|WikiProject Engineering||(Rated Start-class)|
Head design should be stressed. Springs are a compromise between maximum RPM before valve float occurs and frictional losses. Springless (pneumatic) designs were used in Formula 1. Valve size and material play a major role due to the reciprocating forces of weight. More lighter valves can go faster than fewer heavier valves. Lastly, with cam-in-block designs: pushrods are a limiting factor. --Novous (talk) 03:51, 24 June 2008 (UTC)
Everything resonates at a certain frequency--whether it's a guitar string, a house, or a crankshaft. "Resonating" meaning the harmonic frequencies of the object line up and start reinforcing each other. Any substantial time at this RPM and a crankshaft, rod, or piston will literally grenade itself. This is a major contributor to an engine's "redline." This should be included in the article. --Novous (talk) 03:44, 24 June 2008 (UTC)
Do manufacturers really destructively test engines to find the redline? Why don't they simulate or calculate the value? --Mikeblas 00:36, 25 May 2006 (UTC)
- I'd imagine that experimentation with an actual engine would be easier and more accurate than trying to simulate or calculate the value. Auto manufacturers are willing to sacrifice entire vehicles for safety testing, so I imagine that they'd be willing to sacrifice a few engines to determine the redline accurately--Tabun1015 20:39, 5 July 2007 (UTC)
They mathematically determine it, and make tests to make sure. All springs resonate at a frequency, and can only hold so much tension before "valve float" occurs (depending on valve inertia and spring tension). Cranks, pistons, and rods all resonate and can grenade. Engineers aren't building engines and "seeing what happens." It's a very precise process. Novous (talk) 22:29, 28 January 2009 (UTC)
As of 2004, the S2000 redline is 8200 rpm, which would not make it the "highest production car redline" anymore. If 9000 rpm is indeed the highest redline in production, the Renesis would hold that title.
"If 9000 rpm is indeed the highest redline in production, the Renesis would hold that title." - not true, 00-03 models had a the 2.0 liter f20c engine that produced 237 hp and 130 ft/lbs of torque, it DID have a 9k redline, but in 04 they stroked it to 2.2 liters calling it the f22c. The stroking lowered the redline to 8200 rpm, the new engine put out the same hp but had an additional 30 ft/lbs of torque pushing it to 160. The reason for the engine modification was that with the f20c you had to rev it to about 3k to get it moving anywhere, with the stroking came a broader powerband. - gman182 —Preceding unsigned comment added by Gman182 (talk • contribs) 05:24, 23 January 2008 (UTC)
Currently, the article states that the RX-8 has the highest redline of any in production rotary powered car. If it is true that the RX-8 redline is 9400, while the LFA has a 9500 redline, then should the RX-8 even be mentioned? The RX-8 is THE ONLY in-production car with a rotary engine, so mentioning it seems silly since it could have a redline of 2500 and still make the statement in the article technically true. It either has the highest redline, or it isn't worth mentioning.
Piston speed and redline
At the beginning of the article, it is stated that piston speed is unrelated to redline, but this is actually often applicable because it remains relatively constant due to cubed-squared scaling of components and stroke dimensions. While I feel the piece relating it as a misnomer is not incorrect, I do think it is inappropriate to completely dismiss it. — Preceding unsigned comment added by 22.214.171.124 (talk) 02:21, 28 November 2014 (UTC)
Redline relates to cars.
" Examples of performance automobile piston engines"
Agreed - I've cut the list down substantially to a few examples highlighting typical values and well-known vehicles - please feel free to add other relevant examples (other racing engines, N/A diesels and a more up-to-date N/A petrol than the Nissan Micra would be good) but try and keep it to notable examples. Jellyfish dave (talk) 14:11, 30 May 2017 (UTC)