Dyno tuning and Stall questions - Team Camaro Tech
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post #1 of 3 (permalink) Old Jul 12th, 03, 09:14 PM Thread Starter
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Location: Niceville Fl
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After a session on the dynojet today I am left with some questions. My converter is rated at 2400 I can hold it to 3000 and flash to around 3000 all this leads me to believe that it is a 3000 converter. THey dyno refused to read anything before 4000 why? THey told me it was because that is whne the converter finally locked up (turbo 350 trans) Does this sound right?? I was a little dis appointed beause I wanted a full read out.

69 Camaro RS, 383ci,10.5-1 AFR 195's ported, Comp 286HR, 4340 forged Crank & Rods, JE Pistons, RPM Airgap, Holley 750 HP carb, 350 turbo w/ shift kit, 3000 Coan, Be cool, caltracs,12bolt 355 eaton posi..Best E.T. 12.22 @ 112

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post #2 of 3 (permalink) Old Jul 13th, 03, 03:30 AM
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If the converter flashed to 3000, then it is a 3000 stall with your combo. With less power it will stall lower; more power it will stall higher. I am assuming you were on a chassis dyno? If so, it will not give accurate engine hp unless the converter is as close to its lockup as possible, as it only measures it at the rear wheels. If the converter is slipping the hp number is not accurate for true engine flywheel hp. Most converters will slip up to the 10% area in some instances, but 5-8% is common. As for stall speed, if you are a street or street/strip car with no transbrake, look for the best performance if the converter stalls at or just under where the engine torque peak is. For a transbrake race car setup, shift the converter stall to 300-500 over the torque peak for the best performance.

Oldani Motorsports

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post #3 of 3 (permalink) Old Jul 13th, 03, 05:29 AM
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One thing to remember is that on a dyno the resistance is the roller, not the weight of your car. A Dynojet roller weighs 5400#, so most converters will stall considerably higher against that load compared to the load of the car. Another thing that happens is that the trans will kickdown if you mash the throttle at 2500 rpm, leading to a big spikey graph with little repeatable information on it. For diagnostic information, you want a repeatable pull that involves as few variables as possible. Manual trannys are easier, just do the pull in the 1:1 gear, autos require some finesse.
Dynojet also has a loading program that allows you to load the engine at various rpm's and check the f/a ratio, manifold vacuum, timing, etc.

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