Last night, I took my completely stock 07 M6 Z51 to the dragway. My best run was:

60' --- 2.034
330 --- 5.741
1/8 --- 8.769
MPH --- 81.35
1000 --- 11.331
1/4 --- 13.467
MPH --- 105.69

Weight = 3514 lbs
Density Altitude: 1788 feet
Relative Density: 94.87 %

This was my first time to the dragway so I'm not worried about the ET. I really could not launch it well but I figure that will improve with practice.

I made 4 runs and the MPHs ranged from 105.06 to 105.90. I'm concerned because most stock C6 corvettes I see on the forum trap between 109 and 114 MPH.

Is the issue solely based on weight? I did have a full tank of gas and I weigh 230lbs. I would really appreciate some insight.

Thanks,
Paul

 

what gear are you in when you cross the finish line? do the M6's have 3.42 gears? when I first ran my 2001 TA I was slowing down BEFORE the finish line. I did not know where it was. my buddy would run @115 mph and I would run it right after him and run @108. I finally figured out where the finish line was.

Also what rpm are you shifting at? you should be winding it out to over 6k before shifting even if its stock.

 

Thanks for your input...

I tried to shift between 6 - 6.5K on my 1st run I actually hit the rev limiter twice (2nd and 3rd)

I would actually have to shift into 4th just before the finish line. I was annoying but if I didn't it would hit the rev limiter.

Thanks,
Paul

 

Sorry, I missed this. Yes, I'm pretty sure it has 3.42 gears

 

There are a few possible reasons/causes for those results. One could be that there is something wrong with the car (bad spark plug or injector, some sort of binding in the driveline etc.) but I will assume that the car is just fine.
The weight is definitely a factor, your 230 pounds isn't all that bad but that full tank of fuel is adding an extra 60-80 pounds that just doesn't need to be there, even though it could help with traction in some situations. But even with that raceweight and at 1800 feet the car should still be in the high 12s at roughly 110+mph.
I think it's just a matter of staging and getting some more seat time to improve your driving/shifting. If you're lighting up both top bulbs and then still rolling in a little further (aka: deep staging) that will certainly hurt your sixty foot, ET and MPH. Be sure that you're just tripping that second stage bulb and stopping.
Hopefully one of the resident manual guys can chime in and help you with the launching/shifting parts.

And yes, your car has 3.42 gears.

 

Yes I was going to mention that as well, some people do tend to lift just shy of the finish line and that can scrub off lots of MPH depending on where it is so be sure to keep it hammered down until you see a little bulb light up down there or at least until you're absolutely sure you've cleared the line and the score boards etc. But don't stay full throttle too long after, you still have to make the turn off and avoid the sand traps LOL.

 

Great point about the staging. I was nervous and things seemed to be happening very quickly so I wasn't really paying attention to where I staged. I will need to work on that.

Thanks...

 

Good points mentioned above.

Several other things can influence mph as well especially with a manual.

If you hit the limiter it will scrub off mph. It's best to shift as close to redline without hitting the limiter. If you nick it occasional that's good IMO because it proves you are revving the car out. But a clean run will look better on the scoreboard.

Shallow stage. Just trip the 2nd bulb and hit the brakes and make sure you don't creep on the launch. If the car moves before you actually launch you will loose et and possibly mph.

How you shift is important as well. The more time you are off the clutch the better. Powershifting increases mph as well because it causes an rpm spike on the shift which gives additional rpm on both the high end of the intial gear and the low end of the recovery gear.
But I would save powershifting until you have full command of the car going down the track.

Tires will affect mph. The diameter, type of tire, and amount of air in them will influence mph.
Run as high a pressure as you can and still maintain traction. Smaller diameter will increase gearing. Typically a drag radial will mph best over a slick and a street tire for different reasons.

Weight is a big issue. Static weight plays a significant role and rotational mass even greater.

Weather plays a large role. You may see a difference of 8+ mph from one extreme to the next.

You can also log your car to see if the computer is influencing your tune and slowing you down.
But for the most part, my experience has been that the more seat time you put in, the greater control over the car you gain. Combine this with a good launch technique and some confidence and the car will not only et better but it will trap higher.
Trap speed in a manual vette is significantly influence by the person behind the wheel.

 

I can say with almost certainly that your low MPH isa result of engine temp... stock corvettes tha engine fans do not turn on until engine temps reach 230o,at that elevated temp the power control module has taken steps to protect itself EG adjusted the fuel curve,pulled timing out of motor ect....while many factors affect et's mph is a function of HP and vehicle weight pure and simple,weight will affect MPH... 2.73 or 3.42 will have very little effect on MPH. where you stage will change MPH but staging your car 6 inches fore and aft is not gonna yield you any substantcial gains (1 mph ) power shifting VS speed shifting again very little improvement...Try this next time at track make an effort to keep eng temps below 200o...instead of driving car in lanes and waiting with car ideling push car and start at last moment or wire fans to come on manual engine temps below 200o WILL yield the MPH this car is capable of

 

Also true...while I don't think that it was solely elevated coolant temps alone that killed his trap speed, it could've definitely been a contributing/combining factor along with the other points mentioned.
Long staging lane lines and having the motor running at slow speeds/traffic while creeping up to the starting line will take their toll on temps.
Not sure I totally agree with ya on that gearing having little effect on trap speed part though.

 

Gearing will multiply torque which will result in QUICKER ET'S.... MPH is is vehicle weight and HP, OTHER POINTS MADE ARE CERTAINLY VALID BUT TO A VERY MINOR EXTENT (imho) I BELIEVE THAT ELEVATED ENGINE TEMPS RESULTED IN THE BULK OF HIS LOW MPH.THERE IS ANOTHER POST *(HP VS TORQUE WHICH IS BETTER) TONY MAMO FROM AIR FLOW RESEARCH COMMENTS ON GEARING AND MPH...Now if you went to the extreme like starting out in 6th gear instead of going through the gears that would effect mph but going from 2.73 to 4.10 will have very little effect on mph ..it's no mystery here math and physics pure and simple.Its the HP made and the weight it has to carry that determines mph ...PS I consider this a friendly debate it's not a "can you top this"or :"I'M RIGHT ,I'M RIGHT" JUST SHARING INFORMATION WHICH I THINK IS RIGHT AND ACCURATE AND WILL BENEFIT ALL OF MY CORVETTE FRIENDS...KENNY

 

I have a switch in my car so I can start it up, with the AC OFF but turn on the fan "HI" at an idle.... if I do this even in 80+ deg weather, I can get my temp to 175 - 178 just at an idle.. I see a BIG improvement by leaving the line at 170 deg.. as opposed to 200.. I "NEVER leave the line over 180 deg.

 

I know my temps were always over 200 and sometimes near 220 before getting to the line. When I got to the line I have no idea what the temps were because I was just trying to not mess up the burn out or the launch. I was not successful at it either BTW

How much of an improvement in my MPH would I expect to see with a temp below 180 deg?

Thanks for the input...

 

Wow I didn't realize they were that high when you'd first posted, that played a big part in your results for sure.





A lot, 3-4mph easy, maybe more. That combined with everything else mentioned above and some cooler air will have you flyin' soon.

 

With a sixpeed car that has proven not to be the case entirely despite popular belief.

Not to say that this was the cause for the OP's lower than average mph.

Driver plays a significant role in mph that is recorded on the drag strip in a six speed car and vettes in paticular are difficult to run optimally.

If we want to get technical then we should say that the driver is causing the car to produce less hp by less than optimal driving on a given day which in turn produces less mph.

 

Not sure I underestand first statement,while I'll agree that vettes are difficult to get an ET that compares to the MPH and that driver error and inexperience can further compound that fact one must assume that the driver realize's this is an acceleration contest and that he must keep the pedal down,rev it to or near its redline and powershifting is not necessary to get a representative MPH,but the driver must understand he's not on Main St. with his grandmother in the passenger seat next to him.IMHO I think any driver that can drive a stick shift in regular stop and go city driving can get a representative mph regardless if he bogs or spins off the line just hit all the gears and rev it to redline WITHOUT HITTING THE REV LIMITER PS I plan on putting this to the test a friends daughter (26 years old)knows how to drive a stick but has never driven a fast car has expressed an interest in drag racing,she is going to the track as my guest and will be making some passes we'll see how she does.This will be after the corvette challenge series concludes and I will post how she does...we'll see if her MPH matches mine..... stay tuned....

 

Wow. I didn't realize my temps played that large of a role. I know the hotter it got the slower I would go but I didn't really think that 200 -220 was really hot.

So now I want to lower my temps. I'm thinking a 160 deg thermostat to start and then maybe the fans. What would be the best way to control the fans. I wouldn't mind putting a switch in but I do not have an electrical schematic to know where the best place to tap in is. Can anyone provide more specific information on wiring a switch?

Also what are some other tricks? I'm usually alone so pushing the car in the lanes would not be a lot of fun. Plus there is a big hill at the end of the lanes.

Thank you very much for everyone's input so far. I'm finding this really helpful since I'm very new to racing.

Thanks...

 

That statement above has not been my experience over and over again.

Also, The more modified the manual vette, the greater the gap in mph between experienced drag strip driver and inexperienced guy/gal.

Most off the 'inexperienced' drivers mentioned above are very competent handling a manual car on the street. In fact I have a few friends who could teach me alot about road racing with have modified vettes that I can consistently out-mph on the drag strip in their own cars(3-5 mph).

It's not as easy as you make it seem to run thru all the gears in a well timed and coordinated manner, without missing a shift, without a bog on the launch, without hitting the limiter, without lifting on the throttle.

That's what it takes to put up a solid mph. Most people can't do that without the seat time.

Also, IME powershifting can add up to 2 mph and that's with an experienced driver. Alot depends on the setup too in all examples. Some setups may benefit from power shifting more than others in the mph department ( ie. a big turbo vette).

One quick example to take it a step further.

Inexperienced guy launches a manual vette at a high rpm with a poor technique and the motor bogs down to 1400 rpms 20 feet out despite the fact that he is floored on the throttle.

Second guy launches the same car, same conditions at a similar rpm with a good technique and the rpms go from 6000 down to 5000 with no bog and a healthy amout of spin.

The second pass will show a significantly higher mph even if the rest of the passes are identical.

I consider 2 mph significant for a manual vette under same conditions.
Let us know how your experiment goes.

 

I'll let you know how she does good or bad,this girl is a natural with a stick but racing thats another level ...now I'M ANXIOUS TO SEE JUST HOW WELL SHE DOES...Before I comment on bogging and or tire spinning and mph ,perhaps you should check out the post in the C5 tech section"Horsepower vs Torque ,which is better"Tony Mamo engineer,cylinder head designer,from AFR (Air Flow Research) Explains it better than I can.There are no gray areas here this is pure math and physics you weigh XXX your RWHP is XXX YOU'RE GONNA GO XXX MPH .....NOT SURE IF I WOULD CALL 1-2 MPH SIGNIFIGANT It would be fair to say that could be the margin of error as there are outside forces that could affect MPH.. variables we cannot add into the equasion... for example a strong headwind will slow a car down some body designs more than others and it would be more acceptable if a number of runs were made throwing out the fastest and slowest and averaging out the rest.There is a lot of misunderstanding with racers with regards to ET and MPH....MPH IS A FUNCTION OF VEHICLE WEIGHT AND HORSEPOWER NOTHING ELSE..... CHASSIS SETUP,TIRES,GEARS,DRIVER ABILITY, SPINNING ,BOGGING THEY ALL AFFECT ET BUT HAVE NO AFFECT ON MPH

 

Google "Casper" electronics.. they make a plug & play switch that you just plug into the wiring harness near the radiator, it has a wire that has a 3 way switch on it so if you leave it in the center position you fans work normally, push it to the left & you fan will run on low speed (EVEN WITH ENGINE OFF... or if you push it to the right the fan will run HI SPEED .. again with the engine ON or OFF..

and the CENTER position is always NORMAL operation...

I have a 160 T Stat in my car, with the CASPER plug in switch..

After I make a run I drive right to the staging lanes, shut off the engine and run the fan & electric water pump .. it will cool the engine from 210 to 140 in less than 10 min...

If you do not want to spend $600 for the electric WP just get the switch for about $99.00

But then you have to stay with the car because there is no way to circulate the water, so you could run the fan (motor off) for 5 min this will cool the water in the radiator, then start it up for 30-45 sec to circulate the water and repeat the process... BE SURE to get a 160 T Stat,, & reprogram the computer to run the fans at a lower temp (many good Corvette shops can do this)

I'm sorry I don't have Caspers address, but they are on the Internet.

OH.. also if you call to order one be sure to request the new version where the relay and electronics are mounted IN THE CARS CABIN....NOT THE ENGINE COMPARTMENT..

the old version had it mounted near the radiator, and the heat would burn them out..

I have the new version & its fine (almost 1 yr.)

Also... if you get a 160 T State and the outside temp is under 85 deg. you can shut off the AC and turn the fan onto "HI" and let it idle and my engine temp will drop to 175 - 178 in cooler weather (50=60 deg) my engine will drop to 168 just idling in the shade...

The switch is very nice looking it matches all the other control switch's on my C6, and I mounted the switch on the "Tombstone" it looks factory installed..