aye folks,

     i own a 95 240sx with the KA....owned for 4 years now and have been going back and forth all those 4 years about swapping for SR20, RB25, or turboing the KA, and finally ended up just wanting to keep the KA and keep it naturally aspirated.....my thoughts and dreams started with realizing that the S2000 makes 240 crank HP on 4 cylinders, and thinking if i got that level of HP, i'd be FULLY satisfied with the driveability of the car and reliability of the car, realizing that it would be hard, but if achieved, somewhat unique and fun to drive......this months issue put a damper on my dream when it stated that the KA motors have problems with spinning to higher RPM's...i wasn't looking for some mad 9500RPM redline, but atleast 7000 or 7500...obviously it redlines now at 6500, but doesn't make much power past 5500....apparently due to long stroke-to-rod ratio and something about a half-counterwieghted crankshaft....either way....i know i can get around 175-185 wheel HP on this motor just using the slight plethera of bolt ons and a bit of head work, but as for this bottom end....will that be the dead end of the beast?? i'd like some true technical advice.....gracias amigos.....safe driving!!!

-misterbooze  

The biggest problem the KA engine is breathing. Even the later 16v engines do not breath well due to the timid overlap and weak speced lobes on the cams. Take the head off, have it flowed.. I prefer Extrude Hone... and drop in some decent cams.. from there you will have to bore and flow the intake and add a decent exhaust and header.. and you should be good for horsepower.

Remember, yes the S2000 needs to spin to 8500 rpms to make 240hp... but it is only a 2.0 (I know the later models are a 2.2.. but then only spin to 8 grand). Horsepower is torque times speed. The KA engine is a torquy engine. If you can get it to make power all the way to redline, you will hit an easy 200hp... even if redline is only 6500rpms.  

By speed you mean RPM, right?

Torque X RPM=HP?  

yes... speed meaning RPM  

good deal, thanks fellas....any more knowledge helps....but in the recent issue of SCC they talk about the rod-to-stroke ratio being long and that's why it has problems with making power at higher RPM's....so any advice on what to do with that????  gracias peoples....

misterbooze  

you need to re-read it.. the KA engine has trouble revving to high RPMS due to the ratio. The pistons are at near supersonic speeds at 9 grand.. sticking with the stock redline, you can still get the car to make power with proper flowing of the heads, cams, and an intake and exhaust... and perhaps little more fuel  

Go read the current SCC.  They did an article on the KA engine.  BTW, by the time you do the set up you could have paid for an SR20DET.  

I think you're confusing the Nissan KA24DE with the Honda K24A... So bloody similar in naming conventions, it's easy to see how you mixed 'em up. Then again, you'd probably notice a problem when you tried to fix an '06 Civic Si valvetrain to the top of your Nissan block  

well most people call the ka24de the "ka" while the honda k24a is called "k24" but maybe that's just me.  

Because of Honda I should have said KA24DE.  In the current issue they have an article on 240sx build up.  

hey fellas, sorry for all this confusion...i haven't mistaken the two motors, but i wonder why if they have the same displacement then how come the K24(honda) can rev higher AND make power that high, and the KA24de(nissan) for some reason can't....hmmm, i guess that should have been my question in the beginning....and as for the time and effort in comparison to dropping an sr20 in.....i have 2 friends, both with S13's and stock sr20's....just basic exhaust and boost control, and they are always having fuel issues, or some issues...oil problems, cooling problems....just random junk....i figure with the setup i am dreaming, i could maitain a good solid reliable, but more so, a responsive, quick revving, fun motor to hear and drive.....gracias amigos....

-misterbooze  

The Honda engine has Vtec, for starters.  I know Nissan has something similar, but Im not sure if they put it onto this particular engine.  Other than that, the answers have pretty much been right in front of you.  The engine is clunky.  Thats really all there is to it.  

displacement does not mean a thing when comparing two engines.

The Honda K24 is a short stroke, big bore engine. "oversquare" is the term they use. The bore of the piston/Cylinder is larger than the stroke of the crank. This is how Ferrari and F1 engines are set up. They are designed to REV!

The KA24 is a LONG stroke and small bore engine. Much like an ancient MG or other english "tractor" engine. It's piston size is much smaller than the stroke of the crank.

What this means... with both engines at 6 grand on the tach.. the pistons on the honda engine are moving slower because they only have to cover a small distance. On the nissan engine, they have to cover a MUCH longer distance in the same amount of time... so they move that much faster to accomplish this.  

Quote:

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This is how Ferrari and F1 engines are set up.

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I'm just wondering, is there a way to decrease the stroke of the engine.  I'm guessing the better way to go is to increase the bore of the cyinders and pistons.  It seems like it would cost a alot but it might be worth it if the powerband is increased that much right?