Benefit of longer stroke
Benefit of longer stroke
(OP)
What are the pros or cons of a longer stroke crankshaft.
4 cyl 80 mm bore 66mm stroke at moment, possible to go
to 70 mm stroke.
4 cyl 80 mm bore 66mm stroke at moment, possible to go
to 70 mm stroke.





RE: Benefit of longer stroke
Assuming there is a mechanically sound package (crank, rods, pistons) for the 4mm stroke increase, I don't see much drawback (other than the cost) if increasing torque is your goal. You may or may not get an increase in peak power depending on where you are with breathing at the current displacement.
RE: Benefit of longer stroke
You will need pistons to correct pin height and compression ratio.
You will probably end up with different rod to stroke length ratio.
You will probably end up with different piston weight, quench area and skirt length.
The engine will respond to bigger ports and valves and more cam duration.
Regards
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RE: Benefit of longer stroke
Reidh
RE: Benefit of longer stroke
The bad is it will shorten the rod if deck height is locked in. This in turn will put an undesirable angle of attack on the crank. I know there is a lot of big inch motors running the long stroke with the short rod, but at what attrition rate I don't know.
The good is you can up your compression ratio without going to domed pistons..I don't know how this relates to the dynamic compression ratio.
Cheers
I don't know anything but the people that do.
RE: Benefit of longer stroke
RE: Benefit of longer stroke
It really depends on the original layout and where spare room is left.
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RE: Benefit of longer stroke
The first US VW GTI engine included lighter pistons and better rod/stroke ratio, probably to make the engine reduce the secondary vibration and thus less four-y and more civilized with the taught engine mounts. Mine was a very willing performer. A young lady described it (but, sadly, not me) as a frisky pony.
RE: Benefit of longer stroke
RE: Benefit of longer stroke
Thats not right.
The R is short for RON which is an acronym of 'Research Octane Number' and the M is short for MON which is 'Motor Octane Number'.
RON & MON apply to two different measurement techniques for determining the 'Octane Number' of a fuel and, therefore, its preponsity to autoignite.
The (R+M)/2 method, as used in the USA, provides a number refered to as the 'Anti Knock Index'.
MS
RE: Benefit of longer stroke
-Reidh
RE: Benefit of longer stroke
I'm beginning to think electric fuel will be nice - there's only one way to measure it! ;)
RE: Benefit of longer stroke
I have heard that gasoline retailers can be audited for octane, and are subject to punishment if what they are selling is lower antiknock index (R+M/2) than advertised.
RE: Benefit of longer stroke
Read these sites and you might get a lot of news.
http:/
http://naca.larc.nasa.gov/search.jsp?N=17&Ne=2
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Benefit of longer stroke