K24A2 rapid torque dropoff at 5k

[micksellergren]

When posting a KPro problem with your vehicle, please include:
2002 Civic Si
SN 341
KManager 4.3.2
K24A2 with 50* VTC gear limited to 40*
RBB intake manifold with EP3 throttle body
3" intake, 3" Greddy exhaust and OBX race header
310 CC injectors
Hondata heatshield gasket
Lightweight flywheel
Type-S oil pump

A K24a2 was recently swapped into my EP3. The performance of the motor up to 5k rpm is a noticeable difference over the K20A3. But after 5k, the motor falls flat on its face. It feels as if I am trying to inflate a balloon that is already full.

I've had luck with VirtualDyno in the past. VD indicates that while I am producing up to 170 torque, my peak power is only about 150whp because of how quickly the dropoff happens at 5k. By comparison, the K20A3 was peaking at 129 torque and 155whp.

I did a few runs on that K20A3 in virtual dyno which I can't upload, because 5 is the max until you try to upload 6, and then 4 is the new max :) But in those runs, I did find that too much intake cam advance at high rpm restricts torque production. Maybe that's my problem here, it's just such a shock to see how much intake cam advance some people are running (supposedly without negative consequences).

I know the reflash for TSX keeps the torque curve alive until after 6k rpm, so something is definitely not right with my setup. Again, I expect it's the intake cam advance - maybe it needs to get closer to zero and much faster. The graph I attached shows the general (albeit unlabeled) relationship between cam advance and torque production, starting at 40*. But if you have other suggestions for why the motor is such a dog after 5k rpm I would love to hear them. Thanks.

[micksellergren]

Just FYI, the gold is torque and the blue is intake cam advance.

I've attached the same chart showing power as well, with blue as the power curve.

I've included a picture of my K20A3 runs in which 5* of intake cam advance are compared to 10* of intake cam advance at the highest rpms. You can see the loss of high-end torque in the tune with 10* of advance.

[Hondata]

You need tuning. The cruise lambda is way off - +25% fuel trim in places. Full load AFR is lean in places and rich in other places. High cam ignition looks very low.

[micksellergren]

I've started the process of fine-tuning each of the intake cam advance tables. I'm adjusting the fuel and ignition advance on each and then I am compiling the best runs into a composite dyno chart. Already I can see that I have stayed with 40* of intake cam advance for too long and that I should have transition to 30* earlier. I'm still not optimistic that I am dynoing "where I should be".

As I am doing this, I wonder if the differences in the 04-05 TSX motor and my 2006 TSX motor result in substantial differences as far as the intake cam advance is concerned. AFAIK, the 2006 motor has a different head and different cams. Does this mean that the 04-05 was perhaps more responsive to huge intake cam advance whereas the 2006 is less responsive? Or am I likely just seeing idiosyncrasies related to my particular setup?

[micksellergren]

I've tuned for each 10 degrees of cam advance and created a composite dyno curve. I've attached my most recent kal with a datalog where I do two highway pulls going in opposite directions on the same road. Ambient was about 73 degrees and IAT was around 100.

I've attached my newest VirtualDyno run compared with the run in my original post.

I've attached the two highway runs graphed together so you can see the repeatability of the result.

I've attached my K24a2 compared to my old K20a3.

I still don't get it. Where the heck is the torque going? Why am I not making any power?

[josaya]

https://www.hondata.com/techenginetuning.html is worth a read.
Playing with your vtec engagement point is also worth a shot, see https://www.hondata.com/help/flashpro/i ... _point.htm

Different setup, but it took me (complete noob) around 300 datalogs (revision 230ish! at approx 3 datalogs\trips a day) just to get my midrange cam angle and AFR correct (AFR is the easy part with a wideband... which you should do first) within a few degrees vs a "from scratch" full dyno tune (which I paid for one once my throttle electrical issues were fixed). Now if only start up electrical issues were as simple....