I did a bunch of little repairs like exhaust leak, map & connector harness, LCA relocation and bigger air filter. I ran a 14 sec 0-100 when it was almost 90 degrees and last week ran a 13 sec time when it was only 40 degrees. Does the weather affect the performance to cut an entire second off or would my minor repairs play more of a role? Would a supercharged car get more benefit from the colder air than NA? Also does this seem to be in the range of what my car should do or is there still more waiting to be discovered? I have 107K miles with 100% stock internals.

 

I wouldn't think that the temperature would take a whole second off your time. But it certainly does make a difference. I would say that it was a combination of the drastic temperature change and the repairs that you did.

Also, was the amount of traction and 60' foot times similar both runs?

But NA and supercharged cars will tend to run better in the cooler weather. Especially if you are not inter-cooled, then the temp. difference will make a bigger deal.

As far as your times, a 13.0 doesn't seem too far off where you should be with a completely stock motor and 6ish lbs. boost. What was your trap speed though. That sometimes tells more of the story...

EDIT: Just read your post a little better. 0-100 doesn't say too much. You need to take your car to a 1/4 mile track to get a good judge of how its doing

 

Yes this is where your gains came from most likely. Cold weather performance is huge in my car. The best mods I've done to my car are the ones that cool the intake charge. Relocating the Air filter, Meth injection, FMIC, etc... Winter time is a free mod. LOL.

The bad thing about winter is the lack of traction on the cold surfaces.

I think your car has more left in it. Try locking your BLM's at WOT and getting your Air/Fuel Ratio spot on. Generally my car runs a little leaner when the air gets cold. So this might be another reason your car is running so much better.

 

90 degrees F to 40 degrees F is a huge difference. I'm not sure if it is worth 100 HP difference, but it is a large difference none the less.

Both N/A and FI cars will be affected by the temperature difference, however the FI cars will see more of a power gain since not only are you getting cooler air to the engine, but you will be making more boost as well. The same is true about hot temperatures and how they effect N/A cars vs FI cars. Not only will hot air going into your intake lessen your performance, but hot air will also equal less boost for FI applications making them effected more by temperature. How much extra boost will make the difference of how much extra power obviously. But if you figure you get 25 HP or so for every pound of boost, you are looking at some substantial gains from colder air. My car on a very hot humid summer day will only see about 11 or 12 pounds of boost, whereas on a very cold day it has gone more than 15. Each setup will vary for how much boost/power gains you could see per an amount of temperature difference.

I believe there is a certain point at which the cold will peak your performance, and start to not really help you any more. For example, I doubt your car performs as well in 10 degree temperatures as it would at say 40. This is not to say anything about the obvious traction loss you will experience during cold weather running. Ideally I would say for temperature and traction that 45-50 degrees F would be ideal.

 

The 90 degree run was the 1/4 mile. I finished it going 100 mph. It will be a while before i get some track time so i will have to wait and see. I noticed my 90-100 times took longer than any other. My rpm's and even my mph both would drop and and then go back up. I started at 4200 rpm's at 90 and only made it to 4575 when i hit 100. I did relocate the air filter to the bumper corner so it will benifit when it gets hot again. Traction was real good and has been that way since the weather turned cold. I have trouble when it hot getting good traction so maybe its the type of tires.

 

A couple of things to consider, piggybacking on what was mentioned earlier-

By moving the air filter to outside the engine compartment (presuming that it was drawing engine compartment air prior to being re-located), this will definately have an affect as cooler intake air will make more horsepower.

Actually, air temperture is only one of a couple of weather variables that affect a vehicle's performance. In simple terms, the more oxygen that is available in the air, the more potential there is to make power. Temperture, humidity, barometric pressure and a relatively new variable that is taken into consideration now, grains of water/lb. of air, all have a significant impact on an engine's ability to make more or less power. In drag racing terms, the changes are typically looked at as density altitude, which is the pressure altitude corrected for the effects of changing weather, usually expressed in feet. To help understand this, sometimes it's easiest to remember that if a car was drag raced at sea level or 0 feet (such as in the New Orleans area), and then raced again in 5000 feet of elevation (such as Denver), without changing anything about the vehicle, it would be significantly slower due to the fact that the air at 5000' of elevation has much less oxygen available...oxygen is needed for combustion. So when you see a temperature change as drastic as 50 degrees as well as changes in the other variables mentioned above, you have the opportunity to see a measurable increase in performance. Calculating density altitude for a 50 degree change in temperture and leaving all other variables alone, roughly equates to an elevation change of 3000'. That is a significant amount in drag racing terms.

Sorry for rambling on here...

 

Boosted makes a few more good points. However Spokane Washington is not at a high altitude, and the barometric pressure should not vary too much past 29.92 (sea level), so he has some ideal atmospheric conditions other than temperature which varies.

 

Im right at 2000 feet. Not to high but not exactly sea level. I did try only 60% throttle for the first 40 mph and then went wot and the car seemed to respond better than just flooring it when i get traction. If i park the car for 15 minutes or more and then make a run it does a little better then going right after a run.

 

My point in the earlier post was to explain that "density altitude" is a corrected number. It helps to explain how a vehicle will run in different weather conditions and elevations. It will also give the person information to be able to tune for those changes if necessary. For example, you may be at 2000' above sea level, but with 90 degree air tempertures, 70% relative humidity and a barometric pressure reading of 29.75 (these numbers just randomly picked), your corrected density altitude may be 4000'. Now, if nothing else changes weather wise, except the air temperture drops to 40 degrees, your corrected density altitude might then be 1000'. This would be a 3000' drop and would net some noticable improvements in performance.

 

I got your point now. I will make sure when i go to the track to get a good time instead of just racing other cars i will not do it when it 90 and muggy but at the coolest point of the day.

 

Cooler air is more dense. It contains more air per cubic foot. When you insert more oxygen into the engine, it will facilitate burning the fuel more effectively.

Hot air, (not political rhetoric) is less dense, the molecules are further apart, less oxygen per cubic foot. etc.

Being a pilot, cooler air allows the aircraft to lift off the tarmac in a shorter distance.

On the flight computer, we use density alititude to determine our take-off distance. Temperature is one of the two variables (the other is altitude). That's why you don't see many small aircraft taking off from short runways at high altitudes on hot, humid summer days.

Also, humidity will displace air, resulting in a density alititude higher than actual.


Good:
Cool dry air, low altitude

Bad:
Hot, humid, high altitude.