maximize shift points

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Mopar to ya

Mopar to ya

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I am looking to maximize my shift points the next time I hit the track. I hit my best torque at 3900 to 4900 rpm. I had been winding to 6000 before shifting, but I wonder if I should shift sooner and use the torque to pull me faster. Being a novice, I am open to opinions. What do you all think? Here are my dyno specs. I am very curious to hear the responses.

View attachment Dyno specs (567x800).jpg
 
gearing ...converter flash ...tire diameter?

looking at your dyno sheet 12.0 to 1 compression..and Champion RC12YC plugs...need a colder plug...

generally you need to go thru a shift loop...trial and error is the only way to figure out where to shift at...
 
What you do is, you take either the HP curve or the accelleration (G) curves and plot them FOR EACH GEAR. You shift where the crossover happens IE when 1st runs out of steam and 2nd "comes on" that point will cross in the graph.

Once you have a HP curve for something specific such as high gear, you can use gearbox ratios to scale the other gears

I'm having trouble finding a www example

This one is G's vs speed. The crossings are obvious in this plot

fz6r_acceleration_all_gears.png


Here's what we are looking for:

http://www.golfmk6.com/forums/showthread.php?t=29023

What he did in the graph below is took the engine torque curve and constructed individual curves based on the gear ratios in the gearbox.

4thgearshiftpoint.png
 
Yet another. This one plots each gear's torque at the driveshaft with MPH. You can easily convert mph to RPM, and once again, the shifts are at the crossover points

This clearly shows why you do not shift "at max torque," but rather, when torque in the present (lower gear) falls to a lower value than the torque in the next higher gear could produce.

Rimpul4.gif
 
After looking at the dyno sheet, the main issue I see is the big rpm drop from the 1/2 shift with the 200R4. Depending on how the converter works out, I can see another 500 r's on the 1/2 shift to get you even close to the torque peak. Probably 6200 on the 2/3 is close also. As long as the bottom end can take it, i'd bump the shift points "higher" to see how it works out.

What i'm looking at is, if you shift the 1/2 at 6k, mechanically, you'll drop back in the 3400ish range. If you still have some converter slip there, you may be fine. If the converter is pretty much locked at that point, you will have to pull your way up to and past your torque peak. Hence why i'm potentially recommending the higher shift points.

Just my opinion. Good Luck next time. :thumbrig:
 
OldmanRick said:
After looking at the dyno sheet, the main issue I see is the big rpm drop from the 1/2 shift with the 200R4. Depending on how the converter works out, I can see another 500 r's on the 1/2 shift to get you even close to the torque peak. Probably 6200 on the 2/3 is close also. As long as the bottom end can take it, i'd bump the shift points "higher" to see how it works out.

What i'm looking at is, if you shift the 1/2 at 6k, mechanically, you'll drop back in the 3400ish range. If you still have some converter slip there, you may be fine. If the converter is pretty much locked at that point, you will have to pull your way up to and past your torque peak. Hence why i'm potentially recommending the higher shift points.

Just my opinion. Good Luck next time. :thumbrig:
Click to expand...

you mean 700? the 200 has the same shift points as a 904
 
805moparkid said:
you mean 700? the 200 has the same shift points as a 904
Click to expand...

Not exactly, with the 200R4 OD trans 2.74 1st, 1.57 2nd, 1.00 3rd & .67 4th. it has approx. 2% more drop @ the 1-2 and 5% more on the 2-3 then the 904. Not overly huge, I get your point. I suppose I was being a little picky between the two. Just looking at any advantage/disadvantage I could find.


The 700's 3.06 1st to 1.63 2nd is huge though.
I love these wide ratio transmissions for the street daily driver, but i'd truly prefer the closest ratios I could get on a drag strip.
 
70aarcuda said:
gearing ...converter flash ...tire diameter?

looking at your dyno sheet 12.0 to 1 compression..and Champion RC12YC plugs...need a colder plug...

generally you need to go thru a shift loop...trial and error is the only way to figure out where to shift at...
Click to expand...

I run a Dana 60 with 4.10 gears. I run a 27" tire at the track and I have a 3000 rpm stall converter. I am running NGK plugs at this time, but at the dyno it was Champions. I'm not sure of the heat range on the plug right now, I'd have to pull one and look.
 
OldmanRick said:
Not exactly, with the 200R4 OD trans 2.74 1st, 1.57 2nd, 1.00 3rd & .67 4th. it has approx. 2% more drop @ the 1-2 and 5% more on the 2-3 then the 904. Not overly huge, I get your point. I suppose I was being a little picky between the two. Just looking at any advantage/disadvantage I could find.


The 700's 3.06 1st to 1.63 2nd is huge though.
I love these wide ratio transmissions for the street daily driver, but i'd truly prefer the closest ratios I could get on a drag strip.
Click to expand...

so between a .8OD and .7OD is 300 rpm, so 300 x .1 (10%) is 30rpm per .01 (.01 because its 10% of the above OD's split). so your looking at 60 rpm difference between a 1.57 and 1.54, pretty much nothing... all in all it has an OD, very close ratios to a 904...

and the 700 is just wack lol

Ratio's from randy's gear and pinion
DODGE TF9042.741.541.00GM TH200-4R2.741.571.000.67
 
Ed, I see where some of our differences are now. I was thinking of the 2.45/1.45 (904) and you were looking at the 2.74/1.54 (LG 904).

I finally used a calc instead of that empty space between my ears, lol....and came up with this rpm after the 1-2 shift at 6000 r's.

904 ........ 3,551
200R4 .... 3,438
LG 904 ... 3,372

I have to concede, not a ton of difference among them all...

Good discussion, Ed
Thx, Rick
 
OldmanRick said:
Ed, I see where some of our differences are now. I was thinking of the 2.45/1.45 (904) and you were looking at the 2.74/1.54 (LG 904).

I finally used a calc instead of that empty space between my ears, lol....and came up with this rpm after the 1-2 shift at 6000 r's.

904 ........ 3,551
200R4 .... 3,438
LG 904 ... 3,372

I have to concede, not a ton of difference among them all...

Good discussion, Ed
Thx, Rick
Click to expand...

i thought the 2.45 was a 340 deal (stock)??
 
805moparkid said:
i thought the 2.45 was a 340 deal (stock)??
Click to expand...

As far as I know, the 904's were all 2.45/1.45 geared until the early 80's when the A998/999 low gear units began to appear. I believe all the 727's were all 2.45's also. Once they started the RH whatever and 500 designations with the newer transmissions, i'm lost...lol.

I apologize if I hijacked your thread, M2ya.
 
To get back to your original question.....Short shifting, in my experience, seems to work best on lower horsepower cars with a lot of gear. A example would be a small engine NHRA/IHRA "stock" class car with a big converter and 5+ gears. I'm not saying it wont work in your situation, but with your power curve, i'd personally try raising the 1-2 shift point if you just want to post a number. If, next year, you want to go out and win some rounds, I would probably find a comfortable shift point that would give you repeatable times, and a lower shift point may actually help you achieve that, although not running your best ET's, the "W" light is always cool.
 
Winning is always cool. I hit the track just once in my life and it was on a street legal night. $25 all you can run. You need a valid license, a street legal car and a Snell helmet. I got in 5 runs and won all of them. The closest was a Nomad. I didn't see him along side of me, and he wasn't in either mirror, so he was close. I did beat a supercharged Rambler. One thing I did learn was that I would have beaten 3/4 of the cars that were running. Now when I hear all these weenies telling me they have a ten second car, I can say no you don't. That is a very hard number to hit and not many street cars will.
 
I went out today to see what real life rpm was. It is very hard to simulate track conditions since I was on street tires and it's very hard to get any rpm under heavy acceleration without spinning the tires. It is very different on mid acceleration and hard acceleration. On mid acceleration - not hammering but steady accel:

1-2 shift at 5000 rpm dropped to 3500 rpm, 2-3 at 5000 rpm dropped to 3800 rpm
1-2 shift at 6000 rpm dropped to 4000 rpm, 2-3 at 6000 rpm dropped to 4400 rpm

On hard acceleration, pedal hammered, I couldn't get a 5000 rpm shift. It blows through the lower rpm too fast. I had a hard time getting a look at 6000 rpm and I probably shifted closer to 6500.

1-2 shift at @6000 rpm dropped to 4800 rpm, 2-3 at 6000 rpm dropped to 5000 rpm.

So, what are we thinking with this new info? I am thinking a higher rpm 1-2 shift and maybe a little less than 6000 on the 2-3. I never really needed to kick into overdrive, I just stayed in 3rd until I crossed the line.
 
Some light reading. You really should sit down and graph out either torque or HP vs RPM for each gear. The shift points will become obvious.

The point at which max torque/ hp/ acceleration becomes "the same" at the top of one gear as it is in the bottom of the next gear is you shift point.

All you need do is to multiply the figures in your HP chart by each gear ratio.

If you can find someone to build spread sheets you could probably show it that way.



http://www.ls1gto.com/forums/showthread.php?t=334833&highlight=
 
First off, you have a nice running car in street trim.

Second, while this is a nice conversation, and very informative for many, me included.....The bottom line is, we're talking shift points here. What that means to me is we're looking for a few "hun", and possibly up to a tenth max. You're not gonna go 11's by changing them up or down.

The numbers I posted earlier are not taking into account trans/converter slip or tire spin. Your street test proved that. I did a quick look at converter slippage at the top end (109.16, 85" circumference tire, and 6k) and it looks to be approx 8%. Obviously, the closest to zero would be optimal, but that will never happen with a auto trans/converter, especially a streetable one. At this point, i know you want to make the most of your last session of the year, so i'd try a few hundred less and a few hundred more and see how it works out.

I really think to step up significantly next year , you need to work on getting the 60's consistently in the low 1.60's and maybe work on that 109.16, meaning some power tuning.
 
Yes, the plan this winter is either an MSD 6AL-2 programmable or an MSD E-Curve distributor so I can get my timing better locked in with the different octane fuels I run. Some better carb tuning as well. This motor supposedly ran 11.27 in a Swinger with 3.55 gears. I would like to break into the 11's at least. The article 67dart273 linked was understandable in a vague way. It wasn't over my head, but it was close. It boils down to the real reason for this thread. I know I have horsepower. I want to get the most out of my torque by shifting at the proper time and letting the torque pull me though at the best possible speed.
 
I think you will be fine with some work and track time. I do consider the really technical parts/terms of different systems/issues, and i will admit i'm not the sharpest tool in the drawer, but I do like to have "simple" conversations about things that a lot of us can relate to.

I hope you have another good outing next time. Good Luck & remember to keep records, mental and on paper, to learn from the car on every pass. :thumbrig:
 
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