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Bracket Talk Bracket Talk Forum Tech Talk - by Abruzzi mechanical diode questionGo | New | Find | Notify | Tools | Reply | |
| mechanical diode question | Login/Join |
| DRR Trophy |
Hi all , would a mechanical diode hit harder than a regular diode converter ? I run radial PBR 29.5x10.5s . I finally got back on track last weekend . And experianced traction issues . Normally i am fine but 5or 6 of 11 passes spun . I used to leave @ 4500 no worries but couldnt get over 3500 . I also had to loosen ext 2 clicks and tughten comp 2 clicks - on rear Viking shocks . Car is 3780lbs 68 Satellite 4.1 gears . Thanks Tex | ||
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| DRR Top Comp |
You didn't mention how long the car has sat but if it's several months to years the tires could be the issue. Also I believe it's summer time for you down there, maybe the track was junk? . Dave F J B | |||
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| DRR Top Comp |
I think what the OP is saying, is he made it back to the track finally, with a new mechanical diode converter, and now he is spinning the tires. So he's wondering why, also thinking it could be the new converter, he now has in the car. Am I close?  | |||
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| DRR Trophy |
ok thanks guys . Dave , Tyres have been off track since June new late 2020 dated January fitted , track shut due to usual lock down stuff . Car is my daily driver so i have been running my foot brake trans since January when i took out transbrake transmission for freshen and converter for service . Yes its almost summer but has been cool and damp , was high 70sF but mid 80s grains .Track felt ok but ..... There was a little top fuel and pro mod testing the day before so i kind of hoped some carry over . Mike , yes that is it in a nutshell . Car is normally very consistant . Now could the track be iffy , maybe . Just covering bases . I am driving down and racing interstate later this week . South Coast Raceway is supposed to be the house of hook . Too late to change much but information is king . Tex | |||
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| DRR Top Comp |
You're in covid hell Australia, I gotcha. Yeah a converter change can do that. We're watching closely, and support the people of Australia. | |||
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| DRR Trophy |
Mike , we are moved on from there . Bugger so its now juggle to find the sweet spot for the converter Tex | |||
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DRR / Crew |
Well I guess your asking to compare a Mechanical Diode which is a Diode to a sprag? You have Diodes, Sprags and Spragless when it comes to a converter that I'm aware of. Id say no difference in the hit on a Diode to a Sprag but I may be wrong and a converter guy could be more specific. SL... | |||
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| DRR S/Pro |
Yes no difference, a MD performs same function as a sprag, they are stronger. | |||
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DRR Sportsman |
This (1,000 RPM lower launch) will make a bigger difference in tire hit than the diode/sprag. Especially with a big heavy car that has more weight on the front end. I would say adjustments in shock settings and tire pressure will be your best bets. What pressure are you running in your PBR's? And did your shock changes affect the slip much? I would consider going the other way on Compression, and loosening it to transfer more weight to the rear, (although it may also slow your 60' and possibly R/T as well).This message has been edited. Last edited by: FootbrakeJim, Dan "Jim" Moore Much too young to feel this damn old!! | |||
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| DRR Top Comp |
All torque converters multiply torque below stall, on a scale. The scale at which the torque of the engine is multiplied below stall, vary's. You can do more with an active stator converter to multiply torque below stall. However with every action, there's a reaction. The more you do with the stator to multiply torque below stall at the hit, the less efficient at the stripe any converter - sprag - diode - spragless. Otherwise there wouldn't be a scale at which torque converters multiply torque below stall, eh? Common sense, once you understand all converters multiply torque on a scale, below stall. | |||
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DRR Trophy |
I have a spragless FTI that hits extremely hard and is very aggressive, and I have a BTE with a sprag in it that's extremely soft. Those two converters run the same MPH and flash within 200RPM of each other, but the BTE is almost a tenth slow in 60' because it's so soft. I'm not exactly sure how all of that science works, but I assume fin angles on the stator have more to do with how hard it hits? Someone will come along and correct me if I'm wrong I'm sure. Slow S-10 Slower Cutlass | |||
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| DRR Top Comp |
Super Pro bracket racing, I like a spragless converter that flashes high at the hit, 200 250 rpm above observed flash stall at the shift. They're easy on the tire at the hit, and are more efficient at the stripe, comparatively speaking. In other words I like a TSI spragless. | |||
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| DRR Top Comp |
I have a PTC sprag converter that'll go double 0 on the 400 Pro tree at Orlando, staged shallow @ 3200lbs with a 3.89 gear. It slips quite a bit more at the stripe than my typical spragless converters though. Kenny Ford from PTC told me before I ran it according to the part # stamped on it, it would act like this, when I called to find out what it was. It was in a friends attic for ten years. 8" opel core. It's a bad dude for 370 - 400 pro tree index racing, old school Borg Warner sprag. | |||
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| DRR Elite |
Got to disagree, I’ve seen a tenth slower, read below.
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| DRR Top Comp |
Converters are weird, I've had a few duds. Fastest converter I had was a TCI, or at least it did the most with the least, should've never let her go lol. It worked killer behind a steel headed BBC 427 I had, when I sold the engine turn key, I wanted the guy to run good out of the box, so I threw in the converter. Bad idea in hindsight, she was a good one. I could've had her made spragless lol. When you get a keeper, keep her. I got 3 converters now I won't sell, keepers. | |||
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| DRR S/Pro |
Ed I wasn't talking about overall performance, and from all of my experiences, both personally and with others, there has been no differences with any of the configurations. But I have heard that lower HP combo's don't react the same way as higher HP combo's. A sprag and MD perform the same mechanical function in the converter, that's all I was saying. There is certainly a lot going in inside a converter! Even the cores used contribute to the on track performance. | |||
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| DRR Elite |
Agree that they do the same function but they don’t perform the same as it relates to the time slip, at least in lower power cars. That said, I have another friend that has been running a 10” Continental with a MD for over 2 decades, maybe closer to 3 decades and no other converter he has run has his car leaving/60 footing as good as this 10” with MD. The problem with this converter over the decades is it breaks the diode. Several other friends have tried this same converter, all loved the way their car launched with it and all ultimately removed it and went back to their original converter because they felt it was just too aggressive and effected consistency. | |||
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| DRR Trophy |
ok , thanks guys . so it seems the mech sprag diode will be somewhat similar to regular sprag . Tyre pressures in the radial are 19 to 19 1/4 psi on 10"rim . 1 run was 18 1/2 , my mistake , but spun . I have run this pressure since 2018 after trying a few different pressures . Both with trans brake and footbrake . I would have thought with radials i was going right way with shock - hit it and hold it . I do have a T&T friday afternoon so might try going back to 4500 2 step . Tex | |||
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| DRR / Crew |
Best pictures I can get for those who care to know what the differences look like. Top pic is a sprag. Bottom is a diode. Both work similar but they have nothing to do with stall or hit. They both go inside the stator which is the part shown at the top with the blades. a Spragless would just have a solid block in place with splines for the stator tube. That's why a spragless is bulletproof in that area.   | |||
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| DRR Pro |
AGREED Mike. My new convertor (sprag) was cut two times to get it right. It’s VooDoo to me, but know what I want. In spring 2021 I gave my 25 yr old convertor (sprag) that was cut 5x to a racer with a similar car/engine using a wrong stalled convertor. He smiled and nodded his head afterwards whenever we met. | |||
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Bracket Talk Bracket Talk Forum Tech Talk - by Abruzzi mechanical diode question
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NO, it had him running over a TENTH quicker, .05 in 60 foot quicker and over 1 MPH faster! 
He immediately ran all time best 60 foot, ET and MPH the first weekend out with it and has never looked back...