Bad dyno run for my Lude.. huge power drop @VTEC changeover

mercutio · Post by **mercutio** » Sun Apr 27, 2014 2:39 pm

figures look fine to me for a standard lude

Turbomick1985 · Post by **Turbomick1985** » Sun Apr 27, 2014 2:43 pm

I think it's because when the other members of this forum put up dyno runs with their modded to death ludes that gains look massive on the graph and this is pure standard

JMBW · Post by **JMBW** » Sun Apr 27, 2014 3:28 pm

Good point.. if this is the case, I should be able to lock the valves in the short runners position and this should diaspare? (the graph should be somewhat different from 0-5000rpm, but the power dip will be gone.. ?

BMCC wrote:Vtec engages at 5250rpm. The drop in the curve is about 4800 which is when the dual runners in the inlet mani change from the long to short path. So the graph on this aspect is fine.

Post by **Donald** » Sun Apr 27, 2014 3:56 pm

You would probably have an easier time switching to the Accord Type R or Skunk2 inlet manifold as they are single runner as far as I know. The only thing is the ATR one needs modification to suit the Prelude, whereas the Skunk2 is ready to go but you tend to pay a bit more for it. As a standalone mod though I don't know of you'd see the gains you want, would've best with a few other breathing mods and perhaps the A7, A8 or TypeS head. Then a chip at the very minimum.

JMBW · Post by **JMBW** » Sun Apr 27, 2014 4:12 pm

On another note, it seems quite possible that the runners have briefly swapped back to long runners after the initial change to short runners @ 4800rpm?

Hearing the engine acceleration falling on its nose for 1-2 sec and then pick up again where it left: makes it seem like something's off.

The figures and power after the xover is somewhat spot on for a std H22A5, this is not what worries me

It's the apparent power loss around when runners change from long to short and before the xover.

Post by **newkid** » Sun Apr 27, 2014 4:24 pm

The power dip is normal, its one of the sole reasons spoon dropped the vtec crossover on the 4th gens.

BMCC · Post by **BMCC** » Mon Apr 28, 2014 8:34 am

Turbomick1985 wrote:Good point.. if this is the case, I should be able to lock the valves in the short runners position and this should diaspare? (the graph should be somewhat different from 0-5000rpm, but the power dip will be gone.. ?

Don't think so, It is just something you have to live with using this inlet mani. Honda were looking to get the best torque at low revs and high revs. One way to do this was to use a dual runner mani. Too short a path and it only really makes power at high revs and too long a path it only makes power at low revs. One reason why you have to be careful with throttle bodies as the path to the inlet valve gets very short (from the filter).