|
This article was first published in 2005.
|
Check this out! A 1.6 litre four-cylinder cranking out 180kW (241hp) at the
flywheel without the aid of a turbocharger or nitrous; we’re talking about a
performance-built Honda VTEC that spins to 10,000 rpm!
Yes, 10,000.
This particular engine - built by Shane Wilson Competition Engine Developments - is configured to meet Australian Class 2 off-road racing
regulations. Class 2 buggies require a naturally aspirated engine not exceeding
1.6 litres capacity; adding forced induction puts you in a field of buggies with
engines up to 6.0 litres... This means it’s wise to grab the most sophisticated
and powerful naturally aspirated 1.6 litre you can get your hands on. And that’s
where the Honda B16A VTEC stands out from the crowd.
"The owner of this engine previously ran a Toyota 4A-GE 20 valve. I did some
light modification on the Toyota and it went well - but when we wanted more, the
Honda VTEC was the obvious choice," says Shane.
So what’s been done to the engine, you ask?
Well, pretty well everything...
Engine Internals
Shane started off with a late-generation Honda B16A, which has a slightly
higher compression ratio, larger throttle body, different cams and some other
minor differences compared to early versions. Despite its reputation, Shane
tells us it’s a nice engine – but it's not a standout above its rivals.
"It has a full-length windage tray, a pretty good cylinder head and, of
course, VTEC - but when you look at most other parts it could easily be a Nissan
or Toyota," he says.
The original aluminium block has been bored, honed and fitted with a deck
plate that effectively makes it a closed-deck block. Inside
the bores you’ll find CP forged pistons from the US. These increase the
compression ratio from 10.4:1 (stock) to 11.0:1 – still mild enough to let the
engine run on 98 RON unleaded without detonation. Conrods are from Carillo while
the crankshaft is the standard Honda steel item. Everything is balanced and the bottom-end is assembled
with genuine Honda bearings.
Interestingly, the stock oil pump is fitted with billet steel gears to
provide greater reliability at high rpm. Shane also modified the original sump,
increasing its capacity to 6 litres, installing baffles and fabricating a custom
oil-pick up. A high-torque starer motor is also fitted to cope with the engine’s
extra compression.
In the hunt for maximum power it was decided that the standard DOHC, 16 valve
cylinder head would receive the die-grinder treatment. Cylinder head guru Bill
Hanson says he spent considerable time working on the Honda head and his trusty
flow bench revealed an 11 percent potential power increase. A set of US-sourced titanium
valves is also installed. The cylinder head is attached to the block using an
ARP stud kit (which replaces the factory head bolts) and a TODA multi-layer
steel head gasket provides effective sealing.
With the expectation that the engine would run at high revs, Shane installed Crower
high-tension valve springs, retainers and collets. And the cams? Well, they’re
Crower shafts that retain a near-standard lobe profile for low rpm operation - this
gives almost standard levels of drivability and bottom-end torque. However, the
new lobe profile for high rpm operation delivers considerably greater valve lift
and duration as well as altered lobe separation – and this is where much of the engine’s top-end
power comes from. The cams are driven via a TODA competition belt and cam timing
is manually altered using Edelbrock adjustable gears.
|
How Does VTEC Operate?
The B16A’s VTEC system employs three in-line camshaft lobes for each pair of
intake valves.
During low-rpm operation, the two outer lobes - which deliver low-lift and
short-duration - control the intake valves via their own set of rocker arms. A
third set of rocker arms - which align with the centre camshaft lobes - are left
idling during this stage; their movement controlled by a so-called 'lost motion'
spring. Then, during high rpm operation, the engine management system locks the
centre rocker arm to the outer arms using a hydraulic synchronising pin. This
sees the centre camshaft lobe - which delivers high-lift and long-duration -
taking control of the intake valves and giving increased engine airflow at high
rpm.
The benefit of this two-stage system is a healthy spread of torque across a
wide rev range.
|
Induction and Exhaust System
Shane researched aftermarket parts to suit the B16A and decided a US-sourced
TWM induction system was too good to pass up - there’s simply no way you could
fabricate a similar set-up for anywhere near the cost of this off-the-shelf kit.
Purchased from Quantum Racing Industries in Queensland, this particular TWM
induction kit comprises quad 50mm throttle bodies, a relatively long runner intake manifold (with two injector bosses per cylinder), bell-mouth entries and a
composite airbox. Note that the engine was dyno’d without the airbox
attached.
This photo shows the underside of the intake manifold and throttle bodies.
Note the elaborate, fully adjustable linkage arrangement and throttle position
sensor mounted on the third throttle body. It’s a very nice kit...
The exhaust system is uniquely built to suit the off-road buggy chassis. The
4>2>1 headers employ 1 5/8 inch primaries (which step up to 1 ¾ inch a
short distance along their length), 1 7/8 inch secondaries and a 2 ½ inch
tailpipe. Exhaust backpressure at full power is minimal.
Fuel and Engine Management
Fuel is squirted into the Honda motor as far away from the combustion
chambers as possible - Shane uses the injector bosses that are furthest away
from the engine. This helps improve the fuel/air mix and provides a small
cooling advantage.
Interestingly, the fuel injectors, rail and pressure regulator were purchased
as part of a kit along with the TWM quad throttle manifold. The injectors are
400cc units which operate at a rail pressure of 55 psi. A Bosch Motorsport fuel
pump was employed in the dyno cell.
Shane tells us he was reluctant to retain the factory distributor-type
ignition system given the engine’s off-road application – dust and water always
seems to end up inside the distributor cap... His solution is a switch to
direct-fire ignition using a pair of M&W double-ended coils and Bosch 008
modules.
Fuel and ignition are controlled by an Autronic SMC programmable management
system. Shane has added a crank angle sensor to the flywheel and a cam angle
sensor in the position of the original distributor. This photo shows the new cam
angle sensor with a detonation sensor also seen near the foreground (the
detonation sensor was used for dyno tuning only). Note that mapping is based on
throttle position and rpm – there is no engine load input to the ECU.
On the Dyno
Installed on Bill Hanson’s SuperFlow water brake engine dyno, this heavily
worked Honda 1.6 is surprisingly docile. It idles smoothly, happily accepts full
load from 1000 rpm and runs to 10,000 rpm without hiccup. But at 10,000 revs
Shane admits it sounds "busy"...
Tuning began with a lot of experimentation using different cam timing (with
optimised fuel and ignition timing to suit each configuration). Shane settled on
cam timing settings that give the best average power – he says he could
have achieved slightly more top-end by sacrificing mid-range torque, but it
wasn’t worth it.
The optimal VTEC change-over rpm was found by running the engine at wide-open
throttle with the VTEC system locked in each of the two configurations. Optimal
change-over rpm is where the torque curves intersect. However, due to an
inevitable delay to actuate the secondary VTEC lobe, Shane says the switch-over
point is programmed into the Autronic ECU approximately 100 rpm earlier than
this point.
Once the cam timing and VTEC switch-over were set, a Lambda sensor was
installed in each header pipe to measure cylinder-specific air-fuel mixtures. As
it turns out, one cylinder was running slightly lean and another slightly rich.
Shane says injector duty was individually tailored to give consistent mixtures
and an extra 4kW (around 5hp) was found.
The final tune uses 26 degrees of ignition timing at wide-open throttle all
the way from 4500 rpm to 10,000 rpm – and note that the detonation meter shows
no sign of detonation when running on 98 RON pump fuel. A full load mixture of
0.91 Lambda (13.3:1 AFR) gives maximum power.
And exactly how much power are we talking?
Well, this graph shows a peak of 180kW (241hp) at 9500 rpm without any steep
rises or falls. We should point out that 180kW from a 1.6 litre engine equates a
specific power output of 112.5kW per litre – we can’t think of another naturally
aspirated production-based piston engine that comes close! The torque curve (shown in pink) shows
there’s just over 150Nm from 4000 to 5250 rpm, at which point the second stage
of VTEC is engaged. Torque then swells to a maximum of around 200Nm. Note that
engine output data below 4000 rpm was not available.
And, in case you’re wondering, what’s a highly-tuned 1.6 litre beast like
this worth?
Shane says approximately AUD$15,000 - $20,000 - depending how you source an engine,
the exchange rate and a few other variables.
It’s not cheap - but, then again, achieving 112.5kW per litre without a
turbocharger is no small achievement...
Contacts:
Shane Wilson Competition Engine Developments 0409 550 351/+61 8 8724 8000
Bill Hanson Engine Developments +61 8 8362 8545
Quantum Racing Industries +61 7 3290 5911
Did you enjoy this article?
Please consider supporting AutoSpeed with a small contribution. More Info...
|
More of our most popular articles.
|
|
|
Email a friend
Print article
|