not trying to start a debate, just wanted to give an update on the mod for those interested.

here is the dyno that another member posted, im sorry i dont remember your name to give you credit.



no power is gained, but it gives considerable room to play with in vtec and there is increase in power after the shift.

 

Hows does the car feel to you?

I know some members who had done this mod mentioned that the car felt quicker with the AP2 ECU installed. More VTEC powerband is nice, but then working hard to keep the car in VTEC is also fun

 

you can feel less torque in the middle, but it feels good after you get used to it, esp when u see the red flash along with the engine noise only at 9k.

i first met the s2k with the ap1 and missed it ever since.

 

Do you just take it a little further than 8k, or do you take it all the way to 9k on a regular basis? Doesn't there have to be a fairly obvious reason (engine damage or loss of performance) why Honda didn't keep the 9k redline? I'd love to drop the ECU into my car and drive around 1k higher on the tach, but it just doesn't seem like a great idea somehow...

 

FWIW, peak piston acceleration in the 2.2 at 8565rpm is equal to peak piston acceleration in the 2.0 at 9000. Honda knocked rev limit rpm down from 9k(?) to 8200(?) when they went to the 2.2.

They must have wanted increased longevity. Seems to me engine life of the 2.2 at 8565 should be about the same as the 2.0 at 9000. Taking the 2.2 to 9k will increase piston acceleration by ~10% relative to the 2.0. Life vs. stress is a logarithmic relationship, so life of the 2.2 at 9k might be something like 1/2 the life of the 2.0 at 9k.

If my 2.0 ever pops, I'll drop a 2.2 in and rev it to 9k. Everything's gotta die sometime!

 

Due to the modified rod geometry however, piston to cylinder side loads are greater for the 2.2 even when piston speeds are the same.

 

Right. My previous post only looks at peak piston acceleration, not side loads. Increased rod angularity is taken into account, but only inasmuch as it affects peak acceleration.

 

So to increase the Rev limit for AP1 to 9500 would be marginally better then to increase AP2 to 9000?

 

Better THAN, not "THEN"!!!

Ok, now I can answer...

Peak piston acceleration of 2.2 at 9000rpm = peak piston acceleration of 2.0 at 9455rpm.

Should be "better" for performance to have a 9k 2.2 than a 9.5k 2.0.

Generally, the displacement gained by going to a longer stroke gives more performance than lost rpm takes away. This is because loads/stresses increase roughly linearly with stroke, but with the square of rpm. So, if you increase stroke by 10%, theoretically you'll only lose on the order of 5% off of max rev capability.

 

Since the Ap2 will make power past 8k, roughly 8500 without modification, I think that would be a sweet spot for ap2.

* I'm just not sure what reliablity you're taking away from the car *