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Discussion Starter · #1 ·
So I'm exiting a toll gate one day, some hosehead in a Grand Am wants to jockey for lane position so I humor him. And in the process, I notice something odd... Acceleration suddenly becomes considerably more brisk just above 5000 RPM. It's almost VTEC-like. Anyone know why that is, or am I the only one experiencing this? Fuel mapping maybe? This is under full throttle, btw.
 

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If you are stock, then i am not sure what it is that you are feeling, but if you are running turboxs's unichip @ stage 2 which I am doing right now, then I know what you mean, I think it is somewhere at this point where timing is advanced big time, and you can feel the car gain more urge as it runs up to redline. Quite a satisfying furge i should say too!
 

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I feel it in mine too. It feels like it kinda hesitates for a split second and then a power surge up until redline. I have no idea why it does this. I'm stock, by the way.
 

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My car, when it was stock definately pulled from 3K-4.5/5K and then started pulling even harder, I never knew what it was. Now my car pulls hard from 3K ------> until it dies off at 6-6.5K. I wish I were not poor and could get a new turbo that would pull to redline, but......


-joe
 

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i notice it too, at around 5k it pulls hardest. My car is stock right now, an 03. Before on my 02 i had a mbc and it just pulled hard all the time. It's the stock boost control i'm guessing that does this.

jared
 

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i feel it too...i think that it may be when you start to got into a range with a lot of torque....i'm no expert though...a stock dyno sheet doesn't show a major increase though....i'll leave it up to the experts...
 

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Discussion Starter · #7 ·
WRC_Obsessed said:
i feel it too...i think that it may be when you start to got into a range with a lot of torque....i'm no expert though...a stock dyno sheet doesn't show a major increase though....i'll leave it up to the experts...
Nah, that's not it. It really is as sudden as if a second set of valve actuators has kicked in. It's instant, just like that. Besides, WRX hits its torque peak at 4000RPM.
 

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i get it aroun 4-4.5K, i always figure it was the cams getting into the sweet spot. I am really used to this the miata has the same efect around 4K, so i learned to drive between 4-7K. I drive my rex that way, the only hangup is the car falls on it face above 6K. I would like a turbo that spools about 4K and hold good to redline.
IMO i dont like the spooling in the 3k range, daily driving i shift about 3.5K so i get a suge of power then let off to shift and you can really feel the deceleration.
 

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dont have any official links but i think its been determined that around 5k is when the fuel is kicked up from 66% to 99% of the FPR

i remember reading a post from nathan at TXS (maybe not nathan but somebody who ACTUALLY knows what the ECU does) on NASIOC when it was I-CLUB that states the stock fuel system seems to have 3 "levels" of fuel supply 33% is up till like 3000 (which is pretty much why MBC FBPT is bad) 66% is midrange and at 5-5500K the fueling switches to wideopen...the surge is the computer switching the maps(?)

BTW this is just 3rd hand memory recalling something from months past...it could be completely or partially wrong

~wrx300
 

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Most dyno plots I've seen of stock WRX's show a brief but significant dip in power (& thus torque) at 5000rpms before it resumes a rapid rate of climb. I don't know why; it could be engine design or tuning parameters or any combination thereof. That region is a little knock prone so maybe the ECU pulls back timing a bit before it makes its final dash to the redline. Regardless, it makes sense that you would feel the motor pick up after that power trough.

-Pace
 

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hmmmmm interesting
 

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asial713oirx7 said:
I'm a troll.
Huh? English please.

*edit*

Well dammit someone changed the attempt at a post. Oh well.
 

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i posted this over on nasioc, the only response i got was......

"you probably felt the hp peak"

looking at the dyno plot, that makes sense as max hp isn't until 6k..........and the explanation bout the injector duty cycle makes sense........so maybe if we put the two together, we got our explanation(hardly unlikely that simple, hehe)

well, anyway, just wanted to say, i experience the same thing, but can't explain(sounds like the x-files)

anyone wanna chime in w/their theory?
 

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pace said:
Most dyno plots I've seen of stock WRX's show a brief but significant dip in power (& thus torque) at 5000rpms before it resumes a rapid rate of climb. I don't know why; it could be engine design or tuning parameters or any combination thereof. That region is a little knock prone so maybe the ECU pulls back timing a bit before it makes its final dash to the redline. Regardless, it makes sense that you would feel the motor pick up after that power trough.

-Pace
Yeah it's weird, I'm starting to notice this a lot more lately than before...no idea why. It's like it's hesitating, but I thought people got hesitation in lower RPMs, not at 5k...
 

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Discussion Starter · #17 ·
Wow, how'd this Night of the Living Thread get revived? :confused:
 

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one other element

One more element in the puzzle. If you look at the compressor map, the TD04L-13G hits its maximum compressor effeciency right around the flow rates that correspond to 4500- 5000 rpm on a 2 liter block.

I suspect it is a sum of all of the above effects.

Larry
 
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