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Posted: 4/10/2006 11:41:21 PM EST
ok, well ive been all over the engine with my stethescope and i cant find it...

little background info. the car is an 03 WRX that is HIGHLY modded, putting out 360HP at the crank. larger turbo, odds n ends. nothing done to the block / valvetrain.

the car is a buddies and i am contemplating buying it as a streetable racecar project.(full cage, it has JIC coilovers, gonna use them till i can get Zeals. full monoball bushings, seamweld... the list goes on)


ok, heres the deal, this is the symptom: 3000-4000 rpm 30%-about 80% throttle i heard what sounds like a rod knock, but it goes right away with; A: Higher RPM or B:give it more throttle. its from the left bank. a few shops cant find anything wrong with the engine itself, they scanned them... then i used my modis on it... and got no code, no tripped sensors, and no irregularities on the scope.

right now im baffled... i looked for loose items that could be rattling and got nothing. i know that spun bearings are fairly common on higher boost WRXs, but wouldnt it be a constant?

anyone with scooby experiance? or have seen somthing like this before? im almost to the point of wanting to pull the engine and take it apart... anyone that knows WRXs knows that engine work is a bitch in the car. any ideas before i get pissy and pull it?
Link Posted: 4/11/2006 6:53:27 AM EST
Well... what you just discribed is the sound of a spun rod bearing. We spun my friends rod bearing last week, and ended up throwing a rod due to the spun bearing. The most common bearing to spin is number 3 (passanger rear), but the cylinder he spun was #1 (passanger front). Is the sound coming from one side of the engine?

On my friends car, we pulled the engine this weekend, and it was not too bad. We did it in about 5 hours (pulled the tranny out with the engine, that way we could replace the front diff too.

A good way to tell what is going on is to get some oil out of the engine and to send it off for analysis. They will be able to tell you if something internal is coming apart.

Link Posted: 4/11/2006 9:01:27 AM EST
yeah, see i thought it was a spun bearing... but every spun bearing ive seen is a constant noise. i just needed some more thoughts.

its comming from the left bank(passenger side)

i drained the oil, cut the filter in halfe and couldnt see any fine stuff... i havent sent the oil out, i was hoping to avoid it... but thats the next step.


unfortunatly, pulling the engine will be a bitch as i had to sell all of my air tools. after being a cirtified mechanic for 3 years, it bores me, so i want to try somthing else. i ended up selling off a bunch of my tools. so ill be stuck doin everything by hand, in a driveway:/ oh well i shouldnt bitch.
Link Posted: 4/11/2006 9:19:49 AM EST
Piston pin or cracked piston would be my guess. Hope you can get it cheap.
Link Posted: 4/11/2006 11:58:05 AM EST
[Last Edit: 4/11/2006 12:01:31 PM EST by CSeaBass]
its 20k, its far from cheap...


its getting a fully built race block... but i was hoping to use the other block on a "project". i have a couple SR5 corolla GTSs that i want to "mess" with.

or i was lookin at building a slightly larger gokart with it(but not a sand rail)
Link Posted: 4/11/2006 12:08:26 PM EST
[Last Edit: 4/11/2006 8:13:30 PM EST by gus]
I bet you find a bent pin or a cracked pin boss on a piston. Turbo'd engines that get a ton of boost and go lean for even a fraction of a second can have detonation bad enough to do that and more. If/when you buy it, when you pull the #3 piston/rod (assuming that's the bad one), check and see if the bearing half that fits in the rod (not the cap) still holds itself in place from spring tension (assuming it hasn't spun). If it just falls off the rod, it has been pounded hard! At that point you need to really check the crank, that rod, and the block for cracks or other damage.

One thing about race cars - they are never worth what the sum of the parts adds up to come resale time. They are harder to sell because not everybody wants a true race car, and if they are actually raced they take a beating that will instantly diminish its resale value. Believe me, I've been down this road before. Make sure you get it (relatively) cheap. To most, a bone stock WRX would be worth more.
Link Posted: 4/11/2006 12:24:53 PM EST
oh, i know about the values. i have built 2 cars that could be called race cars. both of which were my daily drivers.


this care seriously has about 35k in it, i know the guy personally. its not that bad of a deal. he built it as a show car(not my thing) but damn it has some serious "Go" to it. honestly i can get a used scooby for about 12k, with 50k on the odo. im more or less lookin at an STi. and this car outproforms it in every way, nd is 5k less(what i was gonna buy the race block with)


i dont know... he girlfriend just totaled her car and wants a scooby now. i dont see the point in having 2 of the same car(well i do... but... there are other cars out there i want too) so i may look into a MR2 Spyder and slap a turbo, cage and suspension on it.

or i may just get one of the SR5s running and buy a FD rx7(my dream car), i have stayed away from this for reliability issues on a daily driver.

im still thinkin about a new tacoma too... so many options. but im really thinkin on my buddies scooby.

right now im unemployed so i have the time to work on anything i want(untill the money runs out)
Link Posted: 4/11/2006 1:55:53 PM EST
air tools? You dont need no stinking air tools... We did the whole thing by hand with breaker bars and ratchets... It sucked in places, but was not tooooo bad.

As you know, spun bearings are the most common failure in WRXs... Running that kind of HP (you said 360 at the crank? what is it at the wheels... 300?) should be safe, but if the car has lived a hard life, bearing failure is possible for sure. When we spun my friends bearing, we could not hear it all the time at first, but it slowly became louder and more constant.

It is almost impossible to diagnose via internet, but if the car was tuned and has not had alot of det problems, then I would look to the bearings. Does the car smoke any? Does it use any oil? I have found that oil consumption and smoke are closely related to piston failures. My friends spun bearing provided no smoke or oil consumption until the engine froze up. No smoke at all...
Link Posted: 4/11/2006 2:02:20 PM EST
[Last Edit: 4/11/2006 2:03:03 PM EST by gus]

Originally Posted By nater:
air tools? You dont need no stinking air tools... We did the whole thing by hand with breaker bars and ratchets... It sucked in places, but was not tooooo bad.

As you know, spun bearings are the most common failure in WRXs... Running that kind of HP (you said 360 at the crank? what is it at the wheels... 300?) should be safe, but if the car has lived a hard life, bearing failure is possible for sure. When we spun my friends bearing, we could not hear it all the time at first, but it slowly became louder and more constant.

It is almost impossible to diagnose via internet, but if the car was tuned and has not had alot of det problems, then I would look to the bearings. Does the car smoke any? Does it use any oil? I have found that oil consumption and smoke are closely related to piston failures. My friends spun bearing provided no smoke or oil consumption until the engine froze up. No smoke at all...



Yep, a piston problem will usually smoke, unless it's only around the pin boss. You'll also notice a loss of compression on that cylinder.
Link Posted: 4/11/2006 2:04:00 PM EST
I hope it ain't a case of too many mods and not enough thought. They can be a bitch to fix. Good luck.
Link Posted: 4/11/2006 3:42:15 PM EST
Gus brings up an excellent point that I had forgot to mention, have you done a compression test on this engine to see if one cylinder is low?
Link Posted: 4/11/2006 5:58:30 PM EST
Sounds like a rod bearing or wrist pin. Rev the engine up to 3 grand in neutral and unplug either an injector or coil one at a time on the bank you hear it on. If its in the rod or piston the noise will almost go completely away when you disable the affected cylinder.
Link Posted: 4/11/2006 6:09:46 PM EST
comp test is good on all cyls.


the engine was tuned well but CA 91 pump gas isnt the best. to my knowledge there hasnt been any probs with detonation though. the tuning was done at a rather well known scooby shop. right now its not buring oil, no smoke.. no nothing. just the noise... no proformance loss either... (at least none noticable.)

Link Posted: 4/11/2006 7:14:57 PM EST
check your hydraulic lifters - of your car has them.

they can wear and collapse unless the oil pressure is at a certain level.

cheap fix if it is.
Link Posted: 4/11/2006 8:42:00 PM EST
not that it has any bearing to the discussion but heres a pic of the car
Link Posted: 4/11/2006 9:01:44 PM EST
[Last Edit: 4/11/2006 9:15:51 PM EST by turboman]
Have you referenced NASIOC.com & LegacyGt.com. Nobody knows Subys better than they do. Don't have a "link" because since I traded my WRX and got a Legacy GT turbo wagon I haven't been visiting those forums.

This is my 4th Subaru and my last. When I slip the clutch while parking or backing up the clutch smells like burning manure, only 12K miles on it. . 1000's of others have the same problem and dealers won't admit it's a problem.
Link Posted: 4/14/2006 8:01:31 AM EST
Turn down the boost, then see how it acts. I've seen a few cases where a 3 inch super raspy exhaust tip was just enough to hide a little detonation which slowly turned into a shelled out bottom end.

Take it to someone who knows what they're doing. No offense, but if you haven't found out by now, you should take it to someone who has more experience. While my work deals mostly in domestics, alot of our work comes from people who thought they knew what they were doing but messed their motor up. I'm sure the same goes for imports.
Link Posted: 4/14/2006 11:50:49 AM EST
Piston skirts collapsed?? will still give a good compression reading but allow the pistion to rock in the bore.
Link Posted: 4/14/2006 4:44:19 PM EST
What kind of engine management is he running? See if it data logs...
Link Posted: 4/14/2006 9:29:48 PM EST
[Last Edit: 4/14/2006 9:30:37 PM EST by CSeaBass]
thats just it, nothing is comming up on the sensors or EMS and with a laptop on other occasions.... i sat there with my modis hooked up to the thing for 30 mins trying to get a reading on the scope when it knocked... nothing.

my buddy and i are gonna take it to the sac strip on wednsday... if we blow it, its gettin a new engine... screw it.

me, 2 race engine builders(who are my friend) 3 tuning shops, and 2 repair shops can figure it out.

my buddy says if he pops it, hes just gonna throw a race block in it... im not gonna buy it. i think i want a stock car for now. this way i can do the exact setup i want. im not sure though, im still lookin at a new tacoma:p
Link Posted: 4/14/2006 9:54:31 PM EST
Link Posted: 4/14/2006 10:41:51 PM EST
the owner at this point doesnt care. so im dropping it... he is lookin at it like this, he has the money for getting the race block, but needs to justify spending. so if it pops. theres his justification.


as stupid as that sounds to some people it makes sense to me(im like that too)
Link Posted: 4/14/2006 11:21:43 PM EST
Sac area? So did Vishnu do the tuning? Crucial Racing also seems to get high praise on LGT.com.

Turboman, do you go by that name on LGT.com?
Link Posted: 4/15/2006 12:40:58 AM EST
it was tuned by GruppeS, and it was tuned very conservativly(what ive been told... though im not sure i belive it... 360 at the crank seems pretty high for a stock block.
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the car is in the bay area, my buddy takes it racing in sac.

if it were my car i personally would have gone to vishnu.

gruppe s is pretty well known out here for scoobies
Link Posted: 4/15/2006 1:05:53 PM EST
Here's how we use to find spun bearings on bike motors.

Pull all the plugs.

Start with the suspect cylinder first and turn the motor over until that piston passes TDC and is on the way down.

Slip a long screwdriver or dowel down that cylinder's plug hole until it touches the piston crown.

Now, firmly and quickly, push down on the screwdriver with the heel of your palm. If you feel the piston move, voila.

It may take several tries with the piston at various points and sometimes the feeling is subtle. What you're feeling for is the slack left by the extra clearance on the spun bearing. This doesnt always work, sometimes it wont show up this way but if the piston DOES move, that's your problem.
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