quicsvr

I have a VAFC, though I've not yet had it professionally tuned (I do plan on it, once finances allow it). I had the car dynoed this past weekend, and the plot showed a max hp of 204, and tq was 14(3 or 4). I was happy with those numbers, until I read some threads that were talking about the curves intersecting around 5250. Mine cross well over the 7000 mark. I also have a severe spike in both curves around 3000 rpm and a clear jump when VTEC kicks in (5700). What would cause these things to happen, and what should I change until I can get it professionally tuned? It feels like it's running good, but I'm scared that I'm messing something up. Thanks for any suggestions, other than the obvious 'wait and get it professionally done'.

cthree

Do you have an AEM or Injen CAI? That would explain the bump @ 3000 RPM.

quicsvr

I do have the AEM, but no other mods. Thanks, that answers one part. It's quite a spike at 3000, that's pretty cool if that's just from the CAI.

cthree

Both the AEM and Injen spike there. It's some kind of resonance thing. Too bad those gains don't hold throughout the rev range

ejis

Torque and hp curves cross at 5250 rpm because that's how hp is calculated:

hp = torque*rpm/5250

If they don't seem to cross at that value, then the curves are not on the same scale. Sometimes the hp curve corresponds to a scale on one side of the graph and the torque on the other. They do this because the range of values are different - especially in our cars - so in order to see the details of the curves, you want the scale of the graphs to be different. There is nothing you can do to your car to make the curves cross at a different rpm.

204hp at the wheel is pretty good, especially without really tuning it. As long as you haven't moved the values in the V/AFC around too much, then I wouldn't worry about it.

As for the "spikes", at 3000 rpm it's likely that the tech was just starting to gas it so below that there wouldn't be any data. The spike at the V-TEC crossover point is exactly that...a spike in power, that's what it's designed to do. You can change its characteristics if you want by making changes in the V/AFC.

Post the dyno graph up and it will be easier to speak to it though...since what I think you mean by a spike may not be what you see.

Also, I would wait until an experienced tech is helping you to tune the system at all. It seems you're not too familiar with this stuff (that's not a flame...I don't know a lot either and wouldn't tune a system without an experienced hand helping me). And without a dyno to check the results, your as likely to make things worse as better. To be fully safe, zap the values back to stock until you can get a good dyno tune.

Good luck, and post those dyno graphs!

quicsvr

I'll post it as soon as I get home, and can get to a scanner.

quicsvr

ok, here's a crooked scan of the plot, that I hope you can see..

ejis

Ok...clearly I had no idea what I was talking about with the 3k spike I'd trust the others that it's your CAI. The initial "boost" at V-TEC crossover would be from switching the cam lobes, and the dip after could be a result of imperfect mixture or any number of other things. Those are big torque spikes, but the power climbs pretty well throughout the range. Either way, they can both be worked with the adjustments available with the V/AFC.

And you're curves do equal each other at 5250 rpm, match each curve to its correct axis values and you'll see that they're the same at that rpm (and that hp = torque*rpm/5250 at all rpms).