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No, I'm not reffering to the authors of the classic "Ace of Spades". Now that I think about it, didn't they make an appearence on "The Young Ones"? Sorry, I digest


What I was wondering was what factors limit an engine's max rpm range? In other words, why do some engines max at 5500 and others max at 9k? (and F1 gets ridiculous) Is there anyway to improve it or is it based on the tolerence of the individual components? And what's the weakest link in that senario? Lubrication? Valve springs?

Thoughts? Theories? Sarcasm?

Just being curious
 

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Weight mainly - revolving at high speed and the strength of the components - you probably could increase the rpm range by lightening the flywheel,pistons and rods etc and having the whole lot balanced professionally. Don't foget though that F1 engines are designed for about 200 miles and some of them don't even make that. Lenght of stroke will also make a difference as shorter stroke engines should rev higher but at the loss of torque. Valve bounce, I would think is unusual these days but stiffer springs would take care of that.

Mike
 

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I agree with LocoSaab - reciprocating mass (the pistons, con-rods, etc.) is usually what will break things if you rev too high. However, even if you don't reach this limit, piston speed is a major factor in bore and ring wear. The wear rate increases significantly as the piston speed increases.

A shorter stroke will give lower piston speeds, so the Saab 2.0 engine should be capable of higher RPM than the 2.3.

I know that when I used to tune my Minis years ago, valve bounce was considered to be a limiting factor and a good one to have. Stronger springs would be a good idea up to a point, but fitting valve springs so strong that valve bounce no longer limited RPM was fine except that then the rev limiter became a broken crankshaft. I've no idea how high a 9000 engine will rev before valve bounce becomes a problem, but at least there is a separate rev limiter.
 

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 reciprocating mass  [/b]
That was the word I was looking for but was up just after 5.00am this morning - Bill, I too started with Mini's, Coopers etc and finally a 1275GT with a 1400cc engine from Avonbar Racing in Surrey - used cut down Simca pistons, 45DCOE,544 cam, balanced etc and was producing 100bhp at wheels when I took it to rolling road in Pitsea - can't remember who's - would pull to 7000rpm - pain to drive but fun from time to time. Re-built the engine and box in my bedroom much to parents displearsure and also forgot that I had to get the whole thing downstairs.
 

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theory...
reciprocating mass..most important
titanium conrods and massively cut down pistons help the f 1 boys
stroke length is also a factor
balance of the engine is also a limiting factor 'blue-printing' the engine (matching al the components to very fine tolerances) can help minimise the out of balance harmonics that can shake an engine to pieces at high rpm as 4 cyl 4 stroke engines are inherently out of balance...
valve design to minimise bounce by using
strong springs or a desmodronic (love that word !) action..or air actuators
imho these are the main contributors to rev limitation
 

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Obviously they build in a safety factor when setting the rev limit - I wonder how big it is for Saabs ?

I wonder because my Mazda 2.5l V6 was limited to 7,000 but I read that the mean piston speed is so low in this engine that they could be taken up to 13,500 on the track without any modification the the main moving parts.
 
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