Can anyone explain it? I know generally about it, but I'd like to know the details

 

i second that question (bolsen, im a fellow Mil-town evo owner also)

 

FWIW, during cold start-up metal surfaces in the engine are colld and as a result the fuel tends to condense rather than properly mix with air. To ensure cold start-up and running without stalling, usually there is feul enrichment during that phase to ensure adequate mixture strength.

In emission controlled engines, there's additional concern about getting enough heat into the catalyst for it too do its job. Placing it close to the exhaust port is one of those measures to light it up quickly which obviously flies into the face of making optimum power.

USDM Subarus use tumbler valves during cold start to regulate airflow, combustion and mixture strength. WRX's had a cat before the turbo. One of the reasons Subarus likely need more emission control equipment than is that the path from exhaust to the first cat after the turbo is much longer, something that effects the effectiveness of the cat especially during cold start. The tight package in the motor not only improves spool-up but also emissions, probably explaining why Subaru needed a USDM 2.5 to compete with the 2.0 in the Evo.

 

when i start it up and dont allow it to idle on a cold day before i drive, it usually BOGS when i shift and get into ascending gears. Its not too bad, but i hate giving it throttle, loosing power sa if theres a fuel cut (bog), and then the engine breathes after a second or two. I did notice that it is worse with my catless RS-R exhaust compared to stock.

 

Mine's bone stock and does the exact same thing. If I don't let it idle for a min or two on a cold day and just go, when I shift into 2nd the first time it just totally falls on it's face. Then after a sec or two it kinda revs up... So, I always give it a min or two in the morning to "wake up".

 

Yea yea, ditto. It's MUCH worse for me on really cold days too..then the tranny is *****y as well. I usually start'er up, let the dogs out, put them up, grab a coke...then I'm good to go.

 

Yeah I usually time it by a song on the radio... Most are 3 min long, so if I can get through 1/2 a song I'm usually good. Even that can seem like a long time when you're just sitting there looking at the wall of the garage.

 

Heh, same thing for me when I let the car idle. I'll start a song over on the cd player and wait until 30 seconds or more (depending on the drive) has elapsed. For warming up the car, I start it before putting my daughter in her baby seat.

FB

 

Regardless of the car you have, BUT ESPECIALLY with the Evo, you should let the car warm up for atleast a minute and a half. This will allow the oil to circulate and properly lube the car. When your car sits for a while, your oil collects in the oil pan, barely leaving enough to lubricate the internals.

 

I agree about letting the car warm up (idle) for 30 seconds to a minute. I then take it very easy, below 3000 rpm at least until the temp gauge is in the "normal" spot.

To play devil's advocate, on other forums (audiworld) there were discussions about letting a car idle for too long, which would promot carbon buildup that could hurt performance and efficiency. What are thoughts on this, like what would be too long to idle or is it even an issue?

FB

 

Ok guys, lets get back on topic...

What's the story with closed loop... how long does it stay on? How does the o2 and temp sensors come into play?

 

Closed loop I believe is when the thermostat is shut which doesn't allow the coolant to the radiator or something to that affect. I helps the car warm up faster. The temp sensors tell it when to come out of closed loop.

 

always let it warm up to the C atleast.