wheel speed help

Discussion in 'PSI Superchargers Tech Questions' started by CjRedden, Sep 27, 2014.

  1. CjRedden

    CjRedden Member

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    Back in august i made 3 good runs in my top sportsman nova 526 with hi helix 14-71. That night went 6.91 6.89 and 6.85. Since then i have not been able to make it down the track without shaking pretty much. Weve been low on wheel speed then high on speed. I do not have a leahy box or 6 shooter yet. But i do have only one retard possible which i plan on pulling 3 degrees out from 1.4 to 2.2 to compensate for the bad track i will be on next weekend.

    But anyway my question is what are the recomended wheel speeds at .25 .5 and so on up to 1.5 seconds into the run?
     
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  2. Mike Canter

    Mike Canter Top Dragster
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    What rear gear and slick diameter?
     
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  3. CjRedden

    CjRedden Member

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    We are running a 34.5 hoosier on a 16x16 dbl beadlock with a 4.11. Which is gonna be another question for next year if we should move to a 4.30 gear
     
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  4. Mike Canter

    Mike Canter Top Dragster
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    I don't have data for a 4.11 maybe sonebody else can help. That is just too far off from s 4.56. You should have around 1500-2100 at .25, 2600-3000 at .5, 3100-3500 at .75, 3600-4100 at 1.0
     
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  5. CjRedden

    CjRedden Member

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    Mike, more often than not id say im shaking from low wheel speed. I try and keep a safe tuneup in the motor as this is a bracket car and qualifying isn't too much of an issue. 1.80 1st gear in a powerglide. going shifting at 8k and going through the traps at 8030 at 201 mph. would a 4.30 gear be a good idea, to keep it up on the tire longer on the launch? I will be installing a leahy box and 6 shooter this winter. ive been changing the launch rpms between 4200/4400/and 4600 based on previous runs and track conditions.
     
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  6. Mike Canter

    Mike Canter Top Dragster
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    If you are sure that your wheel speed is too low and you are not have to retard the ignition in launch and you can't make any more power then going to a 4.30 might help. How does your current wheelspeed compare to what I posted?
     
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  7. CjRedden

    CjRedden Member

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    wheel speed is low compared to your numbers. in our best run ever 6.85 at 202 my numbers are .25 1545 .5 1777 and .75 2175

    last night in really good air compare to what I usually see we were .25 1888. at .371sec it got up to 2122 then stuck the tire and dropped to 1969 at .5 seconds. then it took off up to 2324 rpm at .75 seconds.
     
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  8. Mike Canter

    Mike Canter Top Dragster
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    Like I said I have not used a 4.11. I have seen runs from them and it does appear that your wheel speed really drops off after .25.
     
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  9. ProMod83

    ProMod83 Member

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    Hey Mike, are those 4.56 numbers you posted up. I asked because a few have told me I need to be 4000 at 1 second with our 4.56 right now we are about 3650.
     
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  10. Mike Canter

    Mike Canter Top Dragster
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    Yes, they are 4.56 numbers. They seem to be close to the same for other gears down low and separate more after time. They are what I call average that will keep one out of trouble. If the car is real good they they may exceed average. The big thing is to have a nice trace on the Racepak without big dips or peaks. Yes it would seem that your 1 second wheel speed is on the lower edge of the average but that depends on what is happening at the other times.
     
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  11. ProMod83

    ProMod83 Member

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    Thanks Mike.

    I have:

    1880 @ .250
    2880 @ .500
    3460 @ .750
    3330 @ 1.00

    These are numbers zeroing run off of DS rpm. I had it zero'd off of TB button but there is a delay so we really didn't have 3600 at 1 second. DS is pretty smooth but has 1 check in it at .100 I think where it get on the wheelie bar.

    Those numbers are .970 60ft but want to be .950 or better.
     
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  12. Mike Canter

    Mike Canter Top Dragster
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    You start off well then drop a little at .75 and a lot at 1.00. I agree that you should be up around 4000 at 1.00 and up around 4200-4300 at 1.25 and 4500-4700 at 1.50. If you are not doing it you should use less retard about .6 secs or maybe open a Leanout if you can't advance the ignition anymore and if both of those cant be done then maybe time for a first gear change.
     
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  13. ProMod83

    ProMod83 Member

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    Thanks Mike.

    Have been best of a .966 it had 2100 at .25

    We are still learning the car only have about 10 runs so far. We are working in the direction you said. Slowly taking retard out of it.

    Appreciate the info.
    Billy T
     
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  14. turbo69camaro

    turbo69camaro Member

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    How close can you make D/S speed comparisons not knowing low gear ratios between car X and car Y i have 4.56 numbers but i had a 2.49 low gear
     
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  15. Mike Canter

    Mike Canter Top Dragster
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    The driveshaft speed is based on rear gear and tire diameter. The transmission gear is what applies the force to maintain that driveshaft speed.

    what you are really computing via the driveshaft rpm through the rear gear is the speed in which the tires are accelerating the car.
     
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    Last edited: Sep 28, 2014
  16. Blownalky

    Blownalky Top Sportsman

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    Yep, that's because the sensor is after the transmission and before the gear and rear tires. Change the tire or the gear and you will have a different set of numbers.
     
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  17. turbo69camaro

    turbo69camaro Member

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    So when i change from a 2.29 to 2.49 low gear i will not slow down D/S rpm @ the same engine rpm
     
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  18. Mike Canter

    Mike Canter Top Dragster
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    You are 180* out on your reasoning. The DS speed or wheel speed that is as fast as you can go without high speed tire shake is where you want to be during the whole run but most important during the 0 to 330'. You adjust your transmission gear ratios to allow you to use your engine power to do it. If your wheel speed is too low and you can't gat anymore power out if the motor then you need to change the transmission ratios. If it is too high and you are having to detune the motor too much then you need to change the transmission ratios. But the ultimate wheelspeed for your car remains the same with adjustments for track conditions. Understand I am talking abouts Roots and screw blown cars and gave no idea on wheelspeed on a turbo car but I imagine the goal is the same.
     
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    Last edited: Sep 28, 2014

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