My slow L99 is finally waking up a little

[Pentatonic]

I took the car out for a little fun driving a few days ago and it's noticeably faster than the last time I took it out a couple of hundred miles ago; enough to put a grin on my face this time.

When I first got the car new, it felt sluggish. It wasn't as fast as my old LS1 SS with a few bolt-on mods. It kinda felt like if my old LS1 was just getting out of bed...at 7am...after a night of drinking Jagermeister. Slow @ss L99 I thought.

Well, my slow runs were under these conditions:
Car: totally stock
Fuse Pull: Done
93 octane fuel since fuse pull
Conditions: Early-afternoon 83 degrees, humid
Mileage: 2100 miles. Followed GM's break-in procedure

The faster runs:
Car: Corsa exhaust + tinted windows (helps with aerodynamics)
Fuse Pull: Yep, still done
93 octane
Conditions: Late night, dryer air, 73 degrees
Mileage: 2500 miles

So unfortunately I changed at least 3 variables that could make a difference, but none of them by themselves I thought would make too much of a difference, but perhaps in combination they do?

I've yet to try driving the car in hotter, more humid conditions again, so maybe it will be slow again then? We'll see...

[SilverSS3108]

These cars really come alive after 5000 miles... Keep in there... Mine didn't feel like anything to brag about till I got the small bolt ons done (headers, exhaust, intake) and from what I'm told it'll be alot better after shes tuned.

[Bonemaro]

Yeah i seem to have more spirited runs in dryer/cooler air temps. She loves cool nights ie. 65 degrees and low low humidity.

[Scott@Bjorn3D]

Yeah mine really woke up around 12K. The I think Ted woke her up a hell of allot at 29K. 95F outside and roll onto the throttle with traction control on she will bark them. Going to be interesting getting traction this fall and winter. And if I get headers and put another 20-30 to the back wheels, may have to get drag radials to keep traction.

[SGOS252382]

10 degree increase/decrease in temperature = +/- 10hp or .1 in the 1/4 mile (rough average).

So you can see how driving around in 50 degree weather will make your car significantly faster than driving around in 90 degree weather. On a 50 degree day your engine is producing around 40hp more than on a 90 degree day.

Here's an example

A time of 12.93 @ 110 mph (90 degree weather) will equate to
12.46 @ 114 mph in (50 degree weather).

This was calculated using the DA for each temperature (pressure and humidity remaining constant).

Now you can see how guys run such fast times in cold air at sea level tracks.

[cybergrayls3]

Your joking about the tinted windows making it faster right? LOL

[cybergrayls3]

Originally Posted by SGOS252382

10 degree increase/decrease in temperature = +/- 10hp or .1 in the 1/4 mile (rough average).

So you can see how driving around in 50 degree weather will make your car significantly faster than driving around in 90 degree weather. On a 50 degree day your engine is producing around 40hp more than on a 90 degree day.

Here's an example

A time of 12.93 @ 110 mph (90 degree weather) will equate to
12.46 @ 114 mph in (50 degree weather).

This was calculated using the DA for each temperature (pressure and humidity remaining constant).

Now you can see how guys run such fast times in cold air at sea level tracks.

No offense but I don't think this is entirely true.I went with my buddy who just got his SS to do a baseline pull...(the car does have a magnaflow catback and CAI intake)...it made 373 to the wheels...it was 96 here yesterday and the dyno room was not air conditioned. So using your theory if he goes in February on a 36 degree morning he should make 60 more horsepower to the wheels. Which would be 433 rwhp...with an intake and catback...I don't see that happening..I agree it will make more power but not that much more

[SGOS252382]

Originally Posted by cybergrayls3

No offense but I don't think this is entirely true.I went with my buddy who just got his SS to do a baseline pull...(the car does have a magnaflow catback and CAI intake)...it made 373 to the wheels...it was 96 here yesterday and the dyno room was not air conditioned. So using your theory if he goes in February on a 36 degree morning he should make 60 more horsepower to the wheels. Which would be 433 rwhp...with an intake and catback...I don't see that happening..I agree it will make more power but not that much more

That's why dyno numbers are corrected for temp etc (SAE). If you don't correct them your car will make significantly more HP on a 36 degree day vs 96 degree day.
Dyno a car in 36 degree air and then in 96 degree air (Uncorrected numbers) and then post the results.

Also, take your car to the track (NA - Superchareged cars are not affected as much) on a 93 degree day. Then take your car to the track on a 36 degree day. You car will run roughly .6 faster. It could possible run faster than that.


This isn't perfect science (just rough averages). I go to the track all the time and I see about .1 improvement for every 10 degree drop in temperature. That would equate to around 10hp.

[mlee]

Mileage, Mileage, Mileage makes a big difference along w/ what SGOS252382 is saying.

I put 16K miles on my first L99 and started over with a new one and almost wanted my old one back as it was way faster. Now I'm at 11k miles and back to fast again.

Give it time...

[SGOS252382]

Here's another example to show how temperature plays a huge roll in performance.

Assuming a track elevation of 1000 ft,. Temp 36 degrees, pressure 30.0 humidity 50% = DA negative - 354 ft.

Assuming a track elevation of 1000 ft., Temp 96 degrees, pressure 30.0, humidity 50% = DA positive + 3624 ft.

That's a 3970 ft difference in Density Altitude.

A 13.0 @ 110 mph run will correct to 12.36 @ 115.68 mph with a DA of 3790 ft.

That equates to about 60hp or so.

[mlee]

^^^^Yup... that's why we DA correct track runs and SAE correct dyno runs... to compare apples to apples...

[cybergrayls3]

Originally Posted by SGOS252382

Here's another example to show how temperature plays a huge roll in performance.

Assuming a track elevation of 1000 ft,. Temp 36 degrees, pressure 30.0 humidity 50% = DA negative - 354 ft.

Assuming a track elevation of 1000 ft., Temp 96 degrees, pressure 30.0, humidity 50% = DA positive + 3624 ft.

That's a 3970 ft difference in Density Altitude.

A 13.0 @ 110 mph run will correct to 12.36 @ 115.68 mph with a DA of 3790 ft.

That equates to about 60hp or so.

Hey thanks for the explanation...makes sense when i think about it like that...ya learn something new everyday! Sorry if I came across as a smartass...but I'm sticking to my guns that the tinted Windows will not make a car faster lol

[Pentatonic]

Originally Posted by cybergrayls3

Your joking about the tinted windows making it faster right? LOL

Uhmm...no. The guy at the tint shop said it would add between 15-20 hp because it smooths out the aerodynamics of the car. So wait, was he BS'ing me? :(

Originally Posted by SGOS252382

10 degree increase/decrease in temperature = +/- 10hp or .1 in the 1/4 mile (rough average).

OK, so that's the correction factor. Cool, thanks. I was too lazy to look it up myself heheh.

Oh hey, I have a question for some of you engine techies out there; how much does fuel temperature and it's effect on the fuel density matter for these gasoline engines? Of course, air density is a big player, but fuel is the other side of the equation.

I know that on some of the bigger diesels out there; as temperature increases, fuel density decreases and that can decrease power significantly. Some of the diesel manufacturers put a temperature compensating control in their diesel fuel delivery system to combat the effect. But that's for diesels...I don't know gasoline engines as much.

[SGOS252382]

Originally Posted by Pentatonic

Uhmm...no. The guy at the tint shop said it would add between 15-20 hp because it smooths out the aerodynamics of the car. So wait, was he BS'ing me? :(




OK, so that's the correction factor. Cool, thanks. I was too lazy to look it up myself heheh.

Oh hey, I have a question for some of you engine techies out there; how much does fuel temperature and it's effect on the fuel density matter for these gasoline engines? Of course, air density is a big player, but fuel is the other side of the equation.

I know that on some of the bigger diesels out there; as temperature increases, fuel density decreases and that can decrease power significantly. Some of the diesel manufacturers put a temperature compensating control in their diesel fuel delivery system to combat the effect. But that's for diesels...I don't know gasoline engines as much.

That's my homemade formula, but it hold pretty true for stock or bolt on cars. You can expect to run around .1 faster for every 10 degree drop in temperature. My car went from running 12.40s (temps in the 80s) to 12.1s (temps in the 50s).

I don't have a clue about fuel temperature. I just know that cold air holds more oxygen per volume which equates to more HP.