hard vs soft rev limit
5/17/10, 11:41 AM
#1
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hard vs soft rev limit
When it comes to performance cars, I'm old. When I hear "soft limitter" I think of an MSD 6AL.
What does the "hard" vs "soft" limit mean for the new 5.0?
Does the "hard" limit mean fuel cut-off and the "soft" limit mean a timing reduction?
At what RPM do these events occur?
If you hit the limitter, is the ECU going to retard timing for a few seconds after the fact? When you grab the next gear, will it be at reduced timing? The only experience I have to relate to is my GM LT1 where if you get into spark knock, it takes a few seconds for the timing to recover.
Just wondering about all the talk about running through the traps against the limitter and what effect it really has on performance. If you get up against the limitter before a shift, is it going to reduce power and botch your run?
What does the "hard" vs "soft" limit mean for the new 5.0?
Does the "hard" limit mean fuel cut-off and the "soft" limit mean a timing reduction?
At what RPM do these events occur?
If you hit the limitter, is the ECU going to retard timing for a few seconds after the fact? When you grab the next gear, will it be at reduced timing? The only experience I have to relate to is my GM LT1 where if you get into spark knock, it takes a few seconds for the timing to recover.
Just wondering about all the talk about running through the traps against the limitter and what effect it really has on performance. If you get up against the limitter before a shift, is it going to reduce power and botch your run?
5/17/10, 12:11 PM
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Well I can't speak for the 5.0. but I imagine its the same.
On the 4.6 in the Bullitt the ECU starts pulling timing at about 6250 (you can feel the RPM acceleration slowing), but then when I hit 6500 redline the engine just cuts out - like you turned the key off. I let off & shift in one motion, and immediately have full power. The 'reset' must be tied to the drive-by-wire throttle.
Many of the aftermarket tuners will set redline at 6800 - not so you go there, but so you get a full power sweep to 6500 redline.
On the 4.6 in the Bullitt the ECU starts pulling timing at about 6250 (you can feel the RPM acceleration slowing), but then when I hit 6500 redline the engine just cuts out - like you turned the key off. I let off & shift in one motion, and immediately have full power. The 'reset' must be tied to the drive-by-wire throttle.
Many of the aftermarket tuners will set redline at 6800 - not so you go there, but so you get a full power sweep to 6500 redline.
Last edited by cdynaco; 5/17/10 at 12:12 PM.
5/17/10, 04:59 PM
#3
Mach 1 Member
Well I can't speak for the 5.0. but I imagine its the same.
On the 4.6 in the Bullitt the ECU starts pulling timing at about 6250 (you can feel the RPM acceleration slowing), but then when I hit 6500 redline the engine just cuts out - like you turned the key off. I let off & shift in one motion, and immediately have full power. The 'reset' must be tied to the drive-by-wire throttle.
Many of the aftermarket tuners will set redline at 6800 - not so you go there, but so you get a full power sweep to 6500 redline.
On the 4.6 in the Bullitt the ECU starts pulling timing at about 6250 (you can feel the RPM acceleration slowing), but then when I hit 6500 redline the engine just cuts out - like you turned the key off. I let off & shift in one motion, and immediately have full power. The 'reset' must be tied to the drive-by-wire throttle.
Many of the aftermarket tuners will set redline at 6800 - not so you go there, but so you get a full power sweep to 6500 redline.
Soft redline at 6850 is spark. Hard redline at 7000 is spark and fuel. I don't know how long it retards spark after the soft limit, but I am sure it can be modified.
5/17/10, 05:36 PM
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Yes I was speaking about the 4.6 B redline of 6500.
The 5.0 is supposed to be 7000 redline.
But I imagine the effect is the same from the driver's perspective. Power starts fading near redline, engine goes dead at redline, after letting off throttle you immediately have full power available.
The 5.0 is supposed to be 7000 redline.
But I imagine the effect is the same from the driver's perspective. Power starts fading near redline, engine goes dead at redline, after letting off throttle you immediately have full power available.
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