|Track & Race Car
C20XE and LN engine It's
been out of production for over ten years, but Vauxhall's C20 XE/LN
motor is a tuneable classic, as SBD Motorsport's Steve Broughton explained
to Peter Knivett.
Photography: Peter Knivett
TRC showcased a brace of powerplants well suited to budget motorsport
applications and Vauxhall's 1998cc C20XE 16-valve motor came right near
the top of the list. With 150bhp and 144lb ft of torque as standard,
tuners quickly realised the power potential of the C20XE, which could
be readily unlocked affordably and reliably if carried out correctly.
Even today the motor is very popular in a huge variety of motorsport
disciplines from single-seaters, to Westfields, to MK2 Escort rally
cars and track day Astras and Novas, where its reliable, torquey power
delivery and affordable nature are much in demand. But how do you extract
the best from this engine on a budget? To find out some answers, TRC
paid a visit to one of the companies at the forefront of tuning the
C20XE engine - SBD Motorsport Ltd to chat to its founder Steve Broughton.
makes the C20XE engine so good?
to you Steve. "It's one of the last production engines with a massive
in-built tolerance for being tuned up. Most of the components are good
for 250bhp. The rods can cope with that - the only reason we advise
against it is that if the engine is over-revved it can cause problems.
Even the pistons are fantastic. The original piston is a forged item
- it's beautiful."
entire bottom end of the C20XE is very strong, especially the crankshaft.
"It's bomb proof," says Steve. "I've never seen one break.
Even with an engine has run out of oil and the con-rod has disappeared
out to the side of the block the crank is still in one piece!"
Such strength would be useless if the C20XE couldn't produce the power
and torque to exploit it, but the cylinder head is something of a mass-produced
masterpiece, being designed by Cosworth engineering for GM/Opel's requirements.
Packing decent-sized valves and ports and a highly efficient combustion
chamber shape, the alloy 16-valve head will flow enough air to reach
230bhp before modifications are required.
and the Cosworth connection
iron block C20XE motor made its debut in 1988, being based on the
highly successful GM 2.0-litre 8-valve, J-series Family One motor.
Once Cosworth's engineers had finished with their design, the new
16-valve engine was churning out a smooth, torquey 150bhp, complete
with a upgraded bottom end, designed with an eye on Group A and Group
N rallying and touring car racing. Interestingly, Steve highlights
the fact that the GM/Cosworth connection goes far deeper than just
designing the cylinder heads, because Cosworth cast and machined the
early 16-valve units. Therefore any C20XE built up to about 1990 will
use a Coscast cylinder head, whereas beyond this point GM switched
to a production item, cast and machined by Karl Schmidt in Germany.
ignition arrived in 1992, while internally there were a number of
changes, which make the later engines less attractive, as Steve explains.
"They put a big heavy flywheel on and added mass to the crankshaft
so that when they leaned the engine off for emissions (which they
from the 1992 model cars) the heavier flywheel helps keep everything
moving." Meanwhile the cylinder head port shape was revised on
emissions grounds and the forged pistons were dropped in favour of
inferior cast items. Finally the bearing size and material was reduced
in size and quality. These final engines gained a C20XE-LN label,
highlighting the 'Low Noise' requirements as dictated by EU regulation.
During the redesign the block was given a makeover, so ironically
(given the downspeccing of the rest of the design,) the later engine
blocks are actually stronger than the early ones.
final C20XE-LN engines were built in 1993/1994 for the UK market for
fitment into a 'run-out' Cavalier SRi model. "The last batch
had 'Ecotech' on the cam cover and Vauxhall did this because they
wanted to keep running the older engine in the BRCC for as long as
possible," says Steve. That wasn't quite the end of the C20XE-LN,
because the engine was still being produced in 1996 and 1997 for overseas
markets, including Turkey.
should you look for when buying the engine?
engines will be at least 11 years old, but Steve reckons that's
not a reason to walk away, because these motors are tough. "There
are a lot of cars out there that have gone rotten but the en ignes
are good," says Broughton. "We had one recently that
had done 130,000 miles and it was really dirty, but the engine
was fine." If high mileage shouldn't put you off, neither
should a clatter from the top end when cold, because the hydraulic
followers have a habit of making a horrible racket if the engine
has stood idle for some time. "That's because the valve spring
slowly squeezes the oil out of the follower. so when you come
to fire it up, it takes ages for it to stop rattling," says
an easy overhaul Steve recommends the following. "If you're
going to drive it hard and use it for track days, then I'd replace
the followers, drop the big-ends out and replace them and put
a new set of rod-bolts in. I'd possibly replace the oil pump,
plus change the cambelt and pulley idlers. You don't have to take
the engine out of the car to do this, you can do it all in situ."
Interestingly Broughton advises against digging further into even
high-mileage engines, preferring to leave well alone.
the C20XE engine didn't have a problem-free life, courtesy of
the well-documented porous cylinder head issue which afflicted
engines from around 1990-1991 onwards. This coincided with the
switch from a Cosworth-produced cylinder head to a production
GM item made by Karl Schmidt in Germany, which compromised the
original design, particularly in the oil gallery area.
of this problem are similar to those of head gasket failure - a film
of oil in the water and a milky liquid in the sump - but curing it is
difficult. some firms offer to bypass the gallery with external pipes,
but Steve's not a fan of this as a cure, preferring to use only Coscast
heads on his engines. these are identified by a lack of core plug style
casting on either end of the head, plus they have an oval-shaped Coscast
logo embossed onto the front. Finally, don't dismiss the very late engine
that ran 'Ecotech' badging, because it may still be worth a punt. "The
way to tell is the trademark L-shaped spark plug cover," say Steve.
"If it's that shape it doesn't matter what's written on it, it's
a C20XE/LN engine underneath."
the earlier distributor-equipped engine is the one to go for, because
it's more likely to have a Cosworth head, plus the better bearing and
pistons, even though it may have covered more miles. Interestingly,
Steve reckons his ideal combination for an engine that he'd run in near
standard trim would be to run an early crankshaft, in a later block
(which was stronger), with a Coscast head.
performance pointers on the C20XE and LN exhaust manifolds
how do you set about tuning C20XE and LN engines? Well, step number
one is replacing the standard exhaust manifold, as the standard item
was designed to maximise low-end torque. At high revs this becomes a
restriction, so it's critical that it's upgraded at the earliest opportunity.
Steve explains - "Apparently the first pre-production engines from
Cosworth produced 170bhp as standard but they wanted more torque for
the road which they got by making the manifold's pipes smaller. This
also helped reduce emissions by keeping the gas speed up, but when you
get up to the top end it becomes a restriction."
SBD has a huge range of manifolds for a wide variety of applications,
whether front-wheel drive Astra, Westfield, Caterham or rear-wheel drive
Escort or Manta. Prices range from £229.70 to £586.91 depending
on applications, but if you don't attend to this early on, you're not
going to produce the quoted power outputs as outlined here. Bear in
mind that even on a standard engine a 6-8bhp gain can be expected when
used with an efficient exhaust system.
the XE engine is used in front-wheel drive applications it's common
to see the cars puffing smoke during hard cornering on circuit use.
this looks worrying and can cause problems, as Steve explains. "There's
a breather pipe coming out the front of the block which allows pressures
between the top and bottom of the engine to be equalised. Sometimes
on track use under heavy cornering the oil goes up that pipe and into
the cam cover and it can't get out. This can detonate the engine where
the oil mixes with the fuel in the cylinder head, but there's an easy
modification to the baffle so that it dumps the oil back in again and
cures the problem."
the engine is transplanted into rear-wheel drive cars, more work is
needed on the oil system - SBD advises using a hard-to-find Manta sump
- while they produce a sump for the rear-wheel drive Sunbeam. "But
if you can afford it, dry sumping is the way to go," says Steve,
and that's certainly true when the motor is fitted into a Caterham,
Westfield or similar. Expect to pay from £799.00 for this setup.
makes the point that these days switching to carbs' may be a false
economy, particularly as the Weber DCOE is no longer available.
"You need to change your fuel pumps and fuel lines. Yes,
it's a good, quick way of getting the engine to run, but if you
go to throttle bodies you've got all the fuel lines you need already."
Also, if you choose that you'll either need to run SBD's mapped
ignition system of fit a distributor from an early eight-valve
engine, but then you'll need new HT leads and caps. "It seems
cheaper, but then you take the car to the rolling road and spend
£200 on jets and chokes and then you find out that actually
your carbs' are worn. Then when people start to tune them up they
have to go back to the rolling road, so it's a false economy."
These days, he message is clear, sticking with injection will
save you money in the long run.
N replacement ECU 170bhp/173lb ft Unavailable
wef June 2009
that we're sticking with fuel injection, our first port of call
is a replacement ECU. These kits were designed for group N racing
and rallying applications, where a standard under bonnet appearance
was mandatory. Ultimately, almost all the works Group N cars ended
up using this kit. Along with the power increase the biggest improvement
these kits offer is a much quicker throttle response, courtesy
of the MBE ECU that runs ten times faster than the stock unit
and uses a throttle angle control rather than relying on the readout
from the airflow meter.
the MBE ECU is the same unit that's run on SBD's throttle body
kits which makes it easy to upgrade at a later day. Downsides?
Well, for road applications a lack of idle valve control means
you need to keep the revs up until the engine is warm enough to
tick over. Given the price, it's no surprise that SBD Motorsport
is still a popular choice. "It's still got its place, because
a lot of people come to me and say I've got an engine but I can't
afford throttle bodies, so this is the most affordable option.
Then later on, they can easily upgrade to the throttle body kit
and all you throw away is the throttle pot and the idle control
valve, that's it," says Steve.
Multi-throttle injection kit. This was the original twin
throttle body kit developed by SBD in the mid 1990s as an upgrade for
customers running Weber carbs. Featuring a pair of 45mm throttle bodies
and an MBE 967EF ECU it gives a big upgrade at a price that's £300
cheaper than the taper throttle kits that superseded it on both packaging
and power output. Peak power is around 6500rpm, but it'll happily rev
much higher, which is why SBD advises fitting uprated con-rod bolts
as a precautionary measure. "The standard rod bolts are really
horrible, so we think it's a wise safety precaution to fit these,"
says Steve and the result is a bomb proof engine that produces a good
spread or torque and power.
208 Taper throttle injection kit. For those with more
to spend, SBD's most popular kit takes all the advantages of the MT196
a step further. Individual tapered throttle bodies (measuring just 66mm
long and with a 45mm butterfly in the middle) allow more room around
the inlet side of the engine, making this kit a viable proposition in
just about any application. "It's just a straight bolt-on kit,
plus the rod bolts," says Steve, so it's testimony to the brilliant
design of the original engine that so much extra performance can be
extracted from bolt-on tuning components. Peak power is again around
6500rpm, and the kit is designed to use Bosch Cream injectors as fitted
to C20XE engine.
that we're looking at budget horsepower, this is our cut-off point;
beyond this stage tuning the C20XE & LN engines gets expensive.
That said, between 225 and 230bhp allied to 177lb ft of torque is a
lot of performance and it's produced by taking TP208 kit a stage further,
adding a set of hydraulic cam profiles that add lift and duration. this
extra valve lift requires pocketing the pistons, which gives customers
a choice - they have SBD machine their original items or fit purpose-designed
Omega piston. Fitting the Omegas helps keep the compressions up, which
unleashes more torque and power, to the point where 230bhp is a distinct
possibility. This also makes sense on a high-mileage engine, because
the pistons can be used as part of a rebore. With TP225 the standard
valve springs and caps replaced, while SBD includes a pair of vernier
pulleys, to help get the cam timing spot on. The results: an engine
that loses 8bhp at 2500rpm compared to TP208, but "after that gains
torque and power everywhere and keeps going, peaking at 7200rpm and
can rev to 7750rpm," says Steve.
TRC readers on a reasonable budget that's probably as far as we would
go; the next stage gets much pricier, according to Broughton. Even so,
with up to 230bhp available, that's enough to make any road or motorsport
car move in style!
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Surrey. KT6 7QD. Tel: 0208 391 0121.
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