I race in Manumatic because in D it short shifts. These engines have all the power up top. VDC off when you race too, because when it engages it uses rear brake. I last ran in Gainesville, FL last month with JWT popcharger, Z Tube, Megan racing JIC magic custom exhaust, 235 rear tire. I ran 9.4 in the 1/8th and 14.50 at the 1/4(hitting the brakes, I was running bracket). This was all in a 5AT. My 60ft was a 2.200. I dont know if giving you some times to compare to will help. I really think your wheels are what are killing you.

Pop your hood between runs too. After I get my time slip I pop my hood to crack it, and cruise back to my stage lane and that allows some air to get in there to cool the engine while I go 10 or 15mph.

 

^ also remove the weatherstrip toward the back of the bay it will let air flow out

 

Having 20" rims on a car and expecting it to be fast is sort of like having your cake and eating it too.

If you are investing into making your car quick, then you should be racing on some lightweight 17" rims (or 16" if you have an 03-04) and sticky rear tires.

 

Yup. I est that the stock 17 is about 19lbs. A cast 20" wheel can approach 30lbs easy. Cast 19s can easily be 27lbs easy. You just added 11lbs per wheel. Plus the added 20" tire weight vs the stock 17 tire weight. Let's be generous and only ad 6lbs per tire. Total them up and you added an est 17lbs on each of the 4 corners.

 

I met with a couple of engineers I know today to discuss the issue of tire/wheel size and weight and my use of the VDC. Too many unanswered variables, weight distribution of the wheel can vary considerably. Their best guess as to my relative poor performance was due to the use of the VDC this past weekend. The combination of the 20's extra weight with the use of the VDC was like a double whammy. Previously without the VDC, with the wheel spin it allowed me to instantly counteract the excess weight and the rotational forces are working with me after the tire spin. Given my current set up and wheel options they both felt the optimum set-up would be 17's in front, 20's in back, VDC OFF. This is for a straight 1/8 run only!!

My problem with the "manual shift" is the rev limiter. My engine wants to keep reving past my 6,500 redline, it is still pulling hard. If I miss the shift the rev limiter kicks in.

As far as launch in the 2003 A/T, are you recommending starting in "Manual" 5th gear and just leave it alone? That's even easier.

 

It's not so much the weight of the rim that is the issue, but the relative location of the main distribution of mass being further from the hub. The farther away from the hub the weight is, the more energy it takes to spin. Think of a figure skater. When she puts her arms out, she spins slow, but when she tucks them in...she speeds up. Same energy, but the closer to the center of rotation, the easier it is to spin.

Then there is the sidewall..or lack thereof. Short low profile rims have shorter sidewalls which don't give at all when you "shock" them. As a result, it's mich easier to break these short profile tires loose. Bigger sidewalls absorb some of the initial shock on the lauch and don't break traction as easily. If you are spinning tires at the track....you are losing. Spinning tires always results in slower times.

This is an extreme example of what I am talking about here. Smaller diameter rims and big sidewalls flex on the launch preventing spinning and storing energy to propel the car. Short sidewall are stiff and don't flex....so a hard launch spins the tires. What's the best way to make an underpowered car spin the tires easily? Put bigger rims and low profile tires on it.



Vdc does not change performance at all so long as a tire does not spin. It doesn't change shift logic, or horsepower....it just keeps you out of the ditch on a rainy night. Spin a tire, or get sideways and it will kick in applying brake and disabling cylinders and fuel. If your drag racing, turn it off......this isn't the traction control system from a ferrari or formula 1 car. This is designed for commuting in the rain....not performance. Off is the only option here.


20" rims and low profile tires don't belong on the track at all...period. The die hard drag racers were probably shaking their head at you. When I drag my mustang at the track....I take the 17"s off and put a set of 15" rims with drag radials on it. I launch at 4000 rpm dumping the clutch and just hooks and goes. On the 17s with stiff tires....1-3 gear is spin city.

If you are serious about racing....get a second set of tires. Narrow front rubber and a drag radial out back.

Ps....I am also an engineer...and an avid drag racer.

Pps....when i raced my g35...I found a 0.2 difference between d and manumatic. I have awd though...so launching was easy. 2.1-2.2 60-footers were what I was getting.

Ppps....post up time slip for analysis.....complete slip...not just the 1/8th time

 

Heavy weight is only benefical when storing kinetic energy. ie... a heavy flywheel spinning/storing energy for the launch.

Unless you are leaving the line while the wheels are spinning, your heavy 20s are costing you, not helping you. If you note, not even dragsters leave the line while the wheels are spinning. If they do, the lose time, not gain it.

 

OP bottom line go back with VDC off, keep the same rims see what time you get. VDC is the huge culprit here.


Also Drive in MM mode more often, you will learn to perfectly or all most compensate for the lag that it has. keeping it in Drive sucks

 

OP, put your stock wheels on, put trans in MM and shift like a Manual. When car hits 5500 rpm shift up, thats what I do, and it will shift almost exactly at redline. I can chirp second sometimes too. If youre still running 10second 1/8th your car was maybe made on a monday, or look into driver mod.

 

+1 same here perfectly hits the redline on my car with ought hitting the rev limiter

 

Mustang5L5 is spot on the operations of the VDC and also traction control. The VDC/traction control does absolutely nothing to performance until the there is significant spin and/or the car is sliding. I can usually get a few revolutions before I can feel the TC kick in. The VDC steps in much quicker to engage like when I'm putting the car into oversteer. Oddly, the TC seems less intrusive now that I've got an LSD. It must be because the car doesn't peg-leg as badly around turns therefore the TC doesn't get as involved.

At the strip, the VDC should be turned off because if you do get a good amount of spin, these systems can intervene and really slow you down. In my car, it can be pretty aburpt. Usually when I run at the strip, I barely get a chirp out of the tires, but the car still seems to get low to mid 2.1 60 foots on the 17" rubber.

You can also completely disable the TC and VDC by unplugging the yaw sensor located under the center console. I can yank this plug in about 2 minutes.

What I've found works best for my 03 sedan is this:

1) Roll up to the line in 2. This allows the tranny to shift the 1-2. In MM, there is too much of a delay that you can often tap the limiter and that will slow you down. For those with newer cars and the refined shift logic, you'll need to put it into D and then kick it into MM once the 1-2 shift is completed.

2) Once the car has completed the 1-2, you manually shift the 2-3 and hold 3rd the entire run. 3rd is good to ~101mph assuming you've got the OEM tires, gears, and you're not driving an X model. Letting the car shift to 4th will slow you down significantly. The difference between holding 3rd and letting it shift into 4th (using D) is about .3 seconds and 2mph. My 1/8 miles were typically in the mid 9.2 range at 77mph and 1/4 mile in the low 14.3 to low 14.4 range at 97.9-99.8mph. My only mods being a Z-tube and spacer at the time (ran 14.3@98mph a z-tube only). I haven't been the strip in years to test out my gears, y-pipe, etc.

Now that I've got the 3.54 gears, I'm going to have to shift to 4th. I've also got a set of 225/50R15 BFG DRs. These tires are a mere 23.5" tall or nearly 3" shorter than the stock 17s. This increases torque multiplication plus the combo only weighs about 35lbs (~13lbs lighter than stock). With the 3.54 gears and the DRs, the effective rear ratio is closer to a 3.8. I don't know how much of an improvement this will net me, but hopefully by the time I go back to the strip, I'll have the TS ECU installed which will have the increase rev limiter so that I can have some wiggle room in terms of ideal shift points.

 

That low? Really? I shift it at 6-6.1 and it will be perfect (Border of redline), I shifted earlier than 6000 against an Eclipse gst (FWD 210 crank hp + I,E,BOV) and the thing kept up (his bumper to my door). I didn't get a chance to go against him again but i like 6k for shifting, my G is stock RWD.

 

The VQ35DE makes peak power at ~6300rpms and power only falls off about 10% by the time it hits the 6600rpm limiter. Based on my shift point calculations, the 1-2, 2-3, and 3-4 shifts should be right near 6600rpms for maxiumum performance.

 

yea 5.5k is way too early for my 05, I dont really know when to shift I just glance over or hear and feel for it. But its def over 6 before I shift.

 

I bang the redline before I feel any power tapering off.