Andy's a Math Wiz Too

[pdub]

Hey Andy, do you still have that thing you sent me where you figured out how fast Red ran in the quarter while running the Mile?

[Red_Kitty]

Hi pdub

The answer to your question in post #249 is about 13 seconds. By measuring the runway on Google Earth using the painted markers, the 1/4 mile mark is at the end of the first narrow "II" stripes, which in your video is at the 1:29 mark. That also fits to the 1/2 mile coming up in 20 seconds, based on my own times for 1/4 mile and 1/2 mile (1/4 mile => 1/2 mile takes about 50% of the time of start => 1/4 mile), and also fits with Car & Driver's test of the 2007 GT500 at 12.9s 1/4 mile on an unprepped track.

[pdub]

That's neat, how you figured that out. In June, they had a cone at 1/4, not in September. I was curious what difference the new rear end ratio made....I couldn't figure it. Thank you Andy!

[Red_Kitty]

and for Studemax and RockJustRock, here is the math behind the Red rear gear discussion:


As mentioned in an earlier email, getting Red to go faster means making the most of the power you have, and reducing drag.

It sounds like RockJustRock has been encouraging you to consider a 4:10 rear gear, and here's the numbers behind changing rear gears:

Your car came from the factory with a 3:55 rear gear, and the 5-speed has 4th as a direct drive (1:1) and 5th as a long 0.67 overdrive.

To reach maximum speed, the car should be geared to be at peak power in the most efficient gear for best performance. e.g. for my Challenger, Dodge was aiming for a 200mph so peak power in 6th (direct drive 1:1) in the auto with the 2.62 rear gear equates to 202mph, and the car will do 199mph (2-way average).

In your case, I found a contemporary Fast Ford review of a 2006 GT fitted with the Procharger kit you have, and used the power curve data from that. For comparison purposes, I also found a magazine test of the 2007 Shelby GT500 and they recorded 150.2mph in the standing mile, so you are at about the same performance level as that.

With the original 3:55 gear you would hit the rev limiter at about 141mph in 4th and shift into 5th, and be turning around 4570rpm at the mile mark at 149.7 mph. At that point the motor is making somewhere around 355-360bhp.

With the 3.73 gear you have now you would hit the rev limiter at about 134mph in 4th and shift into 5th, and be turning just below 4900rpm at the mile mark at 152.8 mph. At that point the motor is making somewhere around 380bhp, so you got through the first 4 gears faster and now the engine is making 25 more horsepower in 5th - that's how you picked up 3mph.

Now, with the Procharger helping the engine breath better at the top end, peak power comes in right before the rev limiter at 6450rpm, so how close can you get to that on a run?

One option is to actually go down on the rear end ratio and just use 4th gear. As you can see in the table, you would hit the limiter with a 3:31 in 4th at right around 151-152mph, so you would get there faster maybe but not improve on the top speed. With a 2.73 gear you could probably get to around 5400-5500rpm in 4th at the mile marker, with the engine making 420-425hp. So, compared to what you have now, you would pick up another 40-45hp at the top end and have a transmission ratio with fewer losses. However, this would make the car feel way more sluggish off the line and in regular driving - probably more like the car drove before the Procharger fitment.

The other option is to go all the way up to a 4:10 or even 4.30 ratio, and make 5th a proper performance gear.

With the 4.10 gear you would hit the rev limiter at about 122mph in 4th and shift into 5th, and should be turning around 5500rpm at the mile mark at 156 mph. At that point the motor is making somewhere around 425bhp again, so you would get through the first 4 gears faster and now the engine is making 45 more horsepower in 5th than you got in September - that's how you could pick up another ~3-5mph.

With the 4.30 gear you would hit the rev limiter at about 116mph in 4th and shift into 5th, and should be turning around 5800rpm at the mile mark at 157 mph. At that point the motor is making somewhere around 435bhp, so you would get through the first 4 gears faster and now the engine is making 55 more horsepower in 5th than you got in September - that's how you could pick up another ~3-6mph.

However, launching would be more tricky (managing wheelspin), and it would make the car much busier in regular highway driving -you would be turning 2700-3000rpm at 75mph on the highway vs. the 2400rpm you are now with the 3.73. Of the two, the 4.30 would give the potential for a little more top speed (maybe another 1mph) at the expense of more noise and worse gas mileage all the rest of the time, so the 4.10 is probably the best option to consider.

[pdub]

Andy, do you have an in-car video of you getting to 180 mph that you could share with us?

[Red_Kitty]

Yes, but I don't know what format it needs to be in for uploading to the website - mp4 isn't working. What format are you using?

[pdub]

Yes, but I don't know what format it needs to be in for uploading to the website - mp4 isn't working. What format are you using?

Unlike FaceBook.....well, I don't know or do FB. Here on BS I think you cannot post a video directly. I've got lousy editing software which by default converts it to .avi. And then I upload it to YouTube, with lots of lost video quality. That's the answer that I know of. If you get it on YouTube, use the paperclip in the upper left corner of the edit screen to paste the URL for the video on YouTube.

[Red_Kitty]

Yes, just found that in the "Help" section. It looks like (probably for size reasons) you can't post video directly, it needs to be posted elsewhere and linked to.

I'll see what I can do with Youtube.

[pdub]

Andy, put it on Facebook and then post a link to it here. Try that. Your other video worked here that way.

[Red_Kitty]

I don't do Facebook since I got banned for having an illegal user name, but that's another ECTA story. I'm posing to Youtube and will link from there.

Update: I don't do Facebook, but wanted to post replies to the ECTA FB page after the September event so created an account for the car. This failed the FB facial recognition test that popped up about 30 minutes after my account was activated, so I managed to post a few replies that FB later deleted as they didn't think "Red Cat" was a real name.

[Red_Kitty]

This run was from Friday PM I think - I was still using the long return at this point. The GoPro battery went flat on Saturday quite early on.

[pdub]

Hmmmmm.....I'm watching the speedo, I don't think that was the 180 run. And that Dodge rides rough as hell, that track is smoother than that !!!! But it came through just fine, that's how you post a video on BangShift. Yep, you gotter done Andy.

[Red_Kitty]

No, the official 180mph run was early Sunday morning and the battery was done by then. The car rides fine (I had the suspension in "Sport" mode), but the GoPro mount was a cheap Amazon purchase and makes the camera shake worse than it actually did. It was attached to my headrest but not well supported vertically.

[pdub]

No, the official 180mph run was early Sunday morning and the battery was done by then. The car rides fine, but the GoPro mount was a cheap Amazon purchase and makes the camera shake worse than it actually did. It was attached to my headrest but not well supported vertically.

HHAHAhahahAH!!!!!!! Good thing......I wouldn't drive a car that fast that was bouncing that bad.....HAHAHAHAH!!!!!

[pdub]

All of these "wishes." I "wish" I had known you needed your camera charged. I've got a 12 volt setup to keep mine alive. That's what happens when we don't network enough. In that setting, look at the guy next to you. What does he have that I need? What do I have that HE needs? Everything in the world is right there if you made a giant pile out of it but nobody knows what everybody else has because nobody talks about it with one another.