Freise

Trying to satisfy some curiosity here.
I've noticed that different Zs have different types of rev limiters; forgive my terminology but one is a "soft?" limiter where it is software/drive by wire controlled that holds the revs constant:

The other is fuel or spark cut, and gives more of a bouncing "hard?" sensation:

I can't find any information on why there are two different systems, or a pattern on what determines which you have, for example I have an 05 DE that has the same limiter as the HR (solid, dbw), but the second link shows what appears to be another DE (judging from the redline of under 7000) with the opposite limiter system.

92K1500

iTrader: (1)

I think Uprev switches the style because I know before my 2004 would make large cuts for the rev limiter and I don't make a habit of hitting it but it seems like now it just holds steady since I got it flashed.

terrasmak

iTrader: (8)

In uprev you can set the limit and how many RPM drop off to where the engine comes back to life.

I don't know if it's a fuel or ignition cut system

92K1500

iTrader: (1)

That would explain why it seemed different. Neato.

HRMoneyPit

I noticed when revs with clutch in it holds


In gear like say a launch, it'll bounce on the limiter

CK_32

iTrader: (1)

That is kind of interesting.


Anyone know if these red lines can be held? Or are these limiters of death?


I know some MFG's set them with in the engine RPM range. Others set the red line to where if held the dam thing runs it self apart.

MicVelo

terrasmak, 92K and everyone else is correct here.

Just a few other tidbits to complete the story...

Both types of rev-limiters (hard cut/soft cut) GENERALLY use a combination of timing retardation (NOT full spark cutoff-that's old school and really screws up emissions output because it allows raw fuel to be dumped) AND partial fuel cut-off.

Z's before 2005 -IIRC - were hard cut. After that (somewhere in M.Y. '05), they switched to a soft cut system where the system is pre-set by the ECU to slow fuel and retard ignition at a point approaching redline.

Difference between the two is determined by the point in the rpm range where the rev limitation algorithm kicks in and starts to take effect,

In general:

- Rev limitation kicks in when the engine hits redline = hard cut

- Rev control kicks in BELOW (approaching) redline = softcut.

This method both retards ignition and slows fuel delivery to keep engine from revving higher and can be held at the RPM max (redline) as opposed to a hard cut limiter which has a single trigger point at redline and will abruptly drop revs, pick them up again and repeat this every time the engine hits redline.

Uprev does (or can) give options to change earlier rev limiters (pre '05) to softcut as evidenced by 92K's comment. (As well as modify the parameters at which the motor "recovers" and delivers power again, the point made by terrasmak.)

13esim

I noticed my Revup does the same as the first video posted, a couple times at autocross i hit the limiter while the car was sliding and it bounced (like the second video), maybe the lack of grip (from sliding) allowed the engine to go past 7K and then the software caught it.

Maybe it is suppose to work like Cruise Control in a sense where it the computer reads a multitude of sensors to maintain 7500 RPM (or 7K in my case) rather than cut fuel momentarily to limit the revs.

I dunno but thats my guess.

jes1888

iTrader: (2)

a tune with uprev would take care of this, not the cutoff but the fact that it reduces fuel and timing right? That's also why after a tune car feels better? I have a 06 revup and have taken it to redline but havent noticed the 1st video cutoff, just the second. I gotta check again though...