Engine and Electrics on the Soarer

Soarer Engine & Electrics
We all understand what happens when we turn the Key in the Ignition,... don't we!

OK, in its simplest form: - A battery energises two electrical circuits, the first to ready the Coil to create a Spark, the other feeds the Starter motor, this little device turns the engine over for a couple of cycles of its 4 stroke sequence, during this critical time the whole thing must become completely self-sustaining, if not then the damn thing just churns away sounding like a hopelessly huge coffee-grinder.

The valves have to open and close at the right time, that spark has to generated and delivered at the right time with sufficient spite to ignite the correctly metered fuel/air mixture, it must also take care of keeping itself cool, lubricate itself, dispose of its effluent, be reasonably quiet, free from excessive vibration, generate sufficient stored energy to do the trick time and again and after doing all this it has to have enough left over to push indifferently shaped tin cans at speeds suitable to be regarded as effective transport.

The above encapsulates the sequence in which we will deal with the individual elements of the Spark Ignited Internal Combustion Engine and the Transmission as it is on our cars.

Anyone who has visited the Sistine Chapel in the Vatican City cannot fail to have seen the Masterpiece by Michaelangelo titled 'God giving life to Adam', those who have not been, will know the painting as the one with the spark of life passing from the One to the other. And it is a Spark that brings our cars to life, it is not as significant as the 'Great spark' but it is the same!

We, as mere mortals, cannot call on the man at the top of the stairs to get our cars moving (although as a disgruntled Italian car owner I have invoked his name in vain) so we have a humble Battery. Humble but effective, it has to cope with vibration, G-forces- both negative and positive, huge temperature variations, and minimal, sometimes non-existent, maintenance.

A car battery consists of 6 polypropylene cells connected in series, each cell contains alternate plates with opposing charges with separators the charging mass is immersed in Sulphuric Acid/Distilled Water known as the Electrolyte. The low/no maintenance battery is brought about by the simple exclusion of antimony in the Lead alloy plates. This reduces gas generation and so the electrolyte does not so readily boil off. Deep cycle batteries have fibreglass or felt included in the separators meaning the lead does not scale or form sludge when the discharge is heavy or prolonged.

That spark.

How do we get something as spiteful as a really bright crackling spark from something that you can grab by the terminals with impunity?

That's the ignitions' job and it's the Coil in particular that gives the low voltage that it receives the tension sufficient to jump the Spark Plug gap. It does this by storing the bit of power between the sparks and 'grouping' it all into one single slug of spite, this is achieved by the Coil acting as a Transformer jumping the voltage from 12v to 30,000v, lightning in a little package.

Its' delivery is controlled on the Soarer by dint of a Crankshaft angle sensor which supplies the Electronic Distributor with a stream of Timing ticks and from this and other info the spark is delivered at just the right moment.

At exactly the same time there is a drain on the battery for the Starter Motor This is a simple Shunt wired electric motor, Shunt just means the torque is optimised at initial starting, this is essential to overcome the initial mass of the dormant Engine, to start an SI-ICE it needs to turn over at about 80rpm +/- 20 rpm the SM is geared down usually 10/12:1 by putting gear teeth on the outside of the flywheel and a small pinion gear on the end of the SM. There are 3 essential parts to a Starter Motor:

1 Electric Motor. (Capable of circa 1,000 rpm)
2 Pinion-engaging drive. (clutch; inertial or piston or pre-engaged)
3 An over-running clutch.

The operating sequence is as follows:

The pinion gear is forced to engage the flywheel, then the Starter turns, as the Engine starts it will overtake the Starter and the over-run clutch operates. 1 sec of starter use produces only 1/1½ revolutions of the Engine, on the 6 cylinder cars that's just 3/5 power strokes or for the V8, 4/6 strokes, most cars start after about 8 power strokes. Yes, 8 cylinder cars really do start twice as quickly as 4 cylinder.

So, everything's in place to start it, we need to take a good look at what we are about to begin. We should be grateful!

The fundamental question the Car Designer asks is what will this car be for, is it a bolide for hoi polloi or a carriage for the refined, this question is so much more important than you may think.

No car that has any claim on refinement can have less than 6 cylinders, any less and you have to start to put counter-weights, or pulleys and gears on or near the crankshaft. At risk of upsetting the V8 members, the only Engine configuration that is naturally devoid of harmonics is in units of 6. Straight 6 at that, so a V12 or Flat12 is also free of harmonics (it is, effectively, 2 straight 6's), and the Flat6 also, NOT a Boxer6.

The only engine worth its salt after those just mentioned is the twin-plane 90deg V8 with the addition of simple counter-weights it is rendered completely devoid of harmonics allowing its inclusion in the Iain Wiltshire Book of the Great and the Good. Excluded is the latest TVR engine, it is vile, it is a single plane 90deg V8 so it is effectively 2, 4 cylinder engines glued together thus doubling that horrid 2nd order free FORCE, and that's why the 4 cylinder engine is never in a real Gentleman's Carriage.

The 2nd order free Moments can never be eliminated in any V6. I must concede however that a 90deg V6 is very smooth when it has 6 throws of the crankshaft, it has the lowest level of 2nd order harmonics of all the V6's. All other V6's have various levels of harmonics that detract from any virtue they may have gained through outright power.

It is for good reason that Early Bentleys, nearly all Aston's, Jag's, Armstrong Siddeley's, Humber's, big Rover's, you name it, if it has quality (or pretensions of it) then it has/had a Straight 6!

Rule of thumb.
Some V8's are good.
All Straight 6's are great.
V12's are just bloody marvellous.

D'yer remember the song "dem bones"
Here we go:

The piston goes up and down (reciprocates) in the cylinder and is held to the Connecting rod by the gudgeon pin, the connecting rod's connected to the crankshaft by one of the journals, sometimes (incorrectly) called bearings. This turns the reciprocation into rotary motion. Remember, journals rotate about the crankshaft, bearings do not, they locate and hold the crankshaft in its place. I bet you think pistons are perfectly round, well your wrong, they are slightly oval, to allow for the Gudgeon Pin expansion.

The design of the piston top is almost self-made; subject only to what use the car is put to. There may be little nicks and inclusions in it to allow for the valve train but the design is intrinsically simple now computers can define explosion wave fronts. This is not the case with regard to the Gudgeon Pin Location; its location within the skirt of the piston is an area where the Engine designer can show his skill in conjunction with the next element.

I just stopped and went to my library (sounds very pretentious for a bookshelf) to see if I could find any books that give any credence at all to the design of the Connecting Rod. I found nothing in the modern books, but in the Pratt and Whitney Radial Engine Design compendium of 1948 I found a whole chapter devoted solely to that subject! I found the Maths to be simple at first then realised that it suffers from what used to be called Bifurcation theory or as most call it nowadays Chaos Theory! This one of those areas where the intuition/ nous/ skill/ experience of a good Engineer is worth more than theory. Look at it this way, if we imagine a con-rod that was 100mm long and the torque transfer was 100 units because of the nature of this complex piece of metal making it 101mm in theory should give slightly better torque say 101 units, but making it 102mm should give 102 units but it doesn't it gives 99 units, 103mm should equal103units-but gives 105 units its all over the place! Twin plane reciprocating things are like that, bloody unpredictable (mathematically).

It has to be said that BMW were and still are the best at this piece of magic, remember that Pratt and Whitney Radials were based on the BMW blueprints and that the finest example of BMW's handiwork was the transformation of the later versions of the Junkers JU88. This 'plane was robust with a marvellous Airframe which was relatively heavy and the original pair of Junkers Jumo V12's were good but not powerful enough. Our Bavarian enemies designed a beautiful Radial for this 'plane and it was transformed, with its 4 man crew it could now outrun our fastest pathfinder (unarmed, superlightweight) Mosquito's, being capable of 450 Knots flat and level, fully armed. It then became the most devastating destroyer of anything that got in its path, Bomber or Fighter, even the Aircobra Mustangs were prey! Later the Junkers engineers put in 3000HP Diesel engines, so as to keep them in the Air for longer, but it is the BMW powered Ju88 that holds, without doubt, the title of the finest piston engined Fighter-Bomber ever. This is due in no small part to BMWs' innate understanding of the importance of the Piston stroke/con-rod length ratio. It seems to be overlooked nowadays. Sorry, went off on a tangent there.

The Soarer 2.5 TT has a better intrinsic ratio in this respect than the Supra 3.0 TT, the con-rod can define how quickly an Engine can accelerate internally. The gross limit to acceleration remains the same in (nearly) all engines but the amount taken by different lengths and masses is the element that controls the take-up, sometimes less really is more.

The V8 has a con-rod length very suited to Torque generation and long duration at 'constant' revolutions, the TT is set for revving readily, suiting the Ceramic Turbo's.

So to the Crankshaft.

There are two main types of Crankshaft production. The first and most expensive is the Machined Billet, basically one piece of vacuum drawn steel, lathed to its final design with every part machined and polished.

It is the only way to get a truly reliable high revving unit.

The simpler, easier way is to cast the unit to its approximate shape, then it receives the attention of the lathe, but only on the Journals and Bearings and attachment points. Cast units are very good at being smooth running and the V8 is a paragon of smoothness.

The cutaway drawings show the TT with a Machined piece, the V8 with a cast, I have not seen them in the flesh so I cannot be certain, but it would make sense.

Strangely the cutaway drawings show the Supra as a cast unit!

The Crankshaft is held in place by bearings at the bottom of the Cylinder block.

The Crankshaft has to have a series of capillary tubes drilled into it to allow the lubricant to circulate and cushion the bearings and journals.

The parts described above turn Reciprocating motions to rotational motion. Acceleration and Vibration.

There is a physical limit to the acceleration that the individual parts of and engine can obtain, and as stated before, different engine use dictates design.

Lets look at the V8 first, it has a Stroke of 82.5mm this means the eccentricity of the con-rod journal to the main bearings is half that figure, the diameter of the cylinder bore is 87.5mm. I'll let you into a simple engine design 'rule of thumb' 85mm bore is an approximate 'starting point' it produces equal torque and BHP per litre, if you increase the bore you get greater torque and less BHP per litre, and vice versa. The exact same relationship exists with the stroke, but the key figure here is 80mm.

I have just re-read the previous paragraph after a few days break and am appalled by the sweeping statement I have just made, but it is nearly right and as close as I can get to the reality without taking up 50 pages of further explanation.

Maximum Torque is always produced at lower RPM than maximum BHP.

The con-rods on the V8 are also relatively long; this engenders high torque propagation and low explosion-expansion vibration moments, as they are more perpendicular in the part of the crankshaft rotation, which produces the most torque. So all this means that the V8 is designed to be on the torquey, muscular side of the design envelope, coupled to a cubic capacity of 4 litres it is no wonder it seems to feel like being swept forward by a giant hand! It does not need to be revved to produce the goods!

The TT is different in so many ways!

The TT is a short stroke motor; that is to say it is designed to Rev, and does so, readily.

A Stroke of only 71.5mm and the inherent 'turbine' smoothness of a Straight Six, 7000RPM is an easy achievement, and the TT will (if not artificially limited) keep going safely to 7700RPM without demur, the best in Japan (with revised valve gear) pull 9000RPM.

The Bore is 86mm, which is good for both torque and BHP propagation as it is also the Bore of the Supra and Soarer 3ltr motors.

They do not share the same Block; the 3ltr is a simple cast unit with different waterways for cooling, different height and different metal alloy. This was necessary for the greater Stroke, which (thanks to those who confirmed this point to me) is 86mm, making it much more inclined to produce torque.

The TT's engine must have been a loss leader, the use of T2000 steel for the bearing shells shows fanatical design care, the machining of the con-rods is almost sculptural, the pistons are 'single form' units, the alloy in the block the most durable alloy available outside Formula 1, it costs an absolute fortune to be this fussy!

The above also explains why the 2.5TT is superior to the 3.0TT, that Piston has to travel 20% further for each Stroke. This is a huge limitation on the rate at which the acceleration accelerates within the Engine as a whole, by co-incidence the best compromise Stroke for both internal acceleration and BHP propagation just happens to be around 68/72mm

So if you wanted a Turbo'd Straght 6 designed to do what a Turbo'd motor should do, then it will be limited to around 2.5ltrs, 2.0ltrs and the thing would need to rev its guts out, 3.0ltrs and it would be limited in its ability to Rev under load as freely as Turbo'd motors need to release the Turbo's full potential.

I have had the opportunity to run side by side with an Auto Supra TT at 60MPH, on a given signal we both pressed the loud pedal to the floor, he was left behind and could not catch me, I had to 'back-off 'at 110MPH by which time he was 2 car lengths behind, even I was surprised at the margin!

We did the same thing in each other's cars, the same result. But his car definitely seemed to me to be the faster! He did not think my Soarer was very quick when he first drove it, calling it an Old Man's Car, until that moment.

That difference between the 2 cars is also brought about by the B.rake M.ean E.ffective P.ressure, and the working pressure reaches it peak usually somewhere between the peak Torque RPM and the peak BHP RPM, but that's conventional engines, put Turbo's into the equation and it all changes.

To produce optimum acceleration of its components the BMEP must reach 145PSI early and peak at around 175PSI. The 2.5TT has at least 145PSI over a 4000RPM band and peaks at 173PSI, the 3.0TT peaks at 154PSI and only gives 145PSI over a 1200RPM range, this is the most important factor in performance motoring.

The most evident way to feel this is the way our TT's seem to continue to accelerate more aggressively rather than being attenuated by the speed being attained.

Truly acceleration accelerating.

The V8 and 3ltr are almost identical to the 3.0TT in the BMEP stakes! Each one being a couple of pounds down on the other, so the 'pecking' order is:

2.5TT
3.0TT
V8
3ltr

And that is exactly how it should be! Horses for courses.

Just below the Crankshaft is the Oil pan and Sump, this holds the lubricant that keeps all those metal bits from gouging great chunks out of each other, there is a Science entirely devoted to this technology and it is called Tribology.

If these papers continue to be well received and if sufficient people want it I might persuade myself to write a separate paper all about this subject, it would encompass road surface, lubricating oils and Air flow

But as a taster, how about this for something seemingly impossible; the metal that your engine is made of absorbs some of the Engine oil in your car into its surface!

Intrigued?

Advice: When you get your car see if you can find out what oil the owner, or his service agent has used, and stick with it, unless it's poor quality then flush it out in the following manner. I explained this to Jeff Tate on the 'phone as his car suffered from sludge deposits, it is a bit involved but worth telling.

1 Warm the car thoroughly, and drain off about 1ltr of the oil already in the car, replace with a good flushing oil.
2 Go for another good run.
3 Use the car for no more than 300 miles and always decent length runs.
4 After the last run drain all the oil, refill with entirely flushing oil, take her out for another good run, stopping at intervals taking the oil filler cap off and feeling if the sludge becomes less gelatinous and there is a distinctive smell, slightly 'petrolly' in nature.
5 Go home at this point, don't venture more than 20 miles from home, in other words; take a circuitous route until the desired effect is achieved.
6 Drain the oil OVERNIGHT in a warm garage.
7 Do a complete oil change.
8 Do not drive for 30 minutes after filling the car, and before driving check the oil level and top-up to the mark.

Over the next 3 oil changes all the sludge will disappear and then you put Slick 50 in there. NEVER,NEVER,NEVER put Slick 50 in an Engine with sludging, some people have done this in the past, then tried to blame the product for their own utter stupidity when the Engine died.

What is Sludge?

The oils we use are L.ong C.hain P.olymers, and they all deposit themselves on the surface of the metal, it is designed to be wiped off and replaced with other LCP's as the first ones break down. When a different oil is used it may not be able to remove the old LCP but will leave its own new LCP on top and the pollution just continues as one affects the other causing further build up.

Let's go to the top of the Engine.

The Cylinder head contains all those bits that involve breathing, whereas the cylinders are analogous to the lungs, the cylinder head is the throat, I think that is the worst case of a faulted analogy I can think of. Sorry.

Almost all Heads (including ours) are X-flow, simply the In.take is on one side, the Ex.haust the other. Our cars are all 4 valve heads, (2 In., 2 Ex.), they are actuated by D.ual O.verH.ead C.amshafts. Obviously the V8's have 4 Camshafts.

The Cams are turned by the Crank by the Timing Belt, a loop of toothed rubber.

The valves operate at high temperatures and then dissipate this up its shaft into to the cool oil where the cams reside, the way to do this is to fill them with a Sodium substrate that is excellent at heat transmission. The Ex. valves are always hotter than In. valves but not by as much you might think!

They are held closed by powerful composite springs and are pushed open by the Cams, there is another type that you may have heard of, Desmodromic which uses a closed loop to control the valves so that there movement is controlled on both the down and up stroke and therefore cannot suffer from the dreaded valve bounce which does happen in the conventional set-up, but due to their nature, the cam profile that opens/ closes the valve is compromised and therefore Desmodromic valves are really only used in narrow band performance engines, and now that we have computer modelling they are rendered nearly extinct.

That Camshaft profile thing, what's that?

Well, first it's the lobes that are profiled, this profile has to be VERY accurately machined, as that thin shaft must be loaded progressively that is why they are carefully radiused, the contact stress is about 15lb per square mm, look at one of you finger nails, an average mans index fingernail is about 250sq.mm, so that's about 1½ tons pressed on it in a fraction of a second.

The position of these peaks is the timing, and all fixed (normal) valve timing is a compromise, as things need to be advanced or retarded according to Engine speed to obtain maximum efficiency. As I don't know of anybody with a VVT Soarer in our club I will save you the trial of having to read 2000 words describing all the different systems that are in use, however, if in our ranks there is an owner of a VVT and can send me a diagram of the System then I will explain to all how this method of adjustment is achieved.

I hope that it is by a 3 dimensional profile as this is far and away the best and simplest system, also the most efficient in internal losses. I really hope that it is, after giving all the others the thumbs down.

The Right Gear
If you are driving a Soarer then I think almost all of you have dispensed with the fatigue of using the three pedal function, you have an Auto' almost all Drivers in this Country start with a Manual, pass their test then eventually go over to an Auto'. I do not know of anybody who has started with an Auto' and the progressed to a Manual, having re-taken their Driving test which I believe is still a legal requirement.

A GT is meant to have an Auto' box, Grand Touring is about covering great distances or time consuming journeys with the of minimum fatigue possible, and in this respect the Soarer is a peerless companion. Every model is capable of taking its driver and occupants on long journeys without losing his patience or depleting their endurance. Other factors may fatigue you, for me, its ignorant road users, but the Soarers lack of harshness and ready power is always a delight and a soothing influence, the knowledge that these irritations can be left behind at the squeeze of a pedal always gives me that glow of smug superiority.

The part played by the Auto' box is crucial to this equanimity; it does what I would do, but better, smoother and lets me concentrate my efforts on dealing with the Road, NOT the car!

I will lay my cards on the table and tell you straight away that I would have the 4 speed fitted to our cars in preference to a 5 speed Auto', and a Tiptronic type does not appeal at all.

You will see why after you've read this paper.

Now when the Engine turns the output goes directly to the Hydrodynamic Torque converter, the most important parts are the three elements known as the Impeller, the Stator and the Turbine. The whole thing works as follows; the Output from the Engine goes directly to the Impeller, which circulates the hydraulic medium in its casing this fluid has an energy value. The Turbine is connected to the rear wheels which at this time are stationery and as 1st gear is hydraulically selected the turbine slows to about ½ the Impeller speed and the torque is doubled the natural inclination is for the 2 to equalise there rotation speeds and so as the car revs a little the Turbine plays catch-up and as it nears the parity point, the box ups the gear ratio (2nd) and the Turbine plays catch-up again and again the torque is doubled until parity is reached and so it goes. The Stators job is to re-circulate the hydraulic medium and as it also speeds up to the Impeller it eventually reaches a state of 'free wheeling' and the lock-up clutch is activated which 'ties' the Impeller and Turbine together. Our cars and almost all other Auto's use a Fottinger Centripetal system which is designed to give a Torque conversion anywhere between 1.9 - 2.5 to One, the simple fact is that this system will always take into account the loads imposed without any interference and do it about as well as is possible.

That O/D ON/OFF what does that do?

That little switch saves the engine from having to maintain high rev's when we travel at high speed, it is just another gear, but in stead of having all the gears ready for selection (which drains power from the Engine) only the 3 main gears are pre-readied. That means less power is absorbed by the change mechanism which is much smaller than that fitted to a 5 speed Auto', so more power gets to the wheels, this explains why I like the present 'box. The in gear power delivery is stronger as the change up points are further apart and the change system is more efficient. Also the change down from cruising is large enough to make a real difference the shift down from O/D to 3rd is quite a lot bigger than that from 5th to 4th and it is a simple switch out if you want meaning the power jump is instant, quicker than any Auto's hydrochange into 4th and if you switch out at the right moment you get a little bit of Torque multiplication as well, try this out, the effect can be quite amusing!

That switch with PWR/ECT on it, what does that do?

Well if you think about the above you notice that at some point the Torque from the Engine must be such that the resistance at the from the wheels drops below that being taken from the Engine and the Turbine accelerates quickly, this activates the gear change forcing the Engine to pull harder on a higher ratio and so progress through the 'box is achieved. That is great for economy but it means that the car will not go to the red line, or anywhere near it (unless we are on a steep incline), so we have that switch. This is what it does; it holds on to the gears until a certain RPM is attained, it makes the gears direct by locking the Impeller to the Turbine until the next gear is selected, and then it holds that to a predefined limit also, in this mode the Soarer in TT guise is quite astonishing. One can also manually select 1st or 2nd so as to do a final trick, select first, hold the car on the brakes and rev-up to about 2000RPM, release the brakes and put the pedal to the metal, change up at about 6500RPM without taking your foot off the accelerator and do it again changing up to 'D' without the overdrive in at 6500RPM, switch in the overdrive at about 4000RPM it wont come in until 6200RPM by which time you are doing about 120MPH and you would have made your heart thump fiercely in your chest, but keep going, don't take your foot off the loud pedal, take her to 160MPH I've done it and the TT loves it.

This is Race Track stuff, and the Highways are not the place to do that sort of thing.

PWR/ECT is quite enough for the main roads of this Country.

I have long considered the Turbo to be the natural companion for an Auto', the dreaded 'lag' is eliminated by the fact that when progress is required the 'box sets about it, and then the Turbo comes on stream, just as the change down has occurred, with an Auto' 'lag' is an asset, not a fault!

OK, 5000 words Engine and Auto' covered!

When I set about the task of writing a paper on the basics of Soarer Engine/Gearbox design, the first draft was 12000+ words and seemed a little too detailed. I have pruned the content back as much as seems right but some areas have not received a lot of attention, if there are any areas that really should be revisited and expanded upon with an addendum, then say so, please, if you want more detail or just an impression of a subject not covered, state what you want.

The next paper investigates the Nostrils of our cars, Turbo', Fuel Injection, Exhaust and Cooling.

Final thought, if you think hard, then what happens under that bonnet is a little piece of magic, we take it for granted, but it is no less magic for all that.

Go safely out there.

Regards

Iain Wiltshire - Newbury, Berkshire, England. 21 October 2000

©The Lexus Soarer Owners Club