Tuning for more torque at low RPM
 

Hello,

I've been changing my fuel maps in ATR for my 06. I've leaned out the high load high RPM sections above 5000 to around 13.0 AFR and verified them with logs. However, I wanted to see if anybody had any input on what best AFR to use for more acceleration when you first take off WOT. I notice from the logs that the AFR's stay at stoichiometric (14.7) until about 5000 RPM where my changes take effect. I'm looking to maximize torque. Thanks!

-Lawrence

You need to tell us specifically which fuel maps you changed. There are a variety of them that interact to do different things under different conditions. Otherwise there is only so much that can be accomplished with optimizing ignition, fuel, and intake valve actuation. The rest comes down to physical engine configuration.

Hey thanks for responding! I changed only the Air/Fuel Gear 1-3 map which I assume is only used during WOT. In order to reach the AFR target at low RPMs, which other maps need to be modified?

I would suggest looking at "Closed Loop - A/F targets throttle compensation."

The stock map for my car (2005 6MT) calls for 0.04 to 0.08 points of enrichment at throttle duty cycle 70+, which produced AFRs right around 14:1. I guess the AT doesn't do this, so I imagine copying the MT setup is a decent place to start.

Hmm thats really interesting, my table doesn't look anything like yours. I'm missing a lot of cells and the higher load cells read 1.04. Does that mean its leaning out the mixture?

That is an open loop map. Where did the log indicate going into open loop relative to those other parameters?

tigersilhouette, I'm sorry but I don't understand what is up with your table. I wouldn't worry much that it isn't the same size. For that matter, I'd bet that 0.04 in my table and 1.04 in yours in fact represent the same underlying value, 0x24.

However, AFAIK, this table does only enrichment, the 0.71 value just doesn't make any sense to me.

I believe this is highly applicable for this thread: xkcd: Wisdom of the Ancients

I have the exact same question as the OP: what AFR should be used at low rpm, high load for best torque / power?

The exact same AFR that produces the best torque at high RPM high low, or high RPM low load, or low rpm low load.


I know that doesn't help, but that's because the only way to increase low rpm torque in relation to high rpm, using only the ECU tuning, is to detune high rpm so that it isn't so much higher than low rpm. This will be true of all naturally aspirated engines.

What you are actually going for is that you need to figure out how to increase air flow into the engine at low RPM. Naturally aspirated, the only way you can do this is with intake tuning, meaning designing a new intake that changes the lengths of the intake runners. Piston powered cars can also shift the torque peak point with different exhaust designs, but rotaries don't have that option.

Read up about intake runner length and the impact it has on torque peak, and you will find that there is an optimum runner length for any given RPM, and this optimum length gets shorter as RPMs increase.

Then take a look at the RX-8's factory design, and you can understand why Mazda has the complicated intake valving system that it does.

I am familiar with the organ pipe tuning that can be realized on the rotary and that they implemented it with the 3 sets of intake runners. Since it isn't simple to design and implement a new tuned intake, will an AFR of 13 to 12.5 yield any additional power over the stock 14.7 (before the 5000 rpm mark).

I'm also pretty sure the richer mixture has a higher combustion speed which may lead to pinging with the stock timing, so a new balance may have to be created.

And if you haven't read this paper, it's a fun read: http://www.rotaryeng.net/Mazda_R26B_US.pdf

i suspect that making richer will increase power, although i would expect the difference to be small.

in my non renesis rotary tuning experience the leaner mixture is more susceptible to knock than the richer mixture, but YMMV! and from 1000-4000rpm you certainly can get it to knock if you go to far with fuel and or timing.

my 12A P port, will ping a little @1800rpm and part throttle, timing is fixed @18BTDC L&T, and mixture is ~14.2-14.4:1 and the ping goes away with a richer mixture. i think it ultimately wants a timing curve...

Wow, can't believe its been almost two years since I first posted this! I never really got the lower RPM mixture and timing optimized, I only smoothed out AFRs above 5K. I really do enjoy using the access tuner race program, its pretty forgiving as long as you don't start plugging in crazy values. I would experiment and see what works best for your setup.