When I leave work each day I head up a 7% hill. I tear out of my parking spot and hit the bottom of the hill at 70 in 4th, and it's planted for 2km to the top. Usually it's all I can do to sustain 70 on the hill. However, when it is hot out, like 25°C or so, I have to ease well off on the gas at 70km/h or before I know it I'm going 80. The questions is, why? Also, what tuning might make this awesome power available on cold days? It makes me think there is room for improvement in the tuning of the old girl ...
sounds like an air or coolant temp sensor issue..may be running a bit lean and with cooler denser air it doesn't get enough fuel to compensate..
cold motor.... in cold weather the engine is dead cold in hot weather its semi warm when you start it already. You may notice that when its really hot it might not even go into high idle on a "cold start". try letting your truck warm up before tackling the hill. technicaly an engine should make more power in cold temps due to denser air. in theory you are getting more into the combustion chamber per intake stroke, vs hot lighter air where you get less of it.
Not the issue. It is the same if I run at the hill with a hot engine. I sometimes drive to work, get my tools, and then drive to a remote division. In this situation I would not shut the truck off, just dash in and grab a couple of things and then head off with the engine fully heated up. If it's 0600 and chilly, it's slow. If it's mid-day and hot out, it's fast.
the air temp. sensor (which after reading your last post is far more likely the culprit since the condition seems not affected by engine temp) or the idle speed control valve may be allowing too much air into the engine at lower temperatures...the iscv should be on the air filter side of the intake...(another good question would be whether your idle speed is consistant at warm and cold outside temperatures)...the iscv can usually be cleaned by blasting it with carb cleaner after removing the air intake hose..(seafoam spray will work best for cleaning it)...it may however need to be removed to clean the plunger and air passages ..not sure how Subaru meters incoming air temperature but there should be a sensor in the airbox or the air intake hose...it's hard to find much data on the Subaru engines....
I had a old 1973 Tahiti Jet boat with a 455 rocket olds engine. When I first got it it never ran over 160 on the temp. Even on hot summer days when the lake temp. was 80. I had Oscar do a little tune up one day and told him that it feels like it wants to run more. He asked me what the runnning temp was, I said 160. Oscar said let me put a valve in the cooling lines and play wit it till you get up in the 200 temp. range and it will run better. he was right. Seems like it added a 1/3rd more H.P. With all that said on hotter days I would think you are getting a little bit better burn in your cylinders. Just guessing, maybe, I think so, could be, wishful thinking, Hmmmmm?
Thanks fupabox. You always give me well-considered suggestions. The idle is pretty consistent. The old girl doesn't like to idle when cold, but she gets over it pretty fast. I'll look into those items you suggested. Someday you should explain what your handle means!
