Computer Diagnostics and Tuning Technical discussion on diagnostics and programming of the F-body computers

OBDI PCM - Past 7K

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Old Oct 12, 2008 | 12:17 PM
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PWR SHFT's Avatar
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OBDI PCM - Past 7K

Will the stock PCM be able to control the motor past 7K? I know the tables only go up to 7K but I would like to turn the new motor to 7500. Can it do it and if so how?
Old Oct 13, 2008 | 05:17 PM
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Anyone?
Old Oct 13, 2008 | 05:21 PM
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I have a log where I used a air cutter to spin an old distributor.. if I can find it I'll try to get it to you Im sure I went over 7000 a few times.

It probably wont tell you alot but maybe you can get something from it.
Old Oct 13, 2008 | 05:39 PM
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7k ya it will be okay. 7500rpms, no way no how. Not exactly sure how and why the opti wont fire past 7k but it wont do it. Its been a common LT1 problem for a long time.
Old Oct 13, 2008 | 07:04 PM
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I checked my datamaster logs, It shows RPM climbing to 6375rpm then it stops and flatlines until it drops below 6375rpm on every log... dont know if Datamaster 3.4.1 can read past 6375?

Some of the other parameters seem to climb at least a couple hundred rpm past that . Im not saying the PCM wont keep going to 7000 im saying My Datamaster 3.4.1 doesnt display it.
Old Oct 13, 2008 | 10:42 PM
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6,375 is the limit on the 8-bit field. 255 x 25rpm/bit = 6,375.

The Opti continues to put out a reliable signal at least to 8,000rpm... I have a data log to prove it.
Old Oct 14, 2008 | 11:32 AM
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But your not using stock pcm though! Cheater!
Originally Posted by Injuneer
6,375 is the limit on the 8-bit field. 255 x 25rpm/bit = 6,375.

The Opti continues to put out a reliable signal at least to 8,000rpm... I have a data log to prove it.
Old Oct 14, 2008 | 07:30 PM
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OK. So from what I am hearing, If I want to spin the motor to 7500 RPM, I need an aftermarket computer. Can I get away with 7K to start so I don't have to incur the expense right away?
Old Oct 15, 2008 | 02:21 PM
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Originally Posted by PWR SHFT
Can I get away with 7K to start so I don't have to incur the expense right away?
yes you should be able to do it for a while.
Old Oct 16, 2008 | 03:42 PM
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Check around.... I'm pretty sure Rick Abare was running his stock PCM to 7,800rpm at one point.
Old Oct 19, 2008 | 10:09 AM
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Well for the added cost of an aftermarket PCM, I can build a 396 instead of a stock crank 355 and bring the RPM range inside the 7K limit of the stock PCM. I guess I will be adding a post about the Golen Shortblocks and what people think of them.

Thanks.
Old Oct 20, 2008 | 08:08 PM
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Another thing to think about is the amount of force being applied to the rotor assembly. I overspun my OPTI and the rotor flew apart. Car stopped dead in its tracks. Towed it home, pulled the OPTI apart and there were little pieces of rotor all over the place. It knocked out the sensor and metal wheel as well. I was running a Delteq so I replaced the sensor and wheel and didn't put a rotor back in. Worked like a champ. So all I'm saying is that I don't think the design of the OPTI was meant to handle that kind of force. Just my experience, I could be wrong. Good luck, Rob.
Old Oct 20, 2008 | 08:14 PM
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Here's a post by someone running the Opti to 8,000rpm, but not without problems. Point is, he indicated he did this with a stock 92/93 PCM. The problem was the limited programming above 7,000rpm, and the Opti's tendency to disintegrate rotors.

https://www.camaroz28.com/forums/sho...08&postcount=7
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