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STeveD
08-14-2009, 09:10 AM
I drove Serge's GC RS because he was concerned about the shifter feel (he's used to German cars), and because of certain noises (whiney pulley sound at certain RPM's, under load and off, probably actually an exhast shield rattling.)

The thing that I was concerned about was actually the power delivery. The acceleration was kinda moderate until the car hit 5000 rpm and then it really accelerated hard. He is sure that the car is basically stock as it was the daily driver of a female university professor in her 50's, who wasn't interested in performance. Only getting to work from Barrie to York.

Is this power delivery common for the 2.5L stock RS motor? I'm used to Subarus running out of steam much past 5000 with good 3000rpm torque, but it was like a Honda where this car didn't come alive until it was past 5000...? It honestly felt a lot like VTEC or coming into the turbo spool area of a TD04.

AndrewR
08-14-2009, 09:43 AM
What year 98 or 99+

STeveD
08-14-2009, 09:58 AM
I'll ask, but it looked to me like a 2001. But it was dark and I'm not a connoisseur of RS.

Robin
08-14-2009, 10:09 AM
it doesn't sound right.... the 2.5 is like the 2.2 n/a in the power delivery.... it really dies down after 5000rpms.

STeveD
08-14-2009, 10:18 AM
Robin wrote:
it doesn't sound right.... the 2.5 is like the 2.2 n/a in the power delivery.... it really dies down after 5000rpms.

This is what I feared. He mentioned to me that he's redlining the car sometimes while driving it and that sounds pretty un-Subaru. But after I drove it, the car has so little power below 5000rpm that I understood completely. Yeah, I'd be spending most of my time above 5000 if I was driving it in a spirited manner as well.

Okay, so if it is power delivery, what could be causing it? It must be pulled timing, or AFR, no? These cars run off of MAP, not MAF, right?

A plugged cat should be restricting the upper powerband more than the lower.

Chris_Martin
08-14-2009, 10:33 AM
Back when i had the RS motor in my rally car...it was almost like that, but it picked up hard at 4,000 and took off...i found out later that it had Cams in it...explaining it...

Stock wise...they run out of steam above like 5,000.

The only time my motor did something even similar to that, was when the fuel pressure regulator stuck closed and the thing was pig rich.


I'd do all the normal maintenance stuff. Plugs, wires (i've seen some pretty buggered up wires on these things).

Another area to look might be pull the spark plug wires, and see if the tubes are filling up with oil, The gaskets went on these things, and if those tubes are filled up, the spark could be arching all over the place.

if it's a 00-01 it's running off MAP yes.

Robin
08-14-2009, 10:54 AM
if he got it used, did he change all the regular maintenance items? or nothing? was it properly maintained by previous owner?

any CEL?

maybe a cam senor is done?

STeveD
08-14-2009, 11:29 AM
No CEL's. It has 178,000km and the previous owner claims that the timing belt was done as scheduled, but didn't provide receipts.

Can a vacuum leak cause that effect?

Confirmed, it is a 2001.

Serge
08-14-2009, 12:35 PM
Hi Guys!

just to chime in (thank you stephen for making a post, haha)

just to confirm some things

the car, according to the previous owner, who purchased it new in 2001, has had regular scheduled maintenance at a private shop, nothing crazy but she says "the boy that worked on the car" knew his stuff. Then again she knows nothing of the technical side so i cant really take her word for it.

as far as i'm concerned, the car is stock, and according to her, it had a standard plug/belt/oil tuneup before she put it up for sale.

i have not had a chance to do anything with the car yet (only had it for about a month or so), with the exception of changing the transmission oil as i was suspecting that something was wrong there (Stephen alleviated my fears though, thank god, haha)

there is definetly a dip in power between 3000 and 4500 RPM, after that the thing takes off.

In my VW Golf, i hit fuel-cut off maybe 2-3 times in a year, for accidental reasons where i was either in a risky traffic situation accelerating or just being an air head

but within just one month of owning this car i would hit fuel cut off almost daily, the car does not feel like its running out of power AT ALL, so i dont bother shifting (if i'm not looking at the dash), this happens alot on the highway in 3rd and 4th, where i'm too concentrated on the road, and all of a sudden the car jerks cuz ive hit redline hahahaha.


on the other hand, i have read on the RS25 forums that this is normal???

i will seafoam the car soon, maybe that could clear things up.

Robin
08-14-2009, 01:49 PM
How bad is the throttle body? or maybe there's way too much slack on the accelerator cable right by the throttle body (where the cruise control attaches)....

Serge
08-14-2009, 02:06 PM
cable is fine, i tightened it up

but it feels the throttle is a bit sticky, maybe i should try cleaning the gunk out of there (if there even is anything)

STeveD
08-14-2009, 03:23 PM
Joe won't have access to a laptop to post until tonight, but he had another idea. He thinks it's your knock sensor being overly sensitive. Apparently a lot of 2.5L RS owners put an O-Ring between the sensor and the engine to de-sensitize it a bit. The reason he thinks your car feels strong above 5000 is because that's where the ECU begins to ignore the knock sensor and put timing to default values.

Maybe that rattley heat shield has been confusing the knock sensor?

Serge
08-14-2009, 03:42 PM
what kind of o-ring, just like a rubber one or like a metal washer?

well, also due to the old engine and transmission mounts, the whole thing shakes as it is, or would this be that high frequency shake?

STeveD
08-14-2009, 03:53 PM
Just a rubber one to dampen the vibrations.

You're right, I didnt think of that. When your mounts arrive, that might help with the problem and reduce stress on your exhaust so that the heat shields crack less. If your engine is flopping and pitching around, that's not good for the header.

PaulH
08-14-2009, 05:43 PM
If the washer on the knock sensor works just remember to buy quality gas afterwards as the ECU may not be able to determine a knock due to poor gas and will not pull back the timing to prevent further detonation.
Paul

shanehutton
08-16-2009, 06:49 PM
The knock sensor might explain why it is not making power down low but not the seemingly abundant power past 5000rpm when it should be falling on it's face. My first guess (Not a subaru guy) would be that the timing is off. Perhaps the belt job was botched a bit? You guys have 2 heads though so that seems kinda weird as well.

Just thought of something else. What about an exhaust leak killing the back pressure? It would kill low rpm power and would also open up the top end wouldn't it?

JoeT
08-16-2009, 06:55 PM
Nah, in 2000 - 2001, there were a batch of overly sensitive knock sensors. It would confuse the frequency of mechanical noise as knock, specially around 3500 rpm, the car would pull timing badly. This was never recalled because it was not a safety issue, and only caused a reduction in power.

The proper thing to do is to buy a new knock sensor and replace the one you've got. It's located on the driver side of the throttle body, it's a round doughnut looking thing and it's pretty easy to change.

After the knock sensor is replaced, then reset the ECU by unplugging the battery for 1/2 hour, and pushing the brakes while the battery is off.

Then when you connect the battery, start the engine (note, engine may stall at this point), and let the engine idle until the cooling fans turn on. Then shut off the engine, and restart.

You'll find all sorts of power that you were previously missing.

Hope this helps.. Enjoy!!

Serge
08-19-2009, 06:13 PM
Thanks Joe,

i'll give it a go, should i take stephens suggestion and try to find a ring/gasket for it as well?

Also, the 3500 RPM mark is exactly when the rattles start, should then rip off the headshields as well so that the problem does not come back, or is it just the knock sensors being too sensitive, and the new ones simply of better build?

- Serge

JoeT
08-19-2009, 06:31 PM
Do either, meaning, either replace the knock sensor, or cut an old inner tube from your bicycle and use that as an isolator. As for the heatshield, remove them, they are a nuisance.

Welcome to AWD!!

Serge
09-29-2009, 05:26 PM
well, turns out that all the heatshields have been previously removed from the car, with the exception of the catalytic converter ones... one of which is now missing...

however i found out what the ringing was, a left over rivet in the front section of the e-manifold was left dangling loose.


i have added a rubber buffer for the knock sensor while having the battery out of the car for cleaning of contacts and what not.

i cannot say with certainty if it is better or not.. how long does it take to re-learn the maps?


now, for a completly unrelated question.

i have upgraded the tranny mount, and will change the engine mounts soon. But what causes that ridiculous buckling if i was to let go of the gas pedal quickly, it seems like the engine wants to die and really does not take well to a sudden change in intake pressures... whats up with that?

JoeT
09-29-2009, 10:44 PM
A couple of answers then more questions.

1) Learning is instantaneous. Basically it's mostly the timing correction from knock. It goes to it's base map then applies the values for knock correction based on the input from the knock sensor.

Fuel trims are done by the O2 sensor while in closed loop. Once in open loop, the static table is what is read by the ECU using input from the MAP sensor, TPS and IAT sensor to determine fuel requirements.

With regards to the "buckling" from your description, it's hard to determine what it is you're trying to describe. If you can provide some more detail, or show up in Barrie on Sunday, one of us can take your car for a drive and diagnose it. Much easier in person. Besides, it's fun thrashing another persons car in an autoslalom. Who knows you may even like it.. LOL

timc
11-12-2009, 07:57 AM