Turbocharging the EJ Civic 1.6L SOHC VTEC
Our last article on the HKS light pressure turbo project Civic
garnered a lot of interest. That base car was a non-VTEC Civic, with the HKS
turbo generously upgrading its max power to that equivalent to an automatic B16A
Civic but with vastly superior midrange pull. A lot of readers have written to
me asking for more details of the car. However, most of them were driving the
VTEC version of the 1.6SOHC Civic instead. The prototype of the HKS kit was
actually done on such a model, a Malaysian domestic market EJ8 Civic VTi.
Consequently it would be of interest to many to know the result on that
car. Since I had access to the car, I thought that the obvious follow-up article
would be this.
The owner of that Civic, Mike, bought the car because it was
the highest spec'ed EK-Civic available in the local (Malaysian) market at the
time. As the top model, it uses the 1.6SOHC VTEC engine, spec'ed to deliver
around 125ps. Red-line was a high-ish 6800rpm. The car was sold only with an
automatic transmission and carried the high-performance flag for the Civic range
during the EK Civic generation's life-cycle for Malaysia (1996-2001).
Unfortunately, after a few months driving around, Mike was already feeling a
lack of midrange pull from the engine. The car was used for daily driving to and
from work, a round trip exceeding 100km, 90% of which is a 5-lane highway
travel. Mike told me of many 'encounters' with the competitions, typically the
larger engined cars which unfortunately tends to bully their way around such
roads. As a result, he quickly developed a yearning for more power.
A brief experimentation with the typical route of drop-in mods
quickly told Mike that it will not yield the kind of power gains that he was
looking for, which is power gains all through the rpm band of sufficient
magnitude to allow him to handle the larger displacement cars (2.0l-2.2l and
higher) on an equal basis. However, Mike's timing was good because Aerotech, the
HKS specialist for Malaysia was just finalizing the initial design of the HKS
low-pressure-turbo kit. Thus the opportunity to prototype the kit on Mike's car
gave significant cost savings - both to Mike who got the kit at a huge discount,
as well as Aerotech since they were able to have a portion of the prototype's
development cost covered.
1.6SOHC VTEC Low-Pressure-Turbo (LPT)
I got to know Mike just after he took delivery of his car a few
days before. The prototype turbo-kit in his car was basically the same as that
covered in our previous article on the Malaysian 1.6SOHC non-VTEC auto
Civic. It is after all, the basis for that kit anyway ! Mike's car is of course
an SOHC-VTEC version but both engines are very similar in design so the kit was
the same, except for one item - the exhaust manifold.
In a 4 cylinder engines, the power strokes do not overlap.
Therefore in a turbo-charged 4-cylinder, the exhaust manifold to which the
turbo-charger is connected to will need to maintain a steady, consistent
pressure to ensure that the turbo-charger spins at a consistent speed. Special
attention was paid to the design of the exhaust manifold used in the prototype
kit, which was based on that used in the HKS B16A low-pressure-turbo kit. The
manifold has the exhaust from cylinders 2 & 3 and 1 & 4 tied together
before feeding together into the turbo-charger. This initial manifold was built
out of small sections of steel tubes welded to together to form the design. The
intention was to test out the design on the prototype and to then use it to
create the mold with which to make the final cast manifold for the proper
In the event, I have to report that Mike did encounter problems
with exhaust leakage from the manifold. The very high exhaust pressure and
temperature at the manifold often made the welding points crack at several
places. There were a few return trips to re-do the welds. Other than that
though, the prototype kit works exactly as designed which is extremely
well. In the final production kit, the exhaust manifold is a cast-iron
item. Based on data from the prototype kit, the design was able to be simplified
into a "4 to 1" design, with all 4 cylinders feeding their exhaust into a single
point before feeding into the turbocharger. When the cast manifold was
available, it was quickly retrofitted to Mike's car. With the cast item the
problem with exhaust leaks encountered with the prototype kit was then fully
This prototype kit also uses the same HKS FCON-4 tuning
computer as the HKS demo car. In fact, the tuning done on this car was even more
extensive than that on the demo car since a lot of basic research had to be
done. Of special significance is the boost level. Many days of testing were done
before deciding on a boost level of around 0.3 bar. However, as explained in the
demo-Civic article, a problem with turbocharged automatics is the shift-shock.
Since automatic transmissions allows the driver to be on full throttle even
during the automated gear shifts, there will be a shock as the next gear
engages. And with a turbocharger, this will lead to a spike in the running
boost. At one time, a boost level of as high as 0.5 bar was recorded during
shift-shocks and the engine and gearbox were clearly stressed more than is
desirable. At the time of the prototyping, the relief valve solution was not
thought of yet. In the end, very careful tuning and setting were used to keep
the shift-shock boost to 0.36bar.
A Super Powerful Auto VTi
The dyno chart of the car as delivered is reproduced on
the left. As usual, the original, base dyno chart was reproduced together with
the turbocharged version for comparison. The stock car, with the benefit of a
HKS Super Power Flow filter dynoed at 90ps at the wheels. With the reference
30% power loss figure, this works back to around 129ps at the engine, tallying
extremely well with the specified 125ps stock power with the benefit of an
open-element filter. Of special note is the profile of the stock dyno graph.
Note the obvious change in the curve at 4500rpm. This is the VTEC changeover rpm
and proves conclusively that the VTEC implementation in the Malaysian Civic VTi
is a power oriented one.
After tuning was completed, the turbocharged version delivered
117ps at the wheels. Working back to engine power, this topped 167ps. The HKS
LPT upgraded the power of the 1.6SOHC VTEC engine to almost that of the much
higher spec'ed auto B18C !! This was a massive achievement and is
confirmed by the automatic B18C DB8 Integra which dynoed at 118ps at the wheels
featured in our Beyond Stock article on the baseline reference
for the B18C.
Comparing to that car's dyno chart, it can be seen that this
turbo 1.6l SOHC-VTEC has more power in the low-rpm. Power at 3000rpm for the
1.6l turbo was almost 70ps while the auto B18C delivered less than 60ps. This
carried on in the midrange as well, the 1.6l turbo generating >70ps at
4000rpm while the auto B18C did not achieve 70ps. VTEC cuts in at 4800rpm for
the B18C and this gives generous benefit to the engine allowing it to match the
1.6l turbo's power at 5000rpm and above. Of course the B18C have a superior rpm
range, capable of revving to around 7500rpm, almost 1000rpm higher than the
1.6SOHC VTEC. Viewed in this perspective, the HKS kit's upgrade to the 1.6l SOHC
VTEC was huge indeed, allowing it to overcome a 200cc displacement deficit as
well as a lower spec'ed configuration (SOHC vs DOHC), ultimately only losing out
in the ability to rev to very high RPMs.
As with the project Civic, this prototype kit also impressively
duplicated the stock engine's power chart by lifting it by 27ps almost all
throughout the rpm range. Equally interesting is that the turbocharged curve
even has the slight power surge when VTEC activates the wilder cam profiles at
around 4300rpm !
The Driving Experience
Mike was one of the first members of my Honda club. As a
result, I had extensive experience with his car. All the time that he had it, I
was impressed with how responsive and powerful the car felt. Although an
automatic, the power delivery was very impressive, especially when VTEC opens
the wilder cams. I was also treated to many stories of road encounters that Mike
has on his way to and from work. As described, Mike's daily commute to and from
work is around 100km of mostly highway travel. As a result, he tends to have
more than his fair share of encounters with rude or impatient drivers,
especially suffering in the hands of those which have larger engines. In the
event, Mike were now able to dispatch with all of such 'nuisances' with ease :-
probably most of them were taken by absolute surprise from the sheer speed of
his turbo-charged VTEC Civic; as can be seen from the photo, externally the car
does not give away any idea of what's underneath the bonnet - a real sleeper of
a Civic indeed !!
My personal experience with all-out driving of this car was an
even more interesting event. My friend from Singapore, coincidentally also name
Mike, drove his EG9 to Malaysia on a business trip. We met up, the two Mikes,
and a couple of others for a drink on Friday night and subsequently "itchy
feet" got the better of us and we ended up "testing" one Mike's turbocharged
Civic against the other Mike's EG9. That EG9 is the 160ps Singapore version, 5
speed manual and generously equipped with a complete complement of
bolt-on mods; Tanabe header & exhaust, Akimoto filter, SFC a/f regulator,
adjustable fuel pressure regulator, an aftermarket ECU that raised the rev-limit
to 9000rpm and even a very mild head polish. That car as reported elsewhere here on
Beyond Stock, delivered around 137ps at the wheels at that time (we had that
test before the car went for its dyno-tuning session which netted it the 5ps
gain at the wheels).
I drove the turbocharged 1.6SOHC VTEC with owner Mike as the
passenger. The EG9 had its owner Mike and two other of our friends onboard. In
the event, upon peeling off to join the main road, the two cars were neck to
neck. Although the EG9 was ultimately slightly faster, it couldn't overtake
us even on the main road. The midrange superiority of the turbo-charged 1.6SOHC
VTEC allowed us to easily build up an initial lead, despite the large
disadvantage of the automatic gearbox, and even with wild cams screaming until
9000rpm, the EG9 still could not overtake. On the next round, we started behind
the EG9 and I was surprised that I could keep up closely with it.
That "test" was an impressive one, especially when we consider
that the turbocharged 1.6SOHC VTEC is an automatic car, with a redline of only
6800rpm and therefore much lower gear ratios when compared to the NA EG9, a 5
speed manual B16A complete with the close ratio 4.4 final ratio gearbox. In an
all out race, the EG9 with the superiority of the 5-speed manual gearbox and
higher power at the wheels will ultimately win, but it would needed an extended
high-speed chase to achieve the victory. Indeed, had the EG9 been an automatic
like the SOHC-Civic, it would have been easily defeated !
ConclusionI think this HKS light pressure turbo'ed 1.6SOHC VTEC EJ8 is
an extremely fast car, even more impressive than the HKS demo non-VTEC Civic.
The VTEC did contribute generously to the overall power band and driveability of
the car, witness the dyno graph being a nice consistent upward slope. This means
that the car never ran out of steam, and was able to sustain very good pull all
through its 6800rpm, unlike the non-VTEC demo Civic which has a power plateau
after around 6000rpm. As pointed out, its midrange even managed to beat that
from the auto B18C, which is a super high tuned DOHC VTEC implementation
and a very high performance engine in itself.
Owners of 1.6SOHC VTEC Civics are probably a fair bit more
performance minded than that of the ordinary 1.6SOHC version. The VTEC
implementation did allowed a broader powerband to the stock engine, even a mild
bump in the power when VTEC engage the wild cams. But it is the HKS light
pressure turbo that really brings the car to life. This prototype Civic was
every bit as responsive as the demo Civic but more powerful and a broader power
band to boot ! The car was able to take on all of the common "nuisances" Mike
had the misfortune to encounter on his daily work commute. In the end it is
particularly telling that the only car that could satisfy Mike when he decided to
upgrade his car was a manual DC2 Integra SiR.
For readers in Malaysia, to get more details about the HKS
Light Pressure Turbo bolt-on kit for the 1.6SOHC and SOHC-VTEC EK-Civics,
contact Aerotech at 60-3-79556112. The cost for the kit is relatively high
especially for a one-time outlay but for those who demands such large power
increases, it is the only way to go short of changing the engine.
© Temple of VTEC