Acceleration

[91White-T]

OK, so here's what I'm seeing. My car feels a lot faster with 3/4 throttle than full throttle. Does this make any sense at all? It feels really strong while building boost, and 15psi comes on in a matter of one second, but after it hits full boost the acceleration just drops off. If I just punch it, it feels a lot slower than if I give it 3/4 throttle. I still have the stock DP, so could that be doing it, or is it that the turbo's running out of breath really fast? Any ideas? (I realize that this may not make ANY sense)

[vrg3]

Is it possible that the decrease in acceleration you're experiencing is due to high engine speed rather than high boost? The stock turbo does get tired after 5000 rpm or so.

[91White-T]

It's possible but it happens below 5000. Above 4500 or so, it almost feels like the turbo's not even doing anything even though its making ~14psi.

[Aaron's ej22t]

It sounds to me like a lack of top end flow. the small stock turbo is not efficient past 13-14psi. plus, this turbo can't really pull all the way to redline hard. it is good up to 5k. upgrade to a catless downpipe and only run about 14 psi. it will help.

[Legacy777]

The reason you see differences in performance between wide open throttle and part throttle is because of going from closed loop to open loop, and how the maps are setup. At full throttle, computer is just dumping all the fuel it can in, at 3/4 there's probably more accurate measuring means going on.

The resolution, get a fuel controller like the safc to adjust the maps. I know on the imprezas, the safc is pretty much only useful at full throttle.....I think ours are similar, may be more useful across the rev range then the newer cars....but not positive.

[submannz]

Most likely to be the throttle butterfly needing adjusting, it is quite common for the throttle butterfly to over open causing it to partially close, that is one of the first things we check when making performance adjustments to cars.

[Legacy777]

Interesting.......I'll have to take a look at that.

[ciper]

Ive noticed exactly what 91White-T is talking about, 3/4 throttle is best from idle to 4k while WOT is better afterwards. I think Legacy777 is right and that an AFC professionally tuned would result in a significant increase in low end power. My experience is with NA Legacy's.

Though what submannz says sounds interesting. Problem I see is that you might never reach full thottle if you shorten up the top end screw (did that make sense?)

You cant just turn the TPS to compensate because then you would loose the Idle contacts. Im going to try this!