Unofficial 2.4 Blocks Thread
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Joined: Jun 2003
Posts: 697
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From: Nothern CA
Piston accelleration rates will be affected by the rod ratio as piston movement at the top and bottom are affected (long stroke theory, ref. chevy 383s). Piston kinetic stress is a function of piston mass X acceleration/deceleration rate but related to piston speed. The skirt binding type and piston slap effects on the piston will decrease as the pivot nears the crown. Thin lands will support less pressure but thiner stronger rings are a viable option. This approach is being implemented on the 9 and was a friction reduction stategy in the BMW 325 Eta engine.
Just a few points that I hope have value to this discussion.
BTW Piston oil squirters may or may not be required for piston quenching as water, water/meth injection can be used for this purpose.
Just a few points that I hope have value to this discussion.
BTW Piston oil squirters may or may not be required for piston quenching as water, water/meth injection can be used for this purpose.
Originally Posted by Ted B
With a 100mm stroke, the piston travels 200mm/rev, which at 7800rpm = 26.0m/sec
As far as I can tell, the 88mm stroke equivalent at a piston speed of 26.0m/sec is 8863rpm.
For perspective, this is the same piston stress equivalent of a 5.0L Mustang GT engine turning over 10,000 rpm.
As far as I can tell, the 88mm stroke equivalent at a piston speed of 26.0m/sec is 8863rpm.
For perspective, this is the same piston stress equivalent of a 5.0L Mustang GT engine turning over 10,000 rpm.
Originally Posted by propellerhead
What is a realistic redline for a well built stroker using a 100mm crank? I've been quoted "up to 9,000 rpm" by AMS on the phone and I've also read it posted by Buschur as well. Spinning a crank at that speed creates a mean piston speed of 30m/s. By comparison, F1 engines in the mid 90s were seeing mean piston speeds of 27m/s. I'm sure the machine work of an F1 engine is far better than that of the factory and certainly much better than that of any machine shop you'd take your parts to to have balanced and fit. It seems that a maximum sustained redline would be around 7,900 rpm yeilding a mean piston speed of 26.34m/s. How fast can you spin a stock bottom end? I seem to recall that the stock bottom end can handle 9,000 rpm (26.55m/s).
the biggest thing with the 2.4 4G64 liter bottom end is the massive amount of torque your going to make and it has a better rod ratio then the 2.3 stroker in the 4G63 block due to the taller deck height. Your going to make up for the lack of high top end by having crazy low end power. And vice versa, with the 2.0 your going to have less low end and crazy top end. I saw all of RnR's posts about the 2.4 liter being able to rev to 8500 RPMs easy, my car (99 Galant) comes with the 4G64 stock, and it has a factory redline of 6300 RPMs, I dont think your gonna push that motor to 8500 safely, the load its gonna put on the rod is gonna be crazy, the geometry of the motor is mean for the low end power, not high rev ability. Talk to the guys at magnus they have been doing 2.4 bottom ends in 1st and nd Gen DSMs for years, they will tell you flat out, "Do not rev that motor past 8,000" Trust me its a bad idea to rev that high, you will still make plenty of power all the way to 8k and your turbo will probably spool 500RPMs sooner. An interesting concept that magnus did was they put a EVO crank in a 4G64 block, which makes for a 2.1 liter that revs to 9,000, crazy top end power, bore it out and it would be a 2.2 liter, have a little more low end torque because of the longer rod ratio, but still have high rev ability.
Originally Posted by VTEC Killer
Thats why I suggested the EVO crank in the 2.4 block, it makes for a square motor, bore and stoke are exactly the same, i believe 88x88
Hmm, this sounds very interesting. A 4G64 block with a 4G63 crank and head. A little more grunt and 9,000 rpms. I think, in the future, I may have to look seriously into that.
Originally Posted by VTEC Killer
...have a little more low end torque because of the longer rod ratio...
Originally Posted by YellwTyper
Seems to me you guys should consider proper stroke:bore ratios. Once you increase one or the other you have to sacrifice your revs. I like the idea of how the 2.4 block as a taller deck thus you can increase bore to match it but 100mm stroke and 86 stroke sounds like very bad ratios to begin with. A good example of good rod:stroke ratio would be the b16a(might be wrong on coding)with a 86mmx86mm rod stroke respectively. Id say going 2.0 and boring it from a 85mm bore 88 mm stroke to a 86.5mmx88mm would further net us a closer ratio.
To me (86.5:88)0.983 ratio sounds better then a (86.5:100)0.865.
To me (86.5:88)0.983 ratio sounds better then a (86.5:100)0.865.
Keith
Looks like someone was getting rod/stroke ratio confused with bore/stroke ratio.
Where bore/stroke ratio is concerned, the 4G63 is already undersquare, which is obviously intended to give good torque for its relatively small displacement.
Obviously, installing a 100mm stroke crank gives a stroke worthy of a big-block Chevy in this small 2.0L engine. This further increases torque potential, but the tradeoff is increased friction with greater piston and bottom end stresses.
Where bore/stroke ratio is concerned, the 4G63 is already undersquare, which is obviously intended to give good torque for its relatively small displacement.
Obviously, installing a 100mm stroke crank gives a stroke worthy of a big-block Chevy in this small 2.0L engine. This further increases torque potential, but the tradeoff is increased friction with greater piston and bottom end stresses.