2008-07-29, 07:42 PM | #1 |
EJ205
Real Name: Jeremiah Join Date: Jul 2005
Location: Dayton, NV
Posts: 1,888
Car: 2005 Impreza 2.5RS, 2000 Forester L
Class: RNP sometimes (see motto)
"Kids are ruining autocross."
|
Knocking?
As far as I can remember, this has been happening for a few summers (possibly since I got the car, but that was a while ago now), but seems a little more pronounced since I switched to Royal Purple for my engine oil. . .
This really only happens when my car has been sitting out in the sun all day. When I'n going up the hill in to Moundhouse, the engine will make a slightly tinny, rapid tapping sound. It only happens at about 25%-40% throttle in 5th gear - enough to hold 60mph going up the hill. If I slow down or give it more gas, the noise stops. If I'm level, it stops. There's no unusual noise when starting, no noise when driving around town, and when the car is cooler (in the morning,) it doesn't make the noise at all, even when going uphill. I always let the engine warm up before driving, and I've checked the oil - the level is fine, and there's no unusual consumption. The car does not seem to be low on power or doing anything unusual. Gas mileage seems fine. I don't remember this happening in the winter. I don't really want to think knock. . . I'm wondering if this could be something more simple, like just valve tapping, some weird exhaust leak, or maybe Royal Purple 5w30 just thins out way too much in Nevada summer heat. . .
__________________
Small red text that looks curious at first glance but is ultimately inconsequential |
2008-07-29, 09:20 PM | #2 |
Seņor Cheap Bastarde
Real Name: Dean Join Date: May 2003
Location: $99 Tire Store
Posts: 9,294
Car: $.04 STI
Class: Fast,Cheap & Reliable=STI
Deal, did somebody say Deal? Oh, Dean, yeah that's me.
|
87 or 91 octane? AC on/off? Try higher octane and/or turning off AC.
What you are describing sounds like high load low-mid RPM closed loop knock. Oil is not even involved.
__________________
I am a Commodore PET --- Now get off my lawn you kids... |
2008-07-29, 09:31 PM | #3 |
EJ205
Real Name: Jeremiah Join Date: Jul 2005
Location: Dayton, NV
Posts: 1,888
Car: 2005 Impreza 2.5RS, 2000 Forester L
Class: RNP sometimes (see motto)
"Kids are ruining autocross."
|
87 octane, and the AC is off. I'll try some 89 next time and see what happens.
If it is what you named, will I need to have it looked at, or is it relatively common? Now that I think of it, I was running 91 in the car for the first year or so. . . maybe that was why it happened less?
__________________
Small red text that looks curious at first glance but is ultimately inconsequential |
2008-07-29, 10:16 PM | #4 |
Seņor Cheap Bastarde
Real Name: Dean Join Date: May 2003
Location: $99 Tire Store
Posts: 9,294
Car: $.04 STI
Class: Fast,Cheap & Reliable=STI
Deal, did somebody say Deal? Oh, Dean, yeah that's me.
|
Run it almost dry and try 5 gallons of 91...
The fix is downshift and get out of closed loop.
__________________
I am a Commodore PET --- Now get off my lawn you kids... |
2008-07-30, 09:10 AM | #5 | |
EJ205
Real Name: Jeremiah Join Date: Jul 2005
Location: Dayton, NV
Posts: 1,888
Car: 2005 Impreza 2.5RS, 2000 Forester L
Class: RNP sometimes (see motto)
"Kids are ruining autocross."
|
I'll try that. I really don't want to have to switch to 91 for the summer though. . .
So it is common then? I googled and found this: Quote:
__________________
Small red text that looks curious at first glance but is ultimately inconsequential |
|
2008-07-30, 11:16 AM | #6 |
Token
Real Name: Le Stig Afrique? Join Date: Jun 2005
Location: sitting next to a big yellow box
Posts: 3,589
Car: 2001 Impreza 2.5 RS
Class: 05 TDSP
No, I won't work on your car. F* your car
|
You're on the right track I believe. Mine does the same thing, under the same conditions, with el-cheap-o regular grade gasoline.
__________________
"...these condoms have a topical anesthetic to reduce sensitivity, so you can last longer. What a paradox. You can't feel a thing, but you can f*ck for HOURS..." |
2008-07-30, 11:29 AM | #7 |
Candy Mountain
Real Name: Cody Join Date: May 2005
Location: Californication
Posts: 7,751
Car: 03 Pussy Wagon, now with more pink!
Class: TESP
OMG Internet!
|
WRT the oil, most run 10-30 when running RP. Supposedly RP thins more than it should as it approaches the milage/time to change it. Dunno for sure though.
__________________
Slow and low, that is the tempo. |
2008-07-30, 02:17 PM | #8 | |
EJ205
Real Name: Jeremiah Join Date: Jul 2005
Location: Dayton, NV
Posts: 1,888
Car: 2005 Impreza 2.5RS, 2000 Forester L
Class: RNP sometimes (see motto)
"Kids are ruining autocross."
|
Quote:
This kinda bugs me. . . the manual just recommends 87 octane. . . if this isn't unusual, you'd think there would be something in the manual saying, "but if you don't want to knock your way up hills, use 91."
__________________
Small red text that looks curious at first glance but is ultimately inconsequential |
|
2008-07-30, 03:25 PM | #9 |
Candy Mountain
Real Name: Cody Join Date: May 2005
Location: Californication
Posts: 7,751
Car: 03 Pussy Wagon, now with more pink!
Class: TESP
OMG Internet!
|
If I was going up more than a slight uphill grade @ 60mph, I'd try to be in 4th.. It's more important to do so in a turbo car, but I think high load isn't great for N/A cars either. Is your 5th lower than mine?
__________________
Slow and low, that is the tempo. |
2008-07-30, 03:37 PM | #10 | |
The Doink
Real Name: Scott Join Date: Nov 2002
Location: Portland, OR
Posts: 20,335
Car: '09 OBXT, '02 WRX, '96 Miata
Class: PDX/TT-6
The way out is through
|
Quote:
Any chance you're getting a lot of blow-by oil running through the intake? That'll drop the effective octane of the intake charge a bunch.
__________________
Is you is, or is you ain't, my con-stit-u-ints? |
|
2008-07-30, 03:41 PM | #11 |
EJ251
Real Name: Rob Join Date: Jun 2008
Location: Reno
Posts: 679
Car: 2019 CBS WRX Premium
Class: Middle
Shoot for the moon, because even if you miss, you'll still be among the stars
|
i think the 5th in the RS might be lower than the wrx, cuz at 125 my rpms were a lil over 5200, if i remember right... and wrx's have no problem getting to 150 and higher, right?
|
2008-07-30, 03:48 PM | #12 |
The Doink
Real Name: Scott Join Date: Nov 2002
Location: Portland, OR
Posts: 20,335
Car: '09 OBXT, '02 WRX, '96 Miata
Class: PDX/TT-6
The way out is through
|
A bone stock WRX will have a hard time getting over 140. It's aero limited, not gearing limited.
__________________
Is you is, or is you ain't, my con-stit-u-ints? |
2008-07-30, 10:03 PM | #13 |
EJ205
Real Name: Jeremiah Join Date: Jul 2005
Location: Dayton, NV
Posts: 1,888
Car: 2005 Impreza 2.5RS, 2000 Forester L
Class: RNP sometimes (see motto)
"Kids are ruining autocross."
|
I can't find documentation on my gearing, so I'm not sure. It's never been something I've felt the need to look up before. 2500rpm in 5th gets me somewhere between 55-60mph.
Now that. . . I don't even know what that means!
__________________
Small red text that looks curious at first glance but is ultimately inconsequential Last edited by M3n2c3; 2008-07-30 at 10:07 PM. |
2008-07-30, 10:16 PM | #14 |
Candy Mountain
Real Name: Cody Join Date: May 2005
Location: Californication
Posts: 7,751
Car: 03 Pussy Wagon, now with more pink!
Class: TESP
OMG Internet!
|
Are you seeing oil consumption? Blow by is oil that finds it's way into the intake via the PCV valve.
__________________
Slow and low, that is the tempo. |
2008-07-30, 10:23 PM | #15 |
EJ205
Real Name: Jeremiah Join Date: Jul 2005
Location: Dayton, NV
Posts: 1,888
Car: 2005 Impreza 2.5RS, 2000 Forester L
Class: RNP sometimes (see motto)
"Kids are ruining autocross."
|
No consumption, no. I just checked it yesterday - the level's right where it should be, and I'm just about due for my next oil change. I don't know if there's any oil in the intake piping. It's still bone stock, so I've never disassembled it.
Chevron's gas was oxygenated during the winter. Doesn't that effectively increase the octane properties? Perhaps that's why there's a difference now.
__________________
Small red text that looks curious at first glance but is ultimately inconsequential Last edited by M3n2c3; 2008-07-30 at 10:41 PM. |
2008-08-16, 05:46 PM | #16 |
EJ205
Real Name: Jeremiah Join Date: Jul 2005
Location: Dayton, NV
Posts: 1,888
Car: 2005 Impreza 2.5RS, 2000 Forester L
Class: RNP sometimes (see motto)
"Kids are ruining autocross."
|
91 octane seems to cure it. 89 is a little better than 87.
In other news, while I was waiting for the engine oil to finish dripping, I decided to finally pull the intake snorkel out of the fender. It doesn't seem to have changed much except the noise. Perhaps it will result in a little better pick-up in the once summer's over, when there's actual cool air to be had.
__________________
Small red text that looks curious at first glance but is ultimately inconsequential |
2008-08-17, 03:50 PM | #17 |
EJ18
Real Name: Wiles Join Date: Aug 2008
Location: SLT, CA
Posts: 43
Car: bugeye wagon, 02 Tacoma, 04 SV650
The Dude Abides
|
The only thing that is supposed to change is the noise. You aren't going to feel any difference in the butt dyno just from removing the intake silencer.
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Knocking sound? | JC | Technical Chat | 3 | 2005-05-31 09:45 PM |