i don't think it's going to be engine geometry limited as opposed to valvetrain limited. how good are the stock valvesprings? is the stock direct acting setup able to withstand the revs? or would we need to upgrade in terms of materials, weight, etc.?

engine geometery in the 4B11 is SOLID. the K20 has an inferior rod ratio yet can safely rev to 8600. its valvetrain is proven though. if the head is up to it, 9000 rpm is easy.

for reference:

4B11 is 86 x 86 with 149.25mm rod which translates to 1.74 rod ratio.
K20 is 86 x 86 with 138.46mm rod for a 1.61 rod ratio.
and just for fun the F20 is 87 x 84 with153mm rod for a 1.82 rod ratio.

 

Thanks for the data. Seeing this, I definitely agree the valvetrain is going to be our issue (after the stock turbo, of course). Man, that F20 was insane, wasn't it? Sucks it got replaced by the crappy F22.

 

Has anyone actually trapped that speed in a X at that RPM in fourth. I ask because in theory my IX should be able to trap 119MPH @ 7600RPM but that is not the case. Don't forget trap speed is your average over the last 66 feet of the 1/4. From my experience the gear limited top speed per RPM is about 2-3 MPH lower than you will actually be able to hit in the traps.

Meaning that I would guess that 7800RPM in the X is only good for about 114 or so....again just a guess from experience.

 

114 is better that 111. People are trapping 110-111 now holding the limiter.

 

yea, sucks that the F22 makes more HP and TQ

But back on topic, id love to see this motor breath some more in the upper RPMs, but is the turbo up to it?

 

I'm at 7903rpm now. It holds power way better than my VIII or IX did. Its only 3whp under peak at the limiter. That's pretty cool.

 

Wow thats great!

 

Now get on a closed road or the track and see what it will actually hit in 4th gear at 7903. Hopefully close to 120 maybe 118.

 

Don't need a roadcourse. Gear speed data calc says 117.8mph on stock tire size. YMMV a tiny bit due to tire wear, deflection, and amount of inflation.

 

This is going to be all about the valvetrain. We won't see 9k rpm safely untill better cams and valve springs. I wouldn't rev to 8k personally on a daily driver X.

 

Stock fuel cut in the ECU is 7599rpm. I moved it up 300rpm, and the software settled with 7903. This is about 100rpm higher than people set the 4G63. Unlike the 4G63, the 4B11 loses almost no power up top from peak to the new limiter. I suspect it would start dropping rapidly soon after.

I don't hit the rev limiter hardly ever, but its nice to have it if I needed to drag race and hold fourth.

 

I don't think its hurting the motor in anyway, this motor can handle it. I think with MIVEC tuning this thing will be a beast

 

The Mivec tables have been custom tuned in my car, that's one reason it holds power up top.

 

Thats great, glad some extensive tuning has been done, and this is just the beginning. Wonder what we will see when new cam options come.

 

Would you raise it if you didn't have this tune?