Can I just ask about the flywheel job? I didn't think you could mimic the balance shafts using the crank/flywheel because the vibration is 2nd order (twice per revoltion). Otherwise Alfa would have done it.
So whats this about taking a chunk out of it and what is the logic? Cheers
Edit: sorry, read your post again... You are just making the flywheel thinner I think
I was thinking that too. I think the main benefit of the balance shafts - for me anyway! - is to reduce the inevitable shake at low engine speeds caused by that 2nd order vibration (the Bosch Automotive Handbook does a good job of explaining this). FIAT/Alfa had no problems making engines that ran to high revs without destroying themselves and I don't think the balance shafts are for that purpose, and therefore removing them from race engines makes sense. The smoothness at high revs depends on balancing/weight matching the main parts, as Andy is doing - should run great
But when sitting at traffic lights, I like not having the steering wheel shake. I believe that low-speed smoothness depends mainly on how many cylinders there are and how big the explosions are, I don't think the balancing (crank, flywheel, etc.) will affect this but I reckon the balance shafts take out some of the thump. Will be interesting to learn from Andy's experience whether that's actually the case. Two litres was always the reasonable limit for a four-cylinder engine to be acceptably smooth; I think it was Mitsubishi and Porsche who last exceeded this (2.4 and 3.0 litres) and that's when they applied the balance shafts which, I think, were originally a Rolls-Royce patent - Mitsubishi snapped it up when it expired in the 80s? EDIT: no, it was Lanchester, sorry... I don't think many manufacturers have used balance shafts on 2 litre engines - FIAT introduced them for the 2L four in the late-80s Lancia Thema. Must go and have a check on Wikipedia, probably some American econo-luxo-barges had them?
I feel that the 2.0TS is a long-stroke motor (undersquare, stroke larger than bore) compared to old FIAT/Alfa standards. The smaller four-pots in the 1970s/80s were always oversquare, which facilitates smooth high-speed running but reduces torque at low speeds, making it smoother but also less torquey, and torque is what you need for economy/low emissions. Therefore since the '90s the trend seems to have gone back the other way, to the undersquare proportions used before the '70s (excepting Honda, of course). So without the balance shafts I would have thought the TS would feel quite rugged at idle, like a '70s Lotus or tuned Ford of that era (and I mean that in the nicest possible way
) Who cares if it's a race engine - just turn the idle up a bit...
Beats me why four-cylinder diesels don't have balance shafts - I would expect it would help them too... Of course, the FIAT/Alfa solution is to use 5 cylinders...
Useful article here: http://www.autozine.org/technical_sc...ne/smooth2.htm