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Discussion Starter #1 (Edited)
I recently got an 07 WRX (2.5 L) after driving an 04 (2.0 L) for a couple years. I really liked that the 04 seemed to be able to handle being in the 1800-2000 rpm range without lugging as long as I was gentle with the throttle. I've noticed with the new car that it seems to have a higher threshold for lugging - i.e. it doesn't like being in low rpm as much. It's hard to put exact numbers on it, since I don't have the old car anymore. But it seems that the 07 doesn't like being below 2500 rpm, though it depends on the gear and the situation.

I most often encounter the engine starting to lug when coasting to decelerate, as the RPMs drop into the range where it's not too happy. This is the most pronounced difference from my old car, because I remember that I could coast down to quite low RPMs, definitely 2000 or lower, without hearing the engine lug. Even if I got too low and needed to downshift before accelerating, the engine would only lug if I were to put my foot on the gas - not while coasting.

For sure, I've found that it's hard to start in 1st from a stop at lower than 2000 rpm. I can do it, but I have to take it really easy, or the engine will lug, or sometimes shake a bit like it's stalling. Starting at 1500-1800 rpm in the 04 was not like this.

Can anyone tell me if this is just a difference between the 2.5 L and 2.0 L engines? Or does it seem like there's another problem with the car?

Both cars are mostly stock, with 3 inch turbo back exhaust. I'm guessing they are both on the factory engine map, based on the way they drive, though I don't know for sure since I don't have a full history of either car.
 

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Both cars are mostly stock, with 3 inch turbo back exhaust. I'm guessing they are both on the factory engine map, based on the way they drive, though I don't know for sure since I don't have a full history of either car.
I'd guess that's your problem and that's a grade a way to detonate that ej255. You shouldn't ever lug any engine to begin with, and you absolutely never lug a turbo engine. You wind up in overboost area and that can go real bad.

You need to have the car tuned, it's not optional. You need to at that point evaluate again what's going on. I often ran my 2012 around 1800-2k no lugging. I also didn't give a shit about firing out of the hole at the drop of a hat because racecar. I actually thought the 255 had great power low for daily driving. Many other 4bangers I've driven will choke out the second the clutch engaged.
 

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Discussion Starter #3
Just to be clear, I avoid lugging when I drive, and I'm aware that it's not good for the car. You have to know where the threshold is for your car in order to drive it right, and I've noticed it seems a little off compared to my 04 WRX. Hence the question.

XJman, are you saying that with no mods but an upgraded exhaust a tune is mandatory? From other things I've read, that is not the case. I have no experience with tuning though, so I could be mistaken.

It is helpful to hear that in your experience with the 255 the power in low rpm was fine. I'd be interested to hear other people's opinions as well.
 

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Just to be clear, I avoid lugging when I drive, and I'm aware that it's not good for the car. You have to know where the threshold is for your car in order to drive it right, and I've noticed it seems a little off compared to my 04 WRX. Hence the question.

XJman, are you saying that with no mods but an upgraded exhaust a tune is mandatory? From other things I've read, that is not the case. I have no experience with tuning though, so I could be mistaken.

It is helpful to hear that in your experience with the 255 the power in low rpm was fine. I'd be interested to hear other people's opinions as well.
A turbo back is a mod... One that drastically changed the airflow through the engine.

If you have a turbo back you've modified the exhaust dramatically. The wastegate now as a smooth exit and they have the capability of moving much more air. On my 2011 that and a basic tune went from around 200whp to about 240-50. That's nearly a 25% gain.

Because it's capable of changing the airflow that drastically it easily throws the ecu outside of it's programmed tables and eventually it goes south.
 

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Discussion Starter #5
Well, I guess it's been a while since I read about what modifications necessitate a tune. I just looked back at this thread from NASIOC, and there they say that on 04+ WRXs with the stock map the engine can run lean during the transition between open and closed loop fueling. Any modifications (except maybe a catback) could accentuate the risk of detonation.

So that makes sense, and you've convinced me that I should definitely get it tuned. This is something I've been wanting to do, so now I have more justification to do it.

Any other suggestions on possible causes for the behavior I'm experiencing? I'd like to know if there are other things I should check out as well.

Also, setting my current car's issues aside and addressing a more fundamental question, does lugging normally happen for a 2.5 L at about the same RPM as a 2.0 L? Of course, every engine is a little different, but I'm thinking it should be roughly the same or even happen at lower RPM for the 2.5.
 

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Well, I guess it's been a while since I read about what modifications necessitate a tune. I just looked back at this thread from NASIOC, and there they say that on 04+ WRXs with the stock map the engine can run lean during the transition between open and closed loop fueling. Any modifications (except maybe a catback) could accentuate the risk of detonation.

So that makes sense, and you've convinced me that I should definitely get it tuned. This is something I've been wanting to do, so now I have more justification to do it.

Any other suggestions on possible causes for the behavior I'm experiencing? I'd like to know if there are other things I should check out as well.

Also, setting my current car's issues aside and addressing a more fundamental question, does lugging normally happen for a 2.5 L at about the same RPM as a 2.0 L? Of course, every engine is a little different, but I'm thinking it should be roughly the same or even happen at lower RPM for the 2.5.
I assume you have the electronic throttle and may be describing a well known stumble due to fueling. I have had my car tuned and still experience the stumble in that 2000 - 2500rpm range. Suggested fix by the forums and tuners is to replace the fuel lines to a parallel arrangement and zero some tables. I cant confirm it works.
 

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Discussion Starter #7
I assume you have the electronic throttle and may be describing a well known stumble due to fueling. I have had my car tuned and still experience the stumble in that 2000 - 2500rpm range. Suggested fix by the forums and tuners is to replace the fuel lines to a parallel arrangement and zero some tables.
mjtct - interesting, I believe mine is drive by wire (I think all USDM 07s are). I'll do some searching on the issue you're describing and see if I can find more details. Do you happen to know of any forum threads you could link me to?
 

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