Why so fast when cold?

[98GTX]

Why is my car so fast in the first few minutes of driving it? Is it really the computer adjusting and it slowly gets slower and less responsive?

More importantly, will a custom chip make your car always have the "cold" power and throttle response? Will it run all the time like it runs cold? Thanks in advance guys.

 

[Skud]

You know, the same thing happens to me.

I thought it was because I removed the air silencer and after the car warmed up, it was sucking in hot air. I put the silencer back on yesterday, but I don't notice a difference.

It's got balls for the first few minutes, then looses them after it's warm. I'm assuming this has something to do with the closed loop/open loop system?

Riley

 

[Gumby]

It is most definitely because of the open/closed loop system on these cars!!! During the first 2 minutes that the car is running the injectors run in an open loop, it's deceiving though. If you take your car to the track, it'll actually run slower if you do your run within this timeframe, I've tested it!!

 

[Skud]

Reading my Haynes manual, it says the open/closed loop status is derived from the ECT (water temp sensor).

When you first start your car, and the coolant temp is cold, the computer uses a set of factory pre-defined values for fuel, timing, etc. When the engine has reached operating temperature, the PCM switches modes and relies on the sensors to determine the fuel and timing values.

So, by reading that I think that there may be a faulty or poor sensor somewhere. Too bad I don't have a SES light. Then maybe I could get the codes pulled.

Anyone else care to chime in?

Riley

 

[Modular2v]

well it could also be due to the fact that and engine has more power when it is cold that when it is hott.

 

[98GTX]

Thanks for chiming in guys.

For those of you with a tune-- does the power remain more equal when the car warms up? Does the car maintain more of the "cold" power with a custom tune?

 

[Blakers01GT]

yes it has to do with the open/closed loop. the car is more responsive when it's cold, the engine does run stronger when it's cold. But guys, I wouldn't be beating on the engine when you start it up, that's not good for it. Before you start beating on your car, wait till the motor gets to operating temp. beating on it before that is not really good for the motor.

Blake

 

[jeff1414]

Mine is the same way but I let her warm up before I get on it!!

 

[PEWTERPONY]

OK since no one had an answer here....I'll tell ya why. Cold air is more dence, therefore its gona be rammed into the system harder than warm and become more effective at doing its job air especially if you have a CAI. Same thing happens to four bangers and six cyls. stock set ups or aftermarket, cold air will always make the car run faster. Why do you think no one wants to run on a hot day

Run your car on a warm day, then a cool day then a cold day......see the differences

 

[twogts4us]

OK since no one had an answer here....I'll tell ya why. Cold air is more dence, therefore its gona be rammed into the system harder than warm and become more effective at doing its job air especially if you have a CAI. Same thing happens to four bangers and six cyls. stock set ups or aftermarket, cold air will always make the car run faster. Why do you think no one wants to run on a hot day

Run your car on a warm day, then a cool day then a cold day......see the differences

Colder air being more dense has something to do with it, but I believe the question was regarding the temp of the engine. CAI helping is marginal, at best.
On another note - after driving home from work, the C&L aluminum Trueflow tube on my 02 GT is hot as hell. I'd love to wrap it with something to protect it from the engine heat.
I thought Skud and Gumby answered this issue pretty well. But I am surprised nobody suggested changing thermostats..?

 

[GREENBIOCH]

When I changed my thermostat that didn't really help that issue, aqs I still notice it with the 180* T-stat. Maybe if you completely removed it so the engine never has a chance to warm up to operating temp, but I have heard that really isn't good for the car.

 

[1Bad02GT]

Therm Removal

Thermostat removal is a bad idea. Differential metal temps, based on differences in composition, ( alum vs Iron and other alloys) cause imballances and metal "swaps", as in scrapes and gouges. Not a good thing for long life of the engine. Mostly due to unequal heating to design specs.

Just my 2 cents

 

[todd4566]

Thanks for chiming in guys.

For those of you with a tune-- does the power remain more equal when the car warms up? Does the car maintain more of the "cold" power with a custom tune?

I had a custom tune using a SCT chip. I too was hoping some of the cold engine power would stay afterwards, but that is not the case. I believe the cold engine power has to do with the cold air as stated previously. The whole open loop thing could contribute as well. Nonetheless, I try to keep out of it when my car is cold, but sometimes other idiots on the road force me to do otherwise.

Btw, the custom tune got me another 7hp. Not too bad

 

[302fordracer]

my car also does this cold engine faster thing you all are talking about however I really don't beat on it cold cause I also agree it is rough for the engine..but I can tell that it is just more responsive after only allowing 30 seconds to idle rather than a couple of minutes. It is smart to allow a minimal of thirty seconds for the car to idle before going anywhere as there is no oil protecting the pistons...it has all sunk down to the oil pan...additionally fuel economy is best at operating temp...all this may seem obvious but so many do not act like they believe it..

 

[YellowJacketGT]

Zoom Zoom when engine and air is cold

2002 GT KB 14psi kit.

I get the same response first thing in the morning.
I agree cooler air is part of the answer.

I'm no mechanic but I believe timming is the issue why the power disappears after awhile.

The amount of timing is calculated on Water Temperature, Intake Air temperature etc. As the temperature increases the ECU pulls timing to help prevent detonation (Heat is a killer)

Some possible solutions:
Only drive the car first thing in the morning.
Increase capability of intercooling system.
Use water injection
Reduce boost (hence reduce heat which shold alow increase in timing)


This issue is exagerated with my setup because the boost is maintained for a longer period of time than centrifical (Had Vortec/Cooler 14# prior).

I am currently experimenting with reducing boost to 12# so I can get more timing. I have heard of diminishing returns increasing boost. There have been times where a reduction in boost with an increase in timing gave more horespower.

Its funny the first question someone asks is how much boost you running instead of RWH or track times.

 

[98GTX]

I had a custom tune using a SCT chip. I too was hoping some of the cold engine power would stay afterwards, but that is not the case.

Finally I get confirmation that a chip doesnt keep the cold effect. Thanks. I really thought the car would bite all day long like it does when it is cold, when you get a chip. I guess that was wishful thinking.

I think it is mostly related to the open/closed loop issue. For instance, I know people with IS300's that use a "piggyback" system. It completly igonores the stock computer. When the car first starts up it is in open loop- it is not reading from the sensors. When it reaches a warmer temp, it goes into closed loop and reads from the sensors. A piggyback computer keeps the car in open loop all the time and runs on its custom tune. Not to bring in the ricers, but they have the same issue too.

 

[9COBRA7]

Thanks to all these posts I'm not goin delusional anymore. I to have the cold start-up quickness. All my friends were like its in your head.

 

[2012]

IMO, the "extra" power is because of the cold temps. Back when I had the Sentra Se-R, that car would run and pull in the cooler weather. I notice it now with the GT.

 

[jas142]

As an engine heats up it becomes less effective. But like said, its bad to beat on it when its cold.

 

[twogts4us]

my car also does this cold engine faster thing you all are talking about however I really don't beat on it cold cause I also agree it is rough for the engine..but I can tell that it is just more responsive after only allowing 30 seconds to idle rather than a couple of minutes. It is smart to allow a minimal of thirty seconds for the car to idle before going anywhere as there is no oil protecting the pistons...it has all sunk down to the oil pan...additionally fuel economy is best at operating temp...all this may seem obvious but so many do not act like they believe it..

On the 4.6 ohc engine, it's the cams that I worry about being starved for oil. But 30 seconds is excessive, IMO. The quickest way to warm an engine is too put some load on it by driving it. Never excessively rev a cold, unloaded engine...this is potentially very harmful.