down on power?

Vecken

New member
can anyone help me diagnose whats wrong with my subaru? i own 2 identical 2000 foresters 2.5 sohc. no mods. just tested 0-60 times and hp readings with the "torque" app, same profile on both.

black one puts out 90 hp 11.8 time "S" model with LSD
green one puts out 125 hp 8.8 time "L" model basic

these were only single tests im sure I could get better times but one definitely puts out better power than the other. both have o2 codes thrown with pinhole exhaust leaks, while the black one has a p0440 evap code and I can audibly hear a hissing. where should i start diagnosing? already has new plugs and filter, equal compression on all cylinders new head gaskets. did the rebuild myself so im trying to figure out where i screwed up. green one has unknown history. could imperfect valves or timing cause the problem it is ticking rather loudly.

black one definitely feels like its bogging, has no power until 3200rpm, kicks in a bit and then runs out of all steam after 5500rpm

kind of funny that the green one i bought for parts/beater... 
should i just cut my losses and swap the motors? or just figure out the problem with my good one (black S model, no rust)

 

JoshP

New member
When I use the road dyno from Romraider I find wildy random results.  So do maybe 5 runs each and average them out.  Oxygen sensor is pretty important, so get that fixed.

 

Vecken

New member
i did 2 pulls each, it was fairly consistant within 5 hp, but there is a definite hissing or howl from air intake when im flogging it in the black one, where is the most common leaks? 

 

Nigel Prodrive

Dirt surfer
the S model has 4.11 final drive and nice close gear ratios, same in fact as the much-desired 2.5RS box, so it "should" be faster

L has 3.9 final drive and ratios spaced more for fuel economy than quick accel.

so it sounds like the S Foz is kinda sickly (vac leak or bad intake gasket would def affet pwer here) , and the L is pulling as intended. L versions are also somewhat lighter, so that probly helps too.

the torque app relies on the accelerometers in your phone, so it says the faster car has "more hp."

 
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Vecken

New member
Black one has new intake manifold gaskets but I will double check them. They are both 5 speeds. Could a sticky pcv valve be causing any issues or any sensors? I don't think o2 sensors getting bad readings would kill power that badly. Just hurt gas mileage. I just tried swapping the fuel filter out with new high end free flow, no difference. I will be removing airbox and checking all the lines. Where should I start in terms of sensors or common leaks?

The pcv valve hose is nowhere to be found and its pretty hard and dry rotted

 

Nigel Prodrive

Dirt surfer
triple check that intake mani gasket. we had a friggin nightmare trying to cure fuel injection probs on a 911 motor recently. went crazy checking injectors, sensors, vac lines,  and about 24 different connex. discovered a single nut caught under the intake mani, hidden by gasket. bad seal = fast car that ran like shit.

 

Vecken

New member
Thanks! All the symptoms seem to be pointing to the intake manifold, I had to jiggle it a bit to get the intake on after the rebuild so maybe I messed up the gasket somehow. Definitely feels like its starving for gas/ too much air. I just bought new gaskets so in the process of pulling off the whole intake I am hoping I find it.

I need moar Powah! Next step is to go turbo
default_smile.png


 

Vecken

New member
So I got new intake gaskets installed, the old ones were not seated properly, it definitely starts easier and does not bog as badly but it's still very low on power. The green one definitely revs much quicker.

Could it be because I put a dohc block into a sohc car? Not sure if that drops compression significantly enough to cause a good 25% or more power loss. I'll get a tester on it tomorrow now that I have a nice new starter to crank it over. Could valve adjustment be off (set the valves while the heads were not installed on the engine) enough to kill power that badly or an exhaust leak?

 

Vecken

New member
I can get my hands on a long block that needs headgaskets for $200 should I go for it and do it perfectly from the start? If anyone has a 2.5 sohc block that needs resealing I am very interested.

 

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