I also reread the whole post and came to some conclusions. Premium has more light ends which heat up or burn faster which heats up the back ends (gases) to burn instead of exploding like in a diesel, which means a more complete burn of the fuel using less gas because of no knock.

 

I've seen those graphs. Thanks.

Interesting. Which OBD2 logger?



The below is more a note to myself but feel free to correct.

It sounds like the two lookup tables for (max) ignition advance--one for low octane (90 RON) and one for high octane (100 RON)--are modified dynamically during engine-on (ignition=on edge) using a single temporary value between 0 and 255.

The microcontroller could either generate a third temporary table for each trip (after each KeyStart vs. KeyStar) [unlikely], ignores maps and focuses on actual knock [unlikely], or a single value max advance for trip [likely] with a history of past values and feedback loop [more likely]. Ignoring maps and only using actual knock is unlikely if the low octane map is considered a "zero" value (0, 0x00), and the high octane maps is considered the "max" value (255, 0xFF). There is little reason to describe the ignition maps as a min and max if the range isn't used, especially since using values between 0 and 255 allow finer control. A temporary map would use up too much resources (RAM). So a single temporary register value could be used to hold the octane or knock adjustment. A more complex control would have more feedback from past values.

So during each trip or KeyStart changes from 0 to 1, max_advance_as_a_function_of_octane is set to the the max octane value or 255. If knock is detected, then look at the max advance at the specific MAP value where knock was detected. Adjust the max_advance_as_a_function_of_octane down from 255 by some value like small amount (like 4, 8, 16, or 32) depending on knock severity, add more fuel to cover for knock event, and then idle while waiting for next knock event or adjust max_advance_as_a_function_of_octane back up if no knock detected for some time t, etc or whatever feedback loop is desirable.

 

I am still watching fuel trims, I watched the 02 volts and mpg next to each other and nothing I could say coincide with mpg. Load and air has more to with fuel usage along with timing.

On the way home my fuel trim -5.5 LT and -15 short term. Mpg is way up but nothing to say this is why.

DSM your car does look good.

 

Mkchiu, I will let DSM answer that but it looks right. Just adding that there is a Random access memory that stores fuel,timing and other perimeters for faster look up. If you run regular then a tank of premium it takes time for the timing to go full advance because it does not know if the ecu is temporarily seeing those settings. For example max timing at full throttle 20 degrees for regular but see no knock it will add .5-1.0 degree each time it see those conditions up to 26 for premium. Its doesn't add 6 degrees right away in case there is knock. It goes in steps and the same goes for fuel leaning.

There is at least 2 maps for fuel, timing and then there is corrections features that add of subtract fuel,timing. Look at the flash pro help and it what the ecu does.

 

I am under the impression octane is a measure of knock sensitivity or knock resistance.

That is, a higher compression ratio is required before a high(er) octane mixtures knocks, when compared to a low(er) octane mixture under the same conditions. Or higher octane allows higher compression since it does not uncontrollably and spontaneously ignite before the spark reaches it, which results in odd pressure waves or sound / knock.

Although more complex molecules with multiple carbon-to-carbon bonds, rings, etc tend to be more knock resistant than simple straight carbon chains (with the same number of carbons), simple low-weight low-carbon-count molecules have higher knock values than longer heavier strands of carbon molecules. So light (weight) molecules could be considered premium or higher octane.

I meant I don't expect there to be much more RAM for entire temporary tables used as scratch pads (as adjusts for the factory or base tables).Based on what DSM mentioned, the ECU doesn't care what is in the tank, and adjusts down from max_octane / 100RON on every KeyStar(t) event or engine=on vs. adjusting up from min_octane / 90RON (or the last value when turning engine off) as you mention.

I'm somewhat familiar with the other tables. Although I don't really remember much besides air mass a la Volumetric Efficiency, and max timing at VE & RPM.

 

Regular has more heavy ends like in diesel that when the pressure heats it up it explodes like in a diesel. It can be caused by compression or to much timing. Higher octane resists compression knock by heating heavy ends past knock and allowing more timing to run in MBT the timing the manufacture made the car to run. Here is properties of gasolines http://www.energylab.com/pdf-docs/fi...ingerprint.pdf


As far as the ecu its as complex as Microsoft XP 32 bit processor system Hondata ECU Performance - Tech Review - Turbo Magazine
There was a article that explained it better from turbo magazine but its too old and cant find it.

 

I was trying to describe the structure of the molecules without talking about the structures.

4.13 of the gasoline FAQ describes some of the types and weights of the compounds in regular, and premium.
Gasoline FAQ - Part 2 of 4

Internal Combustion Engine Fundamentals, 1998, John Heywood shows some of the complexities or variances introduced by multiple bonds, cyclical ring structures, and aromatics.


Your link to the "fingerprints" is surprising. I didn't expect anyone to publish gas chromatograms of so many different fuel samples. Between the regular (0% evaporated) and premium there are noticeable (increases) in the benzene (C6) spikes around 3 min, what could be toluene (C7) spike at 4.5 min. Likewise the increased percent (mass) bar chart for premium at C6-C7 agrees. I'm not familiar with how aromatics and cyclical structures look like at such high carbon counts as the diesel (#2), but wikipedia's link (Diesel fuel - Wikipedia, the free encyclopedia to the toxicological portion of fuels http://www.atsdr.cdc.gov/toxprofiles/tp75-c3.pdf) indicates around 75% are saturated alkanes / paraffins which don't have double bonds.

So it is not the heavy ends or long chain compounds which allow or disallow heating past knock. (Low octane) diesel is composed of long chains or heavy ends which knock more easily than the short ends found in higher octane regular and premium. Also, premium further improves octane over regular by adding more complex carbon compounds like aromatics which are more knock resistant than even short ends.



The turbo mag article doesn't say anything that would imply a 32-bit microcontroller would be needed for an OE design. A high performance aftermarket control design like hondata might want more clock performance and resolution for finely manage the engine at extremes and to reinterpret OE engine inputs. However, I don't see why OE manufacturers would use a more complex and more expensive MCU when it doesn't appear needed.

From what I understand, Renesas/NEC has 80+% of the automotive microcontroller market. They currently offer both 8 and 32-bit MCUs, but the older (8-bit) models are the most likely to be in current basic ECU products such as are likely found in the Fit/Jazz/City/Aria/etc. (An 8-bit number can have a value from 0 to 255.) Although it's possible to divide a design to operate on 4x 8-bit pieces of a 32-bit architecture, that would be odd at the firmware level which MCU programmers operate at. That kind of thinking is more common at the driver or chip architecture level.
Gasoline Engine, Diesel Engine, Transmission Control | Renesas Electronics America
SH7050 Series | Renesas Electronics America

When looking the hondata cell counts and estimating the size of each table/map, it doesn't seem likely many temporary tables are used. Although the OE tables could be smaller, smaller tables generally negates the need for a 32-bit engine MCU.

 

Thanks for giving me something to think about. There is more alyklates in premium like whats in aviation fuel. Alkylation - Wikipedia, the free encyclopedia. So basically premium is regular with 30 percent aviation fuel and the use of ethers and/or Butanol at least in BP case.


The Honda ecu is a can29 bit processor made by Hitachi. In 2007 Honda made the switch from Keihin processor manufacturers from OKI Semiconductors.

 

i dont know, but when i use shell gasoline i can feel that the car's engine is running " SM00THER". Before i use chevron.

i put in 87 octane

 

Try their premium for three of four tank fulls. You will not only feel the smoothness, but a bit more peppy as well.

 

I run 111 leaded and 93 unleaded. The ecu is able to 'detect' the change in octane as soon as I do 3-5 WOT runs. It remembers the last highest achievable timing between restarts. I can see it detects by periodicaly trying to advance the timing to the highest sustainable level. It also seems to be able to distinguish different rpm bands for advance purposes. If it advances and detects the slightest sign of knock, either through the knock sensor or ckp (knock affects the speed of the crankshaft inbetween pulses detectably, much like a misfire) it will then reduce timing. You can watch it keep pulling timing all the way down to 14 degrees before tdc. If it still continues to knock at 14 degrees, the ecu will initiate what I call a 'soft shutdown' Spark is cut and Fuel is cut until engine speed falls to idle and the ignition circuit is reset. The knock sensing abilities of this ecu have to be pretty damn incredible to keep periodicaly trying to make it knock on purpose! It seems to check for the potential to advance timing once every 3-5 wot pulls. It will more than happily pull timing on the other hand at any time.

 

The ECU wouldn't work like that if Honda had intended for these cars to operate on 87 octane fuel.... The only reason it would be set up like it is would be to make the most power and efficiency as the higher octane fuel will allow it to... If the damned cars were meant to run on regular the stock engines burning premium wouldn't advance the ignition timing to as high as 50 degrees or boosted engines into the mid to upper 40s with octane booster and 93 octane gas.. I guess they have to say that the GEs are recommended to run on 87 octane to please some people but my manual in the glove box warns to use gasoline with an octane rating any lower than 87 or your engine will be damaged and even running boost and using it a lot along with the highest octane we can get the things are like little scalded ass gazelles blowing cars at are sold as performance cars of into the weeds still getting decent fuel mileage and staying together.

 

The ckp part is still speculation but for the longest time I couldn't figure out why the ecu was able to pull timing when no signal was coming from the knock sensor. When I got into the dynamics of how missfire detection works on the ckp sensor I quickly realized the CKP would detect mild knock before even the knock sensor. With sufficent R&D a ckp sensor could distinquish between mild knock and missfire (a normal stroke would show linear acceleration, a missfire would shown linear deceleration, while knock would show chaotic acceleration). I wish there was a way to verify my theory.

 

The 96 NorthStar engine was set to rum premium but would adjust to regular.
It opened the door to reducing the constantly rising cost of fuel for many drivers to save a bit by dropping down a grade or two.
GM didn't plan it that way, it just worked out like that.

Those guys who really paid attention claimed a drop in performance.

You keep hearing people [published comments] insisting that running premium in an engine that runs on regular is a waste.
That concept is rapidly becoming as old school as the 3K oil change.

I'm convinced Coyote has hit it again and Lyon is smacking it square. Knowing where the crank is in relation to everything else that's going on is critical to ECU control over how that engine performs.
Back in the days well before electronic ignitions were even thought of all we used to be able to do was gap the points and twist the distributor.
Now the smart-ass engine figures it all out on the fly and adjusts most all the variables as needed for a programed result.

Nice thing is that my FIT can understand when it gets fed premium and performance does respond.

 

Here is the new processor for Honda motors http://www.datasheetcatalog.org/data...or/mXwuttq.pdf . Hope you have time to read 900 pages but this is the brain for the ecu. I found this from this link and researched it. I understand its a Acura but its the same CAN29 bit process. The modules and actuators might be different but this is the brain I think. This should answer some questions.

 

Good find werewolf killer.

 

After a quick look at the wikipedia alkylation and avgas pages, I think there are too many types of avgas to say premium is regular + etc.

I can agree with alkylation into iso-alkanes since adding alkanes or alkyl-groups to alkenes / olefins provide more knock resistance, as is iso-groups. The critical compression chart shows the same.

I'm not sure why butanol would be used as an octane boost. Maybe as a politically correct concession to people against wasting food-grain to make ethanol-gas... Butanol's wikipedia AKI octane is low 87=(96+78)/2 vs. ethanol's 98=(107+89)/2. Maybe BP tacks butanol onto an olefin to make a some butyl ether...

Ethers are possible, although I think they're used more more their oxygen content (to reduce emissions for EPA) since they have lower RON & MON than higher (octane boosting) compounds. See gas faq 4.13 for octane boosting aromatics with RONs of 98 to 170 vs. MTBE(ther), ETBE, and TAME of 111 to 118. There's a balance between engine deposits, engine performance, emissions, etc so premium could be higher in ether content today than in say 2005. However, I suspect ethanol is a larger part of the modern octane boosting package vs. ether. Ethanol is already 98 octane so I imagine oil companies thinking, why use so much complex dirty emitting octane-boosting aromatics when the EPA is mandating a cheaper oxygenate (ethanol) than MTBE.



I'll look into Keihin & OKI, thanks.

OKI's auto product line looks like it was discontinued or phased out, possibly after being bought by Rohm.

In 2003, Keihin was planning on making "injectors, compressors, and other products for the Honda Fit". I suppose it's reasonable to expect Honda still uses Keihin ECUs since they still have a likely controlling 41.33% interest in the company.
www.keihin-corp.co.jp/english/ir/ar03.pdf
www.keihin-corp.co.jp/english/ir/ar10.pdf

Keihin's 2009 sales of 3.5 B$ pales compared to Renesas's 2010 sales of 11.6B$ (MCUs used in ECUs, etc). The 2.7 B$ sales in 2010 looks bad.

I went back to the J2534 reflash thread confirming the Keihin.
https://www.fitfreak.net/forums/2nd-...tml#post744526

Now details...

I thought it was either EPA / SAE and marketing. Thou shalt market what thou tests with, and recommending (requiring) premium on an economy car is a hard sell for most consumers.

Not that I mind having probably better torque at the tires when running a Fit on premium. And maybe the Fit 1.5L is much closer to a Mini 1.6 non-turbo when both are run on premium.

SH7055. Funny. Renesas took over Hitachi's semi in 2003. The Renesas link I provided mentioned the SH7055 but didn't focus on it. Considering the age of the Hitachi datasheet (2000) it's highly likely it or a modern low cost version of the SH7055 is used in the Fit, etc. No reason to change the code if the design works.

32 bit/cell value * 200 cells/map = 800 byte/map. It could conceivably load all engine maps into the 32KB of RAM from 512KB ROM. Although the ROM limits efficiency of movement by only having 8x 4KB blocks.

Yes, it's CAN2.0B.

I don't know anyone who has time to read all of a datasheet. It's go in and find what you need for the current project task and move on.

 

87 all the way!! Anything else is just a waste of money!

 

 

I even use premium in my lawn equipment... I have an Echo chainsaw that has to be over 30 years old and 16 year old Husqvarna chain saw and commercial grade weed eater that crank up with ease every time and have never had a the plugs changed.