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Old 06-02-2015, 04:38 PM   #11 (permalink)
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Originally Posted by RPM View Post
Thanks, that is some great insight that is hard to get from magazine reviews and the like. In absolute terms the FR-S is pretty small and light, but coming from an MR-S I can see how it would feel quite large and heavy. I am a fan of small, lightweight cars myself. That direct response, the feeling of connectedness… It feels like the car is part of our own body.
Yea, magazines call any car under 3000 lbs small and light and nimble, which is not helpful at all.

I think there's probably more factors than just weight, a Porsche Cayman feels equally nimble as the FR-S despite being 200 lbs heavier. I realized I don't like fat tires, because of how they feel going over uneven pavement. When the edge of the tire catches a ridge or bump much of the tire will stop contacting the ground momentarily.

The MR-S was great because its steering ratio was quick, the wheelbase was short, and the weight distribution was good. When I wrote about the FRS handling on Spyderchat some guy said my description sounded a lot like a Miata. I would imagine a Miata to be somewhere in between the Spyder and FRS, closer to the FRS: more nimble and sensitive, tail end loose but maybe not as loose.

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Old 06-03-2015, 06:33 AM   #12 (permalink)
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Okay I'm finally going to not be lazy now and share some data I formatted into charts. I'll say in advance, I wasted quite a bit of fuel by ecomodder standards, so don't cringe so hard lol.

The first 10 minutes of driving today:


Well immediately, I see why P&G didn't do s***. The accelerator pedal position is not scaled correctly but you can see that one peak where I floored it. Even though I was only pressing the pedal about halfway, manifold pressure is atmospheric and load is 90%, engine is running in the 13.x AFR :/ No wonder people gain so much mpg from just about any performance tune. That said, this means I was burning ~10-15% more fuel than I should have been on the freeway, so with just a throttle remap, 39 mpg => 44 mpg should be easily within reach, and with high load fueling table cells adjusted 45 should be a piece of cake. Who knew this car was so fuel efficient!

As for around town driving, it's basically impossible to not be running rich all the time while accelerating, so that should get a noticable improvement too. Right now I'm getting maybe mid-high 20s mpg "city" driving. Cutting fuel burn by 10% in all cases would kick me up to 30 which is very respectable for a 2800lb car.

I had driven about 1 mile and walked into the hardware store prior to this log, so the coolant temp starts at 65ish. It appears that coolant takes around 5-8 minutes to reach operating temp, seems typical. Cat hits ~225C in 1 minute, which sounds kind of slow? Well, it passes CARB testing so I guess it's okay lol.

Idle fuel flow is 0.26gph at 980rpm fast idle, settles down to a surprisingly low 0.17x ish gph! That's lower than my MR2's 1ZZ-FE at 0.18x! On that note, the engine actually pulls pretty strong at low rpm so I am optimistic about a low idle speed working. The idle does sometimes hunt a little but after 3 years of 1ZZ quirks it doesn't bother me.

Since my P&G was a total fail, let's take a look at some steady state 6th gear cruising data:


It was hard to keep my foot steady but you can see that at just 42% load it's already going rich. As you can see from accelerator position vs. engine load, this throttle is CRAZY sensitive.

Catalyst temperature was right around 600C, if you use that line as a reference you can see around 35% load will hold 65mph, and MAP is at ~6.5 psi ~ 44kpa ~13mmHg. My 1ZZ-FE ran around 9mmHg by comparison, though it was revving 25% faster. That said, it was fighting a bit more aero drag too, so the FA20 represents a significant improvement.

Awesome. Note that catalyst temperature is well below the 700C continuous operation rating, so we have quite a bit of room to play with going lean.

So tuning:
1. Remap throttle, smooth out the requested torque ramp-up. I'll check out the tables other people are using but I feel like to get good mpgs I'll have to smoothen the response a bit more.
2. Borrow an off the shelf ignition and fueling map, then lean out a few more medium load cells. Gotta keep that engine running stoichiometric while pulsing.
3. Set 1600-3600rpm, 2nd lowest load cell up to the 43% load cell to leaner than stoich, maybe like 1.14 lambda. That comes out to the same amount of fuel injected as 36% load at stoichiometric. I'm thinking a few cells can probably go to 1.2, but that'll take experimentation.
4. Check intake cam settings, keep it at max retard for a little longer for low pumping loss if applicable, dial exhaust overlap back a little to stabilize lean burn.

Last edited by serialk11r; 06-03-2015 at 02:10 PM..
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Old 06-10-2015, 06:03 AM   #13 (permalink)
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Okay I bought an Openflash Tablet (arriving Friday) and played around with Romraider today a bit. Idle speed is easy to cut down, since all of the tables have the same speed when the coolant is warmed up.

However the rest are pretty confusing, and worst of all, the fueling table won't take >14.7! Accelerator pedal position vs. requested torque has two different tables which I'm going to need to figure out, but it doesn't seem like it should be that hard. For a start, leaning out the mid-load range is easy to do, so that's good.

The VVT is a nightmare though, I have no clue what to make of these numbers because they look strange as hell. The tables are labeled "Intake Cam Advance Angle ____" and "Exhaust Cam Retard Angle _____" where the blank is Base, Safe, and Normal. I'll have to spend some time digging into some guides tomorrow...

In the meantime though, can someone help out with getting the engine to run lean? I could just rescale the O2 sensor (hooray for wideband O2) and adjust the tables but I don't want the engine to run rough at low speeds. The other thing I'm thinking is set the lowest load cells a tiny bit richer, but since the table is labeled "Primary Open Loop Fueling" I feel like this could be the wrong table to be looking at. @ever_green ?

Last edited by serialk11r; 06-10-2015 at 06:18 AM..
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Old 06-12-2015, 01:08 AM   #14 (permalink)
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No love for my thread...lol

Eagerly anticipating the arrival of my OFT tomorrow. Today I did quite a bit of driving and on some stretches of flat highway I tried P&G again but this time being light on the pedal. This car is awesome for coasting, when I was on the 280, my terminal velocity on the long stretches of moderate downward slope was as high as 75mph! In my Spyder I couldn't even maintain 60, although that car is much lighter which doesn't help.

Cruise control 60mph returned ~42mpg, surprisingly good. It was interesting watching the gauge as cars went into my lane ahead of me, even Corolla leading by 50ft or so would bump me up to 44mpg or so, and an SUV at 50ft would be 45.

Then I tried pulse and glide, letting the speed float between 56-57 and 64-65ish. The way I controlled load was by looking at the instantaneous mpg gauge: steady state cruise is 42mpg, corresponding to ~30% load. 50% load is the highest I can go without hitting enrichment, corresponding to ~25mpg. It's very hard to control the pedal that finely but I kept it between 24 and 30 during the "pulse".

This unfortunately averaged 41.1mpg :/ It seems like 50% load does not give a big enough efficiency increase on this engine to offset the slightly larger average power requirement of fluctuating speed. I might have averaged a little more than 60mph but either way, the results weren't good.
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Old 06-12-2015, 06:29 AM   #15 (permalink)
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Subbed! I would have never thought that a sporty car such as the FR-S would get this kind of fuel economy. With your planned tuning, I'd say 50 mpg will come sooner than later.

Now, excuses me while I order my Lamborghini so I can show you up
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Old 06-12-2015, 08:46 AM   #16 (permalink)
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Can't help you with the tuning, but I'm following with interest.

You should also start a garage entry and fuel log for the car! It looks like we have one guy with a BRZ in there and he is getting 26 mpg...
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Old 06-12-2015, 02:33 PM   #17 (permalink)
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Can't help you with the tuning, but I'm following with interest.

You should also start a garage entry and fuel log for the car! It looks like we have one guy with a BRZ in there and he is getting 26 mpg...
Yea I should probably start tracking the fuel again, but like I mentioned at some point I'm doing weird blends of E85 and gas to increase my fuel's octane rating, and I burn through gas VERY slowly so it's going to be extremely hard to keep track of since I don't even get full tanks much, I just fill up halfway when I see cheap stations. I'll be doing a 35 mile one way commute in 2 months which should give more data points though.

According to the mpg indicator though, in "city" conditions I'm getting high 20s and on the freeway a little under 40 average. The mpg indicator uses MAF/load (g/rev) readings plus target AFR to calculate mpg which is not very accurate though, especially when using an E20-25 blend like I am.
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Old 06-12-2015, 02:38 PM   #18 (permalink)
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As long as you track your mileage it'll all even out in the end. At least you'll know what you're getting even if it goes up and down a lot.
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Old 06-13-2015, 03:14 AM   #19 (permalink)
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Its not that we don't love your thread, there are just not enough FRS/brz owners on here.

I dont know of any "active" wrx/sti owners on here either
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Old 06-13-2015, 04:45 AM   #20 (permalink)
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Okay, got my OFT, but the paint on my DIY bumper exhaust exit cover (I have a single tip exhaust) is still drying so I'm not flashing any tunes and driving.



As you can see, the blue outlined cells were leaned out. Max g/rev on this engine is like 1.33g/rev or something so 0.7 is 53% load, and 0.8 is 60%. Now I can pulse at 53% load on the freeway without triggering enrichment, and up to 60% only going a little rich.

Right now I have around 1.4 gallons E85 to 6 gallons gasoline in the tank, which is a blend of 89 and 91, so it's around 25% ethanol and should be like 96 octane or so, but I pulled 0.5 deg timing on this map just to be a little more safe.

You can also see I've lowered all the idle speeds, I'll see if 600rpm warm is good. I'll try 550 and 500 as well hopefully.

I don't know which "Requested Torque" (A, B) map is the primary throttle control map, and this off the shelf tune already has adjustments so I'll try it first tomorrow. If I don't like it I'll make some changes when I figure out what table does what and reflash.

As for lean burn, here is my progress:
O2 sensor rescaled, AFRs adjusted to approximately where they were before:


Cells adjusted back to "14.7" so that the thing actually learns to run lean, plus small timing tweaks to make myself feel better:


To translate into actual AFR, multiply by 1.099 The 13.34 cells are just barely leaner than stoichiometric, and because of rounding errors the rest of the cells are also leaner by a tiny bit, since you can only add fuel in 1/128 increments (to lambda).

Doing the cams will be a challenge because I'll have to log manifold pressure with different cam settings to determine if anything would help.


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