How do I get an ECU rev limiter like this?
 

https://www.youtube.com/watch?featur...rWuQLeWY#t=133

Jump to 2:15 in the video, if direct link doesn't work.

Is this just a normal scaled "Base timing B" (to 7400 rpm and without a timing drop) plus "Rev Limit A" and "B" set to e.g. 7450/7425?

Or this:

https://www.youtube.com/watch?featur...khJcdjD0#t=238

4:08 if direct link doesn't work (edit 3:58, to hear it twice).

Isnt that one an Aim pro? I think thats a data logger/timer that connects to your OBDII port and is probably extracting the RPM data from that. You could ghetto fab something with Torque and a phone, altho probably not as accurate as that.

He's trying to get a "hard" rev limit vs the fuel cut of stock or the timing reduction of Openflash's soft rev limit.

Yes, exactly. Not to "sound cool", but I want it to stay on power when hitting the rev limiter.

I am going to some drift training tomorrow and had the battery disconnected because the car has been standing for quite some time. As the ECU will have reset anyway, I was thinking to modify the rev limiter and flash it before tomorrow.

Hence, if anyone has exact knowledge it would be highly appreciated as I wouldn't have time to experiment myself.

*added "ECU" to thread title

The rev limit has 2 purposes:
1. Not blow up your engine i.e. to be safe. I don't mean the rev limit is to prevent damage, everyone knows this already, I mean the rev limit itself must not cause damage.
2. To retard the speed of the CAR. Notice I didn't say retard the engine speed. The engine is mechanically linked to the wheels, so it needs to be enough to retard the entire car enough to not over-rev the engine, in every gear, in all conditions. Slowing the engine rpm down on flat road in 4th gear isn't really good enough.

You're going to need to use the fuel cut as per stock, with a lower hysteresis (100-150-200 rpm).

Or use 3rd.

Thanks. Yes both concerns of mine, as I see the FFS rev limiter causes FLKC (regarding your point 1). So I'm not even so sure if a hard limiter is such a good option in the first place?

Over revving the engine in 4th gear or higher (in gear while accelerating) is not that much of a concern though for 3 reasons.
1) The car doesn't have that much power to pull through at that speed.
2) Engine acceleration is quite slow in that high a gear.
3) At that speed, there will be few other distractions (no corners to negotiate etc). So the risk of over revving should be fairly low.

Of course, the rev limiter has to reliably stop the car (in gear) from accelerating beyond the rev limiter in lower gears where there is enough oompf to pull through and everything happens quite fast. With spinning wheels (drift) it's another matter though.

Shiv wrote the following in a VERY old thread:
Ways to 'soften' stock rev limiter?

I was wondering if anyone already experimented with different values?

Or if someone using Ecutek (as being used in both video examples in the first posts), can recognize what hysteresis has been used in the examples (as in if that maybe is a "standard accepted way" of fine tuning the rev limiter with Ecutek tunes)?

Also, your explanation makes me wonder if it could be speed/gear related which Rev Limit A and B is active? Hence, which one to change by how much.

As usual too many parameters!! :D I think I will keep the soft rev limit for tomorrow to avoid any problems.

I wasn't saying the limiter in 4th would be a problem. If it retards enough speed/momentum in 1st, then the rest of the gears will be fine.

You would need to try hysteresis of 200 first around 7000, then work your way down to 100. When you have a final hysteresis value, increase the limiter to 7500 or 7600.


If you get any knock, you can start retarding the timing before hitting the fuel cut.
Example:
7500 fuel resume
7550: 20 deg
7600 fuel cut
7650: 0 deg

Ah I understand now. :) I thought you meant the other way around, the momentum of the car traveling faster in e.g. 4th would make it more difficult to stop the engine from accelerating on.

I liked the soft limiter at first, but I find it increasingly annoying, mainly because there is little feedback. So at times I find I tend to be longer in the area 7400-7550 unintended.

I already tried in my most recent flash to lower the soft limiter from 7600/7550 to 7550/7500. It had absolutely no effect, the timing is already too retarded at that point, so it feels just as mushy.

They way you suggest to go about it, must be very safe - but it that would take a lot of flashes, that I won't have time for tomorrow. If no one (open source) tried it, I might give it a go at some point. Or I might lower the soft limiter another 50-100 rpm, to see if a bit earlier cut would mean it hasn't retarded that much timing yet, to make it feel mushy - this should be safe too, I would think? As it just cut earlier than the soft limit would otherwise do?

Frankly, I was hoping someone had done the work already and just had numbers ready to post up. :)

I.e.: Would this also be a safe way to go about it?

My mod left, standard OTS 2.076 on the right.

My mod cuts fuel earlier, but let it resume with less drop in revs too.

It still has the timing drop but drops faster as rescaled to 7500 instead of 7600. The intention is to ensure a fast timing drop when the fuel is cut to avoid knock when the mixture leans out.

Would there be any concerns about going about it this way?

https://s18.postimg.org/qib8taoqx/Sc...t_02_33_28.png

25 rpm is literally nothing, to the point of it would almost within the margin of error of the sensors. 100 rpm is likely the bare minimum. The 50 in the tune is acceptable due to never reaching it in the first place and by the time it's reached there's so little timing so the engine has no torque anyway.

No one would be able to post up numbers that would work universally. A car with stock headers on shit fuel has bugger all torque above 7k compared to the likes of say 4-1 EL on E85 which will feel like it will go to 8k easily.

If you want a harder cut that upsets the car you can just increase the ign retard.

If you want the bang bang bang cut, you're going to have to start with a big hysteresis and narrow it down, or start with a small hysteresis and just make sure you don't stay on the limiter for more than a fraction of a second.

I'm not sure but changing the hysteresis might also effect the launch control. That would be easy to test. Change it to 200, stomp on it while stopped and see how the LC is effected, then lower the hysteresis down to where it's manageable. Who knows, 25 might work.

You could also close the throttle using DBW tables. I doubt anyone does this because you would have to move the entire mass of the throttle plate from almost fully open to almost fully closed rapidly. You could tune it to drop to a certain throttle angle and stay there, but its effect will vary wildly depending on grade, gear, IAT, and pretty much any other variable you can think of.

It doesn't lean out, it cuts fuel completely. Like when you take your foot completely off the accelerator.

Also, I wouldn't worry too much about timing retard on FFS. Do you know its genuine knock?

If you want a solid limiter, with no bouncing, then set the values as close as possible. 25/50 is probably good. If you want a fast bouncing limiter, then increase that to 100/150. It won't cause you any issues if you're not above stock limits. I don't bother with a timing reduction, it won't help with EGT which in turn will help cause the inset of knock.

You are right, I don't really know if the FLKC during FFS is real. I started another thread about that here, including a log where it has -1.3 FLKC during every FFS. Mind taking a look? http://www.ft86club.com/forums/showthread.php?t=113364

And yes, maybe leaning out is a wrong term (or wrong all together :D ), my thinking is if it's bouncing back and forth, it might cause fuel in inappropriate measurements to be injected?

Anyway, I flashed the mod I did above.

It's better than the OTS soft limiter for my taste. But could need more tweaking when I have time.

The car just sits at the limiter with a slight loss in power. It doesn't have the mushy undefined feeling of the OTS limiter. You know instantly "ok, there is the limiter".

I might take out the timing reduction completely and restore the 7000, 7200, 7400 "Base Timing B" scaling and put the limiter to 7450/7350, for less loss of power and an audible feedback too.