This section will detail the conversion to forced
induction along with the upgrades to other components to cope with the
extra torque available.
(Click on pictures to see larger version)
Why go Turbo and strategy to fit into the cramped engine bay
When the project was initally started the car was due to remain manual
and due to this I prefered the instant on of the nitrous after each gear
shift rather than waiting for the turbo to spool again. Now that I
have moved onto automatics there is no need to lift off the throttle
between gears which has eliminated the problem apart from the initial
One of the major problems with the 2l XE in a mini is that the stock
vauxhall manifold will not clear the bulkhead or the centre crossmember
on most of the frames available for the conversion. A remedy for
this was to box in the QED Throttle bodies but there was was so little
space available that this would be near impossible or use components
from other manufacturers that don't have the same design shape as the
vauxhall inlet, from other forums it was found that the Mitsubishi Evo
exhaust manifold was an almost exact match to the vauxhall one (with
regards to port spacing requiring only a replacement flange) so I
thought maybe the inlet would be similar. The Evo inlet didn't use
the long intake runners as with the vauxhall one and as such didn't foul
on the bulkhead or the subframe and the port spacing looked pretty
exact. It wouldn't be quite so simple as the exhuast side though
as the ports were a much larger diameter and also due to injector
location would be difficult to use the same approach as is taken on the
exhaust side with simply a new flange welded on. Another bonus of
the Evo inlet is the stock throttle assembly has a much larger diameter
than the stock vauxhall setup (a stock Evo manifold can easily flow up
You can see in the pics how close the port spacing is and also get an
idea of the size difference compared to a stock vauxhall inlet gasket.
The Evo TD05 Twin Scroll Turbo has already been proven on several
Vauxhall conversions, the flange is a straight swap from the Vauxhall
exhaust manifold to the Evo manifold (these are available off the shelf
and fitted to an Evo exhaust manifold you supply for about £50) so there
won't be much detail on that part.
The TD05 Twin Scroll unit is ideal for my requirements, it can easily
flow up to 350+bhp without stress and also due to the Twin Scroll design
it has very little lag so launching with the auto's shouldn't be an
Fitting the Evo
I decided that the best approach would be to create an adapter plate
that would sit between the head and the manifold which blended in the
port shapes and provided the correct bolt pattern to attach the Evo
manifold. This section covers the front and rear installations as
they are pretty identical.
This is the prototype adapter plate
These are pictures of the adapter plate in the various stages of fitting, you can see that I have used countersunk
hex drive bolts to attach the plate to the vauxhall head and then normal
studs will be used to attach the Evo inlet. (these have been done on
CAD\CNC so can be replicated for £130 each including the coutersunk
bolts\postage, would be cheaper for a
batch, drop me an email if you are interested. Email link at bottom).
In picture 2 you can see that the inlet stud should be filed flush with
the back of the plate and some gasket sealer (or similar) used on the
threads as this stud overlaps the water outlets on the head.
When fitted you can see just how easily the Evo inlet clears the
bulkhead and is looking good, a side bonus to this setup is being able
to remove the inlet without losing loads of coolant since the plate
remains in place once fitted and keeps the water seal in place.
The only change that I found was needed to the Evo inlet was to slightly
file the top of the lugs that hold the fuel rail in place as these
fouled on the cam cover seal since the Vauxhall cam cover is quite a lot
wider that the Evo one. I have temporarily fitted an air filter so
that I am able to do some quick road testing before moving onto the
turbo install. The 3rd pic is the throttle cable adapter plate
that was made since my Evo manifolds hadn't been sold with the stock
plate installed. The inlet does sit quite high compared to ITB's
but doesn't cause a problem with the bonnet fitting ok.
I will be tidying up the pipework at a later time since some of the
vacuum connections will be used for sensors etc when the turbo is added
but are temporarily blanked off with whatever was lying around in the
garage initally in order to test the running.
I have also found that the 560cc Evo injectors can be used with the DTA
E48 ECU since although the injectors are low impedance so cannot be used
straight with the E48 the stock Evo ECU is also not able to drive low
impedance directly so a resistor pack is used, due to this I was able to
add a 2ohm 50watt resistor to the DTA injector wiring and make use of
the Evo injectors successfully. With a quick flow calculation the
flow of the 560cc injectors at 3bar needed approx 50% of the original
duration to match the Vauxhall beige injectors at 3.5bar so 50% was
removed from the fuel map and the car started up 1st time :o) My
concerns about the Evo idle valve were cleared as this is fully closed
when not powered (unlike the Vauxhall Bosch ones that go into a limp
mode which is open).
Extending the Front to make
The TD05 was a bit larger than expected which meant a
straight fit into the front engine bay wasn't going to happen without a
complete redesign of the cooling system (the TD05\manifold needs approx
240-250mm from the block face to the furthest forward component, the
wastegate actuator and I currently had 200mm), rather than scrap the
current cooling I decided that it would be better to do what several
other 16v mini conversions have done and extend the front end a little
There's still a lot of finishing off to be completed on
the wings\bonnet but for ongoing installation work it will do for now.
The front end popped back on temporarily with a quick
coat of oil based primer on all the bare metal bits to stop it rusting
(I will eventually get round to filling\painting properly to make it
look nice..... honest lol).
Now have the arches back on etc so can be mobile again
on the road and also get a better view of how it looks extended, I
actually don't think it looks as bad as I expected when extended about
I couldn't cope with the random primer and white bits
any longer (especially once the side intakes were fitted) so quickly
slapped on a top coat of red, it looks much better in the pics than it
does in reality but it's still much much better than the mix of colours
it had earlier.
Fitting the Evo TD05 Front Turbo
The TD05 sits very close to the dipstick\head breather
pipe and the stock cast item is just in the way too much so these
slimline stainless items can be purchased off ebay to fix that issue.
Being an XE rather than a LET a Turbo Oil Drain hole
needs to be added, there is already a blanking area where you can drill
a hole and bond in a drain tube here. As you can see in the second
picture the oil drain hole has been drilled and a brass fitting hammered
in there. I also heat wrapped the wiring at the back as although
it's about 10cm away from touching the hot side of the turbo it had
already begun to melt simply from the hot air blasted over it when
driving and that was with a stock non turbo exhaust manifold so likely
even hotter with a turbo.
TD05 in place, with the new extended front it shouldn't
be a problem with space any longer and should be able to get a much
better radiator fan in there now too.
I purchased an Evo 6 downpipe with the intention of
simply chopping it up to make a template which could then be made at a
custom exhaust company but it wasn't too much cutting\welding to get it
to fit anyway without having one made :o) One problem was that the
front crossmember was really in the way so I made up a new one that
clears the downpipe.
I couldn't get the stock LET oil feed piping to fit due
to the alternator and engine mount positions so a new pipe was made up
(a bit crude so will prob replace with a custom made one later) which
routes around the other side of the engine, one word of note is that the
main power feed to the starter is also passed by so be sure and
disconnect the battery first (or else you melt\weld the pipe like I did
on the first one lol) and also check the braided pipe won't bounce
around and short out causing a leak and possible fire. The oil
feed supply on the back of the engine used up the location where the oil
pressure sensor went, due to engine mounts etc there was no other spare
place to take the pressure from so I drilled out the banjo bolt to 8.6mm
and threaded it with a 1/8NPT thread so the pressure sensor can be
installed again in the same location. Since the banjo feed
diameter is much larger than the pipe itself the pressure reading should
still be accurate.
Due to the compression being so high currently (prob
about 9-5:1) running high boost levels isn't a good idea so wanted to
limit it to about 0.5bar max. The stock actuator will create about
0.8bar so in order to lower this a counter spring has been fitted to
pull against the actuator and lower the pressure when the wastegate is
opened. I have now tested this on the road and the boost holds
stable at a near perfect 0.5 bar without any changes to the spring or
There wasn't going to be space for the intercooler to
fit inside the bodywork so it's been fitted to the front lower panel
externally. The intercooler pipes will be difficult to route from
the turbo outlet to the intercooler but not impossible.
After adding the weight of the intercooler the front was
getting much too flimsy at the lower mount points so some steel bars
were added to improve the strength a fair amount.
The front intake pipes have been made up and fitted ok
making good use of the spare space.
As you can see in the previous turbo pictures the turbo
actuator sits in a really awkward place meaning that there wasn't as
much space as i'd originally hoped for fitting the radiator from
extending the front. Above the actuator there was plenty of room
though so I hunted down a different radiator to be as big as possible
but not as deep as the calibra one fitted currently. Eventually I
found that the largest one I could get in there was a Tigra A (94-01)
1.6 16V air-con model (I have the automatic one here so I can cool the
transmission too but the non auto one is the same dimensions). You
can see it's pretty tight requiring a fair amount of chopping and is
actually touching on the edges of both headlights but it is in there, I
also bent this one slightly in the middle to make best use of the space
available. Although not 100% the same cooling area as the calibra
one it's only marginally smaller but due to the positioning it will
get much better air flow and also thanks to the extra space I can fit a
bigger radiator fan than before for sitting in traffic.
The intercooler piping was quite challenging as there
was such a small space to get between the front panel and the exhaust
downpipe but it's all in there now.
Here it is now all assembled and running :o) BOV
has been added to lower the back pressure on the turbo when lifiting
off although this probably could have been left out when running only
about 6psi boost, i've missed the noise :o)
Fitting the Evo TD05 Rear Turbo
As the general fitting to the rear is similar, the
dipstick, oil feed, actuator mods, oil pressure sensor will be the same as
for the front and won't be detailed again in the rear section.
Obviously there will be different intercooler pipework, cooling
pipework etc to cover off here.
The biggest problem that has always plagued the rear was
the cooling as there simply wasn't enough air getting in the back for
long distance cruising or track sessions (it was sufficient for drag
racing though), with a turbo this problem will be increased. In
order to get more cold air into the rear compartment I have added some
side air intakes. One side will be for Intercooler air and the
other for water\oil cooling, the intakes are quite small so may be
replaced with some deeper items as required.
I think the street sleeper \ stealth image will be
difficult to maintain now lol
This was about the largest intercooler I could get into
the rear, it should be ok for up to about 350hp so is plenty for this
years requirements. I fitted a spare manually switched radiator
fan to the cooler so it can get cold air when approaching the start line
of the drag strip otherwise heat soak would likely be an issue effecting
performance until sufficient air flow was attained through forward
The rear turbo in place and all piped up with oil and
Yet more anti stealth pipework for the top rear intercooler
to inlet manifold, the turbo to intercooler piping and the air intake
which is well placed for a cold air feed from the passenger side air
As the very hot turbo sits fairly close to the rear
bulkhead I added some heat fabric and a sheet of aluminium for
protection and also have now wrapped the exhaust manifold to lower the
heat soak in the rear compartment.
Now that the car was turbocharged it obviously needed
boost pressure gauges and I also thought that exhaust temperatures would
be useful. There wasn't really anywhere left space wise on the
dashboard itself, I didn't want to mount them on top of the dashboard as
this needs to be accessible for wiring etc. Normal gauge pods were
too large to mount on the rollcage so I made up a plate and bought some
small fixings which could then bolt to the rollcage.
After the first racing event it was clear that there was
a major issue with grip, mainly at the front but the rear also quite
borderline making the traction control kick in quite a lot and waste
critical tenths on the first 1/8th mile. The best upgrade would be
to fit LSD's to the transmissions but is a massive stripdown\rebuild
which would take me out of racing for likely over a year. A
slightly less effective option (but hopefully still some effectiveness)
is for stickier tyres. Previously I used Toyo 888r 185/60x13's but
since fitting the auto transmissions the car had to be lowered due to
driveshaft angles and these would no longer fit due to an overall
diameter of 21.7" compared to 19.9" for the stock 175/50x13's.
Strangely I found some alternate 888's in 225/45x13 which are actually
smaller overall than the 185/60's coming in at an overall diameter of
21.0" so just over 1/2" larger on the sidewall than the 175/50's which
should just about fit (they may rub on big road bumps\dips but these
will only really be fitted for use on a flat track type surface). They
are very wide and to clear the suspension I had to use the deep dish
type wheels at 7" with -7ET and also a 1/4" spacer so they do stick out