Blacktop Torque Hole

[rocket]

20v Blacktop in an 88 mr2 using factory mr2 trunk air intake, factory Blacktop exhaust manifold and sv3power 2-1 downpipe + exhaust.

What I expect to see:
Torque mostly trends up with rpm until some drop-off point up high.

What I see:
Torque drops out significantly 3250-4400rpm.

What I've tried:
* Factory Blacktop engine and electronics.
* Link ecu with coil on plug ignition and wideband.
* Verified VVT works by enabling at idle, engine runs very poorly.
* Tuned with and without VVT and took higher volumetric efficiency per load cell - less air flows through the torque dip section.

Both of these are in the attached picture. Don't worry about the top end, I'm not really doing a lot of work up there yet. What can I do about the torque hole at 4000 that's present in factory and aftermarket control & ignition?

[jondee86]

Is that on a hub dyno or on rollers ?

Cheers... jondee86

[rocket]

That's a phone dyno. http://tuning.perfexpert-app.com it's very consistent with itself, very low variance between runs on the same stretch of asphalt.

[jondee86]

If you take a look around the interweb you will find a lot of dyno curves for 20V 4AGE
engines, and almost all of them display the same torque dip at around 4000rpm. This
graph shows the same characteristic...


https://www.efihardware.com/products/93 ... toyota-20V

The lower curve is near stock and the upper curve with customs ram tubes. If you look
at the power curve it is much the same as yours. I asked what dyno as hub dynos show
the actual variations in torque much more clearly than rollers. Rollers introduce a lot of
smoothing due to the inertia of the rollers themselves. Also, when you graph with different
scales on the vertical axis, the torque dip is exaggerated.

I'm not exactly sure why there is a torque dip... best guess would be that it is an intake
resonance. The fact that ram tubes were able to tune a lot of it out in the above example
tends to confirm that guess. I wouldn't be too worried about your results as the your
power curve looks to be quite typical for 20V engines, and if you are making 160hp you
would be doing better than most

Cheers... jondee86

[rocket]

Thanks for the reassurance! I'll try tinkering here and there with in-plenum stacks, maybe use this as an excuse to pick up a shiny new exhaust manifold...