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How do you rev limit?

Old 10-21-04, 04:50 PM
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How do you rev limit?

Motor : '86 13B, set up with Weber 48DCO and an FB dizzy.

I curently run a MSD 6A on the leading ignition in a wasted spark set up (direct fire) and the trailing runs the stock ignitor set up through the cap and rotor.

I want to have a working rev limiter. Will I have to run limiters on both leading and trailing or will it work well enough on just the leading? If I do need two seperate limiters, can I stage them so that one cuts out about 200rpm before the other to give a "cushion" to the limit.

I have a Crane HI-6 to install in place of the non-limited MSD6A, but I just wanted to know if I needed another one for the trailing.

Thanks,
B.
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Old 10-21-04, 07:14 PM
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I dono, but nice car.
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Old 10-25-04, 03:35 PM
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I used to run two 6A's rev limited by one Jacob's nitrous mastermind and one Jacob's Optotimer. Worked fine until the Optotimer ceased working. I sold the 6A's (NMM is still for sale!) and installed two 6AL's. It's the best thing I've done in a long time. In place of the rpm pills, I soldered a bunch of resistors to a dual pole rotary switch, so with the turn of one **** I control the rev limiting of both boxes. I have 6k (vallet mode?), 8k, 8.5k, 9k and 9.5k. At the last autocross I had it set at 9k but hit the limiter a bit early, turned it up to 9.5k and cut a couple tenths off of the next run.

Another helpful thing is the 10k rpm shift light tach, but I hook up the stock tach buzzer to the shift light, which is very useful.
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Old 10-25-04, 07:38 PM
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Great! Thanks for the info. I'm probabaly going to go with the Crane HI-6 since I already have one in another car and will swap my MSD 6A for it and then just buy another one.

Did you have the ignition running through the cap and rotor? How long did they last with the MSD's?
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Old 10-26-04, 08:10 AM
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I've run through the cap in the past(15 years ago?), now it is direct fire on the leading and through the cap on the trailing. I'm sure you know this trick, but with this setup, after you fry the cap/rotor, you can just move the wires from trailing to the leading connections. Rumor has it that you get more power running the trailing wires through the leading cap/rotor connections due to smaller gaps to jump. I've never noticed any difference. I think I've emailed you before when you were tuning the RX-M. Other things that I think are important are the MSD Superconductor wires (very low resistance), timing (currently 26BTC L/16BTC T total timing) and BR9EQ-14 (stk # 3129) plugs.
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Old 10-26-04, 12:18 PM
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Using a 6AL on the leading ignition is enough to limit power over-revs
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Old 10-26-04, 01:10 PM
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I think when I was playing around with different setups I pulled over 9500 with the trailing only, probably in 2nd gear. Rev limiting the leading and trailing with 6AL's is cheap reliable insurance, I learned the hard way!
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