HKS EVC III Impressions

From toyota-mods-owner@CyberAuto.Com  Thu May  4 08:11:17 1995
From: "Aaron Buhr" <abuhr@eng.ufl.edu>
Subject: New HKS EVC III impressions
To: supras@cyberspace.cyberauto.com (Toyota Supras ML),
    toyota-mods@cyberspace.cyberauto.com (Toyota Mods ML)
Date: Thu, 4 May 1995 10:56:21 -0400 (EDT)

     Well, I got my EVC ("HKS EVC III") yesterday evening and embarked
on installing it.  It did turn out to be somewhat of an adventure.  I
was able to find a fairly convenient hole in the firewall: there's a
hole in the passenger side that has about 4" of rubber tubing coming
out of it.  I think it's the AC drain spigot or something.  In any
case, I unplugged the tube and pulled it out, then routed the HKS EVC
wiring harness through the hole, then put the rubber tube back in.
Oh, I did have to remove the actual plastic connector from all the
wiring on the EVC harness, because the connector itself wouldn't fit
through the hole, but the wires all bundled together did.  I put the
connector back on once I had it through the hole.

     After I figured that out I had to disconnect my VBC and connect
the up the EVC valve unit to the appropriate locations.  What was nice
about the VBC was that it came with specific instructions and parts
for my car.  The EVC just came with generic parts and generic
instructions.  I hooked the EVC to two of the three places the VBC was
using, but as far as I could tell the instructions indicated that the
third EVC connection was dissimilar from the third VBC connection.  I
put a golf tee in the line for the third VBG connection and put the
new EVC T-adapter in the third EVC location.  Also the hoses that HKS
included to hook into various vacuum lines were smaller than the stock
hoses on those vacuum lines.  I ended up pulling out the stock vacuum
lines from the connection points and replacing them with the smaller
HKS ones, really having to push them to get them on the stock
connection points.  They seem to be holding ok though.

    Those were the two difficult stages.  I decided to put the EVC
control unit in the ashtray location, for now at least.  I pulled the
ashtray out and currently have set the EVC in its place.  Next I
routed both the EVC wiring harness from the passenger footwell and the
power lines for the control unit from the fuse box to the ashtray.  I
powered everything up and it all came up fine first try. :) All told
installation took about three hours.


     Here's the feature list for the EVC:
	- 3 boost settings: low, high, and manual.  Low goes up to 1.0
	  bar (1.0 bar is 14.7 psi), high and manual go up to 2.0 bar.
	- Digital boost meter, reading in bar only.  Updates about 2 or 3
	  times per second.
	- Boost is adjustable in one-hundredths of a bar (.01 bar/.147 psi)
	- "Offset feature.  Alters actual boost curve of turbocharger.  This
	   feature gives you an adjustment window for the self learning boost
	   adjustment mode."  I don't really understand what this is or how
	  it works.
	- Scramble boost feature:  allows you to increase boost above low/high
	  settings at the push of a button, for a given period of
	  time.  You can specify how much boost increase you want and how
	  long you want it to last.  There's a connector for an external
 	  switch you can mount anywhere.
	- Boost warning feature:  you can set the warning threshold to whatever
	  amount you want (up to 2.0 bar) and if boost exceeds that level the
	  EVC will blink and beep, and will instantly return wastegate
	  operation to stock levels.
	- Switch-configurable wastegate type (integral or external).
	- Serial port:  supposedly for interfacing with other HKS units,
	  no current uses that I know of.
	- Fuzzy logic:  supposedly manages the wastegate better than straight
	  digital logic.

     In order for the EVC to "learn" how your wastegate works, the
directions say you're supposed to go 1000 rpm in third gear, then
floor the accelerator.  When max boost is reached the EVC beeps, then
you back off, go back to 1000 rpm and repeat 2 more times.  Not too
bad for single-stage turbo cars, but the directions caution you that
the EVC learn mode is easily confused by sequential turbochargers, and
the process is slightly more complex and apparently fairly difficult.
They actually recommend you bypass learn mode and set the "peak OEM
boost level" manually.

     Now, my experiences so far (2.5 hours driving): I've got a lot
more useable power in first and second gear than I had before.  I can
get max or close to max boost in both first and second gear just by
flooring it, whereas before the only way that would ever happen was if
I did a full drag-style launch from start, speed-shifting through
first and second.  This is due to the EVC keeping the wastegate fully
closed until the last moment, then popping it open.  I have a moderate
amount more power in higher gears, due to the EVC's better ability to
modulate the wastegate than the VBC.  But I still have that &^%!@$%^#
boost spiking problem!

    I've been playing with the EVC, redoing learn mode, etc., but I
still have pretty bad spiking at max acceleration in second gear.  For
example, as the EVC's currently set up (third or fourth learn mode) I
have high mode set to .70 bar (10.3 psi).  However, I floored it
coming away from a light and saw the readout indicate .82 bar (12.05
psi)!  At least the fuel cut didn't happen that time, but the car's
been lurching and bucking like crazy otherwise because I keep hitting
the fuel cut-off while I try to adjust the EVC to a reasonable amount
of boost.  I don't consider 10 psi a reasonable amount of boost for
steady-state operation, when I should be able to get up to very nearly
12 psi.  Those 2 psi are good for about 25 hp.

    I'm hoping that as I mess with the EVC further, calibrate the
learn mode and figure out what the heck the offset mode is I'll be
able to get more precise wastegate control.  But so far I'm not
impressed with the new fuzzy logic.  At the moment I'm experimenting
with setting high mode to 10 psi and just using the scramble boost
control to get that last 2 psi back.  Basically I go on high through
first and second gear then when I shift into third push the scramble
boost control button, and it gives me 10 seconds of 12 psi boost.
It's hard to push the scramble button though, since it's a small
target on the dash.  If I meant to seriously use scramble mode I'd
definitely look into getting the external button and mounting it on
the shifter or something.

    Anyway, it is nice to have digital boost display and digital boost
setting.  I bought the EVC as much to have those features, so I can
precisely set safe boost levels when I do further upgrades, as for
current benefits.  I'll keep everyone posted on how things go.