|
14/5/2002 |
DIY enthusiasts often believe that building an engine
to give excellent all-round road performance is beyond them. Mainly from comparisons
made between what they have been able to achieve and what specialists say
should be achievable from any particular type of engine build. Generally scrambled further by the non-perfect match of parts and
components used between aforementioned specialist and erstwhile DIY-er, and the ritual 'nose-tapping and knowing winks' display
of those specialists. Something you can very nearly 'see' even when
talking to such folk on the phone - or that inimitable 'ah, yes, well…' So some
form of 'black art' is implied. Whilst there is most definitely a degree of
'feel' involved between the real specialist's results and those of just a good
engineer - the bones of the deal is subject to no such thing and is certainly
within the capability of the DIY enthusiast given the necessary information.
And that has been the problem. Despite a true plethora of books written on the
subjects of blueprinting and tuning of all manner of engines (i.e. 4, 6, 8, 12
cylinder and so on) not all of it is relevant to our wonderful, archaic
A-series and not easily transposed by the DIY-er.
What is needed is very specific information appertaining to our unique A-series
engine.
To supplement this, it would be even better if this
would encompass a very specific engine build as far as all components used and
for a specific application. Daunting if you consider the myriad of
cam/head/carb choices voiced by the multitudes of A-series meddlers (not at all
meant in a derogatory way, as I include me in that description) used over the
years. Of which there are roughly four 'camps' - the 'good old boys' from the
Mini's inception, the 'young whipper-snappers' of
more modern technology, the 'liberals' using a bit of both and lastly the
'T-BASE' brigade (those that have read and re-read David Vizard's
'bible' on A-series tuning so that they can quote chapter and verse, strangely
enough encumbered 'Tuning BL's A-Series' - hence T-BASE).
Fortunately this whole tuning deal has gone round very
nearly full circle and has tried just about every combination possible with
whatever modern technology was suggesting was 'the way to go' at the time. And
some very talented and clever folk have given more than their two-penny-worth
into the bargain. What that has given us is a vast reduction in the prolific
list of possible components to make an engine suitable to our needs. Particularly where modern road/street performance is concerned.
The main criteria being an engine that idles smoothly, has exemplary emissions
levels, pulls strongly from low rpm, will give rapid overtaking performance yet
be fun all the way to the useable (sane/sensible?) redline when the situation
presents itself.
It was to this end that I carried out the 1275 engine build
detailed in the relevant articles, and to prove that having to go out to 73.5mm
bore (1380) isn't an absolute necessity to have a blistering street performer.
So given a straight forward engine build with proper
detailing and 'off the shelf' components list consisting Swiftune SW5 camshaft,
Min Tec 'road rocket' type head (as supplied by Mini Spares/Mania), 10.4:1
compression ratio, standard crank, A+ rods, Mini Spares/Mania 'Mega' piston set
+0.040", lightened duplex gear set, single 1.75" HIF SU, Mini Spares
intake manifold, Maniflow medium bore LCB, RC40 exhaust system, K&N
cone-type air filter, 1.5 roller-tip rockers and Aldon Yellow non-vac dizzy,
along with the other necessary engine build components what kind of performance
is easily attainable?
The first rolling road visit was a disaster as far as
I was concerned. When running the engine in it felt terrifically strong. After
400 miles it went on the rollers. The result simply wasn't what I expected - a
measly 78bhp at the crank. I had come to expect around 92-95bhp from engine
dyno tests. The dizzy wasn't giving the figures it should and was making set-up
difficult. So the testing was aborted. I started to think there was something
else to blame. Once home I checked everything from the tyre contact patch to
the carb mouth and everything in-between - tracking, camber, wheel bearing
drag, brake drag, gearbox drag, cam timing, sorted the dizzy advance/ignition
timing problems (not deemed to be causing the massive deficit in power),
valve/cam timing, valve/lash clearances, valves sticking in guides, compression
test, leak-down test, manifold air leaks, carb condition, fuel supply,
everything. Absolutely nothing suggested anything was wrong anywhere. And that
is very annoying since at least if a reason is found it solves the problem and
takes away the doubts.
Then I started to suspect the exhaust system since
manufacturing techniques had altered somewhat from the original RC40 systems. I
decided to run a test on exhausts as part of the re-rolling road test to check
on this (see 'Exhausts - Millennium and others tested'). But even this wasn't
really conclusive in my mind. Then I remembered my notes when building the
engine and went back to them - concerning the 'Mega' pistons. I had commented
on how tight the engine felt when the short motor assembly was checked.
Removing the pistons/rods and re-building/re-testing with the rings removed one
type at a time until only the oil control rings were left I found the oil
control rings were the cause of the increased tightness I was getting. I
decided to re-run the rolling road test with the rings as is and just do the
exhaust swap to see what gave there and deal with the rings if there was still
a major power deficit.
Back on the rolling road with only the dizzy vac unit
removed and re-timed as Aldon suggest and 1,000 miles on the clock, the first
run was done with the mixture as it was last time. And bingo! - the missing power was there immediately! The mixture was
leaning out slightly at the top end, so a needle change was made and a re-run
done. The ignition wasn't changed any from where I set it - at 28 degrees max
advance proving very efficient combustion. The conclusion was that the Mega oil
control rings take a good few miles to settle themselves in (see 'Pistons -
Mega ring performance').
The results were astounding:
|
Road Speed |
Rpm |
BHP |
Torque |
|
30 |
2,800 |
54.1 |
89.54 |
|
40 |
3,700 |
67.0 |
95.10 |
|
50 |
4,600 |
80.1 |
91.45 |
|
60 |
5,400 |
90.3 |
87.82 |
|
70 |
6,300 |
92.0 |
76.69 |
|
80 |
7,200 |
87.00 |
63.46 |
Emissions at idle were 3.5% CO, and only a mere 697
HC!! Where 1200 HC is a vehicle test pass!
I can't tell you how much fun this made the car to drive.
It is blisteringly quick for general road use, has so much urge that
over-taking is a cinch, and would definitely benefit from a final drive change
to a 3.1. With the 3.44 currently fitted you get in to top gear and then just
press the go-pedal no matter what road speed you're at! Incidentally the tests
were all done in third gear to assimilate more closely road driving. It's not
as hard on the car or rolling road either. These figures are almost identical
to those gained from dyno sessions on this type of engine build - so the
exhaust wasn't the problem at all.
These figures are real, no bullshit, achievable
results from simply following the engine build articles and components usage.
Sure, a 1380 will be even better - but not by that much. The dyno results
suggest only a few more horsepower and barely a handful foot-pounds more
torque. Going the +0.040" over-bore route you will still have at least two
re-bores to go on that precious block!
Useful part numbers:
|
C-AHT135 |
Min
Tec 'road-rocket' type cylinder head pre-92 - has by-pass hose and heater tap
take-off - standard spec components |
|
|
|
|
C-HT136 |
Min
Tec 'road-rocket' type cylinder head for twin point injection only - standard
spec components |
|
|
|
|
MSE3 |
Min
Tec 'road-rocket' type cylinder head pre-92 - has by-pass hose and heater tap
take-off - race spec components |
|
|
|
|
MSE4 |
Min
Tec 'road-rocket' type cylinder head post-92 - has no by-pass hose and no
heater tap take-off but not for twin point injection - race spec components |
|
|
|
|
MSE7 |
Min
Tec 'road-rocket' type cylinder head has no by-pass hose and no heater tap
take-off for twin point injection - race spec components |
|
|
|
|
C-AJJ3378-40 |
Mega
piston set +0.040" |
|
C-AHT446 |
1.5
ratio roller-tip rockers |
|
C-AJJ3325 |
Ultra-light
steel duplex kit |
|
Aldon
Y |
Aldon
'Yellow' dizzy, non-vac, pre A+ |
|
Aldon
Y+ |
Aldon
'Yellow' dizzy, non-vac, A+ |
|
WKN1 |
OSET 1 degree offset cam key |
|
WKN2 |
OSET 2 degree offset cam key |
|
WKN3 |
OSET 3 degree offset cam key |
|
WKN4 |
OSET 4 degree offset cam key |
|
WKN5 |
OSET 5 degree offset cam key |
|
WKN6 |
OSET 6 degree offset cam key |
|
WKN7 |
OSET 7 degree offset cam key |
|
WKN8 |
OSET 8 degree offset cam key |
|
WKN9 |
OSET 9 degree offset cam key |
|
C-AHT770A |
1.75"
SU intake manifold |
|
C-AEG365 |
Maniflow
medium bore LCB |
|
RC40 |
Original
RC40 exhaust system |
|
RC40FK |
Exhaust
hanger kit comprising all rubber mounts and hangers |
|
56-9327 |
K&N
cone filter for HS6 1.75" SU |
|
56-
9330 |
K&N
cone filter for HIF 1.75" SU |
|
SDCLEANER |
K&N
air filter cleaner |
|
SDOIL |
K&N
air filter oil |