Slow car down for index race, best way?
10-12-2009, 06:14 AM
#1
Slow car down for index race, best way? Gonna try and run a few index races at the local track. With fair air and so-so traction (low 1.60s) the car will run fairly consistant 11.60s. Was thinking of running the 11.50 index but if its a bad air day and/or the track goes cheep on the prep I'll be running low 11.70s. Car will run 11.40s with good air and mid 1.50 60 fts. Was wondering if anyone has had to slow down a car a few tenths and the way they did it to keep it consistant. Have tried short shifting it with the tune (tunercats) but it doesnt seem to make much of a difference. (pulled about 400 rpm from each shift point). The car is still turning around 6400 across the traps with shift points around 6k. Was thinking of limiting the max mph. Just dont know how consistant it would be. I only have one T&T day before the race and will only get a hand full of passes to figure it out. I thought posting up here might produce some better ideas. Just wanting a few last hoorahs before I put the car up for sale. Any ideas?
Mec
Mec
10-12-2009, 06:29 AM
#2
Just general advice.
To run ANY index, you need to be faster by 3 to 4 tenths on average and know the car well enough to know when to slow it down.
One trick I learned is dont pay attention all that much to the other driver as their car can be different where you think you have them but their set up pulls the last part of the track to get their 11.50.
Basically just run your race knowing what the car will do already. if anything start data logging the weather and results and you can eventually know what conditions dictate your actions during a race.
To run ANY index, you need to be faster by 3 to 4 tenths on average and know the car well enough to know when to slow it down.
One trick I learned is dont pay attention all that much to the other driver as their car can be different where you think you have them but their set up pulls the last part of the track to get their 11.50.
Basically just run your race knowing what the car will do already. if anything start data logging the weather and results and you can eventually know what conditions dictate your actions during a race.
10-12-2009, 07:28 AM
#4
Now I gotta go out and find a 300 pound dead hooker.
10-12-2009, 08:20 AM
#5
Forgot to mention that I wanted to tune for the 12.0 index. My train of thought on this is if I can tune for 11.90 and know that if I cut a good light I will be a 10th to fast. If the car next to me is back just a bit I can let off and stay ahead of him for a win. If hes pulling hard and gets by me I can stay in it and make him pull hard then get on the brake at the end in hopes of him breaking below the index. 3-4 tenths might be a bit much for the way I think but it could work for someone who really knows their car. Thanks for the reply!
Now I gotta go out and find a 300 pound dead hooker.
Now I gotta go out and find a 300 pound dead hooker.
My old auto 383 LT1 could be as consistant as most foot brake cars running in the hundredths in consistancy.
10-12-2009, 09:04 AM
#6
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Try not to effect your launch or R/T. I have several buddy's that race index stuff,
and they can kill a lot of ET with quick shift. That way you still launch the exact same every time.
If 400 rpm doesn't make a big enough difference, try 1000-2000 what ever it takes.
Once your away from the tree, it doesn't matter. One guy did very well running 8.90 class
with a car that ran 8.80 at 95*. Yes you need to have some power to spare, but you don't need .4 @ 95*.
If you absolutely can't hit the index with shifting only, they try sand bags, cheap & heavy.
Good luck.
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10-12-2009, 01:58 PM
#12
I'll be taking two 50 lb bags with me....just in case. Never thought I would have to slow the car down to make a race. Just got used to the brackets. I could try and rev a bit higher and run the 11.50 index but I need a set of springs. Data logs show valve float just past 6300 rpm. The 918s are having trouble with the cam I'm running so I need a set of the Patroit duals. Will probably sell the car before I get that done. I'ts very capable of lower numbers, just needs a bit more weight loss and a few key items + some tuning. I know the car could do 11.teens. Most of a nitrous kit is installed but has never made a pass on the dope. Best est on a 150 shot should put it 10.30s after all of the above is addressed. Just needs some TLC. Time to move on to different things though. I got a father & son project planned on a 71 Chevelle.
Mec
Mec
10-12-2009, 04:16 PM
#13
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I agree with whomever said it first; If you wanna run the 11.50 index, you would really want your car to run 11.20's this way you could safely slow it down depending on conditions. From what it sounds like, you may be better off running the 12.0 index, IMHO.
Best way to slow it down would be to use a throttle stop, if that's not an option, take some timing out out of it. You could also shift the car early as well. (this would be even better if your running an A4 cause you could just set them in the program and be consistent)
Adding weight will work too, but if your track is tight with tech, sandbags won't work cause all ballast must be secured. In addition, if you have add quite a bit of weight it will add strain to the driveline.
Best way to slow it down would be to use a throttle stop, if that's not an option, take some timing out out of it. You could also shift the car early as well. (this would be even better if your running an A4 cause you could just set them in the program and be consistent)
Adding weight will work too, but if your track is tight with tech, sandbags won't work cause all ballast must be secured. In addition, if you have add quite a bit of weight it will add strain to the driveline.
10-12-2009, 04:22 PM
#14
If you can in teh computer, figure out what mph it will take to get the car to run a tenth faster then you need to go that day, and set the speed limiter in the comptuer to that, don't change the shift points, get the car to run as hard as you can to the 1/8th mile, then once it's in 3rd gear limit the rpm/speed.
It's the closest thing you can do to a throttle stop, without actually having one in the car that would probably be illegal for what you want to do.
Adding weight will work, but the added strain on the car isn't something I would want to do... ya have the PCM, try to get it to do the work for you.
Set it for 1 mph more then you know you need to run the #, and just set the speed limiter, should work.
Bring your laptop to the track, set it and see what it does for you, and if it doesn't work, then set the rev limiter to the needed rpm in 3rd and set the shift points 200 rpm lower, that should work as well if the speed limiter doesn't
It's the closest thing you can do to a throttle stop, without actually having one in the car that would probably be illegal for what you want to do.
Adding weight will work, but the added strain on the car isn't something I would want to do... ya have the PCM, try to get it to do the work for you.
Set it for 1 mph more then you know you need to run the #, and just set the speed limiter, should work.
Bring your laptop to the track, set it and see what it does for you, and if it doesn't work, then set the rev limiter to the needed rpm in 3rd and set the shift points 200 rpm lower, that should work as well if the speed limiter doesn't
10-12-2009, 04:31 PM
#16
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It would be a safer tune. Adding weight will stress the drivetrain no?? Less converter efficiency right? I would pull 5*, see what it does and go from there with the weight adding. Just read jl's speedlimiter idea, sounds like a good idea.
10-13-2009, 05:34 AM
#17
If you can in teh computer, figure out what mph it will take to get the car to run a tenth faster then you need to go that day, and set the speed limiter in the comptuer to that, don't change the shift points, get the car to run as hard as you can to the 1/8th mile, then once it's in 3rd gear limit the rpm/speed.
It's the closest thing you can do to a throttle stop, without actually having one in the car that would probably be illegal for what you want to do.
Adding weight will work, but the added strain on the car isn't something I would want to do... ya have the PCM, try to get it to do the work for you.
Set it for 1 mph more then you know you need to run the #, and just set the speed limiter, should work.
Bring your laptop to the track, set it and see what it does for you, and if it doesn't work, then set the rev limiter to the needed rpm in 3rd and set the shift points 200 rpm lower, that should work as well if the speed limiter doesn't
It's the closest thing you can do to a throttle stop, without actually having one in the car that would probably be illegal for what you want to do.
Adding weight will work, but the added strain on the car isn't something I would want to do... ya have the PCM, try to get it to do the work for you.
Set it for 1 mph more then you know you need to run the #, and just set the speed limiter, should work.
Bring your laptop to the track, set it and see what it does for you, and if it doesn't work, then set the rev limiter to the needed rpm in 3rd and set the shift points 200 rpm lower, that should work as well if the speed limiter doesn't
Mec
