VHPD “K series” page
Topics specific to the VHPD engined Caterham 7
The VHPD K series forms
the basis of the SLR and of course, in essence, the new R400. Used in the Lotus
Exige, Elise 190 and now, interestingly, the Elise 2 Motorsport, this motor is
about as highly tuned as a manufacturer will go ex factory!
The things that make VHPD
special are nitro-carburised crankshaft (17% stronger than standard), forged
pistons and rods and of course, solid lifters running quite aggressive (Piper
740 profile) cams.
In original format the
motor made 177bhp but Rover soon came up with the 190bhp ECU. Interestingly the
throttle body manifold was originally very poorly designed on the older VHPD
and it took until early 2001 until a revised manifold was developed by PTP, the
K series development arm of Rover. The new PTP manifold is preferable to the
original “KV16” one if you are buying a used setup.
One big oversight is that
the ECU maps itself for ignition and fuelling against the manifold pressure
present in the inlet plenum. In English this means that the engine thinks it
knows where your foot is on the throttle because it assumes that load is
proportional to throttle opening. This is less than idea in a high performance
motor and peak power and the transient response suffers.
By mapping the curves
against a throttle position sensor instead, ECU specialists like Emerald can
extract in excess of 200bhp from this excellent engine – my own motor made
209bhp with just the Emerald ECU, correctly timed vernier pulleys and a Raceco
exhaust.
There have been some
reports that the VHPD motor is quite variable in terms of maximum output on the
rollers – I personally feel that this is an industry wide issue not unique to
the VHPD alone – Even F1 engines vary and their tolerances SHOULD be perfect!!!
In my experience there is no reason to expect less than 200bhp from a well set
up VHPD.
The VHPD motor, because it
never met EU3 emissions standards (see separate emissions legislation page for
more), doesn’t have the EU3 wiring loom, and so is totally plug compatible with
the aftermarket ECU’s like the Emerald….
The problem with later,
EU3 non VHPD K engines is that the wiring loom is different to the aftermarket
ECU’s, which were made plug compatible with the earlier spec Rover wiring
harness plugs.
Note that Emerald now make
an EU3 plug convertor so that the excellent M3DK system can be plugged into the
lastest K’s.
The new R400 uses the
magnesium roller barrel throttle bodies which on their own are reputedly worth
only 3bhp peak power extra. This occurs because the throttle butterflies
present a slight restriction to airflow on the standard throttle body set up.
The old trick of “knife-edging” the butterflies would work to reduce the
deficit. The power figure of 200bhp quoted for the R400 is obtained, then, by
use of this new induction tract and the fitment of the R500 4 into 1 pipe as
standard, combined with a different ECU.
If you are concerned that
you can obtain similar performance to the VHPD engine for a lot less money
using a base 1.8 K you are quite right; this can be done very successfully but
to dismiss the VHPD is to miss the point of a very fine off the shelf product.
The reason the VHPD deserves consideration is its resilience to wear and tear,
and safety margin built in by the high quality internals.
There has been some
discussion about the need for VHPD motors to undergo very regular rebuilds but
in my experience, with the proper care and servicing the engine deserves this
is entirely unnecessary. Many Lotus Exige I know of have done 40000 miles
without any wear related issues.
Remember that in a 7, the
engine faces the “wrong” way to that originally intended by Rover, so at least
an Anti-Cav tank and preferably a dry sump system should be installed.
I feel it important to
make a point regarding the MBE management on the R400. Please do not assume
that this will allow you to reprogram the system using your favourite tuner at a
later date. The R500 (according to Chris Jobbern at Caterham Midlands) has a
password protected ECU which can’t be accessed by you or me or anyone else
apart from Caterham or MBE. I have no reason to suspect that the R400 will be
any different, which means that you’ll be back to swapping your MBE R400 unit
for an Emerald anyway if you modify the cams/head or whatever! My dealings with
MBE were very polite but they indicated that they are contracted to Caterham
and so won’t help you apart from through Caterham.
There is an issue with the
Rover ECU that I was supplied with for my car as standard. Basically it seems
as though the map for this unit wasn’t redone after the change to the new PTP
throttles with the result that the car runs very badly as standard. A friend of
mine also has a new SLR and his car is the same. I chose to swap out the ECU
from pretty much day one as a result but bear in mind a well set up VHPD should
run nicely and if it doesn’t it will probably be the mapping that is to blame.