Run Data Question - Engine RPM
#2522050
07/15/18 10:15 AM
07/15/18 10:15 AM
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Joined: Jun 2006
Posts: 430 Michigan
HR3128
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mopar
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mopar
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Michigan
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Got out to the track for the first time this year last Wednesday for Test & Tune. Car ran good, no problems. Data for one of the runs is attached. On the graph, engine RPM is flat for about a second just after launch. Then climbs. I would expect to see some kind of RPM increase for the first second. What do you think? Why is engine RPM flat for that time? 60 ft = 1.372, 1/8 mi = 6.312 et/107.68 MPH 93 Daytona, aprox 2600 lbs, Back-half, 4-link, 4.88 rear, Mild 377inch R3/W8, powerglide 1.76, 6K convertor
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Re: Run Data Question - Engine RPM
[Re: HR3128]
#2522120
07/15/18 01:34 PM
07/15/18 01:34 PM
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Joined: Oct 2011
Posts: 3,036 bean town ....Ca
WHITEDART
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master
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bean town ....Ca
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We have found shifting 500 RPM over Peak horsepower with a Glide has been the fastest way down the track.. tuning the flat spot out of first gear is very difficult with a Glide.. do you know where you make Peak power and Peak torque..
In the 8s N/A.with Brett miller W8's 5.07 at 133 at 2700lb
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Re: Run Data Question - Engine RPM
[Re: HR3128]
#2522200
07/15/18 04:37 PM
07/15/18 04:37 PM
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Joined: Sep 2014
Posts: 4,457 Washington
madscientist
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Washington
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I can't see it very well either. Damn glad I'm not the only one who is losing his vision.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Run Data Question - Engine RPM
[Re: HR3128]
#2522209
07/15/18 04:57 PM
07/15/18 04:57 PM
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Joined: Jan 2003
Posts: 4,329 Morrow, OH
markz528
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master
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Morrow, OH
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I don't have an answer but I can tell you mine looks almost identical including the driveshaft rpm. Its a 727 3450 lbs runs 9.60's. Have not had time to investigate it - don't know if it started with the new carb or not. Have not looked at my old data yet.
67 Coronet 500 9.610 @ 139.20 mph 67 Coronet 500 (street car) 14.82 @ 94 mph 69 GTX (clone) - build in progress......
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Re: Run Data Question - Engine RPM
[Re: HR3128]
#2522217
07/15/18 05:24 PM
07/15/18 05:24 PM
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Joined: Oct 2011
Posts: 3,036 bean town ....Ca
WHITEDART
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master
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bean town ....Ca
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If you only have A.2 magnet pick up on the drive shaft that can be a normal look at the hit.. it can appear as wheel speed.. do you have the grid.. we add timing in the first gear where the converter is trying pull the motor down.. don't be afraid to add three or four degrees of timing for the first one to two seconds of the Run.. also adding timing at shift recovery will help ET as well
In the 8s N/A.with Brett miller W8's 5.07 at 133 at 2700lb
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Re: Run Data Question - Engine RPM
[Re: MR_P_BODY]
#2522249
07/15/18 07:31 PM
07/15/18 07:31 PM
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Joined: Oct 2011
Posts: 3,036 bean town ....Ca
WHITEDART
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bean town ....Ca
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Looking at the data it flashes to 5900 and drops to 6000 at the shift.. so the actual stall speed is probably 6000.. he can probably get a few hundred RPM more out of it with timing.. I'm betting the converter is too tight.. but without Dyno sheets we will never know
In the 8s N/A.with Brett miller W8's 5.07 at 133 at 2700lb
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Re: Run Data Question - Engine RPM
[Re: HR3128]
#2522273
07/15/18 08:47 PM
07/15/18 08:47 PM
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Joined: Jan 2003
Posts: 8,222 Plymouth, MI
Blusmbl
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Plymouth, MI
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The stall speed will drop for the same torque input as the vehicle starts moving. What you're seeing is normal. The converter torque multiplication changes as a function of the speed ratio of the converter (engine speed to turbine speed). The torque multiplication is dropping as it is no longer at true stall (0 turbine speed).
As Whitedart mentioned, adding timing will reduce the drop.
'18 Ford Raptor, random motorcycles, 1968 Plymouth Fury III - 11.37 @ 118
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Re: Run Data Question - Engine RPM
[Re: AndyF]
#2522359
07/15/18 11:51 PM
07/15/18 11:51 PM
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Joined: Jun 2006
Posts: 430 Michigan
HR3128
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mopar
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OP
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Michigan
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Looks to me like the car doesn't start to move until the 1 second mark. Is that correct? So the first second of this data log is you sitting on the line with the engine at 5000 rpm? And then at the one second mark you release the brake and the engine speed goes up and the driveshaft speed starts to go up? If that is case then I guess I don't see an issue. That's it exactly. First second is the car staged with rev limit at 4800, brake releases & engine RPM goes to convertor stall of 6000 RPM, driveshaft RPM goes up. It ran good, 6.31, 6.34 & 6.35 1/8 mile times, all at 107.xx MPH. I just expected to see engine RPM climb after the brake release rather than sit at stall speed for a second.
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Re: Run Data Question - Engine RPM
[Re: HR3128]
#2522370
07/16/18 12:14 AM
07/16/18 12:14 AM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Romeo MI
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Looks to me like the car doesn't start to move until the 1 second mark. Is that correct? So the first second of this data log is you sitting on the line with the engine at 5000 rpm? And then at the one second mark you release the brake and the engine speed goes up and the driveshaft speed starts to go up? If that is case then I guess I don't see an issue. That's it exactly. First second is the car staged with rev limit at 4800, brake releases & engine RPM goes to convertor stall of 6000 RPM, driveshaft RPM goes up. It ran good, 6.31, 6.34 & 6.35 1/8 mile times, all at 107.xx MPH. I just expected to see engine RPM climb after the brake release rather than sit at stall speed for a second. If you release the brake and still sit there you have a conv problem if there is no delay in it
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Re: Run Data Question - Engine RPM
[Re: AndyF]
#2522385
07/16/18 01:24 AM
07/16/18 01:24 AM
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Joined: Oct 2011
Posts: 3,036 bean town ....Ca
WHITEDART
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master
Joined: Oct 2011
Posts: 3,036
bean town ....Ca
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The red line would be a g meter.. the line across the top is probably voltage it appears to be steady around 12 volts..
In the 8s N/A.with Brett miller W8's 5.07 at 133 at 2700lb
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