Project peperami - (A2Steve)

Is there any reason why a flywheel designed for a 4 cylinder car won't fit on a 3 cylinder car? I'm wondering whether the imbalance of the 3 cylinders may need a different flyhweel??

Any help greatfully received.



Hmmm. I'm probably no better bud but are the weights to offset the missing section in the push cycle not incorporated into the crankshaft instead? Three cylinders and four strokes and all that? The flywheel carries the rotation through the lacking phase to prime the next compression so I think it's just the mass and size which vary to give sufficient retained energy for the compression, smooth out the power cycle but not introduce too much lag... of course that might be bollocks.


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There is a separate balance set up, flywheels need to be perfectly balanced and so a 4 , 5, 8 , 12 cylinder flywheel at all just balanced regardless of the number of cylinders.

But that is not the only thing to consider, fit and weight and diameter etc. have to be spot on. I wouldn't consider fitting a nin standard one.

Having your current flywheel lightened though is an option, it gives a quicker throttle response, especially on a tuned engine like yours.

Steve B
 
That's the issue though Steve. I don't think a standard one is going to last all that long. I can't afford to change it every 18 months.
 
Is there any reason why a flywheel designed for a 4 cylinder car won't fit on a 3 cylinder car? I'm wondering whether the imbalance of the 3 cylinders may need a different flyhweel??

Any help greatfully received.

Can't find the thread but thought this was discussed recently (with JIGSAW ?) and he had found the 3 cylinder flywheel incorporated additional counterbalance weights because there was insufficient space to add this to the crankshaft bobweights.
He was working on a 4 cyl size flywheel which mirrored the 3 cyl design, and had been talking to a dynamic balancing company about a custom fixture to do the final balancing after machining.

Cheers Spike
 
On a race engine (such as in my previous Drag cars) it was critical to get the flywheel balanced to the "nth" degree, one small imbalance and it can cause a catastrophic failure when reviving that high. So I cannot imagine why you would deliberately imbalance it to compensate for the three cylinder design, there needs to be a different method of making up for the 3 cylinder crank etc. and that is why there is a separate balancing shaft.

I am no engineer and so I may be way off base but I am pretty sure the circular flywheel needs to be perfectly in balance.

Steve B
 
This is an extract from the link Catnip posted and shows why the 3 cyl engine uses a different flywheel solution

Cheers Spike
 

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As I've mentioned previously Steve, I had the UK importers of LuK trying to find a solid flywheel for me a few years back with no joy. Between us, we literally exhausted their entire catalogue, and not just VW clutch kits either.

I suspect that solid would require some customisation of an existing application or even custom making from scratch. However, things may have changed in the interim.
 
As you can tell from my ignorance i'm not massively clued up in this area. What differences are there between the tdi75 solid flywheel and the 90's dmf?
 
I wouldn't have thought that even the remapped 150 will get close to 450nm anyways.

4 year warranty cant be sniffed at but I suppose it depends on any gotchas in the small print.
 
Just heard back from the company and yes it does fit the TDI 90 and they state it will handle up to 450nm. Any opinions from the well informed?
 
When moving from a dual to single mass flywheel there is an inherent risk of gearbox noise (gear chatter) Each engine model will have its own characteristics and it's likely the 3 cyl engine with a short, torsionally stiffer crankshaft may be least affected. Any noise / vibration is also subjective and some owners find it quite acceptable and a worthwhile trade off against the potential future replacement costs of a DMF, especially if the engine is tuned. I've not however found any comments from 3 cyl tdi owners who have made the switch

This article gives a reasonable balanced view of the pros and cons - http://www.torquecars.com/tuning/dmf-solid-flywheel.php

Cheers Spike
 
Thanks again Spike. Where would we be without you? :)

Noise I can live with if it means I can use the cars full potential without worrying about it going bang.
 
Just heard back from the company and yes it does fit the TDI 90 and they state it will handle up to 450nm. Any opinions from the well informed?

What concerns me most about this is that the TDi 75 and 90 have different pressure plate and freewheel diameters. There's around 12mm between them, so I'd assume this kit will include the smaller parts, if it'll fit in the 90, as the 90 parts will not fit into the housing of a 75.

I wonder if they're willing to reimburse two lots of labour if/when their kit is found to be unsuitable?
 
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