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Old 08-13-2008, 07:35 AM   #1
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Default Rev Limiter

Hi Guys

Just had my 1990 MS PNP tuned on a dyno and it turns out that the Rev limiter doesn't work.

Here are the settings...
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... any ideas why it's not working? We tried changing it to fuel and spark and it didnt make any difference, car still revved to 7600
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Old 08-13-2008, 10:21 AM   #2
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did it stop at 7600 on the dash? did it log at 7600 on your log? what im suggesting here is your tach on your dash isn't exactly accurate, like everyone else's
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Old 08-13-2008, 11:29 AM   #3
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I was having the same problem, so I changed the rev limit to 5000 and wound it on up. It stopped just fine, but I did see it bouncing between 4900 and 5200 in megatune. The dash gauge isn't very accurate because now, with my rev limit set at 7200, the needle is burried pretty deep in the red section before MS cuts the fuel. Probably 7600 anyway.
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Old 08-13-2008, 02:44 PM   #4
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do what ski dude said,set it at like 4000, and if it works at 4000 then it must be the tach being off.
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Old 08-13-2008, 03:28 PM   #5
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Quote:
Originally Posted by Braineack View Post
did it stop at 7600 on the dash? did it log at 7600 on your log? what im suggesting here is your tach on your dash isn't exactly accurate, like everyone else's
agreed, the stock tacho's suck ***** for accuracy, they're better with a lower rated cap, but not by a lot

mine reads 7500 yet actual is more like 7250. I have AWD guages, but at idle it reads super perfect ...
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Old 08-13-2008, 03:30 PM   #6
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at 7K im at 8K on the dash.
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Old 08-13-2008, 04:31 PM   #7
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ditto. thought rev limiter wasn't working then i looked at my logs and realized it worked quite well.

definitely scary to watch the dash gauge go well into the red area but make sure you check your logs.
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Old 08-13-2008, 04:51 PM   #8
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I bump the rev limiter all the time. According to the gauge it is way above 7200. I never gave it a second thought. My **** didnt blow up or spin bearings. It's all good.
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Old 08-14-2008, 09:09 AM   #9
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It got to 7700 on the dash and 7600 on the dyno and logs so it's definitely not working!
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Old 08-14-2008, 09:57 AM   #10
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Quote:
Originally Posted by richard_ha View Post
It got to 7700 on the dash and 7600 on the dyno and logs so it's definitely not working!
Set it to 4000 and see if it works at all. If it's set at 4000 but the car still revs to 7k, something needs work but if it's set at 4k and revs to 4500 before it stops, you may just have to set your rev limit a little lower than you need.
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Old 08-14-2008, 07:46 PM   #11
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also try decreasing the soft limit time that helped me a bit too
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Old 08-14-2008, 08:45 PM   #12
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Not to hijack the thread, but what exactly does the soft limit do? I tried playing with it when I was experimenting with a low rev limit but I didn't really notice any difference when I changed its values.
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Old 08-14-2008, 09:18 PM   #13
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My tach reads about 1000rpm short when I'm hard on the gas. If I slowly increased the throttle to redline, it's almost dead accurate... but at WOT, it can't keep up.

Numerous datalogs indicated my soft cut does hit at 6800 and full cut at 7000 (trying to get the motor to last another 8months at 15psi). I can feel the soft cut very obvious and that's when I shift. Tach is at 6k when I shift... about 800rpm off.
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Old 08-15-2008, 12:31 AM   #14
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Quote:
Originally Posted by skidude108 View Post
Not to hijack the thread, but what exactly does the soft limit do? I tried playing with it when I was experimenting with a low rev limit but I didn't really notice any difference when I changed its values.

At the soft cut setpoint, the ignition is retarded to 10 deg. or whatever the "absolute timing" parameter is set to. This results in a massive loss of torque (and hence rev-limited) which can be felt. If you keep the throttle buried for 5 seconds or whatever the "max time" parameter is set to (without hitting the hard cut within that period), the hard cut is activated.

For a turbocharged engine which is likely running close to 13-15 degrees timing at redline, the soft cut may not be as noticeable as on a NA car where the redline timing is more like 25-30 degrees. The NA car also starts to become airflow-challenged at its redline and has already dropped torque, whereas the turbo is supplying enough air (assuming a larger-than-necessary turbo) for the engine to "continue" revving. This is the reason you will hit the hard cut more often on a turbo car. If you want to feel the soft cut, reduce the absolute timing to 5 degrees, it will be more noticeable.
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