[2fast4]

Hey guys,
I know this is usually true that when any car runs better when cold engine. But I'm seeing opposite is true with our, or my car. My car is auto tranny.

After what seems like 10 minutes later, motor is fully quick to react and better shift. Before then, it's not as powerful getting onramp, or eager to shift automatic tranny....it's almost like human being lazy when not fully awake

With cold air and hot motor, my car runs like a bullet

Is this normal? Does the DME cuts boost till motor oil temp reaches certain degree or something?

 

[dhc3]

I would agree, I think most cars run better after warming up.

 

[Squidget]

Hey guys,
I know this is usually true that when any car runs better when cold engine.

Absolutely untrue, as you kinda imply yourself later in the post. Engines run well with cold air, but the engine itself should be as hot as possible.

The combustion process is more efficient at higher temperatures. The only reason engines don't run at thousands of degrees all the time is physical limitations. AKA, fluids vaporize, fuel pre-ignites, and metals fail.

Cold air is better not because "it is cold," per se, but because cold air is more dense then warm air. Air flow is often the limiting factor, so anything that can get more air into the cylinders is a good thing.

 

[CALWATERBOY]

Does the DME cuts boost till motor oil temp reaches certain degree or something?

Most modern engines, diesel included, limit power until operating temp's reached. The days of delightfully rich mix when cold hit the wall of emissions long time back.

 

[2fast4]

Most modern engines, diesel included, limit power until operating temp's reached. The days of delightfully rich mix when cold hit the wall of emissions long time back.

I've been driving mid 90's Eclipse turbo and when started from cold motor, power is delicious till it gets hot. It seems to be that it's contributed by air filter inside the engine bay sucking up hot air. I won't spell their names but I and several people think alike. I also see some of bimmer users got double cone filters injesting hot air too. It can depend on if the air metering is done by Karmen method or pressure method but I don't think it's good idea about the filters sucking up hot air.

Look at some of the drag king cars...with turbo inlet sticking out of front fascia to get the outside(no filter in this case), it shows importance of air source.

But yeah, I don't know how far back it started about the rich mix with cold air stopped, but my old car in mid 90's were full of this cold start power.

 

[Zeichen311]

I also see some of bimmer users got double cone filters injesting hot air too. ... I don't think it's good idea about the filters sucking up hot air.

You are correct; these other "bimmer users" are classic examples of people who make modifications for "moar powar!!!1!1!!" without really understanding what they are doing. All BMWs, for many years now, leave the factory with a cold-air intake system--the intake charge temperature is largely unaffected by the engine temperature. What Squidget told you is correct. The fact that your Eclipse ran better when cold was a flaw (hot-air intake, as you mentioned), not a feature.

 

[2fast4]

You are correct; these other "bimmer users" are classic examples of people who make modifications for "moar powar!!!1!1!!" without really understanding what they are doing. All BMWs, for many years now, leave the factory with a cold-air intake system--the intake charge temperature is largely unaffected by the engine temperature. What Squidget told you is correct. The fact that your Eclipse ran better when cold was a flaw (hot-air intake, as you mentioned), not a feature.

My Eclipse's intake was not flawed with hot-air intake. I chopped off airbox because it seemed that intake hole from outside was kind of small when I installed a much larger turbo. And that the bigger i/c pipe got in the way of stock air box. It ran super fast when cold.

Then, lots of guys changed air metering system that was measuring AFTER the i/c and they used huge i/c. After hot run and stop the car, touch the i/c on inlet side...hot. The other end outlet side is cold. This is with K&N air filter sucking up hot air. So I wouldn't jump on everyone who suckup hot underhood air. Their setup might be different.

You sound though as if Mitsu engineers some how designed to injest hot air...DSMs hold world record for 'fastest 4 bangers', fyi.

 

[CALWATERBOY]

I've been driving mid 90's Eclipse turbo and when started from cold motor, power is delicious till it gets hot. It seems to be that it's contributed by air filter inside the engine bay sucking up hot air. I won't spell their names but I and several people think alike. I also see some of bimmer users got double cone filters injesting hot air too. It can depend on if the air metering is done by Karmen method or pressure method but I don't think it's good idea about the filters sucking up hot air.

Look at some of the drag king cars...with turbo inlet sticking out of front fascia to get the outside(no filter in this case), it shows importance of air source.

But yeah, I don't know how far back it started about the rich mix with cold air stopped, but my old car in mid 90's were full of this cold start power.

Yessir, the laws of chemistry and physics brook no 'parking lot mechanic' interpretation.

Zookie, yer with me, right?

When Kompressing, temp's more critical than ever, thus the huge advantage of FMIC + Meth.

Dual cones for flow, and when movin' hope for cool air, sure. But there's a better way! Not a cheaper way....

 

[galahad05]

BMW's ECU keeps boost down until the oil temp reaches 180F. Heard this from a not-to-be-named-but-very-well-regarded tuner.

 

[Zooks527]

Zookie, yer with me, right?

Yup. Been sitting here nodding.