I read this on the Soarer Owner's Club web page a while ago. It's the webmaster/whatever's rambling philosophy on engine design, and although I am fairly mechanically illiterate I thought it was interesting. What do you think of these 'edited highlights'? Is it all 'o' level textbook stuff? 300zx engine better/worse? (Slightly different take on 300 vs. Supra!)

 

"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! "

 

.....

 

"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. "

 

.....

 

" 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.

 

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 [soarer] 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! "

 

Just wondered what people thought.

I think its *****x! Actually I know its *****x!

Lmfao :d

Is it the wisdom of a nice old gentleman? Like I said, I'm no mechanical guy- just wondered if it really was *****cks. What Japanese engine really is better than a 300?

Nah! Its probably Mycroft!

...What Japanese engine really is better than a 300?

 

Tuned 300 engine! LMAO Or an MR-2 SW20 turbocharged motor and the only reason I say that is because they were built by Yamaha and I love Yam's...R6...R6...R6...yum!!! ;)

Nah! Its probably Mycroft!

 

NOOO!!!! I've heard about him. And seen his publicity snaps.

 

I have owned a Soarer though (and I liked it)

Hang on a mo here, which Soarer engine are we talking about?

 

Coz the 2.5 TT was the one out of the Import mk III Supra, now the 4 litre V8, that's a different kettle of fish altogether.

Gotta be true man we all know supras are slow. Now I understand why, cause their main focus was the design of the upmarket lexus brand :rofl:

He's talking about both engines in the article at different points. The TT is supposed to be about 280bhp and the V8 around 265, 70, 80 (different places seem to say different things). V8 nicer? But not really as tuneable?

 

If the Mk III supra had the same engine as a Soarer it must have been a decent engine to last that long. Mk III supra- any good? They will be nice and cheap now won't they?

Ignore it, its Mycrofts crap, just had it confirmed!

Ignore it, its Mycrofts crap, just had it confirmed!

 

How come? Because I used to have a Soarer I read this stuff on http://www.lexusclub.co.uk/. I thought (in my ignorance) that what the guy was talking about might/might not be true or of interest. It sounded kind of plausible that a 2.5 engine might be a good TT engine and I wondered what people on here thought- seeing as they are 3l TT engines.

 

AFAIK everyone despises this Mycroft guy because he was a prat. And went on about his Soarer and how fantastic it was. Is that the gist? Anyway, That's where I got the stuff from. I love my NA 300, I had a Soarer for a while, and I liked it, apart from anything else it was more 'wife friendly'.

 

Sorry if it caused you offence, I posted it because I genuinely thought it was an interesting point to talk about. Because I don't know that much about engines I thought I might learn something.

 

:nelson:

LOL! Chill Rich, no offence this end:D I agree it makes interesting reading and having had a play with a Soarer on the M1 on the way to TOTB, I appreciate the cars performance. I'm just saying that the amount of dribble to come out of this guys PC, I wouldnt take any notice. Interesting theory but the last paragraph makes me think its pants!!

Is there a smiley for 'paranoid'?

in my 'broad' experience (:D) the Soarer didn't feel at all 'lardy'. Nippier than my NA (obviously) but the turbo lag was very noticeable to me.

LOL, do a search for Mycroft AKA The Devil and your see what we mean. Its nothing to do with Soarer's more to do with the SAS training! ROFLMAO!

I thought you meant you thought I was another Alias for his posting!! I did a search and the name Iain came up- is this Mycroft guy the bloke who wrote the Soarer site?

If you look hard enough, you can always find someone spouting the benefits of the "perfect" engine - at least by their own criteria. Are you talking about primary or secondary balance? (To name just one of the possible criteria).

 

This starts as soon as you get to 2 cylinders: boxer, parallel twin 180 or parallel twin 360. And even with boxer there are at least 2 physical layouts (offset crankshafts or "knife and fork").

 

So to start making claims that "the only car that has any claim to refinement is xxxxx" is complete b****** :D

 

Engine / car design is MUCH more complex than that and EVERY engine design is a compromise and a balance of compromises. That is what engineering is.

That was indeed writeen by me and it is all too true, to argue against any part of it is to fly in the face of reality.

 

A straight six is the ONLY naturally balanced engine, to obtain balance in any V6 you need to 'fiddle' with the crank weights.

 

The rate of acceleration internally is dictated by the natural balance, in any circumstances a straight 6 will be capable of greater RPM/C [the rate of acceleration of the total moving parts of the motor.

 

The same applies to the ''ideal''' size [capacity] of each 'pot' , this is constantly changing due mostly to the everchanging fuel and emission laws... at the time of its' design [1989] the type of fuel and the allowance of emissions meant that the ''ideal'' size was just over 400cc with a good undersquare element to aid free revving. At the moment the fuel and emissions mean that very large bores and medium strokes are best, this is why the 350Z has no Turbo and a 90+mm bore, it is close to the ideal, the design of the car and the history of engine production mean that the compact nature of the V6 configuration has been retained, these elements far outweighing the incremental benefit of a stright 6.

 

You can of course clean and polish a rusty nail to look brand new, you just remove some of its strength in the process, for the most part this small amount of 'loss' will not noticeably effect the performance of this nail but it won't be as good as a nice perfect full sized 'idealised' version.

 

This really is simple engineering arguing against it is to show yourself 'lacking' in real knowledge and only serves to make you sound like a pub loudmouth... this, of course, is your choice... for your intellect... some of you have chosen well.

 

:D