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Abrupt rev limiter..

 
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bstuke



Joined: 25 Jan 2009
Posts: 86
Location: Lawrenceville, GA

PostPosted: Mon Aug 03, 2009 6:10 pm    Post subject: Abrupt rev limiter.. Reply with quote

Hey guys,

Hope you are doing well.

I suspect you know a Cobra is a turbulence pig...

One hundred something on the front straight at Roebling Road, and I bump up against the rev limiter. Wow!

Is there a way to make it a littler kinder gentler? It seems to shut off completely.

Just wondering...

TIA, Bob
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furpo



Joined: 06 Aug 2004
Posts: 1082
Location: Mt Maunganui, New Zealand

PostPosted: Thu Aug 06, 2009 3:22 pm    Post subject: Reply with quote

From pg 19 of the tuning notes.

Quote:
Rev-Limiter settings: ?C? ECU?s include a highly advanced rev-limiting circuit to
ensure safe, precise limiting of RPM. The Rev-Limiter is a ?dual stage?
configuration, first pulling out a pre-programmed amount of timing, then shutting
off fuel and spark once timing retard has been realized. Though there are 2 Rev-
Limiters included in the Configuration screen, Rev-Limiter 2 should be used to
limit maximum engine RPM (fuel cut) due to the electronic design of the circuit.
The first stage is timing retard only, typically all that is needed to suppress the
torque output of most motors is bringing timing back to before 0 degrees. Thus, if
20d of advance exist at full load and RPM, then ?50 degrees for the Rev-Limiter
will be enough to slow the motor down before the second stage fuel cut of the
Rev-Limiter is realized. The second stage of the Limiter is a fuel and ignition cut,
which shuts off power to the injectors and coils - which prevents any fuel/spark
from taking place.
The rpm window in which first the timing retard is applied, then the fuel cut, is
determined by the formula below, and is dependent on the full scale tach being
used:
soft_rev_rpm_start = rev_limit value entered
RPM_FS=Full Scale Tach RPM
soft_rev_rpm_end = ?rev_limit 1? + (.032 * RPM_FS)
hard_rev_rpm = ?rev_limit 2? + (.04 * RPM_FS)
Thus, the timing retard will be manifest over a range of rpm up until the fuel/coil
cut. For example, using round numbers, if a tach full-scale of 10000 and a rev
limit of 8000 are entered, the soft rev limit begins from 8000 rpm to 8320, with the
hard cut at 8400 (as dictated by the formula above).
Also, it is important to note that for proper max RPM rev-limit function, both Rev
Limiter 1 and 2 should be entered as the same value, unless Anti-Lag/Launch
Control is being used (described below under the ?Additional Tuning
Considerations? section).
NOTE ? TACH FULL SCALE MUST ALWAYS BE LARGER THAN THE REV
LIMITER VALUE, OTHERWISE THE ECU WILL NOT CALCULATE ANY
REVLIMITER.


At a guess you probably do not have enough timing retard in the rev limit max retard box for the engine speed to be controlled. Either that or rev limit one and two are too close together.

Roger
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Pantera EFI



Joined: 12 Feb 2005
Posts: 1718
Location: So. California

PostPosted: Sat Aug 08, 2009 7:43 am    Post subject: '882 "B" & "C" Firmware Reply with quote

Hi Roger, thanks for the "C" (Crankfire) rev-limiter discription for Degree Based firmware.

The "B" (distriButed) firmware revision is used for Event Based triggers AND with that we only
"retard" the spark instant which is required to reduce Timing Lag.

I believe that Bob uses "B" firmware with a "fuel cut" only revlimiter.

I would need to add a "timing retard before fuel cut" feature in the firmware.

Lance
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bstuke



Joined: 25 Jan 2009
Posts: 86
Location: Lawrenceville, GA

PostPosted: Sat Aug 08, 2009 7:32 pm    Post subject: Reply with quote

Lance,

Thanks for the info.

I promise FFR Roadster Part 2 will be crank fire..

It might be coming soon to a race track near you.

Cya, Bob
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bradyzq



Joined: 21 Jun 2006
Posts: 141
Location: Montreal, Quebec, Canada

PostPosted: Sun Aug 09, 2009 2:51 pm    Post subject: Reply with quote

Hi Bob,

Have you been to your tuner to get dyno tuned yet?
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Brady Moffatt
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Montreal, Quebec, Canada
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bstuke



Joined: 25 Jan 2009
Posts: 86
Location: Lawrenceville, GA

PostPosted: Sun Aug 09, 2009 4:13 pm    Post subject: Reply with quote

Hey Brady,

Thanks for the note.

No I haven't. I have been having to much fun driving and racing it.

I am seriously thinking about selling it, and buying a challenge car so I can get on the track. I am going to get my provisional over the winter, and start next year with NASA ST-2 and SCCA Club Racing.

I still keep a close eye on the AFR gauge, and plot a lot of my runs, and make small changes in the map.

I recently had to put the cats back in and use new sidepipes to meet a DB rule of 92Dba. It is interesting that a restrictive exhaust means a little remapping, but I think I have everything running really good.

When the season ends, I will get it to my tuner.

I am thinking my neaxt car will be full race, with a 4.6L mod motor, and of course a crank fired Redline ECU..

I'll try to post a recent plot next week.
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