Converter help

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by jay70cuda, Sep 17, 2018.

  1. jay70cuda

    jay70cuda Member

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    new at the converter game. How do you control engagement? Or flash of a converter? I changed a stator to tighten up the slippage at the finish line and seemed to do more damage than good!
    It’s a roots deal with a quickdrive. Does fluid make a difference or who’s converter it is. I’m at a loss without spending tons of money to buy parts just to try out.
     
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  2. TOL

    TOL Active Member

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    What brand converter? Was this converter built for you, or did you just buy it privately, not from the manufacturer?

    There are too many variables to possibly list, and yes the type of fluid can make a huge difference.

    If I may offer a suggestion, figure out who the manufacturer was, and give them a bit of $$, and have them Sheppard you through the learning and dialing in process. They won't do it for free, but once you are a customer they will usually be willing to go out of their way to help.

    Chances are good that you will need to go through several iterations to nail things down for your exact combo. Maybe consider buying a second converter, so that when one is in for rework you still have the other to run, if the budget allows.
     
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  3. Mike Canter

    Mike Canter Top Dragster

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    Was the converter built for a roots blower car with your gearing? It sounds like you went the wrong way on the stator. Normally you want about a 800 rpm drop on the shift to second gear. If it drops more than that then you want a stator that is looser on the shift to tighten it up. It is reverse of logic
     
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  4. jay70cuda

    jay70cuda Member

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    It’s a chance roots deal. 17/30 stator. But it’s tight up front and loose out the back. Converter flash is very low, just seems like I’m battling more than I know.
     
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  5. Mike Canter

    Mike Canter Top Dragster

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    So how much does the engine rpm drop on the shift to second gear. Total drop. On a Quick Drive can you adjust the pressure or change an orifice to change the pressure?
     
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  6. Andy C

    Andy C Member

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    Just call Marty Chance - He wont steer your wrong, even if you didn't buy it from him direct.
    You will need sn# and pump # b4 you call him.
     
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  7. Mike Canter

    Mike Canter Top Dragster

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    Also have your laptop up on the internet and with a good run ready on Racepak. He will connect with your computer and look at your engine and driveshaft and will tell you what to do. Have a notepad ready for when professor Marty starts talking.
     
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  8. drew556

    drew556 Member

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    Like said above if it’s a chance converter call Marty he can get you what you need I have the luxury of living 30 min away from him and worked for him when I was younger stand up guy set our converter up nailed it first shot has worked flawlessly
     
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  9. Jason Green

    Jason Green Member

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    If you get the converter where you want it down track, you can also use fluid manipulation setups like M&M or Snyder has to loosen it up early in the run
     
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  10. td3829mk

    td3829mk Member

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    I don't run a lenco but isn't there a way you can use jetting to bypass fluid to drop pressure? I have heard some mention doing this in the past to get the car to hook up early? Jason is this what you are referring to as fluid manipulation?
     
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  11. dragster156

    dragster156 Member

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    Many of the trans companies offer the bleed system. I know fti does, I believe Coan does a set well. Just call them.
     
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  12. Mike Canter

    Mike Canter Top Dragster

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    Synder Motorsports has a real good solenoid set as does M&M Transmissions.
     
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  13. Jason Green

    Jason Green Member

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    You should be able to use a bypass on any type of converter drive . Most I've seen are jettable and wiring wise you can use a digi set timer that's triggered off transbrake release
     
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  14. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    The most important line I have ever been told in tuning converters was told to me by Brandon Booher when talking about tightening a converter.

    "The only way a tighter converter is faster is if you bring the driveshaft up to the engine. It's usually not faster if you bring the motor down to the driveshaft."

    Us old clutch guys are hard headed on the slippage deal. It's what we look at in high gear. It's a mechanical coupling, so 1:1 is the most efficient output in most cases.

    The converter can be some voodoo, but you have the pump driving the turbine via fluid. Some rpm differential is not a bad thing and in fact the tighter it is the more inefficient it becomes to a point since the fluid isn't moving as much as it is with some slippage.

    When you think about what is going on in that converter for FLUID to pull a 2500-4000 hp engine down at WOT, it's a fluid brake to a degree. So like Mike said, we don't want to pull it down too far, especially in a supercharged application where boost is sensitive to rpm.

    Another thing that most people don't consider when talking converter slippage is you can tighten or loosen a converter based off driveshaft speed. So if you are weak early, you are going to have a bigger pull back at the shifts because the driveshaft speed is slower at the shifts.

    It is my opinion that too tight of a converter is close to twice as bad as too loose. If you are one stator loose, let's say that is .02 slower than the 'optimum' would have been. If you get one stator tighter than optimum, the worse the air is, the greater that will slow you down, but I think in the same conditions, one stator too tight could easily slow you down .04 or more.

    Mathematically, slippage is effectively added gear ratio. So a 5% converter at the finish line on a 5.0 gear is effectively a 5.05.
     
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  15. greenracing

    greenracing Member

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    I think the converter slippage is a bigger effective gear change than that. Wouldn't a 5% converter slippage be like having a 1.05 gear in the transmission? Since you multiply all the gears together to get your final ratio, if you have a 5.0 final, with a 1.05 "slippage gear", you'd have an effective 5.25 final. Or am I all wet?
     
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  16. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    What I call 5% slippage is 1.05 on the engine/ds graph or just divide engine by ds, so it's already factored in.
     
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  17. TOL

    TOL Active Member

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    "Ratio" is a pretty broad term that is often misunderstood with converters.........

    With simple gears and a clutch, ratio is a just a mechanical number. A 2:1 gear ratio for example multiplies the input torque by a factor of 2, assuming nothing is slipping.

    With a torque converter, ratio is an altogether two part deal.

    If the torque converter is not locked solid, and is acting as a fluid coupling device between the crank of the engine and the input shaft of the transmission, then the term "Ratio" has two parts to consider. Lockup converters, once locked up 1:1, are basically like the clutch/gear example above.

    When a converter is open, or not mechanically locked, it will have an inherent amount of slip (speed differential between the input section and the output section of the converter). This alone has a ratio effect from the engine RPM perspective, as if more mechanical ratio (numerically taller) existed between the crank and tires.

    However, the slippage inside the converter also at the same time also causes the fluid inside the converter to create a torque multiplication ratio.

    The magnitude of this torque ratio is a function of the converter design, the fluid properties, and the design "K-Factor" of the converter. This is mostly accomplished with the help of the stator. This multiplicative ratio is transient, and highly dependent upon the torque shear across the converter (load and speed). It results from a complex interaction of operating condition variables, and can't be treated as a constant quantity at all.

    Anything that affects the shear loads across the converter (gear ratios, mechanical ratios, vehicle inertia, aero drag, rate of engine RPM rise, engine output, etc........) affects the shape or magnitude of this torque ratio factor. A very complex thing to measure or predict. The ideal way to measure it is to measure the net driveline live torque live, but mostly this is only done by OE's.

    Mechanical ratio dictates engine RPM to an extent. Multiplicative torque ratio dictates the flow of torque into the driveline from the engine. Both have to be considered at the same time.

    5% converter slip is not really 5% more "Ratio", at the converter. It may look like 5% more engine RPM, but that's about all you can say without considering the rest. A clutch guy with 5% slip in high gear might be freaked out. A converter guy with 5% slip in high gear might not be, if the net ratios work out to a positive run outcome.
     
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    Last edited: Oct 2, 2018
  18. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    Good points. I was referring that slippage equals ratio from a strictly mathematical/rpm standpoint. Once the turbine (input shaft) rpm gets close to the pump (engine), the stator freewheels (if you have a sprag/diode), effectively ending any 'torque multiplication.' If you are looking at a engine/ds graph, this is the point where the line essentially flatlines. This is typically the point where a clutch outperforms a converter, if it's locked up or close.

    Let's just say a good clutch run, locked up, crosses the stripe at 10000 rpm drive shaft with a 4.29. With 4% slippage at the stripe, you would have to cross at 10,400 engine rpm to have 10000 driveshaft. That's static math and nowhere near captures all the other moving pieces.

    I have learned, mainly by different cars I have worked on over the years teaching me the hard way, getting a converter as close to 1:1 is not the end all be all. Slippage is a number you certainly keep an eye on, but it's not something you target. Way too often we set our sights on how much it's slipping, or at least I have. Bottom line, in any car, is generating the most driveshaft and driveshaft acceleration rate (without spinning). In the clutch world, in most cases 1:1 lock up accomplishes this because it's a mechanical coupling. In a non lock up converter, this is rarely the case, with a supercharged methanol car.

    Here's my converter theory, especially as it applies to quarter mile cars. The loss of speed vs a clutch has less to do with slippage than it does with the hp used to drive the input shaft by the converter. So it has the same mass to accelerate the clutch does plus the power it takes to drive the turbine with fluid.

    That's not to be confused with hp "lost" by slippage. I think if this were the case, everyone would just run the tightest converter they could get their hands on. There's stuff out there tight enough to overdrive.

    I am a business major, so I have a real cliff notes understanding of the "conservation of energy" law, but if there was a bunch of power "lost" due to slippage, I think we would see a lot more heat applied to the fluid from the starting line to the finish line than 20 to 60 degrees.
     
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