There is a buffer. Honda designed an engine that will safely rev to 8500+ RPMs, so they set the rev limit at 8200 (300+ RPM buffer).

 

back to the orginal question...

the rev limiter cuts fuel and makes no adjustments to timing.

the different rates of cut out (ba ba.. vs bububbu... - as you call it) is from the difference in rate of recovery.

the limiter works with two rpm points. the rev limiter rpm setting and the recovery rpm setting. the recovery is normally at a lower rpm ~300rpm than the actual limiter. when you hit the limiter the engine dies and will resume once the rpm drops below the recovery rpm. so if you don't lift, it will bounce between these two points..

what you are experiencing is the time it takes to bounce between the two settings. at part throttle the rate at which it bounces off the limiter is slower vs WOT. it's also quicker in the lower gears...


from the flashpro help screens...
************************************************** ***
Activation and recovery

Most rev limits have two parameters - an activation rpm, which is the engine speed when the rev limiter operates, and a recovery rpm, which is where normal engine operation resumes. Normally the recovery rpm should be set 100-300 rpm lower than the activation rpm. A larger different will result in a slower, rougher rev limit.s



Rev limiter type

The ECU uses a fuel cut type of rev limit. The ignition cannot be cut without a fuel cut as this allows the cylinder walls to be washed down by the unburnt fuel. Note that if using a wet type nitrous system with a fuel type rev limit it is important to set the nitrous to be switched off before the rev limiter, otherwise a lean condition will exist when the ECU activates the rev limiter.

 

so how high is too much? folks are running ap2's with stock interals with ap1 ecu and turning them 9k.

so can the ap2 take a soild 8600 rev limit without killing the timing? the reflash is 8600 (and my dyno runs hit 8600), but all the flashpro calc. are at 8500 - hondata backing up a little on the can tunes?..

looking back over a few datalogs - i bounded 1st a couple of times with a max 8550 rpm reading, but on the same datalog 2nd gear bounced few times and recorded 8700 rpms......

 

I think this is backwards. The rev limitter should be much more rapid sounding at part throttle (BABABABABABA vs BAAAABAAAABAAAABAAA) since it won't overshoot the limit as much, and also because the RPMs will fall a bit faster under vacuum.

 

Are you sure that the Hondata Reflashes had the rev limit set to 8600 RPMs? Where did you get that information? If it just came from the dyno, then I wouldn't consider that as a difinitive source. When I set my rev limit to 8500 with the FlashPro, I can still hit 8700 RPMs in 3rd gear due to overshoot.

 

So the buffer is to 8,500 and two of you are hitting 8,700?

 

I'm not hitting 8700 any more, since I took Hondata's advice to soften the rev limitter. I added some fuel and retarded timing (a lot) to reduce power above 8400 RPMs. I don't really feel a reduction in power, but the rev limitter is MUCH softer, and more rapid (BABABABABABA instead of BAAAABAAABAAAABAAAA). Now I just hit about 8550 RPMs.

 

may drop faster - not sure.. but would definitely climb slower at part throttle....

 

It's the combination of it climbing slower and dropping faster that makes the rev limitter more rapid.

 

hondata's orginal specification was 8600 but could have been a typo. and reason i say that is because i've found a couple before.

one was on the reflash specification. their orginal spec on the vtec windows was 5600-6000 and 4200-6000rpm for the stock and toda reflashes. one day i noticed that the window was actually 4200-6400rpm on my toda reflash and they confirmed this on their fourm via a post, you can search on my handle (thesilverbullet) on hondata's forum. so maybe it was never 8600...

looking at the dyno plot it runs out to 8600, but maybe that was overrun.

so i just checked the raw data and at 8600 the hp has droped to almost nothing -

207hp@8.58rpm, 57hp@8.59 & 39hp@8.60

fyi - peak hp (220) was at 8.04 rpm..

so it looks like the cut was at 8500.