Ideal shift point article

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reading that is too theoretical. you go to the track, you make some runs , raising the shift points a little each run=real world
 
Cliff notes from thread: "Sorta confirms what I have always been t5old that the best shift point is roughly 1000 rpms past peak power. Assuming as you correctly point out that engine/drive train can handle it."
 
If that is true I'd be shifting at or over 7,000RPM. I'll pass
 
The way to do the shift point, is to know what rpm your horsepower and torque start dropping off. Then test it at the track for your best shift point. Thats were it nice to have your dyno results.
 
I didn't read all of it but to make a blanket statement that is shift 1k above peak is just stupid.


Did the guy account for what the transmission gearing was?

You figure the gearing splits and shift far enough above peak to keep the engine above peak torque.

That's why an engine with a flatter HP peak is easier to drive than an engine with a sharp peak. The sharp peak can be quicker, but it's harder to drive.
 
Shift when the blue light next to the tac comes on :thumbsup:
set the the blue light to come on at the rpm that gets you the best et :popcorn:
 
I understood that perfectly. And that is why I have GearVendor and use it as a splitter. It's the closest thing to a CVT you can get,to handle 400 hp. My car is faster and quicker with a 276/286/110 cam, and the 3.09low box, and the GV, than it was with a 292/508/108, and 2.66 box.
And now I can run 3.55s . And overdrive. And cruise at 65=2236rpm. And I get to pass by a lot more filling stationsl.

The point of his story is this; the power at the outshift should be about the same as the power at the drop in. Some tranny ratios are so far apart that you might have to shift MORE than 1000 rpm for this to occur. Other ratios are so close together that 700 will do it. And the same tranny could have two or three different overruns. Using the dyno graph and overlaying the tractive force is the easiest way to determine the shifts. It will save you dozens of shift loops, and a lot of wear and tear.

The 727 is a prime example.The splits are pretty wide, at 59%, and 69%. Outshifting at say 6800, the incoming rpms will be 4012, and 4692. The power peak should thus be close to half way in between or 5406, and 5746. Well guess what 6800 less 5406 is 1394, and 6800 less 5746 is 1054.This is somewhat of an oversimplification, but the example clearly supports a shift-rpm at least 1000 rpm past the power peak. This is the only way to optimize the average hp put down during the run.
Anyone short shifting a 727 is asking his engine to claw it's way back up from the basement, and is forfeiting maximum average hp.
Now for my combo;
To quarter mile, I would use the first 4 ratios available to me. Namely; 3.09-2.41-1.92-1.50. The splits are 78% and 79.7%, and 78%. Outshifting at 6600 the drops are to 5148, and, 5260, and 5148. The power peak should thus be close to half way in between or 5874, and 5930, and 5874. And the shift point is therefore about 700rpm past the power peak. So my little 367 has a pretty flat power band up there, and the average power put down on the run is relatively high compared to the power peak.
If you want to see proof of this, just install a G-Tec pro on your windshield, and go have some fun. Save your engine/run it on the primaries only.lol
For my next cam, I think I'll go down one size and adjust the LSA for a narrower, but more powerful peak. She only needs a 1400 rpm powerband, with the current gears. Then I could pass even more filling stations,lol.

Now I just know somebody is gonna ask;so

>With the 292cam and 3.55s my car went 12.9@106 the one and only run I ever made. I was just there for a timeslip.The tranny ratios used were 2.66.1.92,1.40
The final drive ratios were 9.44-6.82-4.97
>With the 276cam and 4.86s, the car went 7.92@93(1/8th) on the only successful run of 4. I was just there for the time slip.The tranny ratios were 3.09-2.41-1.67-1.30. First gear was useless, and I punched it into O /D as soon as I left the line, and I slipped the clutch a long,long, ways.60fts were 2.2 and change.
The final drive ratios were;15.02-11.71-8.12-6.32
Because of the starting line issue, I believe I would have been just as well off with way less gear. With 3.23s the final drive ratios would have been; 9.98-7.78-6.20. This would have brought my trap rpm down to a more sane 6900ish,too, instead of 7050ish.
>7.92 translates to about 12.4seconds in the qtr, and that comes in at about 111mph.
The rest of the car was about the same.
Less cam + tighter ratios = faster and quicker.
Your results may vary
 
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I actually run the 1/8 miles drags in 2nd gear OD. Puts me through at 6200, same as if I was in 3rd in the 1/4
 
roccodart440 said:
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I actually run the 1/8 miles drags in 2nd gear OD. Puts me through at 6200, same as if I was in 3rd in the 1/4
Click to expand...
I would love to have an overdrive for the hi way. but my I think my engine will have enough torque to not drop out of the "power band" w/ a stock geared 727.
 
I used to run a 833 O.D behind a mild 340. worked great ! I would drag with 1-2-3 and cruise with 4th ( errr 3rd..).
the 3.09 would get me 1.6 60 ft's and I could pull a 12.9-13.05 1/4 running 4.10s...and drive to the strip ...which sometimes was in Spokane or Seattle or Portland or Woodburn OR BIR in MN ! yeah... I actually drove 1400 miles to Minnesota and raced then drove home. It was a blast !
 
AJ/FormS said:
I understood that perfectly. And that is why I have GearVendor and use it as a splitter. It's the closest thing to a CVT you can get,to handle 400 hp. My car is faster and quicker with a 276/286/110 cam, and the 3.09low box, and the GV, than it was with a 292/508/108, and 2.66 box.
And now I can run 3.55s . And overdrive. And cruise at 65=2236rpm. And I get to pass by a lot more filling stationsl.

The point of his story is this; the power at the outshift should be about the same as the power at the drop in. Some tranny ratios are so far apart that you might have to shift MORE than 1000 rpm for this to occur. Other ratios are so close together that 700 will do it. And the same tranny could have two or three different overruns. Using the dyno graph and overlaying the tractive force is the easiest way to determine the shifts. It will save you dozens of shift loops, and a lot of wear and tear.

The 727 is a prime example.The splits are pretty wide, at 59%, and 69%. Outshifting at say 6800, the incoming rpms will be 4012, and 4692. The power peak should thus be close to half way in between or 5406, and 5746. Well guess what 6800 less 5406 is 1394, and 6800 less 5746 is 1054.This is somewhat of an oversimplification, but the example clearly supports a shift-rpm at least 1000 rpm past the power peak. This is the only way to optimize the average hp put down during the run.
Anyone short shifting a 727 is asking his engine to claw it's way back up from the basement, and is forfeiting maximum average hp.
Now for my combo;
To quarter mile, I would use the first 4 ratios available to me. Namely; 3.09-2.41-1.92-1.50. The splits are 78% and 79.7%, and 78%. Outshifting at 6600 the drops are to 5148, and, 5260, and 5148. The power peak should thus be close to half way in between or 5874, and 5930, and 5874. And the shift point is therefore about 700rpm past the power peak. So my little 367 has a pretty flat power band up there, and the average power put down on the run is relatively high compared to the power peak.
If you want to see proof of this, just install a G-Tec pro on your windshield, and go have some fun. Save your engine/run it on the primaries only.lol
For my next cam, I think I'll go down one size and adjust the LSA for a narrower, but more powerful peak. She only needs a 1400 rpm powerband, with the current gears. Then I could pass even more filling stations,lol.

Now I just know somebody is gonna ask;so

>With the 292cam and 3.55s my car went 12.9@106 the one and only run I ever made. I was just there for a timeslip.The tranny ratios used were 2.66.1.92,1.40
The final drive ratios were 9.44-6.82-4.97
>With the 276cam and 4.86s, the car went 7.92@93(1/8th) on the only successful run of 4. I was just there for the time slip.The tranny ratios were 3.09-2.41-1.67-1.30. First gear was useless, and I punched it into O /D as soon as I left the line, and I slipped the clutch a long,long, ways.60fts were 2.2 and change.
The final drive ratios were;15.02-11.71-8.12-6.32
Because of the starting line issue, I believe I would have been just as well off with way less gear. With 3.23s the final drive ratios would have been; 9.98-7.78-6.20. This would have brought my trap rpm down to a more sane 6900ish,too, instead of 7050ish.
>7.92 translates to about 12.4seconds in the qtr, and that comes in at about 111mph.
The rest of the car was about the same.
Less cam + tighter ratios = faster and quicker.
Your results may vary
Click to expand...
just curious, how did you get your percentages of gear splits?? I tried the usual method and came up way different percentages.
 
perfacar said:
just curious, how did you get your percentages of gear splits?? I tried the usual method and came up way different percentages.
Click to expand...


I'm not 100% sure but when I read his post it sounds like he's splitting the OD. Didn't know that was possible, but I'm old school and wouldn't use an OD if it was free.

For me, a 4.56 is about the perfect street gear. No OD needed.
 
As to splitting,yes.
As to splits; if you have two gear ratios; one of 3.0/1 and one of 2.0 to1; The rpm drop going from the granny to the second is 2/3 or to .66666 of the shift rpm. Shifting at 6000, then the rpm will drop to .6666 x 6000=4000. Thus the rpm drop is 2000.
That's how I do it.
I ran 4.88s on the street. And I ran 4.30s on the street. And I ran 4.10s on the street,and I ran 3.91s on the street, and I ran 5.13s on the street,and I ran 3.55s on the street,and I ran 3.23s on the street.... But never 4.56s
With a 3.09 low and a GV you can run anything.
4.56 x 2.66(the standard A833 low) nets a starter gear of 12.13. Using a 3.09 low this would require just 12.13/3.09=3.925.
I found this much gear-reduction (12.13) on the street to be semi-useless,a tire-burner. A hot 360 stick-car,with a street cam and adequate compression,needs no more than about 10.00 starter. 11.00 tops. Otherwise I was grabbing second almost right away. Or I was moving out like a Mustang; reving it out to over 3000 before shifting. That's just sooooo wrong. That's for 5.0s. I have a 6.0, and it has way more torque. Shoot I can shift it below 2000 when I'm just tooling around. Well below. It's a 6liter for Pete's sake.
While big-number gears can be fun;IMO, on the street, they are more or less just trading away hi-way cruise for tire-smoke. That's the conclusion I came to,anyway.
 
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yellow rose said:
For me, a 4.56 is about the perfect street gear. No OD needed.
Click to expand...

I'm with you on the 4.56's but I use an OD. 2500@60mph, 6200@114mph

For a guy that is mostly around town with shorter jaunts on the highway 4.56's with no OD and 28+ tires is not only fine but in town they are perfect.

I suspect if you were given a GVOD you'd fall in love pretty quick and even your engines couldn't break one.
 
I get what you are saying about the 4.56s. With 28s, the rpm at 30mph is 3152 in second(1.92). That is a really nice jumping off rpm. 60mph will thus be 6304, top of second.
With 3.55s and a GVOD that same jumping off rpm is 3080 in 1st-over (3.09x.78=2.41),and 60mph will be 6160,still in 1st-over.
Of course with 3.23s that same jumping off point is now 3093 in first gear (2.66), and 60mph will be 6186, at the top of first.
 
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roccodart440 said:
I'm with you on the 4.56's but I use an OD. 2500@60mph, 6200@114mph

For a guy that is mostly around town with shorter jaunts on the highway 4.56's with no OD and 28+ tires is not only fine but in town they are perfect.

I suspect if you were given a GVOD you'd fall in love pretty quick and even your engines couldn't break one.
Click to expand...


Maybe so, but I'd rather that Santa brought my fat *** a Passon 5 speed. That would make daddy very happy.

Hard to convince the wife I need a gear box when she wants new hard wood floors and widow covers. Damn.
 
You should go ahead and order it now if you expect to have it by the time you get those floors and windows done! LOL take your time....
yellow rose said:
Maybe so, but I'd rather that Santa brought my fat *** a Passon 5 speed. That would make daddy very happy.

Hard to convince the wife I need a gear box when she wants new hard wood floors and widow covers. Damn.
Click to expand...
 
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