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  1. #1
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    Drag Racing: effects of shifting..

    So, Nothing better to do than E-Racing on a rainy day.

    If redline is 6800RPM, When do we want to shift, and how does it effect ET vs MPH?

    Some say shifting @ 6200 is the best to keep it int the powerband. Is that better for ET/MPH or both.

    How does it compare to shifting @ 67/6800 RPM?

    Does it matter how much boost we hold to redline?



    Discuss

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    great question

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    i thought so.. maybe someone should attempt to answer it Click here to enlarge

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    post your dyno graph

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    Everyone says to shift at 6200-6300, my best times have been from shifting at 6600-6800. This is with 24 passes on the car, so I've tried several variations. Also when ever I'm running on the street, I usually shift a bit closer to redline. I have no scientific proof on which is better though.

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    Too add more I wonder what that 6200-6300 shift point is referring to. Is it AT cars or MT cars? I've heard if you shift at 6200 *AT* that the tranny doesn't really let out until closer to redline almost like it's confused. Seems like an old wives tale to me, but who am I to say. Once I get a chance to take the wifes car to the track I'm going to do some testing with shift points.

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    It depends on the car but with the N54 your torque falls off a cliff at redline so going to the highest possible rev isn't the best for you. Your upgraded turbos hold power better to redline it seems so that doesn't go for everyone. In general though, you want to be at torque peak with the N54 and that isn't at redline.

    With the S65 and S85, rev the $#@!.

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    this is an easy question. imo its about the powerband. if you make peak power at redline, and hp builds from the start, shift at redline. if it rises and holds at peak or near peak (+/- 10 whp), shift at redline. if it rises, and falls as torque dies off faster, then you shift at whatever rpm the band shows to be peak, unless they have the same good hold of hp in the higher rpm band. no?
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    Click here to enlarge Originally Posted by oddjob2021 Click here to enlarge
    this is an easy question. imo its about the powerband. if you make peak power at redline, and hp builds from the start, shift at redline. if it rises and holds at peak or near peak (+/- 10 whp), shift at redline. if it rises, and falls as torque dies off faster, then you shift at whatever rpm the band shows to be peak, unless they have the same good hold of hp in the higher rpm band. no?
    Yep, well said.

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    you have to look at your dyno graph...on a stock turbo N54 with a 6MT I've been recommending to people to shift as soon as their RPM needle hits 6100rpm latest...this is because the power curve stays in the top most portion when you do your shift...if you get your shifts fast enough (less than 0.3s, i got mine down to 0.22s and 0.18s even sometimes) this will give you 120+mph traps on a 6MT...

    also when shifting don't press down on the clutch pedal ALL the way to the floor, you only need to go about 2/3 of the way and the clutch is disengaged and ready to engage a gear...too much time gets lost on 6MTs with less than ideal shifting...datalog your runs and train shifting and see how fast you shift by looking at the TPS line (on your JB3) or the Throttle graph (procede) and see how long it takes between on/off throttle and you'll know how much you're losing out while shifting...

    6ATs shift in about 0.1s so 6MTs are at a disadvantage there unless you get your shifts "trained" properly...keep in mind your RPMs will fall approx. about 1500rpm when you get them sorted out (if you shift at 6100rpm on your 2-3 shift say, your 3rd gear will pull at about 4600rpm)...take this rough approximation when looking at your dyno graph and determining where the shift sweetspot is on your car...
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    I will try find some Vbox results on a N54 with the torque drop off and you will notice that the G's the car pulls from 6200-7000 are greater than it pulls from when it has shifted in second. So theoretically it should accelerate faster when reving to the max but then and again in practice it seems shifting earlier is better. Quite confusing stuff. Might have to do with the fact that when you shift earlier the drop of is at a higher torque rate and the average G's are greater.

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    Good information. I think based on the consensus here I've been shifting too late. I guess I'm going to have to bust the laptop and dynolicious out and do some work.
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    exactly why i asked.

    now, how wil it be affecting the et/mph at the end, in the context of, how high will we be revving in 4th when we cross the trap? shifting earler all the way will mean we are in 4th faster, hence higher rpm right?

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    When I ran my 11.7 I shifted at exactly 6000 rpms each shift. I use my paddles and I notice there is a slight lag when travelling at high speeds so I click my paddle at about 5800 to ensure an optimal shift.

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    Ohh and I am almost at redline in 4th when I cross the trap.

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    Click here to enlarge Originally Posted by Irishace Click here to enlarge
    Ohh and I am almost at redline in 4th when I cross the trap.
    That is where you want to be crossing the traps.

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    very interestingg! can anyone else chime in on this? Was looking to 1/4 mile my car for the first time this week coming. This would be very helpful info!

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    I'm in with the other guys, dyno graph would be the best way to tell when and where to shift, so you can get optimal shift points based on how much power your car is making Click here to enlarge

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    Click here to enlarge Originally Posted by goodfella69 Click here to enlarge
    very interestingg! can anyone else chime in on this? Was looking to 1/4 mile my car for the first time this week coming. This would be very helpful info!
    Are you manual, or automatic? Mods?

    If auto just let it shift, if manual, try to shift a little earlier depending on your curve.

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    I say shift where you're making peak power. But not if you're about to cross the line then the extra shift will cost you time.

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    I will be testing next weekend at the track. I yesterday managed to swop out my 3.85 to a 3.15 from a DCT so all my existing data is useless.

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    I have AT and 67/6800 RPM work the best
    Click here to enlarge

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    Click here to enlarge Originally Posted by George Smooth Click here to enlarge
    I will be testing next weekend at the track. I yesterday managed to swop out my 3.85 to a 3.15 from a DCT so all my existing data is useless.
    That is a huge difference, why did you go so long?

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    Click here to enlarge Originally Posted by FR305 Click here to enlarge
    I have AT and 67/6800 RPM work the best
    for ET-MPH or both?

    and no other changes? no difference in 60'? different days etc...?

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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    That is a huge difference, why did you go so long?
    so long? stock manual is 3.08, stock auto is 3.46, he got the 3.85 from an M right? or was it the 3.15 dct diff? you didnt read the thread about how he changed to the m-diff and liked it at first (probably because of the positive traction) but then felt the ratio was not right for the engine.. so props to him for trying a new ratio Click here to enlarge you know for the n54, it makes so much torque so low, that you can really just start in 2nd, in that case, even lower than 3.08 could possibly yield better results, because then 1st maybe useable at upp'd turbo levels, but a 2.xx ratio seems sooo low LOL just like a 4.15 or whatever sounds very high for a street car.
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