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Why do Impreza's let go?

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Old 19 December 2006, 09:48 PM
  #31  
Butty
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Subaru must think there is some value added by switching the feed sequence around on 2003> Spec Cs:



Is there something they know about 320+ hp engines?

Nick
Old 20 December 2006, 11:40 AM
  #32  
silent running
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Originally Posted by Shark Man
Depending on model year, the main breather (crancase) Tees off the return pipe from the dumpvalve just before the turbo, which is down stream of the MAF sensor. There is also a PCV valve somewhere that also sucks directly into the inlet manifold when off-boost. The rocker cover breathers draw in fresh (filtered) air (well, they are supposed, at least)
Oil filming problems often do occur after an over-enthusiastic oil change. But as Shark Man says, the breathers go nowhere near the MAF. The breather flow is through the turbo, intercooler and into the throttle while on boost, and when in vacuum, through the PCV valve directly into the inlet manifold plenum. I'm still trying to figure out whether the rocker cover breathers ONLY ever draw air out of the inlet pipe, or whether they also vent out INTO the inlet pipe on full boost. According to the Subaru workshop manual they are strictly one-way, but I'm not so sure. There's oil in my inlet pipe that has clearly come out of that rocker cover breather pipe and blown along the inlet pipe toward the turbo.
Old 20 December 2006, 11:41 AM
  #33  
silent running
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Not familiar with the later layout...looks like the earlier one has the regulator at the rear after #3 cylinder, and the Spec C has the regulator at the front end?
Old 20 December 2006, 12:11 PM
  #34  
Shark Man
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Oh look....the pressure regulator vacuum hose on stock cars attaches to no.3 intake runner. Coincidence? Surely? Of course it is

btw top picture doesn't seem right (upside down? ) the pressure reg is nearest the turbo, well, on Classics it is anyway

Last edited by Shark Man; 20 December 2006 at 12:19 PM.
Old 20 December 2006, 01:54 PM
  #35  
Butty
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Picture is as you would see the newge rails looking from drivers seat.
The top one is a std fuel rail with FPR on drivers side as per all classics?
Bottom is the 03> Spec C version with FPR on pass. side and 1&3 injectors fed first.
Nick
Old 20 December 2006, 02:01 PM
  #36  
Shark Man
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Ahh, that explains it. I was looking at it as if looking at the engine from the front. So the FPR would be on the left (driver's side) on a standard classic.
Old 20 December 2006, 07:44 PM
  #37  
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classics have the FPR at the rear of the drivers side rail (no.3), new-age have it at the front of the drivers side rail (no.1) and cetain spec-C & Sti's have it at the back of the passenger side (no.4)...........

alyn
Old 20 December 2006, 10:33 PM
  #38  
Bob Rawle
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Reversing the fuel flow on a GC8 car reduces egt's by about 60 degrees on a modified car, fpr is not in the same place on a new age eurospec and was moved again on jdm MY03 cars on so depending on model year fuel balance vary's.

If the car has just been serviced then was the **** procedure followed, you know, fill the filter properly, dry crank it to get the pressure up etc (don't forget to sit down while doing).

Also what oil grade has been used. I have info on so many cars that lose big ends just after service, I also know of two dealers whose incidence of failure went to zero when the converted to the procedure described above, one in the south west and one in the south east.

The oil breathers don't feed close to the maf Mike, unless air is exiting the airbox instead of entering then it can't get there as they are all down stream (suction side).

Most big end failures are due to over heating the cylinders/pistons and nipping them in the bore which bangs the ends, that can be caused by det of course but also simply cos clearances can be virtually zero. (MY98 cars and piston slap have a lot to answer for !!)

cheers

bob
Old 20 December 2006, 10:41 PM
  #39  
Shark Man
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Most big end failures are due to over heating the cylinders/pistons and nipping them in the bore which bangs the ends, that can be caused by det of course but also simply cos clearances can be virtually zero. (MY98 cars and piston slap have a lot to answer for !!)
So slappy engines is now a good thing.

Not that nearly every k-series and Honda D16 out there does it when cold too. Yet nobody ever kicked a stink up over them, now did they? Go figure
Old 20 December 2006, 10:53 PM
  #40  
rigga
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Originally Posted by Bob Rawle

Most big end failures are due to over heating the cylinders/pistons and nipping them in the bore which bangs the ends, that can be caused by det of course but also simply cos clearances can be virtually zero. (MY98 cars and piston slap have a lot to answer for !!)

cheers

bob
Bob.... are you saying post 98 cars with the tighter piston/bore clearances to negate the slap problem, are more likely to have pistons nipping up if not warmed up correctly to temp before running hard on boost? and then having big end failures?

martin
Old 21 December 2006, 04:09 PM
  #41  
MikeWood
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[QUOTE=Bob Rawle]
The oil breathers don't feed close to the maf Mike, unless air is exiting the airbox instead of entering then it can't get there as they are all down stream (suction side).

That's true but I have seen oil contamination of the MAF (and the rest of the intake system) perhaps because there's a fair amount in the intercooler and it's vented under pressure back into the intake pipe when there's not much air flowing into the turbo and hence minimal vacuum in the intake pipe.

Mike
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