High Revving KA24DE Theory help

[kpjo4]

Hopefully I can get a good tuner to tune in and school me; food for thought :).


I understand the KA24DE is an undersquare motor, and one of the main characteristics is that undersquare motors are not rev happy. My question here is how does Honda get their undersquare motors to rev that high? There Bore to stroke ratio in the GSR B18C1 are near identical to the ka24de, what is the main fault in the ka24de that limits this?

My initial guess was that the main reason why they are kept in the lower range in the power band is the head flow of the factory head; now when you compare the head to a SR20DET the factory SR head outflows the KA, but since the width of the KA is different there is more potential and it will eventually out flow the SR Head when both are ported to the max and polished. Would it then be able to use the higher RPMs of the KA, IIRC the valve port of the KA is a bit longer to also help accommodate to create some TQ compared to the SR.

Another though why I feel a high revving KA is superior to a SR is due to the tappet design vs the rocker arm setup.



Unless my theory of the KA head flow efficiency to rev range what is the major weakpoint of a high revving characteristics of the KA? Rod design, Rod Weight? I'm calling bullocks on anyone that says the conventional crap saying because of long stroke, as I stated High revving B series Honda motors have near identical bore/stroke ratios and are both undersquare.

Please keep this thread serious and no ignorant comments please.

[Frank_Jaeger]

Would need a fully counterweighted crank and cams to move the powerband somewhere useful. Power falls off before redline with stock cams. Really no point to a high revving KA though.

[Kingtal0n]

RB26 is not fully counterweighted.

It has more to do with the intended use of the KA than anything. Clearly it was intended to be a work horse, not a horse work.

[Bambi]

*sits back and waits for educated responses*

[[email protected]]

Assuming lubrication and bearings are capable of sustaining the load/speed... piston speed is the biggest factor in limiting rpm

It's not so much the "undersquare" as the total rotating radius, and to some extent rod length

[Juantwo3]

*also sits back and waits for educated response*

[GroundPerformance]

It's really is the long stroke of the KA that plays a huge role for it not being safe to rev high primarily due to high piston speeds at higher RPM. Just because the R/S ratio of the KA24DE is optimal just like the B16a motor @ around 1.7x:1 there a big difference in rod length and Piston size which also adds a big factor for piston travel and overall weight. You'll notice most NA high revving piston motors have smaller pistons, shorter rods and typically very skinny rod to reduce overall weight of the rotating assembly.

If you want a high revving KA this company pretty much addressed this issue by doing a hybrid L series block and KA24 Head.
L18/L20 Bottom end with KA24DE Head.

- It's running a FCW crankshaft.
- L20 rods @ 130.5mm/ Stroke 78mm which RS ratio of 1.67:1 which is about the same as K20A R/S ratio

Les Collins Racing - L18 KA24 V4 conversion (http://lescollinsracing.com/engine/projects-engine/l-series-4v)
http://lescollinsracing.com/images/Engines/Nissan4V.jpg

9aKPNevTxkk

[Yellow4g63]

A little off topic but you might want to look into a VVL setup. Not sure how much the one in the video cost tho. The fwd guys make some good n/a power out of the 2.1's to 2.4's.
http://i646.photobucket.com/albums/uu185/JosePayu/fb3c97b1-ea59-4a4b-b1fe-0bed567b6c97_zps615ea486.jpg
That one is a 88mm with 12.5:1 compression ration on 93 pump gas
http://i646.photobucket.com/albums/uu185/JosePayu/20140111_162855_zpszgtredpg.jpg
Same motor running M5 fuel.
Some of the 2.3-2.4's put down 300ish whp on the motor.

[Kingtal0n]

completely pointless. Hey everybody lets throw thousands of dollars at a naturally aspirated 4-cylinder to make what a stock 2.0L turbo does.

[waxball88]

Just boost it. Talon is right to spend that much money there are just better options. Why rev it high when a decent set of cams, proper turbo, and boost will make tons of power and torque to redline, then shift and the torque comes back in quickly.

[coty_garcia]

*brings popcorn, also sits back and waits for educated response*

[drunkmunky]

Does anyone know if he sells his intake manifold, itb and velocity stack setup?

[kpjo4]

bump! getting a bit interesting