From the 300 board, I love the last para!

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! "

Isn't that some of Mycroft's work?

The Iain Wiltshire name involvement should give you a clue to the intrinsic value of the thread...as a self abuse aid for Mycroft

that and the need for a scroll button...

Wow, he knows all that and thought the Soarer had sequential turbos

From what I've picked up over the years....why doesnt he just marry his soarer? Seems pretty obsessed with proving its the best car of all time. I mean, we all like to think the car we have is the best...it justifies the money we spent on it but unless its Mc F1 it aint. Kinda feel sorry for the guy.