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Hitting rev limiter to early?

Posted: Sun Jun 14, 2015 7:00 am
by simon21
Hi Guys,

I was having a weird problem on the dyno a few days ago, the car was hitting the rev limiter way too early,
3 times in a row, on the 3 last high power pulls.
The limiter was set to ~10500-10700 in the ecu (and 10000 on the dyno), but it was hitting the limiter at around ~9200-9700
according to the dynapack.

Does anyone has a clue why the rpm all of a sudden jumps 1000-2000 rpm in the logs? (mostly on high power levels)

Worth mentioning, the car was on the same dyno last year pulling good to ~10200 without a issue (before I lost 4th gear) at around 900 whp
and I haven't changed anything other than increased the coil dwell times to exactly match kpro dwell times, and a new liberty dogbox for that matter.

My setup is a 84mm GSR, GT42, ID2000cc, Pro1 cams, S300 V1, CPR with RRA Coils, tuned on E92 at around 950 whp/800 wnm.

Thanks // Simon from Sweden

Re: Hitting rev limiter to early?

Posted: Sun Jun 14, 2015 9:05 am
by AREA876
Looking at your calibration the rev limiter is actually set at 9715rpm

Re: Hitting rev limiter to early?

Posted: Sun Jun 14, 2015 11:04 am
by simon21
AREA876 wrote:Looking at your calibration the rev limiter is actually set at 9715rpm
no shit!? ;)
it was set at 10500, even 10700 at the time being, to AVOID going into rev limit in the dyno, the dyno lockup was set to 10000

Re: Hitting rev limiter to early?

Posted: Wed Jun 17, 2015 12:17 am
by forevertrj
very bizarre as it looks as if you're within all the parameters of the calibration then all of a sudden your injectors shut off, the RPM spike a bit but your still WOT on the TPS sensor, and your max speed is like 13Km/h below the maximum limiter for speed, the injector duty cycle is pretty high, reaching a whopping 97% duty cycle, possibly reaching their maximum output maybe there is a duty cycle limiter somewhere built into hondata we are unaware of? also the activation rpm for the rev limiter is set to about 100rpm below the maxium as stated in the help file, maybe set this to late instead? I'm really curious about the injector duty cycle though and whether or not there is a limiter hidden somewhere for this.

Re: Hitting rev limiter to early?

Posted: Wed Jun 17, 2015 12:34 am
by forevertrj
you can see in the datalog that yes the rev limiter is switched on at about 9566RPM, my only recommendation would be to set the rev limiters even higher than 10500RPM, and make sure that speed limiter is increased past 158MPH.

Re: Hitting rev limiter to early?

Posted: Thu Jun 18, 2015 5:54 am
by simon21
I doubt its related to injector duty cycle, because last year it was running ~100% all the way from ~8250 to 10000 without an issue (log attached), 4th broke before we had any chance to lean it out.
I'm more into that it's ignition related, because when I recalculated the coil dwell times I completely missed the rpm compensation...

for an example, the values for 9000+ where 60 (dwell angle, cam degrees)+14.74 (rpm compensation) +15 pre-ignition = 89.75 degees total,
maybe that's too tight in the 90 degree window between cylinder event, and then maybe the ecu loses itself because of the huge variation in engine rpm? (which in turn may depend on all vibrations?)

you can see in the logs that every time it goes in the rev limiter, the pre-ignition goes up to 16 deg... and then your out of the 90 degree window...
is it possible that the ECU and the CPR gets lost because of this? and goes into rev limiter...

// Thanks

Re: Hitting rev limiter to early?

Posted: Thu Jun 18, 2015 9:43 am
by Spunkster
What is the reason that you changed the dwell angles? DId you have a problem that this was compensating for?

Re: Hitting rev limiter to early?

Posted: Thu Jun 18, 2015 11:19 am
by simon21
Misfires... Last year we started out with 0.03" gap - misfires. Gap them down to 0.02 - misfires. Gap them down to 0.014 - STILL misfires!
Also worth mentioning, the car was running e100 last year.

Then we added 5 deg dwell angle at 6019 rpm and 10 deg to 8976, misfires totally went away!

This year I wanted to be able to go back to ~ 0.02" gap by increasing the dwell angle to exactly match kpro dwell angles.

To give me 3.55ms at 3000, 3.05ms at 6000 and 2.701 at 9000 rpm. (calculated, as in Kpro)

// thanks

Re: Hitting rev limiter to early?

Posted: Thu Jun 18, 2015 12:46 pm
by Spunkster
You will need to post new datalogs with the calibration being used as this calibration has a lower revlimit set than what you are trying to reach and the posted datalogs make sense with the calibration posted.

You may not be hitting a rev limit, but are getting too weak of spark from having gaps that are too small and getting misfires. What spark plugs are you using?

Re: Hitting rev limiter to early?

Posted: Thu Jun 18, 2015 2:02 pm
by simon21
Well... that's easier said than done as I'm not in the dyno anymore.

But can't you see in the sensor list that it actually hitting the limiter, regardless what the calibration tell you? And that the rpm shifting from 9500 to 10500 even 11500.. (in one jump)

Because I'm telling you, the limiter was set to 10700 at the time being (when the log was recorded) and lowered to 9700 when we were finished.

And according to the film that was recorded, 
it is hitting the limiter, no doubt about it! No misfires..

I'm using bkr9eix right now but bkr8eix and bcr8es were also used/tested

Re: Hitting rev limiter to early?

Posted: Thu Jun 18, 2015 9:39 pm
by forevertrj
not sure if it's worth mentioning, i know the traction control isn't enabled in the calibration but as soon as the rev limiter kicks in, i see the ECU enable 60% traction control, practically mirrors the rev limiter, super weird what could this mean?

Re: Hitting rev limiter to early?

Posted: Fri Jun 19, 2015 11:15 am
by Spunkster
Do you have Traction control?

Re: Hitting rev limiter to early?

Posted: Fri Jun 19, 2015 11:51 am
by simon21
No, I haven't, why?
But it doesn't seem to engage every time it hit the limiter, when the rpm spikes?

Re: Hitting rev limiter to early?

Posted: Mon Jun 29, 2015 10:14 pm
by simon21
Ain't it nobody that has an idea?

Re: Hitting rev limiter to early?

Posted: Mon Jun 29, 2015 10:54 pm
by forevertrj
Try checking in your options-> sensors settings and look at rpm mine was set to 9500 as a max value, try increasing it to 11000rpm? Also that dwell angle hypothesis seems legit but it didn't look like you were out of parameters, is too bad the sensors list doesn't have more sensors to display under datalogging