Might there be space to get sneaky and have a 91oct map and a bonkers map based on the coding plug? Good Fuel here in VA is hard to come by.

 

What actual full timing advance are you using? Any experimentation on that?
upstate bob
79 5sp. no drips.

 

I have already removed some of the coding plug checks.
Eventually, I would like to remove all of them and use the coding inputs for other functions (EG. with a DIP switch).
Some of the CP pins are variable voltage, so they could be used for a potentiometer, or a temp sensor.

Most simply, if I finish removing all of the branches, I could make it so that if the coding plug is in place, then it is 91- octane. Remove it for 92+.

'85-up have ignition advance maps so it depends on rpm and load.

Generally where the engine breathes well, at the TQ and HP peaks, requires less advance.

The S4 is weird because it knocks where it is not making power, EG around 3900 rpm (3600 is where the intake flap opens).
It could be the dynamic compression there is too high for the available octane.


Map is read from upper right to lower left as rpm and load increases.

 

If the dynamic compression is too high there for advance, that means better cams might actually allow improved power down that low even though they have more lift and are a "higher rpm" cam.

Hmm.,

 

I think the S4 106' cams might be the issue.
After everything is sorted out at zero, I will try some cam retard again. It was able to take more advance at 4K with it.

 

I am a dork. Of course it knocks at 4000. That's the stock, flappy open, TQ peak.

With exhaust, fuel, and ignition tuning, the peak stretches to a hump, peaking at around 4500, which eclipses the harmonic peak at 4K.


Glovebox manual power curve.


Flappy open vs. flappy closed.

 

Ken

Are those curves telling us the flappy should open at 3600 rpm? Slightly earlier than the stock setting of 3660- I thik you recommned a bit earlier still in an earleir post.
After that,those curves suggest there is no point in it closing again at 5580 rpm or am I mssing something?

Regards

Fred

 

If you look at most S4 dynos, there is a saw-tooth drop in TQ/HP at 3700.
You may feel the notch as a 'moment of blah' at that point, similar to when the EZ detects knock and puts in some retard.

As you increase the power output the flappy-closed curve gets higher and a bit wider, but always drops off quickly past 3200 because the pulse effect which creates the first peak is rpm dependent.
As you increase the power output the flappy-open curve gets higher all over so you can open the flappy sooner to match the drop of the closed curve.

To complicate things even more - the strength of the first, flappy-closed TQ graph is very dependent on weather conditions. The ideal crossover point may change when there is colder, higher pressure air.
In my testing, airflow from 4500 up doesn't change as much with temperature/pressure - I imagine this is because the intake and/or exhaust is restricting airflow past this point.

Also, the flappy doesn't open instantly. I found it's better to give it a little extra time.


Note the higher output on the flappy-open curve below 2400. In order to take advantage of this, I have reversed the flappy code.
The flappy is normally open, only closing long enough to take advantage of the flappy-closed curve from 2500~3500.
I lowered the load threshold as well so it would close on part throttle.

I would like to try tuning both the ignition and fueling with the flappy fixed - never closing - to see how well it could be made to dyno without it.



In the two runs of my '88, the blue line is where I opened the flappy sooner (stock EZ, LH tweaked).
The red line shows where I closed it later, but forgot to move the open point to match (EZ and LH tuned).

On Jim's graph, he is making some nice numbers on the blue line, but you can imagine that the closed graph (second TQ peak) would cut right through the notch if the flappy opened sooner.

 

OK. So I am addicted to 110 'shots' in the morning. Better than coffee!


Some examples of closed vs. open flappy runs. Temps stabilized.
Weather: 30' 75F 29.99" 59F dew = 101.1 SAE 1210'

Minor fuel tuning to stop it going too rich at the missing peaks, no ignition tuning.


Flappy open consistently breathes better below 2000 rpm.

It's tempting to assume the smooth transition from flappy closed to open at 3700 is where to set the flappy open point, based on the airflow.
My dyno testing shows that the sharp, lower airflow, intersection avoids the dreaded shark-tooth drop, however.


It's close but flappy open beats flappy closed...if you are stuck in third...but it's a bit faster to have both.
If you take it to red-line, they will both be going the same speed, though.

One hates to admit the Kibort-unit is correct: the flappy is unneccessary for racing.


I did not test open/closed/open vs. stock closed/open/closed/open - I should have...


Closed over open.


Closed over open/closed/open.


Open over open/closed/open.

 

Nothing like real world results to spoil wishful thinking.

At SAE temps, at least, it's not worth the extra coding. I guess I'll use the stock flappy operation, but for opening it ~100 rpm sooner.

At least the fueling looks p-e-r-f-e-c-t, run to run.

Stock over always open, closing for just the first peak.

 

The problem is the dip is so big in the first place. Doesn't that just mean the intake volume is too small for such a large engine? And with a bigger volume intake the dip would not be so severe?

 

Why are we getting spam on this thread. Can someone in charge please delete. Post 222

 

Installed a SLC-X (h/t Shane).

The SLC made a smoother AFR graph vs. an Ott, even without retuning. (Not necessarily faster, though.)
For best effect, different areas required more or less fueling and ignition advance.
Max HP, around 6000, needed less fuel and less ignition advance.
Max TQ, around 3000, took more fuel and more advance.

What finally flattened out the area past 5600*, however, was changing the injection advance time (aka opening time).
Increasing the injector advance (in milliseconds) adds to the front end of the injector pulse.
To compensate you have to decrease the injector constant (size), IE. the back end, to keep it at the same AFR.

I coded a separate advance time for WOT so as to not interfere with part throttle. (Adv time is a 9 cell table by voltage.)

I was surprised at what a large effect it had at high rpm, since the LH is batch fired.
Perhaps it changes the fuel calculation to something less error prone.
Correlation or causation - it does seem to be less jumpy with sub 92% injector duty.


I read somewhere to increase the advance time until you reach a max rich AFR level.
I increased the time by a percentage of the stock setting until I could not easily lean out the AFR with the injector constant, then backed off.
About 50% higher did the trick for WOT, 0.95 to 1.46 ms.

I bumped up the part throttle time just a touch, too.
Eventually, I will try and code an external adjustment for the advance time, along with, or perhaps instead of the CO adjustment.


Overall, with the SLC and (extensive) retune, response is much improved and the car seems to pull a lot better.
Heavy part throttle provides some nice thrust. Pushing farther to WOT kicks it up a notch, with a bit of a supercharger feel.
It is getting closer to having the sense of 'get into trouble' I had with my black car at WOT.

At full throttle, the wholly flat AFR sounds and feels like it has the stock mufflers back on.
Electric motor smooth with a woosh-like exhaust note.



*To help keep the region past 5600 flat, I also changed the 'slope' of the MAF ideal table from 12:16 to 12:32 at the last row.
This region reacts too quickly to temperature changes. Airflow is not keeping up with rpm so the WOT addition is dropping like a rock past 6000.

 

Salivating!!!

 

I'm sorry, these logs probably all look the same.

No changes in the LH chip all this week. Warm to hot, it keeps making this same graph, ±0.3 AFR.
For me, the log below is perfect, sub-12.5 up to 6000 where it slowly leans out. Less fuel = more air!

With the fueling set, I have been slowly whittling away at knocks (-0.4° at a time) - even after back to back to back runs.
It hurts us to keep reducing the amount of advance, but the best power comes just below the knock threshold.


Cooler weather predicted for next week. Dyno time!

I reckon peak HP will be around 6260, but there will be pretty much the same HP from 6000 to the rev limit.


(No smoothing!)