Hi all,

When i drive the STI and about to shift, let's say from 1st gear to 2nd gear, at the time i press in the clutch and change the 2nd gear, the engine revs to about 2000rpms. Meaning while my foot is still on the clutch(neutral), the rpm rises to 2000rpms. This is the case for all gears. it only happens when the car is rolling or moving though, when it's still and i press the clutch down w/ a gear in place the rpm stays low. Anyone know what this is due to? i don't know if i'm being clear about my question, but when i asked my co-worker he said the engine is still rough since i only have 150mi on it. He told me to drive it till 1500mi or so and the engine will be much smoother and the problem will cease. Is this true? Thanks for all inputs.

I think your describing compressor surge. The bov can't keep up with the surge when you're at high rpm and lift too quickly. Its normal; all you have to do is slow down and be more fluid when you lift off the gas pedal.

yeah, lets not jump the gun here and start blaming the problem on the engine just yet

Originally posted by Procrastinazn
Hi all,

When i drive the STI and about to shift, let's say from 1st gear to 2nd gear, at the time i press in the clutch and change the 2nd gear, the engine revs to about 2000rpms. Meaning while my foot is still on the clutch(neutral), the rpm rises to 2000rpms. This is the case for all gears. it only happens when the car is rolling or moving though, when it's still and i press the clutch down w/ a gear in place the rpm stays low. Anyone know what this is due to? i don't know if i'm being clear about my question, but when i asked my co-worker he said the engine is still rough since i only have 150mi on it. He told me to drive it till 1500mi or so and the engine will be much smoother and the problem will cease. Is this true? Thanks for all inputs.

Are you saying it rises by 2000RPMs on shifts or that it is steady at 2000RPMs while rolling in neutral?

-st

I am speaking of rolling at 10 Mi/Hr w/ my foot in the clutch and my car in gear. I don't think there is any boost as an variable here is there?

Yea you have to be more clear,

Do the RPMS increase by 2000rpm when you shift (ie shift at 3000 and rpm's climb to 5000 while clutch is engaged)

OR do the rpms rise TO 2000rpm. IF SO what rpm are you shifting at????? A rise is normal of a couple hundred rpm. But if it is a 2000rpm increase then your foot is still on the gas when you engage the clutch...Simple as that.

My experience with the STI has been the same. I believe the drive by wire system is a bit slow to react to a closed throttle but it is most likely programed that way by Subaru.

Yes, it is strange!

Phil (motoxphil)
www.elementtuning.com

RPM rises to 2000 when it should really be less than 1000 because my foot is not on the gas. it slowly rises when my foot is stepping on the clutch and the car in gear (rolling thru traffic rush hr). There is no way my foot is on the gas b/c i made sure neither my foot or carpet in on the gas, tis weird....

Originally posted by Element Tuning
My experience with the STI has been the same. I believe the drive by wire system is a bit slow to react to a closed throttle but it is most likely programed that way by Subaru.

Yes, it is strange!

Phil (motoxphil)
www.elementtuning.com


I don't think that's it. The rpm rise on lift off also happens with the WRX 2.0. There are a few theories about it, but none of them relate it as a technical problem.

Car has now 1200 Mi on it and the same prob exists, called the dealer and he said it would happen to some cars during break in, but *Shrugs*

I don't think its a problem. I believe it's programmed to do so.
Here is what I think the engineers are doing with this.
The ECU is seeing vehicle speed thru the vss and knows you are rolling also abs see's movement. The computer keeps the rpm's up to prevent stall and it is anticipating you getting back on the gas again. There used to be a caddy back in the early 80's with a Bosch fuel injection system on an oldsmobile engine when you would rev the engine and let of the gas real fast it would cut fuel untill rpms dropped to idle level then idle again. It sounded like the engine died because it did until it met base idle! They did this to save the catylitic converter.
When you are letting off the gas-throttle shuts and you have a very quick rich condition. Too much fuel over time kills cats. Turbo cars are known for flames between shifts due to lots of fuel from a rich exhaust while your "gettin it" then BAM throttle closes for a shift=rich exhaust. I believe Subaru is doing this to keep the emissions in check for the warranty period and it helps with driveability of the car also.
Or I'm completely wrong.
Dwight

Most cars have a higher idle RPM when you're moving then when you're not. 2000 sounds a little high but doesn't sound like there's a problem.

Example, idle rpm - 750rpm, coasting in neutral = 1500 or 1200

Originally posted by 2003 sedan
I believe Subaru is doing this to keep the emissions in check for the warranty period


This would be my best guess :)

emissions...
happens on the sti too.

engins bumps up 200rpm or so if you started the up shift with the intention of following through, but then had to back down...
ie "here i go here i go here i go.... oh, no wait......"
happens in rushhour traffic, and in parking lots...

Originally posted by DISCOPOPE
emissions...
happens on the sti too.

engins bumps up 200rpm or so if you started the up shift with the intention of following through, but then had to back down...
ie "here i go here i go here i go.... oh, no wait......"
happens in rushhour traffic, and in parking lots...

My wrx did this, but have not noticed this on the sti.