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We
profiled the lightweight carbon composite PCD 'Saxon' (1100cc racing
car class) hillclimber in the July 2001 Tech Focus and at that time
this superb race car had yet to turn a wheel. So, just over a year on,
how has the car performed on track, and what development issues have
been encountered? We persuaded owner Rob Barksfield and designer/constructor
- and former Lotus F1 cheief designer turned freelance - Martin Ogilvie
to demonstrate the world's lightest racer (probably...) at the Chobham
test track.
When I
interviewed Rob and Martin for that original Tech Focus feature, one
of the refreshing things about their attitude was their willingness
to take risks with the car's concept and design. That was, to a large
extent, what enabled them to get the PCD down to a starting weight on
just 208kg - fuelled , oiled, watered and ready to go. But equally,
they both went in with eyes wide open, knowing that risks don't always
pay off, and portions of humble pie might need to be dished out later.
As Martin put it, with some things "you just don't know until you
try." They also expected there would be paddock detractors, and
sure enough, that turned out to be the case too, with a predictable
degree of rumour and misinformation being bandied about on and soon
after the PCD's debut.
But what
really matters in the wonderful world of motorsport is performance on
the track, and how the car stood up against its opposition and to the
rigours of competition. A few problems had been encountered in the run
up to the first events. Early testing had shown the amount of oil that
had to be carried in the wet sump was critical because of the slightly
more inclined installation angle of the engine in the PCD. It also became
evident that the crank was thrashing around in the oil, so a slightly
deeper sump pan was made with modified baffling to enable sufficient
oil to be carried without the crank wasting energy by splashing around
in it. There was also an issue with the differential mounting. The original
6mm bolts proved too fragile and sheared, so the bolt size was upped
to 8mm. And one of the diff bearing carriers was also modified to stiffen
and strengthen the diff support. Which just went to show the level of
loads encounterd, even with a very light car.
But its
debut at Gurston Down in June 2001 gave a good indication of overall
potential, as well as the areas that were going to need development.
With a best-in-class power to weight ratio Rob and Martin were always
confident in the car's ability to accelerate, but to be fair to them
they were always less certain what the car would be like to get off
the startline. Sure enough, the sheer lightness of the car, coupled
to the readiness of the Ray Debben-tuned Suzuki to light up the rear
wheels made it difficult for Rob to achieve consistent, good starts.
That the car also originally had a very short throttle pedal movement
didn't help with the driver's control of wheelspin either and the evidence
was plain to see. Most major hillclimbs provide not only elapsed run
times. trap speeds and halfway split times but also first 64ft times
too, and the latter figure gives a very good indication of the quality
of start you achieve. Rob was losing between two and three tenths to
the opposition in the first 64ft, a lifetime at the sharp end of such
a competitve class.
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But
once the car left the line its performance was very good, and
trap speeds were generally right up there with, if not better,
than the best opposition. Bearing in mind that the car's spring,
damper and geometry set-ups were all complete guesswork at this
stage, two second places at that Gurston double-header debut meeting
represented a very repsectable beginning. Rob was only beaten
by the top man nationally in the 1100cc racing car class in 2001,
Mark Budgett aboard his well-developed Force Suzuki. In fact in
the Sunday event Rob was only three hundredths of a second hehind
Budgett, which was all very heartening.
The next stop was Shelsley Walsh, and the startline problem was
as bad here as anywhere, exacerbated by the Shelsley startline
having gotten very slippery over the years (it was resurfaced
on the 2001/2002 winter for that reason). Rob was 0.3 to 0.4 seconds
down on start times here, but was able to claw most of that back
by the finish. His elapsed time on his first competitve run was
staight into the 28-second bracket, just 0.15 secs away from the
old record, and his trap speeds were five to 8mph better than
the opposition. Forced to miss the second timed runs in order
to dash to catch a flight for a business trip, Rob nevertheless
hung on to second place on the strength of his only timed run.
If only the car could get off the line better...
And
that became the major quest in the car's development really, for
the problem was also evident in accelerating out of slow corners.
Rob and Martin played with the rear cambers, tracking, damping
and springing, and also with the diff, running it anywhere between
open and locked.
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Going stiffer
on the rear suspension proved to be the wrong way to go, and subsequently
they have been going softer with possibly a bit more to go in that direction.
On the diff front things were less conclusive, and another type of diff
is set to be tried once Rob gets up and running this season - work commitments
and other projects on the car have significantly delalyed the start
of Rob's 2002 campaign "We had a reasonably structured test plan,
but we're chasing a set up with nowhere really useful to test, as you
can't easily simulate a hillclimb at a test track," Rob said.
But at
least that first season, in 2001 brought the first class win at Gurston
in July, and in eight evetns Rob achieved first, seconds or third place
finishes every time out, only failing to start one event when a grumbling
diff hearing forced withdrawal. Rob, in fact, extols the positives:
"Just about everything has worked, so the fundamental design is
very good. The engine has been totally reliable, temperatures have been
right, the small (rechargeable NiCad) batteries have worked, the tiny
(1.3-litre) fuel tank, the small driveshafts, the small suspension fixings,
the remote starter, the samll diff - everything has worked.
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"The
brake capacity and feel is good. We did have to change the clutch
master cylinder size to reduce the throw on the clutch. But the
steering and driveability are very good, and there are no handling
vices, although because it's so light it can break away pretty
easily, it is sensitive to over-aggressive driving. But it is
very good to drive and has been pretty trouble-free. The only
issue is traction off the start and from slow corners, but you
can take quite a few liberties with it. Incorrect damping did
cause problems over the bumps at Wiscombe Park (in Devon), but
in fast corners the car is absolutely planted so the aerodynamics
are certainly working well, and still enabling good top speeds.
And one of the very positive things has been the plaudits from
the paddock. The car has got a bit of a 'wow factor'. We got used
to it working on it for 14 or 15 months before its debut, but
it did attract a lot of interest and curiosity. Some of it was
of the 'it will all fall to bits' variety but in general there
have been lots of positive comments from people at all levels
in the paddock. And I think it's fair to say that it has raised
other peoples' games too.
"It
crashed pretty well too!" joked Rob in reference to a costly
off into Wiscombe's unforgiving tree-lined boundaries. But the
suspension sheared off and the nose deformed and broke off as
they were designed to do. The chassis took the impact well and
only two small cosmetic repairs were required - all reassuring
stuff. The detachable, frangible front wing supports also proved
thier worth in an earlier off, saving the nose and wing. So, where
to from here? "We feel we haven't concentrated on springing
and damping as we probably should have". Contined Rob. "But
it's difficult to find the resources and time to solve probles.
Even last year with two events per month it was very challenging
to do changes and make progress." Unstated in this remark
is that Rob spends much time away from home on business, and also
that by its very nature hillclimbing offers little seat time in
which to evaluate changes. Furthermore, as one circuit racing
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preparation
expert commented ot me recently on his first trip to hillclimb, there's
no scope for warming up, not even the luxury of an out-lap before you
go for a time. On the hill you have nail it from cold and hope you aniticipate
the grip levels correctly. In those circumstances it's inevitable that
sorting a new car takes many months.
Another
aspect to be evaluated is that of tyres. It was always matter uncertainty
that putting 208kg car on tyres designed (structurally) for a Formula
3 car wieghting two and a half times much was the right thing to do.
But there isn't a great deal of choice available in truth, although
Rob has some narrower Hoosiers to test against the F3 size Avons. The
other major change to the car is that Maritn had another front monoshock
mechanism made up over the winter to accommodate a bigger anti-roll
spring wire diameter, which will offer increased roll resistance, This
could have the dual benifits of shifting some dynamic weight transfer
from the back to the front, and reduce roll angles, both of which may
help with rear end grip when exiting corners.
And the
most obvious visual change to the car since we last photographed it
is the appearance of a stylish, hopefully downforce-inducing, underbody.
Martin designed it and had it made - in carbon of course - and says
it's a case of "trying it to see whether it's excess baggage or
not." As I said earlier, it's this willingness to take risks and
experiment with an open mind that makes this project so interesting,
and there are certain to be yet more radical developments to this amazing
car. And you have to admint that, so far at least, humble pie ain't
on the menu.
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| UNDER
NEW MANAGEMENT |
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The
biggest development leap that has been made to the PCD Saxon is
in the engine, and our 'old' chum Steve Broughton at SB Developments
has become deeply involved in this. As regular CCC readers will
know, Steve is a whiz not just with Vauxhall engines, but also
with engine management systems generally. And as he was keen to
demonstrate that management systems could be successfully retrofitted
to bike engines that originally breathed through carbs, it was
entirely logical that a partnership developed with Rob. It seems
there has been a perception in the world of bike engine tuning
that the management systems would not produce the goods. SB: "
I think people sometimes reckon you only need maximum power at
maximum rpm and they're not looking at what's happening up to
that point. And apparently even some of the bike manufacturers
have said that carbs are better. But for driveability you need
to look at management systems." Martin Ogilvie chipped in
"Even Formula 1 is going for driveability now." And
Rob Barksfield picked up the theme: "There's too much misinformation
about and that has soured things a bit. Maybe other people [who
have tried management] used inadaquate hardware. And in truth
the development curve is pretty steep. But Steve knew how to make
it work."
So
how did SBD go about converting Rob's already potent Debben Suzuki
to a full EMS, and why did he succeed at the task where others.
apparently, have not? Interestingly, things were kept as simple
as possible. For starters, standard Suzuki Hayabusa throttle bodies
and injectors were used rather then getting anything custom-made.
The spacing of the inlets were a bit different, but the throttle
bodies connect via rubber pipes so that was no problem. Because
of the different engine installation angle between the GSXR and
the Hayabusa, the throttle bodies were inverted so that the injectors
fired downward at the back of the inlet vlaves - this worked out
just right, apparently. And Steve already knew that the standard
Hayabusa injectors should flow enough fuel for approximately 200bhp,
and you might recall from our previous feature Rob's engine was
stated at 190bhp at the crank on carburettors.
The
MBE 967E ECU was selected. SB: "This provides 'grouped' injection
rather than sequential, or in other words it fires all four injectors
every 360-degrees, rather than firing them individually every
720-degrees. This is better for response and driveability because
it means there is always fuel in the intake ready to be drawn
in. Sequential is theoretically better for peak power (and economy)
but drivers usually find grouped injection to be more responsive.
The only downside, especially with a high revving engine, is that
you can run out of time to open and close the injectors. The bike
injectors are 14-ohm reisistance, which take about a millisecond
to open, and the same to close. Lower resistance injectors are
faster but the software 'drivers' are not readily available. They're
also not as suitable because they're bigger, which is not necessarily
good for idle. "However, with the Hayabusa injectors we are
running close to the limit, using up to 85 or 90 per cent of their
capacity. This means the injectors can get hot, and also doesn't
leave too much 'space' capacity for the extra fuel demands of
lower ambient air temperature or higher barometric pressure. So
we may switch to Peco injectors that can flow more fuel."
So
were there any tricky problems? "We thought there would,
for example dealing with rapid throttle changes and reapid rpm
increases. But we really didn't find any issues. Not that it was
easy. but it was less complicated than we expected. Essentially
we did the first dyno runs with Dave Iles and Dave Midgley at
Griffin Motorsport in Swindon on carbs to see what the power was.
The engine was already on an MBE ignition system, but we still
weren't sure how the injection would work. So then we switched
to the injection system and we found that where the carbs wouldn't
allow the engine to pull on full throttle until about 5000rpm,
with the injection it would pull on full throttle from as low
as 2200rpm." Rob confirmed the assessment following testing
at Avon Park and at Chobham: "That's the biggest transformation,
there is torque available immediately and it is so much more driveable.
This must be the way to go." Which is particularly interesting
when you learn that Ray Debben had also done some more mechanical
engine tuning work on Rob's engine prior to this management project.
Rob describes it now as "more of a drag race set up, with
a radical top end. It's very sensitive to valve spring pressure
and valve seat seal, and is much less a 'fit and forget' set up.
The compression is up considerably too" The cam profiles
are also somewhat more radical, and the throttle body size is
now bigger.
So
it was no great surprise that the engine now produces about 10bhp
more than it used to, meaning the car is approaching its target
of 1000bhp/tonne. But as Rob remarked "that's why the mapping
has been so satisfying because the engine responed so well. The
carbs were very good at wide open throttle, but we don't do that
very often. We need the enigne to be optimised at part throttle
for driveability, and we have got 1500 to 1800 more useable bottom
end rpm on full throttle and the part throttle response is phenomenal."
That, in conjunction with peak power that has to be around 200bhp
sounds like a formidable combination. The decision to go to a
full EMS was, Rob says, partly down to the expected better mid-range
response, but also because it would enable the exploitation of
launch and traction control. This should help to make starts more
consistant and effective and improve exits from slow corners
Also,
as you may have noticed from the pics, the PCD has been fitted
with a steering wheel-mounted, paddle operated gearshift. Powered
by compressed air, and controlled by a pretty sophisticated box
of electronics and software, this mechanism is going to take a
while to develop, but Rob reckons it shows the promise of being
a very good, reliable system. Once developed and sorted, you too
could buy one, so watch this space....
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CONTACTS
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SB
Developments: Tel 0208 391 0121, email:sbdmotorsport@btclick.com
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Griffin
Motorsport: Tel 01793771802, email:griffinmsport@btclick.com
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| Martin
Ogilvie at Prototype Car Designs PCD, email:mbo@paston.co.uk |
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SBD
Motorsport Ltd, Unit 15, Red Lion Business Park, Red Lion Road, Surbiton,
Surrey. KT6 7QD. Tel: 0208 391 0121.
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