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  1. #1
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    Default Converter issues, slow 60 foot

    I have VE GXP Maloo ute I have recently done head, cam and converter on.
    The converter manufacturer had all the specs for the engine combo as well the correct weight, gear ratio and tyre size.
    The requested stall speed was 4500-5000 but the stall speed according to my data logs is around 3400.
    My best 60 foot time is 1.68, it usually 1.7, I feel the car should be capable of a 1.60 or even high 1.5s.
    Best pass so far is 11.44@123. I only have 8 passes on the current combo, I know it has more in it once I get the 60 foot down and fix up my gear shifts,the 6L80 is struggling to stay of the limiter.

    I have spoken the converter manufacturer and they just basically said all combos are different and to send it back and he would adjust it but Iam a little concerned that either they have missed the mark by so much, or there is something else going on.

    I have done leak down and compression tests, everything is as it should be. Not really sure which way to go, either I have the stall adjusted and hope they can get it closer or try to increase the torque by changing timing or converting to E85.

    The Ute specs are;
    LS3, Trickflow heads, solid 240/252 cam, ~0.700inch lift, 12.5:1 compression, Fast 102 manifold with mid length runners, 1-7/8 Difillipo headers,dual 3 inch exhaust. It made 486rwhp with the converter unlocked.
    6L80E transmission, 3.45 rear end, 28 inch tall drag radials, 4000lb race weight.

    What would you guys do? give the converter manufacturer another shot at it or is there another issue I should be chasing? Is my timing too low at low speeds/loads dragging torque down and lowering stall speed? would the extra torque of E85 help get the stall speed up?

    [IMG]https://i1060.photobucket.com/albums/t457/Xjas396/Screenshot%2063_zpskisrp1ju.png[/IMG]
    [/COLOR][/FONT]
    Last edited by Xjas; 05-08-2019 at 10:40 PM.

  2. #2
    Do you ever leave? EH179's Avatar
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    3.45 gears, 28" tyre and 4000 lbs?- no wonder it's a 3 legged Tortoise.

    What is the first gear ratio in a 6l80E, please.

  3. #3
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    6L80 1st is in the order of 4:1 (slightly lower actually)

    That 28" tyre is likely gonna need near 3.9 rear end to just get back to the original gearing, 4.11 or lower would be a great start without changing the cruise RPM, but then again methinks that much cam is gonna require a much higher cruise RPM than even a 4.11 gear would offer.

  4. #4
    Part of the furniture 46Crab's Avatar
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    The info I have got for the 6L80E is 4.03 first gear ratio.

  5. #5
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    While I have considered lowering the diff gear ratio I'm not sure if it would be an improvement.
    Considering the 6L80 has a 4.03 1st gear ratio with the 3.46 diff ratio that is a total ratio of 13.94.
    A TH400 has a first gear ratio of 2.48 so to achieve the same total ratio a TH400 car would require a diff ratio of 5.62.
    Based on that logic in first gear my current set up is equivalent to a TH400 with a diff ratio of 5.62 which should be fine with 28 inch tyres I though, at least as far as the 60 foot is concerned.
    Also if I understand it correctly, lowering the diff ratio will reduce the load on the converter and make it stall at an even lower speed than it is now.

    I have seen that some of the faster NA LS3 6L80E Camaros in the US running 3.9s or lower but I think they are launching in 2nd gear which has a 2.36 ratio.

  6. #6
    Do you ever leave? EH179's Avatar
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    You still need to accept the fact it weighs 4000 lbs...that's a heavyweight.

    Are you getting wheel spin on launch?

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    I know its heavy, I've taken out what weight I can. No wheelspin, dead hooks when I have the tyre pressure right.

  8. #8
    Part of the furniture monaroman76's Avatar
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    Quote Originally Posted by EH179 View Post
    You still need to accept the fact it weighs 4000 lbs...that's a heavyweight.

    Are you getting wheel spin on launch?
    No wheel spin according to the log.

    I'd be sending the converter back, they missed the mark by a long shot. Nothing you could change would get you any where near the 5000 RPM stall you need. K factor of the converter is roughly 150, you'd need to double your torque to get that converter to stall to 5000rpm. It'd be nice if E85 and more timing could do that

    123mph @ 4000lbs indicates 575hp. You should be able to shave at least 0.15s off your 60' which should get you into the very low 11's.
    Did you tune this? I'd expect you could squeeze a bit more out of it with a few degrees more timing and perhaps even fattening it up a bit. Your static comp is up there though, so perhaps this was a limiting factor for timing.

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    You need to know the converter body type or diameter.
    The converter mob you used would be reluctant to to reduce the diameter to what you need as the lock up plate would be too small or would need to be removed completely.

    You should be able to get the stall speed up to where you need it, using a neutral or negative impeller will help if yours has a more positive angle.
    Then you can change or alter the stator to get more out of it.

    You shouldn't have to worry about inducing too much converter slip as the lock up clutch will come on and pretty much eliminate all of that.

    What strategy do you have for your converter clutch apply ? will it apply at WOT.

  10. #10
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    I do tune it, that's why the gear shifts are a mess, first 6L80 I've tuned and its been a battle, I can only adjust shift points at the track as it just blows the tyres of on WOT 1-2 and 2-3 shifts on the street.
    Tried adding/removing fuel and timing on the dyno but nothing seem to make much difference, a few HP either way was I there was in it. I usually run it around 12.7AFR, cant remember why its different in the above screenshot. Another trip to the dyno might be in order though, when I got home from the last session it was pushing coolant out under both head gaskets, turned out the outside row of head bolts were bottoming out slightly due to the heads being shaved, not sure if that was affecting compression on the dyno or not.

    The aim for the car is to run a high 10, almost half a second is a lot still to find but I think I have a lot of things I can do to get it moving in the right direction. Getting the 60 foot where it should be will definitely help and I think getting the gear shifts sorted should see an increase in ET and MPH.

  11. #11
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    Quote Originally Posted by HQ 368 View Post
    You need to know the converter body type or diameter.
    The converter mob you used would be reluctant to to reduce the diameter to what you need as the lock up plate would be too small or would need to be removed completely.

    You should be able to get the stall speed up to where you need it, using a neutral or negative impeller will help if yours has a more positive angle.
    Then you can change or alter the stator to get more out of it.

    You shouldn't have to worry about inducing too much converter slip as the lock up clutch will come on and pretty much eliminate all of that.

    What strategy do you have for your converter clutch apply ? will it apply at WOT.
    Invoice says its 265mm.
    I'm not locking the converter at WOT at this stage but I will look to do that in future.

  12. #12
    Do you ever leave? paulzig's Avatar
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    11.44@123

    Even at 4000LBS its making good power, if you put this on an engine dyno with open headers you would be close to 600HP

    This should be a 10.90 car even at 4000LBS. The 60ft should be 1.5s..

    If your invoice says 265mm thats 10.5" no wonder it stalls 3400, I cant see something like this being adjusted to go to 5000, that stall speed is for smaller 8" odd converters

  13. #13
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    Hopefully its got a 10.9X in it, I think does, SQP ran in the 10.9Xs with a cam only LS3 VF ute so I'm pretty confidant I can get there eventually.
    Would hope the converter manufacturer can get at least 4500 out of it as that's what I originally asked for, and paid for...

  14. #14
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    Quote Originally Posted by Xjas View Post
    Would hope the converter manufacturer can get at least 4500 out of it as that's what I originally asked for, and paid for...
    One should hope so, its making power based on the MPH thats for sure... Your 60 ft is letting you down, get that down to 1.5 and there is your 10.90 maybe even better

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    That's certainly a bigger converter body than I would have anticipated, not what I would have gone for.
    That body I have used in things making 1500+ hp or so, not something like you have.

    There isn't a lot of 265 mm stuff floating around in our market and it would need some boost or a decent spray to get it up there.

    Sonnax and other converter parts suppliers will have some parts to make something better of it but I think you'll be heading to a smaller body converter in all honesty.

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