eng warming up

[foxhu]

I've had a question long time ago but didn't ask, imma do it now.

when the car start its at high rpm(cold start), but in a few sec later (sometime 20 sec to a min or so) then the rpm dropped to 1k rpm, is it normal? it's the 2nd car I owe the first one didn't do that, so it's kinda weird to me at least.

can anyone tell me if it's normal and does your car do it?

[ft_sjo]

It's normal.

The first 20-30 seconds is the cat warm-up period. After that it just goes to normal warm-up where the idle speed will gradually drop as the engine warms up to temperature.

It's fine to drive the vehicle during both scenarios.

[DaJo]

Very normal with these cars. "Fast idle warmups"!

[gzpermadi]

normal, even my bike is doing same

[Chimpo]

It's not just our cars that do this... while there is probably an exception out there, I can't think of any modern (more specifically built in at least the past decade) car/truck I've been in that doesn't do this.

[Rayme]

Fuel needs to be warm to combust well. It's been true with all gasoline/diesel engines since ever. That's why every car idles high to warm up faster.

[SliverBrz]

all cars do this... I haven't seen one that didn't.

You sit there long enough they idle down to around 700 thats normal.

[strat61caster]

Originally Posted by ottopilot

Fuel needs to be warm to combust well. It's been true with all gasoline/diesel engines since ever. That's why every car idles high to warm up faster.

It has more to do with bringing the materials and oils up to temperature inside the engine and lighting off the catalytic converters than it does with combustion efficiency. Back in the old days the choke existed because carbs were tuned to work well at operating temperature, when cold the passageways aren't "tuned" properly and the car won't run well so extra fuel was added to ensure a stable idle, injectors don't really need that with modern ECUs. Fuels are generally kept as cold as possible until they enter the combustion chamber at which point the fuel actually acts as a coolant to the engine, if a "warmer" fuel was advantageous then the fuel tank and lines would be placed closer to the engine which would heat the fuel, cool the engine AND centralize the mass of the vehicle in one location, as we can see from modern design; this isn't the case, 911's and other mid engined cars have the fuel up front AWAY from the engine and the same for front engined cars with fuel tanks in the back.

Just an FYI

[foxhu]

my civic would warm up at high rpm but it wont drop to low rpm in like 20 sec or so....it takes forever to warm up that car, thats why I got worried, but guess I worry too much thxxxxxxxxxxx you guys!