Car seems Fast when cold

Really random question, but hay never herts to ask. I notice when i start my car up in the morning and let it sit for a few seconds, jsut to get the oil and heat sirculating. by then the oil temp is just a bit above the C on the dash. I proceed to the highway and floor it to get on the highway and WOW. seems like boost hits really hard and everything just seems a bit faster....? any reasoning for this or is it just in my head?

 

*Edit*
No idea. I'm a moron.
I do not collect go, and do not collect $200.00.

 

Yeah true. so its just sucking all that cold air in the engine from being cold and that's why for a bit it's faster?

 

thats the sweetness of the car running itself into self destruction

 

cold air is more dense thus carrying more oxygen and making your car "faster" than if it was 100 degrees and the ic was getting heatsoaked. I'm sure it has to do with the ic being able to run more efficently in the cold also. I wouldn't take my car up to redline until the needle is in the "warm" area, it takes longer than you think for a car to warm up.

 

LOL i love it! just great

 

boost creep for me happens easily when its less than zero out. zero humidity air that is dense with oxygen burns a lot better

the car not being properly warmed up, well your fluids have more viscosity, causing the engine to run harder. Its not faster but hey maybe it sounds like it. at any rate its not good for it

 

<noob.
Define boost creep, please?

 

Wait, is this a freaking joke? Honestly, it takes my car around 5 min of acutal driving to get the engine oil up to temp. Don't pound on your when it's cold.

 

I really hope you meant "boost spike." As in, when you pound on it, it spikes goes above target in the midrange RPM. I've still have yet to see a 2.5L WRX with stock turbo creep...ever.

Boost creep is when the wastegate of the turbo cannot pass enough air, and your boost exceeds targets. This typically happens in the high RPM areas, and/or on cars with catless exhaust and larger turbos.

Boost spike is when boost exceeds target due to improperly tuned wastegate cycles, and often is seen on cars using OTS maps (IE; cobb stage 1 or 2). I've also seen it on cars with fairly aggressive tunes that don't have the correct IAT compensations (this is common for all tuners, as you aren't often tuning in both 80 and 20 degree weather at the same time).

 

No. just wondering.
and yeah that would be obvious

 

Hrm. Ok. Does "cold air makes more power" work as an answer for you?

 

Ah, gotcha, thank you.
So on my stock 02 WRX, If I have it floored in 5th gear and the boos gauge normally stops at 15, but sometimes goes up to 16 or 17, that's what you're talking about, correct?

Does thist also happen when it's not so cold out, or only when the air is more dense?

 

Well, kinda. Just simply seeing your boost gauge blip at certain RPM or certain outside temps doesn't tell us anything, however. Boost creep is a mechanical problem due to the design of turbocharged engines. Basically, creep occurs when your engine flows more air then the wastegate of the turbo can bypass.

Boost spike is pretty intuitive. It's simply due to the engine tune overshooting the target boost, and then settling back down.

99% of the time when people complain about boost jumping higher then target, it is due to boost spike.

By "stock 02 wrx" do you mean "stage 2 02 wrx?"

 

O no way cold air makes more power. how so.....

 

Don't feel too crazy, I've noticed this too (unfortunately).

This usually happens to me when I don't get a chance to warm the car up before going somewhere and there's some asshat on the road not letting me in or something.

I always just chocked it up to cold air being denser and never really thought of it much.

The IC isn't heat soaked and the block is at 30° instead of whatever its supposed to be when its at temperature (230°-ish ?? I have no idea).*

 

is this a joke? :ugh:

 

Ok, yes, you got me. Here I actually thought you where actually going to contribute something worthwhile to the club.

 

Ha yeah i dint know bashing was contributing to the club either....

 

I would think that redline + cold engine = destroyed valves

 

Ok i should have put it in your words. I guess you get what i was saying. thanks!

 

you were the one to make this thread my friend, re-read your own post. pretty sure you can figure out why you are getting the responses you are getting.

 

A series of lolz.

#1 Oil temp
#2 "Just above C"
#3 "Everything" seems faster

 

ok read it, and yes i did start the thread. correct. i was asking for an answer and not crap. what ever end thread.

 

Ahhh yes Jokes on me today!

 

Umm, it definately takes more than five minutes for your oil to get to temp, unless you like to hammer on a cold engine. Even with the oil to water cooler/warmer it takes longer than the coolant to get to temp.

Do you have an oil pressure gauge and a REAL water temp gauge? Thats the only way you would know. When my oil pressure is down to 20psi at idle, I know the oil is at temp. It never goes below that , even during the summer. Cold idle can be as high as 60psi when below zero.

This is with a 10mm pump though.

 

If you want, we can data log a few pulls with your car if you want. See how off your timing is :biggrin:

I've got everything you'd need.

 

Yeah, my 5 min number was a bare minimum. I don't stopwatch time it, but it typically takes my car 10-15 to get the normal idle PSI.

 

everyone needs to chill. not everyone understands exactly how an intrenal combustion engine works... basically if you understand that air and fuel mixed with a spark creates a combustion that pushes down on the piston and turns the crank shaft. this brings us to our point. cold air is more dense than warm, thus when it is mixed with fuel and then ignited, a bigger explosion will occur, which pushes harder on the piston, making power. that is why turbo's are so effective, they force more air into each cylinder to create a bigger ka powwy.

...i tried to make it easy

 

yeah i didnt notice what mnstilynwrx said to get bashed on, Bullwinkle

 

I suspect this is the case.

the turbo is cold, the IC is cold, the intake mani is cold. so the intake charge all stays much cooler than when all of the above is hot.

 

Quoted for truth.

Anyone who thinks that an '06 WRX (with the stock td04) has boost creep doesn't know wtf they are talking about.

Hooray for the NASIOC clowns spreading garbage for information.

 

5 minutes? lucky
Its takes me at least 10 and I parking in a 60F garage.

 

-20 degrees outside and full throtte. I believe what I saw. It was spiky/creepy, but above gauge normal for sure.

sorry i guess i dont know wtf i am talking about.

 

Believe what you want.....

Run a vacuum line directly from the compressor to the wastegate actuator -- ie, remove your bcs from the equation -- and then try to prove to me that you have creep.

You map isn't completely set up properly like Bullwinkle alluded to.

 

Higher gears = slower acceleration = more exhaust pulses to hit the turbine in the same rpm window (ie, a range of something like 3500 - 3550 rpm or whatever) = more boost.

This will typically be the case for any car regardless of the temp outside.

The thing with tuning boost is that it is kind of a balancing act between your rpm window time and the amount of pressure you want to divert away from the wastegate actuator via your boost control thingy.

On a 5-speed WRX, most are tuned to hit target boost (thanks to the balancing act) in either 3rd or 4th gear. As a result, you will end up with a slight overboost in the taller gears; this can be removed for the most part by futzing with the turbo dynamics but can never really ever be totally removed. You will still see a slight spike and then have the boost settle back down since there is always going to be a delay in the PID system.

You'll also see less boost in 1st gear......would you call this vacuum creep?

 

i totally get the idea of boost spike and creep. ive seen weird things in the cold with my car. if im in a higher gear like 4th and if i hold the throtle down, my boost spikes and then ill hit a fuel cut....(so i think thats what it feels like) but its only when i spike. probably leaning out the car too much so thats WAY more air than fuel. i need to get an AF gauge so i can keep my eye on that. and when its REALLY REALLY cold.....ive seen (only once this has happened to me) my oil pressure kinda drop. it hasnt ever done it sinse but it really freaked me out.

i pulled up to a light and when it got down to idle it was having issues holding idle for a few sec. i reved it a little and it was fine....is that too thick of oil? or what? its been bugging me that it only happened once and i hope never again

 

Are all you guys running a GM BCS? I had a nasty boost spike on initial spoolup. It would overrun by about 5-6psi. I did some reading and realized that they(BCS's) really don't like to be run at over 20hz. When I changed my BCS frequency down to that, I've had no issues. Granted I have a Link Plus.

 

I am running the stock BCS

 

There is a table in the ecu that tells the car to cut fuel when boost goes above a certain threshold for a given barometric pressure.

The problem that everyone is having is that there is another table in the ecu that either adds or subtracts WGDC based on intake temperature, ie, it will remove WGDC from your base settings when it is cold and add in some when it is hot.

Unfortunately, this table is not correct. I have found that on my '06 that the slope of the table isn't steep enough. In other words, not enough WGDC is trimmed when it is really cold and not enough is added when it is hot. In lamen's terms, the car would overboost in the winter and underboost in the summer.

This issue will get even worse is somebody decides to start messing (aka "tuning") with their target boost and initial and max WGDC tables without correcting the temp compensation map. Like said earlier, that map isn't steep enough -- so if you tune the car in normal weather, you are going to end up overcompensating on your WGDC map and add too much to it.

Then when it turns to winter you now have way too much WGDC as your base and not enough of a compensation to trim off due to the colder, denser air -- and end up with huge boost spikes -- and then claim ZOMG I'm suffering from boost creep!

Like Nate said earlier, boost creep is a mechanical issue due an unbalanced ratio of the wg size to the compressor and engine size. 99.9% of the problems reported with the 2.5 WRX (and stock turbo) are due to ecu calibration issues (even while stock).

 

GM BCS here. No issues.

However, the issue is that your set of compensation tables needs to be calibrated for the BCS at hand. This typically isn't the case, even with the stock one.

Subaru/Denso didn't do a very good job at this and most tuners never touch these tables because they either don't understand them or take them to be correct since they came from the factory that way.

 

Wow, good info from both you and Bullwinkle on this. I've yet to run logs this winter but noticed my actual boost being higher then my target boost by about 1.5PSI on cooler days (for about 1500RPM). It's never seemed to be an issue as far as I can tell. After looking at the WGC (IT) tables on both the stock and tuned maps they are both the same. Thanks for pointing out where to look to help correct that. :biggthumpup:

 

Good post's Tom. I like the use of the technical term "boost control thingy." :laugh::biggrin:

Great post, and I completely agree. As long as we're on the topic of the GMBCS, I should note that I almost completely flattened this IAT WGDC table when using the GMBCS.

Regarding Piddsters GMBCS overboost, when using the stock ECU, I typically solve these type of problems using the Turbo Dynamics section of the stock ECU. This section controls the activity of the WRX PID controller (for those who don't know that term, click here, and here).

 

Yup, it sounds like your temp comp table isn't correct for colder temps. Thus, you are overshooting boost a bit and then your turbo dynamics kick in and pull in the reigns and pull WGDC to lower boost back to target -- as seen by your 1500 rpm spike.

Getting your entire boost system to work correctly for all conditions takes a ton of time. One thing I found that was helpful with my car was that the stock temp compensation map is 0% (ie, no compensation at that temp) somewhere around 65-60*F (I can't exactly remember off the top of my head). I can't even count how many days where I'd notice that it was exactly that temp outside and would basically drop everything so I could further dial in boost without having to account for compensation. Once I got that squared away, it was just a matter of continuous tinkering in different temps to get the correct temp compensation dialed in.

Fun stuff. :biggrin: