Introduction
The CVH engine has been around for over 20 years now, but can still be the
basis for a very reliable power unit. Sadly most original engines are
now at the end of their life, meaning that very little can be done with
high milage units unless the engine has either been rebuilt or is going
to be rebuilt. For ease of clarification we have divided the levels
of tune into stages, and although any combination of modifications is possible,
we have simply tried to represent the normal tuning stages that we
normally recommend.. You will also notice that there is no mention of
increased engine capacity. This is because we have developed our 1.6 engines to give the ideal combination of
increased bhp whilst maintaining a flat torque curve as this increases
drivability by reducing midrange wheelspin, but should you wish to follow the large capacity
route we can advise the best components to use.
We do offer 1900cc CVH's and similar tuning methods can be applied to this
engine, so don't hesitate to contact us for advise.Stage 1
This involves the fitment of a Garret –31 actuator, replacement spark
plugs, a special bleed valve system which eliminates boost pressure drop at
high rpm's, boost is set to hold 10psi and fuelling and engine are setup
to suit. This is a basic conversion that really transforms the standard
car and will give around 150bhp.
Stage 2
Stage 2 involves the fitting of a new EMS "chip", and coupled
with a Garret –31 actuator, a bleed valve system and new spark plugs
the boost is now raised to 14psi. At this stage we also advise the fitment
of a larger intercooler, our favoured choice at this level being a GRS
double pass large intercooler. However due to the additional costs some
people do not want the intercooler but want to still run the higher boost
stage 2 offers. This is an acceptable combination but we advise that ACT's (air
charge temperatures) will become very high especially in 4th
and 5th gears and performance will suffer. The car will again
be setup and fuelling adjusted accordingly, but the issue remains that
14psi of boost is simply too much for the standard intercooler to cope with.
Power outputs are around 170 bhp with the standard intercooler or around
180bhp with the GRS cooler fitted.
Stage 3
This involves the fitment of all the equipment at stage 2, but the GRS
intercooler is now essential. At this point a 2.5" free flow exhaust
must be fitted, but as with the Cosworths, several after market exhausts
have restricted bore silencers that negate the point of fitting the
exhaust in the first place. Again we can advise the best route to follow.
A K&N type cone filter will now be added along with a performance cam
kit and vernier pulley. A set of suitable boost hoses is now required as
the original turbo to air flow meter hose can become very soft with oil
contamination and restrict airflow. In addition an uprated breather system is
now fitted, and the original full and part load
breathers removed. At this stage we also advise one of our stage 2 hybrid T3's as the
standard turbo really is at its limit. The fuelling and engine will be setup appropriately the
boost raised to 18psi and the power will have risen to around 200bhp.
Stage 4
This is the first point at which the engine must come apart. Assuming all
the modifications at stage 3 have been carried out, the next step is the
fitment of a ported big valve cylinder head. (Commonly termed a stage 3
head though lower spec heads can also be supplied) This will be coupled
with ported and blue printed manifolds. At this stage it is essential to
fit a hybrid turbocharger and depending on whether punch or top end
power are your requirements either a stage 2 or 3 hybrid T3 will be
fitted..
The engine will be fully setup and the fuelling adjusted
accordingly. The boost however will remain at 18psi and the power will be
in the region of 220bhp.
At this level a suitable clutch will also be required and we offer two
options at this power level.
Stage 5
The engine must now come apart completely, the bottom end being rebuilt to
the highest level, featuring low compression forged pistons, and a fully
lightened and balanced bottom end fitted with an uprated 4 paddle clutch. At this level I advise the fitment of
our stronger steel H section con-rods as this is the absolute limit for std items. Coupled with
a stage 3 cylinder head
and camshaft setup and
all the previously mentioned modifications, one of our double core Cosworth intercoolers is now fitted with reverse charge carrier. A 5th injector and
MF2 fuel driver is now fitted, both the fuel
and ignition ecus are fitted with new "chips" raising the
rev limit to 7200rpm. The final piece of the jigsaw is a stage 3
hybrid 0.48 T3 and along with 23psi of boost generates around 260bhp and is
what we consider the best all round drivable package. (Our Cosworth
management conversion can be added to this setup instead of the 5th
injector route for a more refined setup but power will remain the same)
Stage 6
The
engine must once again come apart and the fitment of our steel H section con-rods and
stronger forged pistons to lower the compression ratio is now essential. Coupled with all the modifications
carried out up to stage 5 a hybrid Garrett T34 is now fitted with a Cosworth
based exhaust housing. A custom exhaust and down pipe is now required,
and coupled with our Cosworth Management conversion and a set of 803
injectors the boost is now
raised to 25psi. The fitment of an uprated gearbox is now essential. At this level there are many additional minor
modifications required to cope with the power but this can be advised at
the time. Power levels are now at 300bhp.
Stage 7
In
light of our on going development of our CVH engines during 2004/5 we
have started to offer our highest specification CVH engine ever! For this level the previous stage 6 engine can be
used as the basis, although the cylinder head is now upgraded to stage
4 specification. (Larger ports) . Keeping with our Cosworth management
conversion, the exhaust manifold is changed to a tubular item with
custom 3inch exhaust system. Fitted with a slightly larger T34
than used in the stage 6 engine the boost is now raised to 29psi, 403
grey injectors used, and the power is approaching 350bhp!
Please also note
that conversions from stage 5 require serious chassis, brake and
transmission modifications to cope with the increased power!
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