Re: Starting line RPM with brake
[Re: rickraw]
#3059574
07/16/22 12:25 AM
07/16/22 12:25 AM
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Joined: Dec 2005
Posts: 11,621 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,621
Fulton County, PA
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Just keep turning the RPM up until - it slows down, it won't hook, or it goes too high. Of course, getting after it, it may want to have some suspension/shock adjustments to take full advantage of it.
Our pro tree car had no chip in the low side, went 5800 on the mat and liked it.
Super Stock car I help with we tried some stuff in the past. Went higher and faster every time we turned it up. I think he has it at 3600 now. We did some up grades and I think it could stand some more. But it's consistent, hooks, has a good 60' and not violent, so he hasn't fooled with it.
Last edited by CMcAllister; 07/16/22 12:27 AM.
If the results don't match the theory, change the theory.
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Re: Starting line RPM with brake
[Re: A727Tflite]
#3059612
07/16/22 08:28 AM
07/16/22 08:28 AM
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Joined: Jan 2003
Posts: 3,874 Smyrna, South Carolina
STEFF
master
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master
Joined: Jan 2003
Posts: 3,874
Smyrna, South Carolina
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With peak HP at 7500, I wouldn't hesitate to have a converter that flashes at 67-6800. Especially with a flat torque curve, get the flash closer to the hp peak versus peak torque. RPM on the brake, start at 4000-4500. Work it from there.
Last edited by STEFF; 07/16/22 08:30 AM.
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Re: Starting line RPM with brake
[Re: STEFF]
#3059614
07/16/22 09:12 AM
07/16/22 09:12 AM
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Joined: Mar 2003
Posts: 2,516 PA
moparacer
master
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master
Joined: Mar 2003
Posts: 2,516
PA
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Closer to peak torque the better, as long as it hooks. Like Steff said upper high 6000's range on the stall.
67 Barracuda street/bracket car 11.27-119 68 Dart 502 BB 8.70s-152 414 cid SB Dragster 7.65-174
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Re: Starting line RPM with brake
[Re: moparacer]
#3059642
07/16/22 11:38 AM
07/16/22 11:38 AM
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Joined: Jan 2003
Posts: 11,722 Portage,michigan
B3422W5
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 11,722
Portage,michigan
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I haven’t seen RPM at launch make much( if any difference) in 60 foot or ET, footbraking or using a brake. Talking a 9 sec 3350 pound car. Just have to experiment with rpm to where the car consistently hooks and works the best. I would probably start out somewhere around 3600-3800 and see how it likes it. And adjust from there. Mine liked around 4100 best. On the same night, racing two classes, one on a 400 pro tree with brake, other class footbraking, car would ET the same off the foot leaving at 2000 as off the brake at 4100, 60 foots were typically pretty much identical as well. Moving the RPM around most definitely will effect reaction time though, lower the launch rpm, the “ slower” your reaction time will be, higher, “ quicker” reaction time. Just what I have seen I am not a proponent of the common belief a car is faster off the brake, because I have never seen it myself. I think it also has a lot to do with the convertor well sorted to the combo too.
69 Dart GTS A4 Silver All steel, flat factory hood, 3360race weight 418 BPE factory replacement headed stroker, 565 lift solid cam Best so far, 10.40 @127 1/4 1.41 best 60 foot 6.60 at 103.90 1/8
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Re: Starting line RPM with brake
[Re: A727Tflite]
#3059995
07/17/22 05:23 PM
07/17/22 05:23 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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I didnt use any starting line chip..I left at 6200 RPMS on all passes.. I would go WOT then either use the delay or let go of the button... I normally had .010 to , .020 lights and had a pile of .000 lights(and also reds).. car weight was 2400 lbs at the line... you just have to play around to see what it likes... my 60' time was always 1.19(every time)
Last edited by MR_P_BODY; 07/18/22 08:19 AM.
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Re: Starting line RPM with brake
[Re: MR_P_BODY]
#3060016
07/17/22 08:00 PM
07/17/22 08:00 PM
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Joined: Jan 2003
Posts: 19,377 Las Vegas
Al_Alguire
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 19,377
Las Vegas
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Combination and driver dependent. If you cant hit the tree you will need more RPM, so if you cant at 3000 go up. If the car has a way tight converter go up, etc etc. Lots of variables. In theory IF the driver can hit the tree it is usually best to leave as low as the combination will tolerate. And that varies greatly from car to car and driver to driver.
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: Starting line RPM with brake
[Re: Al_Alguire]
#3060038
07/17/22 09:28 PM
07/17/22 09:28 PM
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Joined: Mar 2011
Posts: 3,088 Michigan
A727Tflite
OP
master
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OP
master
Joined: Mar 2011
Posts: 3,088
Michigan
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Combination and driver dependent. If you cant hit the tree you will need more RPM, so if you cant at 3000 go up. If the car has a way tight converter go up, etc etc. Lots of variables. In theory IF the driver can hit the tree it is usually best to leave as low as the combination will tolerate. And that varies greatly from car to car and driver to driver. Al, hopefully a test day is close in the future to try stuff out. Play back tach didn’t, track was not optimal, found a bald spot, blah, blah, blah. Lowering the engine speed made it quicker but I think because the track was not any good. It got on the bars after lowering the engine speed 600. Driver can hit the tree. In theory I thought the use of a brake approximated a manual trans. If that is true then doesn’t leaving at a higher engine speed mean a better 60’ as long as the car hooks ?
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Re: Starting line RPM with brake
[Re: A727Tflite]
#3060051
07/17/22 10:55 PM
07/17/22 10:55 PM
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Joined: Mar 2009
Posts: 2,467 Sydney,Australia
tex013
top fuel
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top fuel
Joined: Mar 2009
Posts: 2,467
Sydney,Australia
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my Higher rpm faster sixty , traction dependent . With 6000 stall I lam leaving @ 4000 at the moment with nearly 3800lbs , have used 4500 . I am bottom bulb racing . Sixty will be 1.45s give or take . Best of 1.42 With footbrake and a little tighter , 5000 stall , vert i was leaving @ 1350 for 1.49-1.52 sixty best of 1.46 . Leaving just after the 2nd bulb is on . Car will run about a 1/10 quicker et and a hair more mph off the brake . BUT i have run similar PB et of 10.25s I race on radial slicks . So normally quicker sixty = quicker et . My reactions off the brake are normally a tighter grouping average than footbrake . We do not get the track time like in USA . Tex
New best ET 10.259@129.65 . New best MPH 130.32 Finally fitted a solid cam, stepped it up a bit more 3690lbs through the mufflers New World block 3780lbs 10.278@130.80 . Wowser 10.253@130.24 footbraking from 1500rpm Power by Tex's Automotive
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Re: Starting line RPM with brake
[Re: A727Tflite]
#3060074
07/18/22 02:56 AM
07/18/22 02:56 AM
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Joined: Aug 2003
Posts: 43,237 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,237
Bend,OR USA
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My old S/P car left between 5600 and 5800 RPM at WOT off of the trans brake, 1.23 60 ft times, 5.50 at 125.+ MPH in the 1/8 mile I never tried anything lower Still didn't win any races with that car
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Starting line RPM with brake
[Re: Cab_Burge]
#3060160
07/18/22 11:47 AM
07/18/22 11:47 AM
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Joined: Dec 2005
Posts: 11,621 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,621
Fulton County, PA
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You know what Scotty says, "rev up your engines!"
If the results don't match the theory, change the theory.
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Re: Starting line RPM with brake
[Re: CMcAllister]
#3060189
07/18/22 12:17 PM
07/18/22 12:17 PM
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Joined: Jan 2003
Posts: 19,377 Las Vegas
Al_Alguire
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 19,377
Las Vegas
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Here is a couple examples for you all to chew on. The heads up car we leave to 38-4400rpm on the brake. It is adjusted to make up for driver reaction time, he dont race much. Car has been 1.09 60' converter stalls at 9200 rpm! Higher has done nothing for anything but reaction time on a .400 pro tree. I found the same results with our dragster and the Stratus, 1.02 and 1.00 60'. Since we both leave off the top bulb on a full .500 tree we are both at 4000rpm. Nothing found going higher in RPM on either car other than more delay. But as I said t is very combination dependent. HP has a roll to play here as well. FWIW both the latter cars have converters that stall at 65 and 6700. My 64 we leave at 3900coverter stalls at 6600 and the 60' SUCKS but we are pulling alot fo timing and they click the 60' clock with the back tires...But it helps me with the bottom bulb for sure.
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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