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  #1  
Old 01-06-2010, 10:45 AM
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Rev limiter - hard cut or soft cut?

In most autocross courses, I find myself fitting nicely inside the engine's RPM range in second gear. Some of the longer-legged ones allow for higher speeds, which concerns me.

Second gear in my SVX (ECUTune 1v5, 2000 RS trans, 4.111 final drive, stock size tires) comes out roughly to 60mph. Many tracks get close, but some get there, and I can tell because I'm hitting the rev limiter. Most of the time, it's not long enough to shift to third and gain anything; common thinking says to stay in second. I'm concerned for the safety of my engine at the limiter, though.

If it's a soft cut system, then there shouldn't be any reason for concern. I'm not sure that's so, though - I'm pretty sure the "bam bam bam" cut is a hard cut.

Can anyone offer some insight on this?
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Old 01-06-2010, 04:22 PM
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Re: Rev limiter - hard cut or soft cut?

It is a hard cut... Hydra has programmable soft or hard cut rev limits

Tom
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Old 01-06-2010, 04:30 PM
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Re: Rev limiter - hard cut or soft cut?

I don't know for sure but I think that when the RPM rises above the upper limit, the ECU sets the injector pulse width to zero until the RPM drops below the lower limit. I would call that a hard cut.

To resolve your problem, I suggest raising the limit a little. Maybe also try reducing the difference between the limits from 100 to 50.
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Old 01-07-2010, 07:21 AM
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Re: Rev limiter - hard cut or soft cut?

Does your memory adaptor hold two ROMs or one? I can make you a ROM with a higher rev limit; you probably aught to switch to the aggressive software anyway.
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Old 01-07-2010, 10:16 AM
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Re: Rev limiter - hard cut or soft cut?

Tom - I'd love a Hydra. When the stimulus program offers a package for it, I'll be on the phone!

Phil - If that's the case, my old 3.3 had two long summers!

Mike - I'll get back to you on that.

Thanks!
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