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Author
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Topic: Convertor slippage
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67mustangdsa
Journeyman Posts: 45
From: Xenia Ohio
Registered: Jan 2004
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posted 12-22-2004 10:15 AM
   
Hey Alex or any class racers,
What convertor slippage do you shoot for? I ran an ATI this year and I was getting around 9.3% at the finish line. I think this is a little much. I am going to have Dynamic build one soon. I am making a bunch more power now and want to do up a new convertor for the new combo. In would really like to see 6%. Is this realistic?
Shawn[This message has been edited by 67mustangdsa (edited 12-22-2004).]
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CometGT1974
Gearhead Posts: 393
From: Asheville, NC USA
Registered: Jan 2002
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posted 12-22-2004 10:24 AM
I can't help you on this but i'm curious as to how you calculate your converter slippage?
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Moneymaker
Administrator Posts: 26513
From: Lyons, IL, USA
Registered: May 99
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posted 12-22-2004 10:40 AM
Shawn, we actually have a higher slippage percentage than your calculation.
We have learned that a greater lock up will actually slow you down.
We tested a lot of converters for JPT in all three cars.
With a 3 speed and todays aggressive cam grinds you need to keep the engine in the power band, or the recovery drop off kills ET. Consequently more slippage is the lesser of two evils.
A mechanical diode or other style lock up converter is the only way to avoid slippage in high gear. Both are not legal as you know.
I would talk to Jim at JPT or Mike Munsinger before you make any moves.
Both have more FoMoCo converter experiance than all other brands combined.------------------
Alex Denysenko
Co-Administrator and Moderator NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA & SS/MA National Record Holder '00,'01,'02,'03,& '04
First SS/MA in the TENS!
IHRA division 5 Superstock Champion
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28 The Barry of BarrysGrrl Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com
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67mustangdsa
Journeyman Posts: 45
From: Xenia Ohio
Registered: Jan 2004
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posted 12-22-2004 10:58 AM
Thanks Alex. The convertor I have now actually does a great job on the bottom. I was amazed how much information I gained by using a recorder tach. I learned a lot about flash and rpm drop from the shift. I always thought they were the same before. I will get on the horn now that I have my dyno info. To calculate slippage, you calcuate what your rpm would be based upon your finishline speed, tire circumfrance, and final gear ratio assuming no slippage. Then you compare that theoretical rpm to your actual rpm at the finish line to see how much you are slipping. I set up a spreadsheet to play with numbers to decide what rear end gears to use. You know, overengineering everything.
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Hans olsson
Gearhead Posts: 670
From: Sweden
Registered: Apr 2000
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posted 12-22-2004 12:07 PM
With no tire growth and no slippage our rpm across the line should be 6800 rpm but is more like 7200-7300.That is 6.5-7% at the line.With 2% growth it increases to 8%.This is with a 8 inch JPT converter. Maybe we need more slippage? Hans ------------------
- VIN 1F05M139343
- 71 Mach 1 Ram-Air
- 351C 4V 285 HP
- F-G/Stock Aut
- Stockers are way cool!
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Rustang
Gearhead Posts: 775
From: Clarion PA
Registered: Nov 2000
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posted 12-22-2004 12:34 PM
quote:
Originally posted by 67mustangdsa:
I was amazed how much information I gained by using a recorder tach. I learned a lot about flash and rpm drop from the shift.
I started using one at the end of this season. I'm curious what you see on launch? Mine leaves at 5200rpm, rpm doesn't "droop", just sets at 5200 for maybe 1-2 seconds and then the rpm's start to climb 
BTW my slippage calculates out to about 6% ------------------
'68 mustang 351 clevor- 10.92@124
'67 Stang, 351W -11.18@118
'69 351C Torino-14.90@100
'78 Pickup 351W-15.56@88
'79 Pickup 460 ET=?? [This message has been edited by Rustang (edited 12-22-2004).]
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67mustangdsa
Journeyman Posts: 45
From: Xenia Ohio
Registered: Jan 2004
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posted 12-22-2004 12:37 PM
What I mean by flash and drop is this. Basically, at launch, it will flash and stay at 5400 until the engine catches up. But when I shift from 1-2 or 2-3, the rpms drop to 6000. I was always under the impression that it would drop to the flash point but it is actually higher.
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Hans olsson
Gearhead Posts: 670
From: Sweden
Registered: Apr 2000
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posted 12-22-2004 12:46 PM
Our flash is 4900 and drops to 5500 with each shift.Shawn,what rpm do you shift at? Hans
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- VIN 1F05M139343
- 71 Mach 1 Ram-Air
- 351C 4V 285 HP
- F-G/Stock Aut
- Stockers are way cool!
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67mustangdsa
Journeyman Posts: 45
From: Xenia Ohio
Registered: Jan 2004
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posted 12-22-2004 01:02 PM
1-2 and 2-3 at 6800 and cross around 7200. My new combo peaks about the same place but with 50 more hp and 30 more ft-lb. Plus, it will be 85 lb lighter at C weight, which I think it will like. I am considering different gears and slicks. If only I could test in the snow! [This message has been edited by 67mustangdsa (edited 12-22-2004).]
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scottford351
Journeyman Posts: 92
From: reedsville ohio usa
Registered: May 2003
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posted 12-25-2004 05:57 PM
While were on the subject of torgue converters, what effect does sprauge/spragueless have on converter slippage? I dont know much on this subject, could someone clue me in?
Thanks guys. ------------------
91 LX 398w street/bracket 6.67@105 1/8 60FT 1.51 [This message has been edited by scottford351 (edited 12-25-2004).] [This message has been edited by scottford351 (edited 12-25-2004).]
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Moneymaker
Administrator Posts: 26513
From: Lyons, IL, USA
Registered: May 99
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posted 12-25-2004 06:53 PM
None. It does not effect the stall speed or lock up.
Spragless converter is a reliability gimick, not a performance inhancement. ------------------
Alex Denysenko
Co-Administrator and Moderator NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA & SS/MA National Record Holder '00,'01,'02,'03,& '04
First SS/MA in the TENS!
IHRA division 5 Superstock Champion
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28 The Barry of BarrysGrrl Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com
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Rory McNeil
Gearhead Posts: 1572
From: Surrey, B.C. Canada
Registered: Nov 2000
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posted 12-26-2004 12:45 PM
Experimenting with $$$ convertors, slippage, icky red fluid...Man, that just sounds like a royal Pain in the a$$!!  No wonder I run a stick! Seriously, 67mustangdsa, I assume that you are running a 390, right? C4 or C6? A good buddy who ran a SS/GTF&GA 86 Mustang was killed by a drunk driver in August, & I recently went over most of his race stuff at his shop for his family. He ran a low compression 74 460 combo with a C4 in his S/Stocker.When I was there, I noticed 2 8" Munsinger convertors in the boxes. One looks brand new, the other 1 I believe had been in the car for a short time. There was one other unpainted converter, which I believe is his older Len Schnieder unit. He had been running the early 460 crank, which takes the same larger converter snout, the same as a FE. The family wants me to help them sell off his stuff, I may put some on EBay, local swap meets, & likely some on various forums. I will have to double check, as he did run a C6 when he first started running the Mustang over 10 years ago, but I THINK he sold all of his C6 stuff. I don`t know a whole lot about these converters, but he only revved the engine about 6500, and the car had gone over a second under. I don`t know when the family will give me the go-ahead to start selling, but Ill let you know, if you are interested.------------------
78 Fairmont 428 4 speed 10.20@130mph
80 Fairmont 302 5 speed 12.8@105mph
85 Mustang NHRA M/Stock 302 5speed. [email protected]
59 Meteor (Canadian Ford) 2 dr sedan 332, auto
74 F350 ramp truck 390 4spd
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kid vishus
Gearhead Posts: 6220
From: middle of NC
Registered: Oct 2000
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posted 12-26-2004 12:50 PM
quote:
Originally posted by Moneymaker:
A mechanical diode or other style lock up converter is the only way to avoid slippage in high gear.
I wondered what the mechanical diode did. KK's convertor has a mechanical diode in it.
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