Lightweight Engine Internals & Flywheels Pro's Cons

[924Srr27l]

Lets start with the Crank first:

Lindsey Racing's website suggests:

Knife edging the crank is mainly for increasing horsepower by reducing the windage loss in the crankcase while reducing the crankshaft's rotational mass, allowing for the engine to accelerate faster.

My 951 worked Full Lighten Spec Crank above the stock 2.5 N/A

More power ? Any Opinions fire away.......

R

 

[John Sims]

Best if you just tell us all about it Rodge as none of us are going to know as much as you.

On those lines, considering Porsche might know a thing or two about manufacturing engines could you explain why they make their cranks the way they do rather than the Lindsey way which you obviously consider far superior.

 

[Cater_Racer]

I had the crank knife edged on the Mini Cooper S with great results, but I think it is one of those things that only makes sense if done in conjunction with lightened pistons (Omega flat tops on the mini).

It's a bit specialist I leave that to the engineers at MiniSport. Wouldn't even consider it on a road car.

 

[924Srr27l]

Best if you just tell us all about it Rodge as none of us are going to know as much as you.
On those lines, considering Porsche might know a thing or two about manufacturing engines could you explain why they make their cranks the way they do rather than the Lindsey way which you obviously consider far superior.

Thanks John,

When I was building my project I scanned many forums, and internet write up's on many components and many have conflicting
responses and advice. It's often difficult to know what's not marketing, whats Hype and what the real truth is about many changes
that can be made to any car to Improve Performance. Hence we are all , or should be learning New things every day and a group discussion should be possibly to sift the truth from the myths, only as per your Recent Post any adverse Forum etiquette is not assisting anyone, the members, the club etc..

I don't think you seriously don't understand the differences from standard production use and modified road car's
(Lets leave dedicated Racing car's away from this) and asking things like why didn't Porsche do this, fit this etc...is not
appropriate as most people should know or be made aware performance modifications have their downsides hence why Porsche and other manufacturers will not fit or produce a car that may have some adverse characteristics and impede sales.

R

 

[924Srr27l]

I had the crank knife edged on the Mini Cooper S with great results, but I think it is one of those things that only makes sense if done in conjunction with lightened pistons (Omega flat tops on the mini).
It's a bit specialist I leave that to the engineers at MiniSport. Wouldn't even consider it on a road car.

Thanks Cater.. that sounds like a good result for the A series, and your right often his type of subject and purchase
is in the hands of builders you hear and are told things which are commercially driven, in your case and mine the differences
are massive and hence I'd report to anyone asking it's a Plus.

However I'm aware that there are pitfalls for a lighter crank for road use unless the car's mass has also been lightened too which was lucky in my case, but in a stock 3.0 S2 for example or 952 it could be a duff move.

R

 

[John Sims]

....I don't think you seriously don't understand the differences from standard production use and modified road car's
(Lets leave dedicated Racing car's away from this) and asking things like why didn't Porsche do this, fit this etc...is not
appropriate ...

On the contrary. I think it is entirely appropriate in a thread dedicated to fitting alternative parts. Surely in fitting something non standard one should understand why the original is the way its is and what the pros and cons of the alternate part might be.

And therefore, why don't Porsche (a sports car manufacturer) make their cranks like Lindsey do?

 

[BlackMagic]

A significant element is likely to be the trade off between power/drag and rotational mass, and the desire to make a long lasting, smooth and civilised engine. Losing that much weight off the lobes is likely to change the balance of all the rotating parts (remember that the lobes on the crank will be part of the moving mass that includes the pistons, con rods, etc.).

Also remember that Porsche built in balance shafts to help smooth out a very high displacement 4 cyclinder engine. If you really want to cut down on rotational mass take out the balance shafts and associated bits but I am not sure I would want it as an everyday engine.

William

 

[924Srr27l]

....I don't think you seriously don't understand the differences from standard production use and modified road car's
(Lets leave dedicated Racing car's away from this) and asking things like why didn't Porsche do this, fit this etc...is not
appropriate ...

On the contrary. I think it is entirely appropriate in a thread dedicated to fitting alternative parts. Surely in fitting something non standard one should understand why the original is the way its is and what the pros and cons of the alternate part might be.

And therefore, why don't Porsche (a sports car manufacturer) make their cranks like Lindsey do?

Ok fair enough i must be mistaking you for another member as I thought some of the characteristics have been
in our conversations before?

It's very Simple, lightening the crank loses build up inertia from the heavier crank that Porsche designed for these road car's
Think of it as heavy v lighter revolving shaft (weight) which for example on tickover the heavier crank has more (Inertia) power
Once you engage 1st gear and release the clutch the car will only require a very small throttle application on a stock car because the heavier reciprocating mass has (stored energy) to get you moving.

A lightweight Crank has less built up energy and will require more throttle (RPM) to get the car moving and will be difficult to
pull away smoothly. (Not ideal for Joe bloggs who's wants a nice drive in his Porsche production car)

If you lighten the car this effect will become less so, as my example which has a substantial loss of inertia from standard.
I've got my tickover set at 1000rpm on purpose to assist pulling away.

The benefit's of a lightweight Crank & Flywheel are for more performance , a faster car that's all I'm interested in.

Porsche did not fit a knife edged crank because owners would have issues not just when pulling away, but also at other speeds, and even in deceleration a lighter crank will slow down quicker as it's not got the heavier inertia to keep the mass going along. This will reduce Fuel consumption another downside for Porsche if they decided to fit a lighter crank.

There's not many performance components that when fitted to a car will have a downside.

R

 

[924Srr27l]

A significant element is likely to be the trade off between power/drag and rotational mass, and the desire to make a long lasting, smooth and civilised engine. Losing that much weight off the lobes is likely to change the balance of all the rotating parts (remember that the lobes on the crank will be part of the moving mass that includes the pistons, con rods, etc.).
Also remember that Porsche built in balance shafts to help smooth out a very high displacement 4 cyclinder engine. If you really want to cut down on rotational mass take out the balance shafts and associated bits but I am not sure I would want it as an everyday engine.
William

Yes, Well described and as you say it's not for everyone in an everyday car, or even a weekend drive.
I've only got away with it, because the car is 250kg less than it was originally.

I paid particular attention to balance all the reciprocating parts and the 6+ hours of Mapping
perfecting the tune (Air / Fuel Mixture) make for very able and placid car to drive at low speeds in high gears.

I also reduced the Balance shafts to "half" weighted & Polished version's from an American company Broadfoot Racing

R

 

[John Sims]

With regret - in accordance with the admin post - Forum Etiquette. This thread is now locked.

 

[John Sims]

I have cleaned this thread and reopened it. I would be obliged if people would read again the notes in the thread "Forum Etiquette".

We are a forum known for its friendly camaraderie (and a little leg pulling) and will not tolerate name calling and other unpleasantness.

We will not be dictated by mob rule. If you have a personal issue with someone then PM them and discuss it with them personally. Perhaps they might better understand your grievence and you come to appreciate their stand point.

As volenteers the admin and mods don't have time to run around sorting out every issue or hold people's hand in the playground. You are all adults now behave like it.

If I have to close another thread I'll be putting people on moderation and won't be in any hurry to appove their subsequent posts.