Update:
I went to the strip again and pulled a 12.8 @111mph. Driving technique-wise, I did nothing different from the day that I recorded the times below. I suspect my power was being pulled from heat soak the first time I went out, but 100hp?
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I went to the dragstrip last week (Speedworld in Orlando) with my '05 Z51 6mn 1sb vette. This was my first time drag racing ever, but I know I'm not this sucky of a driver. Here are my times:

1st Run, 2nd Run:
60' = 2.373 2.302
330' = 6.162 6.152
1/8 = 9.206 9.234
MPH = 81.08 80.25
1000 = 11.771 11.826
1/4 = 13.913 13.972
MPH = 104.27 103.66

Now, this has been really bothering me, because I know there's more wrong here than just my driving, my traps should not be so low. Being a poor college student, I don't want to spend money on a dyno, so I decided to do some power testing of my own.

First, I took a sample dyno graph of an average stock C6 mn6. Using the torque curve, vehicle w/driver mass, different final drive gear ratios, drag, rolling friction, and shift times, I did some integrations and created a program which closely simulates how a stock z-51 mn6 C6 accelerates (I'm majoring in engineering). I've compared my program to other timeslips (jschindler's and others) and it's VERY close to reality.

Not only used to simulate quarter mile times, my program can basically calculate the time it takes to accelerate from any given initial speed to any final speed. It even approximates the top speed to be around 185mph, which just about right on.

So, looking at my time slips, it took me 4.707 seconds to get from 81.08mph to 104.27mph. That's all in 3rd gear too, so I didn't shift during that time, all I had to do was hold the gas pedal all the way down.

According to my program, the average Z-51 mn6 C6 should be able to accelerate from 81mph-104mph (in 3rd gear) in about 3.77 seconds. I decided to test my car out on a backroad, and I did two runs and got 3.6 seconds on one, and 3.8 seconds on the other. Pretty damn close to what my simulation said I should be getting, but way faster than what I pulled that night at the dragstrip.

I did some other tests and my horsepower seems to be all present and accounted for, according to my program. So, something had to have happened at the dragstrip that made my car have so much less HP.

Here are all the things I can think of that may be important:

-temp/hum were the same between last week and tonight's testing

-My front and rear tire pressures were low at the dragstrip (about 25psi all around. I didn't purposely make them low, but the temp outside had dropped a few days before and they dropped from 30psi to 25psi, and I hadn't aired them back up. I know, I should have). My psi for my tests tonight were at 31psi all around.

-The day I went to speedworld, I filled up to 3/4 tank on some po-dunk gas station (93 octane supposedly) that I ran into. At the time I filled up, I hadn't planned on going to the dragstrip, else I would have found a more reputable gas source and filled up only 1/4. Tonight, I had a quarter tank of 93 octane from a busy BP.

-When I was waiting in line to race, I left my engine running, instead of turning it off and pushing it. I had also just driven 1.5 hours to get to speedworld, so my engine was already hot. I would have turned it off and pushed like everyone else, but I don't know how to turn the engine off w/o locking the steering column. During tonight's testing, I started the engine from being cold, warmed it up to an oil temp of 150', and did my testing.

-Last week and tonight, I had my TC/AH turned completely off.

So, can anyone tell me why my engine wasn't putting that much power down last week, but is this week? Which of the possibilities I listed above is most likely the biggest problem? Thanks,

Joe

 

That says it all.

Though this deals with the C5 Z06, this was an interesting thread and applies here. Specifically the #7 post by Ranger.

http://forums.corvetteforum.com/show...94&forum_id=49

 

Yes but, look at the time it took to accelerate from 81mph to 104mph at the dragstrip, and then look at the time it took tonight.

 

Couple of things: Did you turn off AH AND Traction Control? I can tell you that that made about .4 difference in the 1/8th for me. Also, these computers have a mind of their own. Heat soak can and will cause the timing to be backed off which will give you crappy runs. Haven't found the cure for that just yet but I suspect it is in tuning. Out of curiousity, how many miles are on your car?

 

The PCM is monitoring and controls launch, wheel hop, and traction control.
The biggest loss to time and speed would be depending on how you launched and at what RPM and how much wheel spin or hop.
On launch alone if PCM saw a need to kick in the launch control it does not command more injector flow and pulls timing costing time for about 2 seconds.
PCM monitors each gear and if the torque exceeds the values in their torque tables will pull timing.
Experiment with different launch methods and time them to see at what RPM car can be launched without kicking in launch abuse control for the MM6.

 

Oh ya, your 60' times are also a problem but they are for most people until they get used to running these at the track. After a few passes, you should have no problem picking off 2.0 60' times and you will surely see a difference then.

 

I'm not worried about my 60' times though, they'll get better with practice.

What I am worried about is why my 81-104mph run at the track is a whole second slower than it was tonight.

 

It goes back to this crazy computer. I turned 8.40's one week in 80 degree weather. When back a few weeks later in 60 something degree wheather fully expecting 8.20's. Couldn't get out of the 8.70's. No rhyme or reason. Same shifting, same track, better temperatures, slower times. Only thing different is my battery was accidentally run dead same day. I can only figure that something in the computer was reset.

 

Thats barely better than my 93 Mustang when it was new. It only had 205hp. WTF?

Anyway, I'm convinced the C6 is plagued heavily by computer tuning problems created by our own GM. Too many people are not running the number and the MPHs are WAY WAY off. I remember reading a long while back that the new computer "learned" the driving habits and adjusted according to make driving the car smoother. I think there are torque reduction alogrithms eating ETs away. I would sit back and wait until a good set of calibration data is available for the LS2 then ~maybe you can tune away at least some of the problems.

Your 2.37 60ft stinks. But, if you got traction, your MPH should be there and its not. Leave at idle until you learn how to drive the car. This will prevent tire spin.

 

I am in no way at all intending to call you a crappy driver, but I think a lack of familiarity with how this car operates on the track is more to blame than anything for your bad times. I ran my car for the 1st time on the track last night (1/8 mile) ansd made 4 runs. 1st run was a 9.2, but I was launching high, and spinning the tires way too much. I started launching at about 12 or 1300 rpms and got my 1/8 down to 8.8 right away. Traction was still an issue and I think if I feather the throttle I will easily be able to get it down a decent amount lower. 60 foot was 2.207 and mph was 83.02 These numbers were my 1st time ever on the track with this car and it is completely stock.

Take a few more runs in the car and get a feel for it. Traction is an issue in these cars.

 

www.dragsource.com put in the pertinant info and see what comes up.look in the right>>>column for the correct title(drag strip calculator something or other).http://www.dragsource.com/index.php?...s&calctoview=5

 

The most important question I can think of is: how was your shifting (did you shift fast and slam the shifter hard) and at what RPM were you shifting to the next gear? Don't get stuck on your third gear 81-104 test. Test results like that are difficult to replicate and there are many factors at work here such as speedometer delay, slope of the road, differences in intake/engine temps due to heat soak, difference between the influence of torque management when doing a hard shift from 2-3 versus just doing a rolling test run in third, etc. One major contributor could be that 81 MPH is close to the 2-3 shift point and TM could have pulled timing and kept timing back for a second or two after the 2-3 shift, affecting your run at the track where you were shifting hard, but not your test.

One thing that people never seem to realize or bring up on these forums is that TM is there for a reason and one of those reasons is to protect you from sloppy shifting and the effects that it can have on your drivetrain. Learning how to shift the car just right will allow you to skirt the edges of TM without activating it. For example, slamming the shifter, not lifting your foot off the gas, and popping the clutch with a poor speed-to-gear RPM match might activate TM and drop your timing but a shift that is almost as fast but less "violent" will allow you to proceed with no (or little) TM, actually giving you better times. So learning to shift properly can actually reduce the effects of torque management.

My .02



Mike

 

Jesse12804,
Actually, those numbers are pretty close. Like they said, with a perfect driver and condition.

 

Very good points.

 

Your launch is what sucks with your 60ft times in the 2.30s.If you get your 60ft in the 2.0s your car will be running about a half second faster which would put you in the low to mid 13s which is about right considering you were running the car hot and the computer would surely be taking away timing,which will rob you of at least .2 to .3 tenths.Nothing is really wrong.Your 60ft times are your biggest problem.

 

I'm thinking your car ought to trap about 110 regardless of driver skill. So something is low on the power. The heat from leaving the car running while waiting could account for some of it. I think I'd disconnect the battery and force the PCM to relearn its knock control parameters. You really need to put it on a dyno and download a log file to get a solid answer.

 

Mikeyc6, I think you may be right about hard shifts activating TM, which would pull timing for a second or two after each shift. The reason I agree with you is because I did some more testing involving shifting, and the time it took to get from one speed to another speed in the same gear AFTER a hard shift, was much slower than if I did it from a roll with no shift before. I will be doing a lot more testing.

 

Let us know how the testing goes. Your testing sounds interesting and may shed some light on TM and how to work around it.

Mike

 

It really seems that the manuals have far more issues. Yeah we know when all is well they are quicker then the A4/A6. But there seems to be so much more to booger up.

 

Don't feel too bad. You aren't the only one running those kind of times. My best is a 13.62 at 106.2mph, 2.21 60ft, and I had plenty of 13.9's with 2.4's before that.
The other two C6's that have showed up haven't done any better.

Obviously I am not a great driver, but I believe there is something slowing the car down massively. Whether it be timing retardation due to low octane or heat, or just TM rearing it's ugly head, I don't know. But I am determined to get to the bottom of it, and run the 12's this car should run