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Tight Vs Loose converter; Ideal drop back on the shift
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DRR Sportsman
Picture of Mike Frizie
posted
Im bored at work with noting coming in the door. I wanna hear everyone's thoughts on the ideal set up. Beating Dead Horse


Michael Frizie
ET 2471
 
Posts: 571 | Location: Winston, GA | Registered: April 10, 2002Reply With QuoteReport This Post
DRR Pro
Picture of Don Higgins Crew Chief Pro Software
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About this...Smile 7792 shift 6900 drop.

4.45 @ 156


This message has been edited. Last edited by: Don Higgins Crew Chief Pro Software,



Crew Chief Pro 7.980. It is not an evolution in Crew Chief Software, it is a Revolution in Crew Chief Software
Drag Racing Software and Professional Weather Stations(309) 688-2990

Visit us on the web at http://www.crewchiefpro.com

Are you a Producer or a Parasite?

Author of the book, "But Who Will Save The Children."
 
Posts: 1378 | Location: Bartonville Illinois | Registered: October 18, 2002Reply With QuoteReport This Post
DRR Elite
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My door car and dragster this past weekend...

Firebird
•Converter flash 6200+
•7400 shift chip
•7500+ actual shift
•Converter fall back 6480

Dragster
•Converter flash 6500+
•7500 shift chip
•7500+ actual shift
•Converter fall back 6677
 
Posts: 13522 | Location: NJ | Registered: August 20, 2000Reply With QuoteReport This Post
DRR S/Pro
Picture of "The Bender"
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You guys don't want to know what the fall back was on my deal..........apples to oranges though.


272" Spitzer
540 Chevy
The Blower Shop XR1
FTI XPM Series Converter
FTI Level 6 Powerglide
3.69@199
.916 60'

2017 Bradenton Heads Up Madness
Open Outlaw Champ

2018 PDRA T/D #5
2019 PDRA T/D #2

2020 Retired From T/D Competition....

2020 Bradenton NMCA Hemi Shootout Winner

2021 getting back into bracket racing with a Gen3 Hemi powered 87 Cutlass.
 
Posts: 3088 | Location: Yes | Registered: July 08, 2009Reply With QuoteReport This Post
DRR Top Comp
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quote:
Originally posted by "The Bender":
You guys don't want to know what the fall back was on my deal..........apples to oranges though.
300-400 rpm short shifting for torque (boost)
 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post
DRR S/Pro
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quote:
Originally posted by DRB Motorsports:
Im bored at work with noting coming in the door. I wanna hear everyone's thoughts on the ideal set up. Beating Dead Horse


Assuming your looking for the ideal drop back after the shift(s) to achieve the best ET, the answer is, it depends on the motor and it's power curve based on the build. As trans gears increase, you can build the motor to run in a tighter rpm range so a 2 speed car vs a 4 or 5 speed car would need a broader/flatter torque curve an the 4/5 speed deal would have a narrower & peakier torque curve.

Typical race combo 2 speed PG trans have between 800 to 1200 rpm drop at the 1 - 2 shift. The looser converter the less drop and visa versa.
 
Posts: 2122 | Location: Tewksbury, MA,USA | Registered: November 03, 2000Reply With QuoteReport This Post
DRR Top Comp
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All the big gains in et drag racing, are in the front half (60ft). Because the converter multiply's torque by as much as 2.5 times depending on the stator, you want the stall 200 to 400 rpms above peek torque for the stator to direct oil onto the pump in order for the converter to multiply the given torque by anywhere from 1.8 times to 2.5 depending on the stator in play. The drop back can be whatever you want it to be depending on if you ring it out (rpm) or short shift, relative the engines latent potential for rpm.
 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post



DRR S/Pro
Picture of "The Bender"
posted Hide Post
quote:
Originally posted by Mike Rietow:
quote:
Originally posted by "The Bender":
You guys don't want to know what the fall back was on my deal..........apples to oranges though.
300-400 rpm short shifting for torque (boost)


You are correct on the fallback, but not short shifting, gotta keep that blower spinning to keep the boost up.


272" Spitzer
540 Chevy
The Blower Shop XR1
FTI XPM Series Converter
FTI Level 6 Powerglide
3.69@199
.916 60'

2017 Bradenton Heads Up Madness
Open Outlaw Champ

2018 PDRA T/D #5
2019 PDRA T/D #2

2020 Retired From T/D Competition....

2020 Bradenton NMCA Hemi Shootout Winner

2021 getting back into bracket racing with a Gen3 Hemi powered 87 Cutlass.
 
Posts: 3088 | Location: Yes | Registered: July 08, 2009Reply With QuoteReport This Post
DRR Top Comp
posted Hide Post
quote:
Originally posted by "The Bender":
quote:
Originally posted by Mike Rietow:
quote:
Originally posted by "The Bender":
You guys don't want to know what the fall back was on my deal..........apples to oranges though.
300-400 rpm short shifting for torque (boost)


You are correct on the fallback, but not short shifting, gotta keep that blower spinning to keep the boost up.


No, I'm correct in both regards. Short shifting relative the engines latent potential for rpm.
 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post
DRR Sportsman
Picture of Mike Frizie
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Keep seeing 800-900 on the fall back. interesting. shift mine @ 7200 falls back 600 to 6600.


Michael Frizie
ET 2471
 
Posts: 571 | Location: Winston, GA | Registered: April 10, 2002Reply With QuoteReport This Post
DRR Elite
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how are you determining that?
 
Posts: 13522 | Location: NJ | Registered: August 20, 2000Reply With QuoteReport This Post
DRR Sportsman
Picture of Mike Frizie
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Watching playback from Racepack of recorded run.


Michael Frizie
ET 2471
 
Posts: 571 | Location: Winston, GA | Registered: April 10, 2002Reply With QuoteReport This Post
DRR S/Pro
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quote:
Originally posted by DRB Motorsports:
Keep seeing 800-900 on the fall back. interesting. shift mine @ 7200 falls back 600 to 6600.


What happens if you shift at 7400 or 7500? A converter acts as a load sensor, the load is created by the HP/Torque the motor produces vs the load required to accelerate the car. I would say that you will see more fall back shifting higher.
 
Posts: 2122 | Location: Tewksbury, MA,USA | Registered: November 03, 2000Reply With QuoteReport This Post
DRR Top Comp
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My observed stall is 6200 rpm. If I shift 6300 rpm, take a wild guess how much it drops back?
 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post



DRR S/Pro
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Interesting results from some of you folks. During wide open runs the rpm drops back from 7500 at the shift RPM to 6200. Seems a bit too low on the drop back. If this was yours would you loosen it up?

Bob
 
Posts: 3044 | Location: Lakeside, Ca | Registered: February 15, 2003Reply With QuoteReport This Post
DRR Elite
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quote:
Originally posted by DRB Motorsports:
Watching playback from Racepack of recorded run.

so you noted the exact rpm the fall after the shift stops and confirmed that the very next tap of the arrow key has the rpm climbing?
 
Posts: 13522 | Location: NJ | Registered: August 20, 2000Reply With QuoteReport This Post
DRR S/Pro
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On a given day, drop back rpm is typically a few hundred (+/-) higher than stall in low gear.
 
Posts: 2122 | Location: Tewksbury, MA,USA | Registered: November 03, 2000Reply With QuoteReport This Post
DRR Sportsman
Picture of Mike Frizie
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from what i've seen. the converter flashed to 6600 off the trans brake release ad falls back to that speed on the shift from 7200 rpm. racepack UDX dash.


Michael Frizie
ET 2471
 
Posts: 571 | Location: Winston, GA | Registered: April 10, 2002Reply With QuoteReport This Post
DRR S/Pro
posted Hide Post
quote:
Originally posted by DRB Motorsports:
from what i've seen. the converter flashed to 6600 off the trans brake release ad falls back to that speed on the shift from 7200 rpm. racepack UDX dash.


That's very close to what I would expect, your shifting at a low rpm vs stall which is why your seeing 600 rpms.
 
Posts: 2122 | Location: Tewksbury, MA,USA | Registered: November 03, 2000Reply With QuoteReport This Post
DRR S/Pro
Picture of Big Steve
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On a bracket dragster I liked to keep it around 600 rpm. In top dragster anywhere from 400-600 max depending on what stator is in the converter, what blower pulley and how much power I am making that day. Like Bender said earlier, ya gotta keep that blower singing
 
Posts: 2370 | Location: Moving back to the door side | Registered: April 30, 2010Reply With QuoteReport This Post
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