poor results at the 1/4... does this seem right?

[bhuff30]

My dad and I went to KCIR and ran the 1/4 mile the other night. He brought his 06 GT and I brought my 88 2.3l.

It was a quite hot day, around 90F and the track is at 800ft elevation. Using an online calculator, the alititude density was ~3500ft.

The car is an 06 mustang GT, automatic, with less than 15K miles. The only major change is GT500 wheels and tires, which I can imagine are a little heavier. His best run was a 14.649 at 95.05 mph. This seems WELL short of what one would expect since magazines have tested stock GTs to as quick as 13.6@102mph. His 60' times were around 2.2s, which seems a bit sad too.

Shouldn't the car be a lot faster than this, even in hot conditons? Even if you correct the 3500ft altidude density to sea level using NHRA correction factors, it's still only 14.02@99mph. He had absolutely no wheel spin. Does the stock wheel/tire combo allow a bit of wheel spin to get the rpms up faster? The traction control and AC were off. He would stomp it from the line and get no wheel spin at all.


Bottom line: is this right or is something terribly wrong? Do these car's really roll over dead like this in hot conditions?

On a good note, I improved my best times a lot, running 13.73@99mph with a 4cyl in the heat. hehehe

 

[BJ1000RR]

He should try stalling it up when lauching.

A 2.2 60ft should still put him in the 13's.

something doesn't sound right.

 

[cowtown]

Doesn't sound like he's getting the most out of his car but yeah 3500FT is a real killer. Try out here this week, my handy little portable weather station has been metering over 6200 DA with the wack weather we've been having, the car she dunna like it!

We'd need to know more about the runs too. I found my best times were always with OD off and running the car up against the stall converter has mentioned above, easily a tenth or more just in the launch.

I'd also be suspect of what the online calculators say for the DA, I had one night last month where a guy used an actual portable weather station and read the DA as 5100ft that night, my calculations when I got home said 4100. It'd trust the calibrated instrument first myself.

Get an intake and tune on that auto STAT! Just switching to a Diablo & C&l combo got me 2.5 tenths and 2.5MPH, I upgraded to an SCT tuner with Brenspeed tunes and my car shifts like a bear at WOT now, picked up another tenth and a little MPH.

 

[Five Oh Brian]

GT Automatics need more rear end gear. My 07 GT Automatic is bone stock with the factory exhaust, factory air box, and heavy 18" wheels. With just 4.10 gears and a Diablo Tuner, I've run a best of 13.40 at 102.9 mph in the 1/4 mile on a 2.0 sixty foot time with factory tires. Runs consistent 13.40's all day with a DA of 600' at my local track.

100% factory stock, the vast majority of GT AT's are running high 13's and low 14's at about 98-100 mph in the 1/4 mile.

 

[ski]

Another thing to be aware of with these cars is the stock tune pulls timing when the ambient air temperature gets hot in order to prevent pinging.

 

[bhuff30]

We'd need to know more about the runs too. I found my best times were always with OD off and running the car up against the stall converter has mentioned above, easily a tenth or more just in the launch.

At first, he was just stomping the gas on the 3rd yellow. He later tried reving the engine against the torque converter, but I'm not sure how much, probably just enough to get the rpms up instead of loading the driveline hard. I'd guess he left the OD on and of course let the transmission do the shifting.

Another thing to be aware of with these cars is the stock tune pulls timing when the ambient air temperature gets hot in order to prevent pinging.

I was wondering about this, but really 30hp worth of timing?! The other thing I was wondering... does it have a knock sensor? Maybe it was detecting knock and pulling timing, but I would think the runs wouldn't be so consistent then.


He bought the 'power pack', but didn't install it yet. Obviously, if it is down 30hp, then we should figure that out before putting on mods I would think.

 

[xtweakerx]

Racing in the heat = sux.

So far my best bone stock in 5spd was 13.9 @ 100 w/ 2.1 60 foot.

However i won't race it now until i get a intake and tune.

 

[ski]

I was wondering about this, but really 30hp worth of timing?! The other thing I was wondering... does it have a knock sensor? Maybe it was detecting knock and pulling timing, but I would think the runs wouldn't be so consistent then.

It's not 30 hp worth of timing, but when combined with a lesser amount of oxygen per cubic foot of inlet air at higher ambient temperatures(and at high relative humidity levels), then the engine's power output will be noticeably reduced.
The engine has 2 knock sensors. However, it's the MAF sensor that detects the ambient air temperature, and sends a signal to the ECM, which then pulls timing if the ambient air temperature exceeds a specific level. This happens before any pinging occurs.
Also, a hot engine compartment will slow down these cars for the same reason. Did your Dad open the hood and turn off the engine for at least 15-20 min before each race?

 

[bhuff30]

It's not 30 hp worth of timing, but when combined with a lesser amount of oxygen per cubic foot of inlet air at higher ambient temperatures(and at high relative humidity levels), then the engine's power output will be noticeably reduced.
The engine has 2 knock sensors. However, it's the MAF sensor that detects the ambient air temperature, and sends a signal to the ECM, which then pulls timing if the ambient air temperature exceeds a specific level. This happens before any pinging occurs.
Also, a hot engine compartment will slow down these cars for the same reason. Did your Dad open the hood and turn off the engine for at least 15-20 min before each race?

Nope, he left the hood down the whole night. You really gain that much from opening the hood and letting the engine compartment cool down? I thought these cars sucked in air from the inner fenders instead of from underhood from the factory? Sounds like next time, there are a lot of little tricks to do, and combined with cooler temperatures should produce the expected results. On searching, it still seems a lot of people are getting only 2.2 60' times... I figured these cars would do 2.0s from the factory.

 

[ski]

When the car is standing still or moving very slowly, the engine will inhale the underhood air. When it's moving at a faster speed, then the outside air is forced into the air intake, but it takes a few seconds before the outside cooler air starts flowing into the engine.