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Lightened flywheels are known to have a negative effect for going uphill, or at least such a steep hill that engine speed will reduce.
Fruity, I partially disagree. As I said in another post, it's only the first part of an incline in which a heavier flyweel (rotating mass in general) is of some assistance.

However, it will still accelerate slightly better going uphill.
Yes. If the car were to start the climb from a standstill at the bottom of the hill, with a lesser flywheel effect (lesser rotational inertia from any source) the car would accelerate from rest all the way to the top of the hill with somewhat greater alacrity, than it would with a greater rotational engine mass.

A side effect of a lightened flywheel is less large-diameter gyroscopic mass. I'm not going to try to explain about that so just accept that reduced gyroscopic mass helps the car turn easier when travelling at speed.
This is an interesting thought. It has crossed my mind before that at least theoretically there must be some degree of gyropscopic action (associated primarily with rotational engine mass, but also gears and wheels etc.) that would assist the car to change direction when steering one way, but hinder it when steering the other way. I can't say that I've ever felt a difference that I could attribute to such an effect. I'm fairly sure such an effect exists, just not at all sure what magnitude it might have. I assume it would be different for engines mounted east/west than it would be for engines mounted north/south.

If anyone doubts the existence of this effect, take a bicycle wheel and hold it in front of you with both hands (by the axle) at arms' length, have some rotate it fast, and then 'steer' it to the right, then 'steer' it to the left. You'll feel the gyroscopic affect, quite different left vs right. The wheel will 'steer' easily one way, and be quite resistant 'steered' the other way (can't remember which way is what, years since I did this experiment). The wheel will also try to rise higher when 'steered' one way, and try to drop lower 'steered' the other way.

I'm sure I read that removing around 5kg of flywheel mass is equivalent to removing 100kg of chassis mass. On a TS a lightened flywheel feels like less than a 50kg weight loss to me.
The improvement in engine response is probably the main gain.
Agreed. I don't know what the equivalence ratio is (differs at diferent rpm I'm sure), but it is quite significantly harder to get a rotating mass to move forward than an equivalent mass that is not rotating. Gyroscopes don't 'like' to move, other than rotationally.

Regards,
John.
 

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I replaced the stock 1.4kg damper-pulley on my 2.0 TS for a 380gram billet alloy pulley
So you lost a tad over 1kg of rotating mass from the damper / pulley. But, this mass is lost from a position only a few cm from the crank axis (the closer a mass is to the axis of rotation the less rotational effect that mass will have, because the mass moves a lesser distance per degree of rotation if it is closer to the axis). How much would you gain from taking 1kg off the flywheel, and that 1kg from a position a lot farther from the crank axis? I suggest it would not be noticable...

with 15% reduced diameter, to reduce drive to the ancillaries. I didn't notice any drop in steering assistance when at idle which was nice, nor did the battery light come on even at idle with all electrics turned on. So maybe you could go more than 15% reduced diameter, I'm not sure. For me it worked very well, the car felt noticeably quicker off the mark, 1st & 2nd gear felt way better. I also took the balance belt off at the same time though, so not exactly scientific. Both mods together made the car a nice bit quicker, so for me it was worth it. Had no issues for years afterwards. That's not to say I disagree with the theory posted above.
I've removed my balance belt. The difference in acceleration is barely perceptible, so slight I could be imagining that I can actually detect it.

As for pulley diameter reduction, well I'm very skeptical, and suspect a placebo affect. I do agree that the PS will be somewhat less parasitic, but doubt the difference will be significant. I have my doubts about reducing the power lost to driving the alternator with a smaller pulley diameter, as I've already said.

Of course so far this is all theoretical and subjective on all our parts. Engineers have a saying; "in god we trust, all others bring data". Not that I believe in God mind you...

Regards,
John.
 

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Apparently at 7,000 crank rpm, the balance shafts (which would be spinning at 14,000rpm) consume 7hp. No idea if its correct but I've heard it a lot over the years particularly on this forum, it sounds plausible. Looking into the factory power data, the 1.8 TS makes 82.4hp per litre, the 2.0 with balance shafts makes only 78.7hp per litre. 3.7hp less per litre. 7.4hp less than it "should". Hard to say how noticeable it is to add 7hp to a 150hp engine but to me, the car certainly felt perkier, particularly at low engine revs. I was happy with what the modifications cost to do and would do so again, placebo or not. The interesting test would be to revert back to standard and see if the opposite effect was noticed.

Anyway, there's some good discussion here on Pistonheads which you might find interesting:

https://www.pistonheads.com/gassing/topic.asp?h=0&f=66&t=1220819&i=0
 

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I think it will be a bit of a lucky dip. A lot would depend on the specific engine and its' crank harmonic characteristics, and how it's used.
I don't know if it's lucky dip, but IIRC, when we make such a pulleys, have them ordered for numerous drift used BMW's, few Civic's, Saxo's, Peugeots, and only god knows how many TSparks.......At least 70% of the cars was driven on track only, and still don't heard about any pulley related fails......
One customer even wants pulley for it's 145's JTD.....he did same endurance races which i did with no problems....except numerous turbo failures......
So as Pud said, i may agree with 80% of the theory above, but practice sometimes different......
For me, damping pulleys, heavy FW are made for comfort, and engine smoothness......
I don't know if its true, but some said to me that bigger FW allows car makers to pass emissions easier......test is conducted with steady RPM, and that make sense for me.......

I also took the balance belt off at the same time though, so not exactly scientific.
Forgot to mention that did that since i got the car.......my other 2.0TS uses regrinded 1.8 block which is lighter and don't have balance shaft......
 

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So, let's imagine a hypothetical engine that has a critical crank resonance at and very close to, oh I don't know, let's say 5,200rpm. The crank isn't at risk at any other rpm within the usable rev range, but at 5,200 it starts to generate a 'resonant oscillation of death'.

However, the resonant oscillation does not instantly reach a dangerous level the moment 5,200 rpm occurs, it takes at least a few seconds for the torsional oscillation to start getting out of hand. Not unless the rpm are held steady at or very near to 5,200 for a significant number of seconds does the resonance climb toward catastrophy.

But, in hypothetical practice this is something that just never actually (hypothetical actuality) seems to happen with this engine. Rather, the rpm are always rising or falling as they pass through the 5,200 rpm danger zone, so there is not ever time for the 'death resonance' to reach a destructive level.

When the car is cruising the rpm are always well below 5,200. None of the speed limits correlate to 5,200 rpm (nor the speed somewhat in excess that the driver has a habit of trying to get away with...). The car is always accelerating hard when 5,200 arrives and is then quickly exceeded. As rpm fall, say when shifting gear, they tend to drop straight past 5,200.

Were this engine to one day unusually be asked to hold 5,200 rpm for even a short time, then it might not be a happy day for the engine, or it's owner...

Sounds a plausible possible reality to me. It would explain why a car maker would fit a harmonic damper, i.e. because they know that a dangerous crank resonance exists at a certain rpm and of course would want to avoid waranty claims and reputational damage that might come from potential quite foreseeable failures. It would also explain why a certain number of users of this engine can remove the damper and suffer no adverse consequences.

Regards,
John.
 

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Apparently at 7,000 crank rpm, the balance shafts (which would be spinning at 14,000rpm) consume 7hp. No idea if its correct but I've heard it a lot over the years particularly on this forum, it sounds plausible.
There'd be some 'drag' from the oil in the shaft bearings, and creating a vibratory force to counteract engine vibration will require some energy, the belt would be very slightly parasitic too. Seven HP at 7000rpm seems plausible, but of course will be less at lower rpm.

Looking into the factory power data, the 1.8 TS makes 82.4hp per litre, the 2.0 with balance shafts makes only 78.7hp per litre. 3.7hp less per litre. 7.4hp less than it "should". Hard to say how noticeable it is to add 7hp to a 150hp engine but to me, the car certainly felt perkier, particularly at low engine revs. I was happy with what the modifications cost to do and would do so again, placebo or not. The interesting test would be to revert back to standard and see if the opposite effect was noticed.
My 2 litre TS, I rarely rev it over 5,500rpm, there is just no point, the power is not up that high, certainly not at 7,000rpm. Therefore, I won't be getting close to a 7hp reduction in parasitic loss from having deleted the balance shaft belt.

I think the 2 litre engines' power drops away at higher rpm because (it's my understanding) that it has the same sized valves as the 1.8 litre has. So, the 1.8 makes its' best power at higher rpm than the 2 litre does. This may well account for the per litre power difference between the 1.8 and the 2 litre engines, i.e. the 2 litre is a bit strangled by its' valves...

Regards,
John.
 

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Lifted the following from an interesting discussion on the eng-tips forum:
https://www.eng-tips.com/viewthread.cfm?qid=402821

"The presence of damper on the original engine strongly suggests that the design engineers determined that there was as speed at which the combination of drive train inertias (not just the engine components) and the relative flexibility of those components in torsion resulted in excessive crankshaft torsional vibration or twisting.

Please know that the specifications of the damper were not chosen arbitrarily. A random selection of components is unlikely to result in an improvement in vibration damping. The calculations require considerable amounts of data and measurements not easily performed.

Without the damper, the engine will rev faster and some racers may choose to remove the damper for this reason. If the engine does not spend much time in the critical rpm they may get away with this practice." (EHudson)

Regards,
John.

PS Harmonic crank twisting will of course vary from engine to engine. I have read 1° of twisting oscillation quoted a few times for various undamped cranks (also seen up to 4° claimed, but I'm a bit skeptical, but perhaps with a particularly flexible crank). I'll take it as a given that a correctly designed and selected damper will substantially reduce oscillatory twisting.

A single degree of elastic twisting doesn't sound like all that much, but look at the crankshaft, how massive and thick it is, how substantial and serious a piece of metal. Think how hard it would be to twist that thing by 1° using a breaker bar. There is a fair degree of force involved with that 1° of twist, and that twist will be highly 'energetic' as the crank very rapidly twists back and forth around its' axis.

The crank twists more further away from the flywheel. So, if we assume that the crank position sensor is near the flywheel end of the crank, then when twisting is occurring the ECU must have a somewhat incorrect 'idea' of where TDC actually is, for all but the cylinder closest to the sensor. This would affect things that are electronically controlled, throwing timings at least a little bit off.

Also, when crank oscillation is occuring (with more flexure toward the front), because the camshafts are driven from the front of the crank the valve timing will be correct at cylinder No:1, but progressively less correct for cylinder 2, cylinder 3, and most incorrect for cylinder 4 (even so, not hugely wrong, but valve timing is being thrown off to some degree).

And, crank oscillation may affect the consistency of the timing belt tension (or chain), which could cause valve timing to become a bit 'scattered' (might also lessen belt life...).

So, a potential number of cascading issues related to crank oscillation, that could affect power to some possibly significant degree (over a narrow spread of rpm) if significant crank oscillation is occurring? Unexplained 'flat spot' in the power band perhaps...?

Regards,
John.
 

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I found a fascinating article here:

Damper Technology White Paper : HarmonicDampers.com by BHJ Dynamics, Performance Harmonic Dampers, Harmonic Balancers and Specialty Crankshaft Vibration Dampers

Relatively easy to understand the main points, with no in depth and utterly bamboozling mathematics. The article confirms some of the things I thought I knew, and some of my speculations. But it did boggle my head a bit with the complexity of the physics behind damper function and development. I can't imagine that an engine manufacturer would go to the trouble and expense if their engineers didn't think it necessary to use a correctly designed damper...

Regards,
John.
 

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There'd be some 'drag' from the oil in the shaft bearings, and creating a vibratory force to counteract engine vibration will require some energy, the belt would be very slightly parasitic too. Seven HP at 7000rpm seems plausible, but of course will be less at lower rpm.



My 2 litre TS, I rarely rev it over 5,500rpm, there is just no point, the power is not up that high, certainly not at 7,000rpm. Therefore, I won't be getting close to a 7hp reduction in parasitic loss from having deleted the balance shaft belt.

I think the 2 litre engines' power drops away at higher rpm because (it's my understanding) that it has the same sized valves as the 1.8 litre has. So, the 1.8 makes its' best power at higher rpm than the 2 litre does. This may well account for the per litre power difference between the 1.8 and the 2 litre engines, i.e. the 2 litre is a bit strangled by its' valves...

Regards,
John.
You could be right about the valves, the complete heads, induction and exhaust system are the same. 1.8 TS is rated as 144hp at 6,500rpm and the 2.0 as 155hp at 6,400rpm. Surprised yours doesn't pull much above 5,500rpm, it should do. Mine didn't suffer much drop off after 6,500rpm. I'd not hold it there beyond 3rd gear but in first and second it was useful to rev it to the redline as the next gear would be closer to peak power.

From the Alfa technical documentation it suggests the balance shafts were to stop "secondary vibrations" being transmitted through the engine mounts into the cabin, affecting driver comfort. I'm sure they weren't in any way designed to protect the engine.
 

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Period roadtests generally found best progress with a 2.0TS was made by changing up at roughly 6800rpm. I agree with that.

Even my JTS is best going to 6500rpm as the inlet ports are not yet full of carbon since rebuild.
The JTS makes maximum power at 6500rpm according to specification.

I'd check your MAF readings on live data if it drops off at 5500rpm. You are looking for a maximum MAF voltage of as close to 4.5 as possible. That equates to a little over 400g/sec of inducted air.
I think the highest I found was 420 for a TS but strangely I recorded around 460g on the JTS after rebuild.
 

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You could be right about the valves, the complete heads, induction and exhaust system are the same. 1.8 TS is rated as 144hp at 6,500rpm and the 2.0 as 155hp at 6,400rpm. Surprised yours doesn't pull much above 5,500rpm, it should do. Mine didn't suffer much drop off after 6,500rpm. I'd not hold it there beyond 3rd gear but in first and second it was useful to rev it to the redline as the next gear would be closer to peak power.
At least with my engine, I don't find that the power drops away above 5,500 rpm, just that it doesn't feel to be making significantly more power above that. If I change up a gear at 5,500 (or thereabouts, maybe 6,000, I'm not transfixed by the tachometer, I'm generally looking at the road...), I find I'm still in the fat part of the torque curve in the higher gear, so acceleration is still quite acceptable. I'm not looking to maximise acceleration to the nth degree (I'm not on a race track). Habitual high rpm does nothing for engine longevity either...

From the Alfa technical documentation it suggests the balance shafts were to stop "secondary vibrations" being transmitted through the engine mounts into the cabin, affecting driver comfort. I'm sure they weren't in any way designed to protect the engine.
Agreed. Quite a few people do seem to think that 'balance shafts' are in some way important to 'protect' the engine, because 'common sense' says that without them the engine will obviously be 'out of balance' (whatever they think this might actually mean). Of course this is completely wrong. They do nothing to eliminate or lessen the 'second order' imbalances that are inherent in the way in which all reciprocating engines operate (though more or less apparent with different configurations, number of cylinders and engine capacity).

There is no way that these secondary imbalances can be lessened or eliminated, they are inescapably inherent with the way a piston goes up and down relative to the circular motion of the crankshaft to which it is attached (it's a geometric thing, caused by the piston moving a lesser distance in the upper part of the stroke than it does in the lower part of the stroke, relative to the rotational angles of the crank, and this principle is the same for any reciprocating engine).

Some engine configurations are often described as having 'perfect' secondary balance, the straight six being the most commonly quoted example. It doesn't really. Every cylinder in any engine has its' own personal secondary imbalance, but with some configurations the secondary imbalances from some cylinders tend to 'cancel out' the secondary imbalances from other cylinders (to greater or lesser degree depending on the configuration). The imbalances are all still there, but don't result in as much apparent external vibration (compared to to other configurations where these forces don't tend to counteract each other as much).

'Balance shaft' is something of a misnomer, they would be better described as 'anti vibration shafts'. All they do is to 'artificially' create other 'out of balance' forces which act in opposite phase to the inherent 'out of balance' vibrations, so that there are opposing forces within the engine which to some degree cancel each other out (and so reduce apparent external vibration). This is only to do with making the engine vibrate less, all the forces that cause the inherent vibration are still there, just 'covered up' by the additional forces created by the balance shafts. So, eliminating the shafts (or just taking the drive belt off) does nothing to degrade reciprocating or rotational 'balance', nor in any way make the engine less reliable.

Regards,
John.
 

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There'd be some 'drag' from the oil in the shaft bearings, and creating a vibratory force to counteract engine vibration will require some energy, the belt would be very slightly parasitic too. Seven HP at 7000rpm seems plausible, but of course will be less at lower rpm.



My 2 litre TS, I rarely rev it over 5,500rpm, there is just no point, the power is not up that high, certainly not at 7,000rpm. Therefore, I won't be getting close to a 7hp reduction in parasitic loss from having deleted the balance shaft belt.

I think the 2 litre engines' power drops away at higher rpm because (it's my understanding) that it has the same sized valves as the 1.8 litre has. So, the 1.8 makes its' best power at higher rpm than the 2 litre does. This may well account for the per litre power difference between the 1.8 and the 2 litre engines, i.e. the 2 litre is a bit strangled by its' valves...

Regards,
John.
Don't know which 2.0 TS you have but if it you don't rev it past 5500 there's something wrong with it, cause in both my 2.0 ts you can really feel it change the cam profile (at least this what i always thought because its such a big power increase) at more or less 5500rpm and it goes frenetically fast till the rev limiter.
 

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Peak power is at 6,300rpm in a 2.0 TS CF3. Rolling road figures here.


I used to find with mine it was worth revving a bit higher because changing up a gear in the 5ks would leave you out of the power band when you were in the next gear.
 

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Peak power is at 6,300rpm in a 2.0 TS CF3. Rolling road figures here.


I used to find with mine it was worth revving a bit higher because changing up a gear in the 5ks would leave you out of the power band when you were in the next gear.
Peak power at 6300rpm way past the 5500 mark, but that doesn't means it will drop like its falling of a cliff after the 6300rpm, but it looses some momentum after that point for sure, i can feel that.
But you have to rev it past 5500 rpm that's where it starts to push more frenetically!
 

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Well yes, there was something wrong with my engine, as it turns out...

The story starts with a suspicion that maybe I had an issue with one or more of the injectors, and it wouldn't be a bad idea to investigate...

So, I made a little jig that allowed me to spray 'throttle body / carb cleaner' directly through the injectors (on the bench). This was so that I could observe the spray pattern to see if one or more of the injectors was / were obviously spraying badly. The jig has an arrangement of tubes which connects the spray can nozzle tube to the inlet end of the injector, and an electrical connection from a 12V battery to the injector (wired through a button that allows me to pulse the injector open / closed by pressing the button).

Using this device showed that a couple of injectors at least looked like thay had a somewhat less defined spray than the other two, though the difference wasn't dramatic. Two of the injectors didn't visually appear to be spraying quite as 'mistily' as the other two, so it seemed a fair assumption that they may well have been performing at least somewhat 'sub-optimally' relative to the other two.

Using my new jig I then sprayed quite a lot of 'carb cleaner' through the possibly bad injectors, not that I expected this to do a lot. After a fair bit of cleaning fluid had been used, pleasingly the spray from each 'bad' injector visibly looked to have improved, and in the end I sprayed the entire contents of the large can of toxically strong hydrocarbons through all four injectors. All four injectors seemed to now spray better than they initially had, and equally (as far as I could tell without actually measuring fuel flows), but it was a very subjective judgement.

On the road, yes, the engine now runs better, so not a waste of time. Throttle response improved immediately, and at first power also felt to improve noticably. However, after the next few days, power felt to increase significantly more... (all this is purely subjective though). Power now doesn't seem to plateau above 5,500rpm like previously did, but acceleration continues strongly enough up to about 6,500rpm (or maybe a bit more, give or take).

So, the assumption / theory now is that probably two and maybe all four injectors were likely impaired by deposits and so not spraying optimally (i.e. bad pattern with poor 'mistification') and / or just not flowing enough fuel. The maximum flow capacity may have been diminished to the point that at higher rpm the injectors couldn't flow enough fuel and the AFR leaned out, causing some loss of power above about 5,500rpm. Not proven but doesn't seem unlikely considering the above...

I still don't rev it much higher than that (except on very rare occasion...). It just feels a bit brutal to habitually thrash a road car engine like that, and of course it uses a lot of fuel, is inviting potential trouble, and, I'm a grown-up now...

Regards,
John.

PS
All four injectors showed a visually 'flat' spray pattern, which at first seemed odd and wrong since each injector has four tiny spray holes seemingly equally oriented in a radial square pattern at the tip. Even so the four holes don't all spray in the same direction (relative to the tip). It occurred to me that since all the injectors were doing this that it must be correct, but it took me a while for the penny to drop.

The flattened spray pattern is squirting what are in effect two side by side spray clouds (but coming from four jet holes) in a pattern where one 'spray' is pointing directly at the back of one inlet valve and the other 'spray' directly at the back of the other inlet valve. This must assist fuel vaporisation because the valves will be hot, as well as reducing formation of larger droplets, 'port wetting', and fuel pooling because fuel is NOT sprayed as much onto the relatively cold port walls...

Regards,
John.
 
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