyone welcomed.
thanks for the great help
Frank

 

wow - hardly seems worth the effort at that rev range. guess i've only
driven the later more sporty vtecs.

 

VTEC and VTEC-E were actually used at the same time, the VX got VTEC-E
and the Si and EX got VTEC in the 92 - 95 model years Civic (I believe
the VX changed name to HX some time during those model years). The
VTEC-E is optimized for fuel economy, not power. The '92 VX was rated 48
MPG city, 55 MPG highway. The Civic Hybrid manual of 2005 is rated
46/51. So, in my mind, the 13 year old model wins on both looks and fuel
economy.

 

:

At this point I would get an oil pressure gauge and measure the oil
pressure. The service manual for 1994 lists minimum pressure at idle as
10 psi // 0.7 kg / cm^2 // 70 kPa. At 3000 RPM the minimum is 50 psi //
3.5 kg / cm^2 // 350 kPa. All numbers apply to warmed up engine. The
service manual says to connect the oil pressure gauge in place of the
oil pressure switch above the oil filter (NOT the VTEC pressure
switch!).

 

makes sense. the most economical of all should be the 1996-2000 civic
hx cvt. the cvt is capable of keeping the engine in a /very/ narrow &
therefore fuel efficient rev range. can theoretically tune the engine
for a very specific power band.