1. WhoolioPreludee's Avatar
    So this has been bugging me about v8 engines, if pretty much all engines use the Otto cycle (yes, I know Atkinson is somewhat popular for its efficiency ) four stroke then why do v8 have their firing/compression cycles in the way they are. In other words are the cylinder cycles arranged the way they are? What if they were arranged to fire like a 4 cyl ( and yes, I understand this would make the engine be really a v4x2 with common crankpin and so on) if it were arranged in 4 cyl fashin wouldn't the power stroke be twice as powerful? And maybe lessen the need for counter-weights. The only conclusion that I can come to is that they are made the way they are for A: fuel efficiency by only running one cyl at a time (though shut-off systems are getting pretty good) and, B: so that each cyl has a power-stroke from another to help it with the compression/drag losses. Also while I know that dohc is more popular than sohc and dohc is better at fine-tuning valve actuation, doesn't dohc put more strain on the system? More oil for both cams, more friction. Plus engine has to overcome the cam's weight/innertia. And yes I know modern vvt/vtec there is no real explanation why this can't be done with a single cam. (The mitsubishi vvt uses oil pressure to var valve actuation by pressurising oil through chambers where the cam connects to the timing chain) one last thing why are engines touted as being ie: 2.4l, 5.9l, 2l, etc. When they really aren't. A 2.4l engine is really only 2.359cc. And yes I know its not a lot but then its not a true 2.4. The same applies to 4, 5, 6, 8 cyl engines. While its pretty much nothing but whats the point. Is it a tolerance issue? Is it to give the piston/rings space for expansion. The only engine that I recall is the evo 4g63 2.0l turbo engine that is the closest to their advertised engine size at 1.999cc and i remember manufacturer having more, im not sure if it was a viper or a corvette but it was .09cc over ie: 8l -8.009 cc. Anyway thanks for reading my super long post.
    Anyone got knowledge about this?

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    Last edited by WhoolioPreludee; 10-22-10 at 12:32 PM.
    10-22-10 12:20 PM
  2. syb0rg's Avatar
    Are you asking about a L8 cylinder? like a straight 8.... They have made those before. And there are very few V4 cylinder cars that were even made. Most of those belong to Fiat.

    Fuel efficiency ? Not really. Most MPI cars, including older TBI cars and Carb cars. You have fuel entering the compression chambers every time the intake valve is open... So it's really not a fuel efficiency thing. It's most likely a vibration thing. i mean if you had 1/2 of the downward pressure on half of the engine at the same time it would vibrate your teeth out of your head.

    And OHV (Overhead valve), SOHC, DOHC do allow for more power in that order due to the nature of the beast. the cams really do not put that much strain the on the crank shaft because it's still a rotational mass. Vs going from a rotational mass to a vertical pushing (push rod)...

    And the VTEC engines..... most of your early model Hondas that are VTEC are 16V SOHC engines.

    and the EVO is not a 4g63 engine. The 4G63 engine is a L4-1997cc 2.0L F/I Turbo that fit in GSX Eclipses. The 2005 Model Evo is know as a 4g63 but it is a 1997CC engine.

    but you are correct the Evo VIII is a 2.0l / 1999cc engine.

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    Last edited by mjneid; 10-22-10 at 12:46 PM.
    10-22-10 12:41 PM
  3. BigBadWulf's Avatar
    Would it be off topic to discuss rotaries?
    10-22-10 10:11 PM
  4. the_sandman_454's Avatar
    The general public are idiots. They'll get confused if they advertise as 1.999L.
    10-22-10 10:47 PM