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Discussion Starter · #1 ·
..... How to determine an optimum RPM setting for Trans Brake launch ... 3600# ... 5000rpm stall ... 4.86 gear ... 28 x 11.50 bias ... 1.44 60' ... 6.70's in 1/8th .....
 

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I like getting a run at the converter.
You also don't want to go too low and make the engine unhappy.

I have absolutely no clue about a car that slow, but I would bet 4000 would be a decent place to start.
Should be high enough to leave crisp, and still give a nice run at the converter??

Good luck, race safe.


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I like getting a run at the converter.
You also don't want to go too low and make the engine unhappy.

I have absolutely no clue about a car that slow, but I would bet 4000 would be a decent place to start.
Should be high enough to leave crisp, and still give a nice run at the converter??

Good luck, race safe.


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On good tracks we set at 3400 on our 6k converter. Track gets hot we up the rpm. Seems to help us in that scenario by not hitting the tire so hard. 2900lb ladder bar car 1.24-.26 60ft on 10.5 slick.
 

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First things first. A 28" tire and 4:86 gears? How much power are you making? Must be 1/8th mile? Might get better results from foot braking, because there is no way your going to launch that at a very high of rpm without blowing the tires off.

I run a 28 x 10.5 tire. As the power increased, the numerically lower the gear went to calm down the launch and pick up MPH. 60 improved and so did the mph. I started with 4:56 gears and currently have 4:10 gears in there now. 3400lbs. I intend on upping the power even more and have already purchased a set of 3:73 gears due to it is right on the edge of spinning on the launch now. I set the 2 step at 4000 and loosen the front shocks on no prep, and up to 5500 on a good prepped track. Basically have to see what the track will take, as well as your chassis. You don't want to wheelie either. I have a nitrous motor and don't like to launch less than 4000 to reduce the chance of backfire.
 

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Just went through this with my car. Was footbraking off 2 step at 4000 60' was 1.54 average, flash converter to 5300.
Added tb left 2 step at 4000, 60' was 1.59 only flashed to 5200.
Set 2 step to 5000, 60' now 1.48 and flash to 5500, much better.
 

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Discussion Starter · #6 ·
Thanks for the responses ... engine was dynoed at 628 hp @ 6800 rpm a few years ago ... 1/8th mile only ... tried 3000 rpm last weekend and was lifting the wheels while trending red .010 - .024
 

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Take out the chip from tb slot, push the button and mash the throttle, see where the rpm stops. Dont hold it there too long, just few seconds to observe the rpm.
Then 500 rpm below true stall speed is a good starting point. On a poor track move closer to stall speed as it hits the tire softer.
 

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You should just try different RPMs and find out which setting plants your tires and offers consistent 60 foot times for different track conditions. There's a lot variables that come into play and convertor stall is only one of them. The time slips and how the car responds will tell you all you need to know.
 

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Discussion Starter · #10 ·
Thanks for all the responses . If the weather would co-operate a little and quit raining every evening , I will try to get to a TnT event this week . Otherwise , there is a race this Saturday at Bradenton with TnT before and usually one time run . I have about 8 passes on the trans brake now and am developing a rythm .
 

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Take out the chip from tb slot, push the button and mash the throttle, see where the rpm stops. Dont hold it there too long, just few seconds to observe the rpm.
Then 500 rpm below true stall speed is a good starting point. On a poor track move closer to stall speed as it hits the tire softer.
I'm curious where that philosophy comes from? Our car had a 245/275 with 645 HP.(Superstocker) Stall was well over 6000. I'm not going to say it on here as I will get phone calls bitchin me out if I do. But using your formula I would have been chipped at at LEAST 5500. With a 5.57 gear and a 2.63 first gear....I would have flipped completely over on my back ! LOL
I would tell the op to just keep increasing the chip 200 RPM every pass until the car, or your lights rebel. The higher the better...
 

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Hey wanger It's not a philosophy just tried and true method with many SST, SG, and SC cars. Your setup for sure is way too extreme to utilize that formula lol
but we have found that to work on bracket combos. Some guys leave 1000rpm below but my own ride I get tire shake, lacking power there.
 

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Hey wanger It's not a philosophy just tried and true method with many SST, SG, and SC cars. Your setup for sure is way too extreme to utilize that formula lol
but we have found that to work on bracket combos. Some guys leave 1000rpm below but my own ride I get tire shake, lacking power there.
Just pissin with ya ... :)
There's no true science to this shit, if there was we would all be winners .....
 

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I see where Finnish is coming from. On a well developed .4 tree combo, I would say approximately the same as him. Most full tree cars have quite a bit of stored energy so it gets too extreme. Lots of variables though.
 
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