Forum » General Tuning Discussion » Some general questions about rotary tuning (knock detection, ignition timing)

Some general questions about rotary tuning (knock detection, ignition timing)

General Tuning Discussion

Discuss all things tuning in this section. News, products, problems and results. 


Page 1
Author
121 Views

Hey guys, this will be my first forum post here, because after doing a lot of reading/research, I'm not really getting the answers I'm looking for. This winter, I will be rebuilding my series 8 FD for the first time, and I decided to make the jump to a single turbo system too. I have bought an Adaptronic pnp ECU for the S8 FD, and I'm really impressed with the videos Adaptronic puts out, and the ECU pin mapping which makes everything easier.

I have a few questions related to rotary tuning, first of all, I have zero practical experience, but I have followed all tuning courses on HP academy, and reviewed them several times, I also browse the internet/forums a lot to absorb as much information as possible.

When it comes to piston engines, it's common to detect knock using the knock sensor, in combination with a pair of headphones. However, after seeing a lot of videos of rotary tuning (for example Abel Ibarra) I have never seen anyone tune a rotary engine with headphones on. Now I have 3 theories why this might be:

- Theory 1: Listening to knock makes no sense, because when you hear it, the apex seals are already damaged, but I don't think this is the case, I assume you can hear knock before it really gets out of hand, just like in a piston engine

- Theory 2: Some sort of knock safety is used in the ECU

- Theory 3: An experienced tuner probably knows what timing works well, and keeps the AFRs in check to prevent detonation

I hope somebody on this forum can enlighten me on this, I don't really know how to get in touch with experienced rotary tuners, and I'd rather not use up their time with my questions. Right now the only thing I have trouble understanding is tuning the ignition map of a rotary engine, and how to handle detonation. After hearing that rotary engines don't really respond to ignition timing like piston engines, I started to think that people can perhaps run conservative timing, and simply increase the boost, however this must also increase EGT's.

Any help is greatly appreciated, I've been completely hyper focused the past few days to learn as much as possible, and I really want to tune my own car, in a safe way of course. I hope I can ask any further questions here.

- Nick

Attached Files

Okay, I feel really stupid right now. Just found the webinar about rotary ignition tuning (and fuel tuning) and I think most of my questions have been answered. Knock = really bad news it seems, and a knock strategy would be silly. I will be using Goopy apex seals, because I've heard good things about them, but I don't expect them to willingly accept detonation... So from what I learned from the videos: Start conservative, get the AFR dialed in, do ramp runs and increase timing by 2 degrees until the torque seems to plateau, and back it off.

I'm not aiming for big power right now, so I will try to keep things very conservative, and monitoring EGT's.

If any experienced rotary tuners want to chime in on this, please do!

It looks like you've answered your own questions. I'll reiterate however that at least in my experience listening for knock is not much value on a rotary because when knock occurs you'll be picking apex seals out of the back wall of the dyno cell. Being conservative is the usual aim but fortunately a rotary engine is not as sensitive to ignition advance as a piston engine so you can be conservative without leaving a huge chunk of power on the table.

I'd suggest not trying to find MBT timing but rather set the timing where you start to see the gains in torque become less significant. This will give you a nice wide safety margin. It's also a wise idea to aim for an AFR that's quite a lot richer than a piston engine. I'll generally be in the region of 0.75 lambda for a turbo rotary at modest boost levels.

We are running a rotary but we are drag racers. So my advices must not fit to your engine :-).

As Andre said you dont need knock sensors on a rotary engine. Broken apex seals will tell you that knock occured ;-).

I only have some values on E85 regarding the ignition and afr ( but now we are running on straight meth ).

On E85 we ran 25° to 33° at vacuum. 23° to 30° at atmospheric pressure. 15° to 21° at 1 bar of boost and 9° to 13° at 2 bar of boost.

Never had a broken engine because of knock so it should be safe. Unfortunately i dont have any experience on pump gas.

Lambda was 0.82 at idle, 0.74 at 1 bar and 0.71 at 2 bar.

EGT was up to 880°.

Attached Files