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Cosworth BDG 1978 Specifikace

 
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Založen: 19.1.2006
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PříspěvekZaslal: 25. říjen 2007 13:08    Předmět: Cosworth BDG 1978 Specifikace Citovat

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Cosworth BDG 1978 Engine Specification
COSWORTH BDG 1978 ENGINE SPECIFICATION SHEET
Capacity: 120.5cu. in Bore: 3.543? Stroke: 3.056?
1975cc 90.0mm 77.7mm
Compression ratio: 12.0 to 1
H.P rating: 280bhp @ 9250rpm
Torque: 175lb. Ft @ 7000rpm
Cylinder numbering: Front 1 ? 2 ? 3 ? 4 Rear
IMPORTANT DIMENSIONS
Crankshaft: End float .002? / .011?
Main bearing dia. 2.1260? / 2.1255?
Crankpin dia. 1.9375? / 1.9370?
Connecting rods: End float (big end) .004? / .012?
Jackshaft: End float .003? / .007?
Jackshaft part no. BA0502
Jackshaft pulley is bolted to jackshaft with 1off bolt 3/8unc
and 1off BA0510 washer.
It is recommended that ?silastic? is used under the washer to
prevent oil leaks.
Oil pump: Backlash of oil pump gear .003? / .005?
Timing belt tension: Taken on long slack side of 90 / 100
belt with Burroughs gauge
(see instructions).
Gudgeon pins: End float .001? interference / .001? clearance
Piston rings: Gaps on all rings .015? / .022?
Valve timing: Inlet valves fully open 102o a.t.d.c. +1o (F1 cam)
Exhaust valves fully open 110o b.t.d.c. +1o (BD4 cam)
Lap pulleys onto cams. With timing set correctly and belt correctly tensioned, timing marks on
pulley rim should line up horizontally in the centre of engine, when No. 1 piston is at t.d.c.
firing. If the marks do not line up it is advisable to remark the pulleys so that the engine may
be easily re-timed on rebuild.
Valve lift: .410? less the tappet clearance. F1 inlet
.432? less the tappet clearance. BD4 exhaust
Tappet clearance: .009? / .010? inlet .012? / .013? exhaust
(cold)
Cosworth BDG 1978 Engine Specification
Valve springs: Cosworth part no. PP1656 (pair of springs)
Fitted length of outer 1.26? / 1.27?
Free length of outer 1.44?
Fuel injection timing: No. 1 starts to inject at 80o a.t.d.c with No. 4 firing.
Ignition: Firing order 1 ? 3 ? 4 ? 2
Lucas ?Opus? ignition with distributor fitted with Cosworth type solid mounted pick-up.
Ignition timing is about 34o b.t.d.c. Timing is set on test with timing light at 7000rpm, and may
vary slightly from engine to engine for maximum performance.
Oil filter element: Part No. PP0404
Oil system:
See Cosworth drawing BA0330 for layout of recommended oil system, which shows oil pipe
sizes etc.
Note that pipes into the oil / air separator, built into the top of the tank, should enter
tangentially with the oil scavenge pipe ahead of the engine breather pipe.
Oil pressure when hot should be 70psi min. rising to 80 ? 90 psi at normal running speeds.
Care must be taken to allow the oil temperature to reach 50oc before exceeding 7000rpm
otherwise bearing failure may occur due to running at high speed with cold oil.
Maximum permissible oil temperature is 100oc, measured in the tank.
If the oil pumps are dismantled for any reason, it is essential to check that the shaft turns
freely on re-assembly before fitting to the engine. If it is not possible to turn the shaft easily
then the drive gears may suffer. Any dirt in the pumps will have a similar effect.
Fuel Injection
See Cosworth drawing BA0331 for layout of recommended fuel system.
The metering unit fuel cam is set to the correct stroke during assembly, and the settings
currently used are, .005in. stroke at closed throttle and .056in. stroke at full throttle, using fuel
cam part number BA0456 and datum pin part number EA0230.
These figures are achieved with the datum pin set at 1 notch from lean. The stroke should not
be less than 0.56in. at full throttle otherwise piston life will be shortened. (NB. 8mm metering
unit.)
Full throttle position of the cam is when its straight edge is at 45o to the axis of the metering
unit. At this angle the stroke should be adjusted, if necessary by shimming to give full throttle
stroke as above. Then, with the metering unit mounted on the engine, the threaded rod
should be adjusted so as to hold the cam in the 45o with the throttle fully open. From this
setting one or two turns of the threaded rod will give the correct stroke at closed throttle.
DO NOT open the throttle by moving the fuel cam.
(NOTE: It is not necessary to have the cam at exactly 45o at full throttle since the cam gives
constant stroke over a large number of degrees near full throttle)
The low pressure ?Bendix? pump passes fuel around a primary circuit to supply fuel at a
positive head to the high-pressure electric pump, (Cosworth part number DA8059).
Cosworth BDG 1978 Engine Specification
The Bendix pump should have a capacity of at least 20galls / hour at 1psi and be mounted as
low as possible in the chassis.
The high-pressure pump is to be mounted with its outlet union vertically upwards. Both the
Bendix and the high-pressure pumps are to be left switched on whilst the engine is running.
The de-aerator should be about 2in. dia x 6in. high (min) to allow air bubbles to rise to the
surface and escape, thus providing air-free fuel to the high-pressure pump. Inlet and outlet
unions should be arranged tangentially to induce a rotary flow in the fuel.
Fuel should be 99octane (RM) min. and metering unit feed pressure should be maintained at
120 / 140psi by adjusting the pressure relief valve if necessary.
NOTE: Fuel pumps should be left on during short pit stops, to prevent fuel from evaporating
from the metering unit thus possibly causing a failure of cable drive soldered joints, due to
increased friction in the metering unit.
Throttle slide:
It is advisable to dismantle the throttle slide assembly whilst still bolted to the cylinder head
otherwise balls and / or rollers from the slide bearing track may fall down the inlet ports. After
removing from the cylinder head it may be carefully dismantled on the bench, noting the
arrangement of the balls, rollers and spacers in the bearing tracks, in order that they are reassembled
in the same sequence, as any change in the arrangement will result in slide
inefficiency see drawing number BA0332. The nylatron packing on the right hand of the
manifold should be positioned on re-assembly to give a slide opening of .030? and the screw
tightened to trap the packing. This will give the throttle setting for idling. Ensure that the idling
stop abuts to the slide over the full width.
Electrical system:
See drawing number BA0382.
Current engines use PP1117 (Thyristor speed limiter) set to cut out at 9500rpm.
The engine must be connected to a negative earth (ground) system.
It is advised that all electrical connections are smeared wit silicone grease (we suggest
Midland Silicones MS4) especially when the engine is operated in wet conditions.
Spark plugs: Champion N54R or equivalent
If cold starting proves difficult on N54R, a set of N61 may be used for initial warming-up but
should not be used for racing purposes. Before removing plugs, clear all dirt from recess. Use
special pliers to remove HT leads ? do not pull directly on the leads. Use graphite grease on
plug threads and torque to 9lb. ft.
Cooling system:
Refer to drawing number BA0383.
A ?barseal? capsule should be added to the cooling system each time the engine is fitted in
the chassis. In cold weather the usual precautions should be taken against freezing.
GENERAL INFORMATION
Starting from cold & warming up:
Cosworth BDG 1978 Engine Specification
Set mixture datum pin to full rich, switch on electrical pump, fully open throttle and crank for
three or four seconds with starter motor. Ease off throttle to approx. 1/3 open and switch on
ignition whilst engine is being cranked.
Reduce throttle opening when engine fires.
Observe that oil pressure has come up, adjust rpm to 2300 and hold at this rpm or reading
near this, which gives best running and minimum clatter.
As soon as the water temperature gauge needle is off the stop i.e. 30oc increase rpm to
between 4000 and 4500, again choosing a point which gives best running and minimum
mechanical clatter. Turn mixture datum adjusting pin to middle notch to weaken mixture.
Keep rpm steady until water temperature reaches 60 ? 70oc and oil temperature is rising. See
also under oil system.
Cold weather conditions:
It has been found that some fuel metering unit failures have been caused by attempting to
start the engine in very cold weather. We therefore suggest that when the general
temperature is below 5oc the metering unit is warmed before any attempt at starting is made.
Rev limits:
Recommended limit is 9000rpm; 8.500rpm in first and second gears.
Drivers should be aware that due to the tachometer reading lag it is quite easy to exceed
8500rpm in low gears even though the tacho reading is well below 8500rpm. This is a major
cause of engine failure. The engine must not be allowed to idle under 2000rpm or excessive
cam and tappet wear may be experienced. ALSO SEE NOTE UNDER OIL SYSTEM ABOVE.
Tappets:
Standard tappets may be used, but the modification shown in the sketch below is
recommended to avoid excessive wear of the tappet bores, or use:
BA0276 Tappet piston ? exhaust side only
FA0196 Tappet piston ? inlet side only
Both of which are already modified.
Camshaft oil seals:
Cosworth part number PP5228.
Cosworth BDG 1978 Engine Specification
To prevent failure in service it is recommended that the garter spring is removed, the ends
untwisted, de-greased and reassembled with Loctite 602.
Cam carrier:
It is recommended that ?silastic? is used to make as oil tight joint between the cylinder head
and cam carrier and that the paper gasket is omitted.
Belt tension and valve timing:
All pulleys are to be sprayed with a.d.f. (air drying lubricant film ? molybdenum disulphide) on
initial assembly.
Belt tension should always be set with a cold engine. Tension is adjusted by moving the
eccentric idler pulley.
To check tension, turn engine in its normal direction of rotation to t.d.c. number 1 cylinder
firing. Tension should be checked midway between the exhaust camshaft pulley and the
crankshaft pulley. It is important that each time the tension is being adjusted and checked the
engine is brought up to t.d.c. number 1 cylinder firing in its normal direction of rotation. It is
essential that the belt is not over tensioned, as this will result in premature tooth failure.
We recommend the use of Burroughs tension gauge BT 33-86F 4 ?18 and the tension should
be set at 90 / 100 gauge reading. Alternatively a Gates tension tester may be used, and for
½? belt deflection a gauge reading of 11 / 15lbs should be obtained.
On new engine build the camshaft pulleys are marked on the front rims on their horizontal
centre line. These marks line up in the centre with the engine at t.d.c. number 1 firing. A
further mark is on the rear rim of the exhaust camshaft pulley, which lines up with a scribed
line on the cam cover, with the engine again set at t.d.c. number 1 firing. When checking the
timing marks, or timings, always turn the engine in its normal direction of rotation, with the belt
correctly tensioned.
The camshaft pulleys are a taper fit on the camshafts, and have two ¼? unc tapped holes to
facilitate removal. On new engine build the end of each camshaft and pulley hub face are
scribed with a horizontal line in order that the pulleys can be re-fitted in their original position.
Injection timing:
Unscrew the banjo from number 1 cylinder fuel outlet and carefully remove the banjo body
from the fuel metering unit. Remove excessive fuel and turn engine to normal direction of
rotation until the inner rotor port just starts to crack open. This point should be 80o a.t.d.c.
with number 4 cylinder on firing stroke.
To re-time the metering unit, set engine at 80o a.t.d.c. Slacken exhaust camshaft retaining
bolt and turn the metering unit drive pulley in normal direction of rotation until number 1 port
cracks open. Re-tighten camshaft pulley bolt and carefully replace banjo.
Tappet adjustment:
Rotate engine forwards to t.d.c. (cam pulley marks lined up). Mark metering unit drive pulley
to housing and remove belt. Remove main camshaft belt, having slacked off eccentric pulley,
to remove tension from belt.
(N.B. always re-fit belts to run in the same direction as before)
Retain tappet up against the cams, preferably by inserting 8 spring clips between adjacent
tappets. Remove surplus oil from tappet chambers with a syringe. Slacken off hex. Head
bolts, ensuring cam carrier lifts evenly. Carefully lift cam carrier assembly vertically until clear
of the valve stems and shims. Some shims may stick to the tappets and some to the valve
stems. When re-building an engine it is advisable to stick the shims to the valve stems with
Cosworth BDG 1978 Engine Specification
grease, whilst carrying out tappet adjustments, to ensure the shim remains on the valve stem
whilst removing the carrier.
Cylinder head:
Number bolts 1 ? 5 exhaust side, 6 ? 10 inlet side, then order of tightening is as follows:
8, 3, 7, 4, 9, 2, 10, 1, 6, 5.
Exhaust systems:
With BA8128 trumpet assembly use 4 into 1 exhaust system made of SWG tube.
4 x 2 1/8? o/dia. x 27? long into 1 x 2 3/4? o/dia. x 26? long.
Running in:
Standard running-in procedure on a dynamometer is as follows:
Torque rpm time
44lb ft. 3500 to full oil pressure
52lb ft. 4000 30min
70lb ft. 4500 30min
88lb ft. 5000 30min
105lb ft. 5500 30min
Then inspect tappets and test.
Related drawing:
BA0335 Engine general assembly (2 sheets)
BA0330 Recommended oil system
BA0331 Recommended fuel system
BA0332 Throttle assembly
BA0382 Ignition and charging circuit diagrams
BA0383 Recommended cooling system
BA0543 Exhaust flange
FA0289 Crankshaft bung assembly
Bolt torques:
Engine oil on threads and under head unless otherwise stated.
Flywheel / crank (12 bolt) 3/8 unf 50 ? 55lb ft.
Big end 41 ? 42lb ft.
(anti-scuffing paste
under head engine
oil on threads)
Cylinder head (soc cap hd) 7/16 unc 62 ? 65lb ft.
(oil under head)
Main cap 7/16 unc 65 ? 70lb ft.
Cam pulley 3/8 unf 15 ? 20lb ft.
Jackshaft pulley 5/16 unc 15 ? 20lb ft.
Cosworth BDG 1978 Engine Specification
Jackshaft pulley 3/8 unc 20 ? 25lb ft.
(BA0509)
Idler pulley nut 7/16 unc 30 ? 35lb ft.
Crankshaft pulley 7/16 unc 35 ? 40lb ft.
Cam carrier / cylinder head 1 /4 unc 8 ? 10lb ft.
Clutch bolt nuts 5/16 unf 13 ? 15lb ft.
Sparking plugs 10mm 9lb ft
(graphite grease on
threads)
Other
1 /4 bolts (sump, front cover etc.) 5 ? 7lb ft.
5/16 10 ? 15lb ft.
3/8 20 ? 25lb ft.
Pistons ? 1975cc:
(PA0112)
Gap on all rings to be .015 / .022? when fitted in the bore.
Pistons are normally supplied with gudgeon pins ground to the correct length and circlips
ground flat and parallel. Circlips are to be fitted with their ground faces outwards and the
gudgeon pin end float should be .001? interference to .001? clearance measured at room
temperature.
It is necessary to do a trial assembly to check the pistons for squish clearance at t.d.c. The
piston crown should be .000 / .002? above the top face of the block at t.d.c. and it will be
necessary to machine the piston crowns to achieve this figure.
Pistons also require machining for gasket clearance, details of which are shown below:
Cosworth BDG 1978 Engine Specification
Cylinder block:
The cylinder block should be finally cleaned before assembly. Main oil gallery bungs and the
cam carrier / camshaft oil feed restrictor can then be fitted. The restrictor, part number
BA0356, should be fitted flush to just below the cylinder block top face.
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