C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Shifting rpm range

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Old Oct 22, 2020 | 08:37 AM
  #21  
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Originally Posted by sstonebreaker
Ddidn't realize it was that modified. Yeah, you probably need to shift higher.
Think it will ET better once shifting it higher?
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Old Oct 22, 2020 | 09:01 AM
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Originally Posted by krackenvette
Oops, I made an error, meant to say 10% above peak HP not torque. Thats how old that thought process was, when I was running my 70 Chevelle Big Block.
Ah... Got you. ....that is a great starting point.
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Old Oct 22, 2020 | 09:36 AM
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My guess is you want to shift between 5500 RPM and 6000 RPM with that combination of parts. Manually shift it once and see how it performs. If it works well you would need to adjust the shift points with a B&M governor recalibration kit, to dial the shift points in where you need them for full auto shifting. The kit is not that hard to work with, if you play with it for a afternoon you will probably be close. Note: Decreased spring rate has more effect on the 1/2 shift and less on the 2/3 and 3/4 shift, and decreased weight has less effect on th 1/2 shift and increasingly more effect on the 2/3 and 3/4 shift. Assuming that you are trying to raise the shift points, Take good notes and after two set-ups you should have enough data to dial in the set-up by the third try.

Also you want to shift above your HP peak to maximize the time under the HP curve not the torque curve for best ET and MPH. The engine probably peaks HP in the 5500 RPM range so shifting at 5500 to 6000 RPM should work well.

Last edited by bjankuski; Oct 22, 2020 at 09:41 AM.
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Old Oct 22, 2020 | 10:45 AM
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Originally Posted by bjankuski
My guess is you want to shift between 5500 RPM and 6000 RPM with that combination of parts. Manually shift it once and see how it performs. If it works well you would need to adjust the shift points with a B&M governor recalibration kit, to dial the shift points in where you need them for full auto shifting. The kit is not that hard to work with, if you play with it for a afternoon you will probably be close. Note: Decreased spring rate has more effect on the 1/2 shift and less on the 2/3 and 3/4 shift, and decreased weight has less effect on th 1/2 shift and increasingly more effect on the 2/3 and 3/4 shift. Assuming that you are trying to raise the shift points, Take good notes and after two set-ups you should have enough data to dial in the set-up by the third try.

Also you want to shift above your HP peak to maximize the time under the HP curve not the torque curve for best ET and MPH. The engine probably peaks HP in the 5500 RPM range so shifting at 5500 to 6000 RPM should work well.
This is my wifes car she said she is more then happy to manually shift it I'm thinking 5500 2nd to 3rd let 1st to 2nd shift on it's own think that's a good idea? Will we see any ET improvement?
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Old Oct 22, 2020 | 10:47 AM
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Originally Posted by 383 First
No dyno numbers As of yet we had a new s60 dana rear installed and they said 500 miles break in period when the break in was done the shop who did our work his dyno was down we have to go back but we got excited and wanted to see what it would run..i think it did ok but honestly I think it should go a little better...
I'm in Northern NJ, who are you using for the dyno? Where are they located? Do the dyno tune ?
Thanks.
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Old Oct 22, 2020 | 10:53 AM
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Originally Posted by vette196
I'm in Northern NJ, who are you using for the dyno? Where are they located? Do the dyno tune ?
Thanks.
I used JS performance in pa he built the whole car..he doesn't have one right now its done... my car has a holley hp efi system he street tuned it for now.
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Old Oct 22, 2020 | 11:11 AM
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There's got to be a bunch of chassis dynos around your area...?
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Old Oct 22, 2020 | 11:22 AM
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Originally Posted by Tom400CFI
There's got to be a bunch of chassis dynos around your area...?
Im sure there is..it will go on eventually I'm not in a rush honestly im waiting on him so he can dyno it and re tune. Car will be parked soon for winter we just wanted to get out 1 or 2 more times this year we had no idea it was going to go this well now im excited to see if we can get it to run 11.99
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Old Oct 22, 2020 | 11:23 AM
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Originally Posted by Tom400CFI
There's got to be a bunch of chassis dynos around your area...?
Not that I know of (especially dyno tune). As I get closer to needingone I will find one (the OP place is about 2hrs from me). Id like to do a baseline dyno and go the route of dyno tune or pcm4less. I was thinking of calling the manufacturer to see who they sold a dyno to in my area
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Old Oct 22, 2020 | 11:24 AM
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Originally Posted by Tom400CFI
There's got to be a bunch of chassis dynos around your area...?
And I really didnt want to spend money twice especially since were throwing an old school paxton on it so it will need a retune bigger injectors bigger fuel pump I'm guessing


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Old Oct 22, 2020 | 11:25 AM
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Originally Posted by vette196
Not that I know of (especially dyno tune). As I get closer to needingone I will find one (the OP place is about 2hrs from me). Id like to do a baseline dyno and go the route of dyno tune or pcm4less. I was thinking of calling the manufacturer to see who they sold a dyno to in my area
Where are you located
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Old Oct 22, 2020 | 11:44 AM
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Originally Posted by 383 First
Where are you located
Park Ridge...last exit on the garden state pkwy before the NYS boarder
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Old Oct 22, 2020 | 11:50 AM
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Originally Posted by 383 First
This is my wifes car she said she is more then happy to manually shift it I'm thinking 5500 2nd to 3rd let 1st to 2nd shift on it's own think that's a good idea? Will we see any ET improvement?
I do not know if you will see improvements, but I think you will,
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Old Oct 22, 2020 | 11:52 AM
  #34  
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Originally Posted by vette196
Park Ridge...last exit on the garden state pkwy before the NYS boarder
there is a shop up that way that does full tuning and has a dyno I'll get you there name.
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Old Oct 22, 2020 | 11:52 AM
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Originally Posted by bjankuski
I do not know if you will see improvements, but I think you will,
All we can do is try lol if it wasnt getting max hp by short shifting im sure we should see a little improvement.
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Old Oct 22, 2020 | 11:56 AM
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Originally Posted by vette196
Park Ridge...last exit on the garden state pkwy before the NYS boarder
Syngarage they are in Ringwood NJ
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Old Oct 22, 2020 | 02:06 PM
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Originally Posted by 383 First
Think it will ET better once shifting it higher?
Probably, but hard to say without seeing a dyno graph.

Have you thought about just putting in a ratchet shifter instead of altering the transmission?

BTW, what kind of racing are you doing? Bracket racing?
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Old Oct 22, 2020 | 02:20 PM
  #38  
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Originally Posted by sstonebreaker
Probably, but hard to say without seeing a dyno graph.

Have you thought about just putting in a ratchet shifter instead of altering the transmission?

BTW, what kind of racing are you doing? Bracket racing?
Eventually she will do bracket racing this is just test and tunes right now..

No ratchet shifter we had a B&M mega shifter in it what a piece of crap never again..either I'll have to play with the governor to get it to shift higher or she will have to manually shift it herself..
I'll do some data logging see what it shifts at on it's own the see if it improves shifting it thats the good thing about the modern holley efi in the car I can see what's going on and correct it..
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Old Oct 22, 2020 | 04:16 PM
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I've spent much time dialing in the governor of a 700r4. If you want to raise the shift points at wot, you can carefully grind some some meat off one or two of the governor weights. Do this carefully, test and you should see results. The stock weights are very heavy. I have played with aftermarket weight spring kits. Working with those is a very time consuming task. The springs affect mostly part throttle shifting, the weights mostly full throttle, however, they are interrelated. Keep it simple and lighten the stock weights and try it out. It costs nothing.
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Old Oct 22, 2020 | 04:26 PM
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You run island right?
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