Pappy

USA Today quotes a Honda engineer as saying that the new Accord V6 with 240 horsepower would increase to 250 horsepower and 10 extra lbs. ft. of torque when premium gas is used. I believe the article was in todays paper (8-2-02). What do you think they're going to do for Acura in 2004?

jimcol711

that sounds like a load of shit...just using premium gas?? 87 vs 91 octane?? thats 4 octane points = 10 hp and 10 ft lbs of torque?? thats bullshit, in that case, how about we put fucking 110 RACE GAS in our CL-S...would that give us an extra 30 hp????? jesus....

Pappy

That's the quote from the Honda Engineer.

Slimey

I thought that engines (with their computers) are tuned to use certain grades of fuel and that increasing the octane does nothing for increasing performance - just decreasing knock if there is any.

Any engineers out there to clarify?

hornyleprechaun

I'm no engineer...but i've heard the exact same thing you just said..

CL'S

bone_stock

That depends on the car. My supercharged T-Bird has a sensor that detects octane. If you run 89 octane or lower you only get 8 lbs of supercharger boost. If you ran 91 or higher octane you get 12 lbs of boost. Furthermore, my old SVO mustang had the same capability on a rocker switch.

EricL

From my 6+ tests, the CLS wants more than 91-octane in 70-degree F weather... (Ok, so what does this have to do with anything?)

Is the gas just better? (Who knows what fractions are changed that are not directly related to octane... And, how much can a “reactive” system [knock sensor] do for ignition advance?)

The car’s computer certainly knows WHEN the knock sensor returns a "signal" (in crank-degrees @ rev @ TP (throttle position)). It can certainly use this signal as an "octane" indicator, and "move" the baseline ignition curves. There is no reason, that I can think of, for not using a pre-existing signal to "gather" more performance. It would not be hard to look at a gas cap open/closed signal as a "sentinel" to "relocate"/"move" an ignition timing table or three to optimize the car's power, economy, and emissions by using a pre-existing sensor (the knock sensor). In lieu of simply "winding" back the spark based on "knock signals", it wouldn't be too difficult to use the "trend" to "detect" gas quality as well, and adjust parameters for the current gas load accordingly.

$0.02

Pappy

I'll read that again when I'm sober.

Slimey

So maybe I need a little more gasoline edumacation...

Does increasing your octane increase performance? As I said before, I was under the impression that the engine is tuned for a specific gasoline grade and changing the grade will do nothing to performance (HP/Torque/etc).

Maybe a better question is: What determines the octane grade of gasoline that we use in this car? or: Why does the CL-S require premium gasoline and a Camry (for instance) reqire regular?

Pappy

I'm no engineer, but I think it's the compression ratio that determines what grade of gas you use. In the old days (I'm 55) you could get more performance out of your car by increasing the octane rating. The kids who were dragging their muscle cars back in the 60's would use 105. I think Sunoco had it. Anyway, it sure did give a boot in the ass. Times are different now, so I don't know if it still the case or the extra octane is wasted.

EricS

Yeah, in simple terms: not meeting octane requirements will cause knocking (detonation) in which the ECU will then retard the timing, thus reducing power output.

Anything over the recommended octane ratings will not magically gain you any power. But if you use below recommended you can reduce power.

Taken from: http://www.faqs.org/faqs/autos/gasoline-faq/part1/

6.13 Can higher octane fuels give me more power?

On modern engines with sophisticated engine management systems, the engine
can operate efficiently on fuels of a wider range of octane rating, but there
remains an optimum octane for the engine under specific driving conditions.
Older cars without such systems are more restricted in their choice of fuel,
as the engine can not automatically adjust to accommodate lower octane fuel.
Because knock is so destructive, owners of older cars must use fuel that will
not knock under the most demanding conditions they encounter, and must
continue to use that fuel, even if they only occasionally require the octane.

If you are already using the proper octane fuel, you will not obtain more
power from higher octane fuels. The engine will be already operating at
optimum settings, and a higher octane should have no effect on the management
system. Your driveability and fuel economy will remain the same. The higher
octane fuel costs more, so you are just throwing money away. If you are
already using a fuel with an octane rating slightly below the optimum, then
using a higher octane fuel will cause the engine management system to move to
the optimum settings, possibly resulting in both increased power and improved
fuel economy. You may be able to change octanes between seasons ( reduce
octane in winter ) to obtain the most cost-effective fuel without loss of
driveability.

Once you have identified the fuel that keeps the engine at optimum settings,
there is no advantage in moving to an even higher octane fuel. The
manufacturer's recommendation is conservative, so you may be able to
carefully reduce the fuel octane. The penalty for getting it badly wrong,
and not realising that you have, could be expensive engine damage.

Slimey

Thanks - but your answers brings us back to the subject of the thread - how can putting 91 - 93 octane gas in the Accord push the HP up by 10. As jimcol711 said - why don't we just put race fuel or airplane fuel in our cars? If it increased performance wouldn't that be a 'cheap' mod (at least for one tank)?

IntegraVT

iTrader: (1)

Here's the link to the USA Today article.

http://www.usatoday.com/money/autos/...1-accord_x.htm

If you just want the quote, I'll save you guys the trouble.

"The Accord V-6 ratings assume regular-grade fuel, and Honda will market it as a regular-fuel engine. But — pssst — it's good for another 10 hp and 10-plus lbs.-ft. on premium, acknowledges V-6 engineer Asaki."

EricL

Something for the third six pack:

http://www.autoshop101.com/forms/h59.pdf


AND for the forth six pack:

A 2002 Lexus ES 300 spec list

Estimated EPA Mileage Ratings (mpg)
City 20
Highway 29
Recommended Fuel 87 Octane Unleaded (91 Octane Premium Unleaded for improved perf.)
Tank Capacity (liters/gal.) 70 L / 18.5 gal.

AND

The bottom line -- just using "better" gas will allow the knock sensors to adjust the timing for more power...

And finally -- an instructive experiment:

http://www.installuniversity.com/ins...m_8.012000.htm

EricS

Because, from the link IntegraVT posted, it's being marketed for use with regular unleaded gasoline. This way telling the consumer he can use the cheap gas with no ill affects. (This car sells well because of its affordability.) The ECU will notice the knock, and retard the timing. But if you run on the premium gas it will adjust the fuel map to the optimum settings giving you more power.

Was the CLS marketed as having to use premium gas, but optimally runs on race gas? I doubt it, but someone get on a dyno with premium pump gas and then with race gas....

Slimey

Ah ha! Now I get it.

Pappy

No one has addressed the 2nd part of the question. What do you think Acura will do for us in the 2004 model year? This will be very interesting.

EricL

1. Swirl has a large impact on combustion and octane requirements. Modern engines are basically stratified charge (AKA lean burn) engines. They get a rich plume of fuel-air swirling that gets diffused as it gets burned. The net effect is: the mixture is rich enough in the region near the ignition source (spark plug tip) and gets it burning (really well). Once the fuel is burning, the idea is to get the flame front to move fast enough to produce maximum power, but not too fast. AS a note, there are various notes that relate flame propagation time to octane, and this is not always correct.

2. The old engines in the ’70 muscle cars did not have the advantage of CAD/CAM/CAE computers, exotic combustion modeling tools, didn't have very sophisticated real-time tools and models to refine combustion chamber and port design, and did not have a full suite of electronic sensors and a super atomized fuel spray sitting right at each and every port.. The fuel mix – in most of the carbureted muscle cars (single carb. Per barrel Webber’s excepted) -- was terrible at best (you would think it was good, but being within a few percent is nothing to brag about). Current engines have enough computing power to adjust the timing, fuel-mix, and other parameters to assure that each cylinder can make optimum power without concern for the fuel quality (well, there are limits).

There is a point were an increase in octane will NOT increase power output. However, if an engine timing is being rolled-back by its knock sensors (they even have dual sensor, and so on) to compensate for high-temperatures, high-pressure, or other factors that cause an engine to increase its need for octane, it can (and will) retard the timing and in general, this will reduce power output. Most cars are designed for octane that is a bit higher that most pump gas (You don’t think that all of the gas stations out there supply octane that meets the pump label – hey?)

Some people think that there is only a cycle-by-cycle retard action that only allows for timing retard up to a given maximum. However, with the wild variety of fuels currently available in different regions, a more "adaptive" approach is required. It would be foolish to limit peak power output if fuel is available to provide additional economy from the higher advance that can accompany higher-octane fuel.

Finally, with California’s adoption of CO2 standards, plan on seeing even more cars with multi-fuel/octane requirements.

Pappy

Hey EricL...What do you do for a living?

scalbert

If the car is rated at 240 HP on a certain grade of fuel, say 89 Octane, by increasing the octane will not yield more power. In fact you can loose power.

However, if the engine has problems where knock is detected the ECU will back off timing reducing power and adding a high Octane fuel will help reduce deto and bring the timing back. But you really end up at or just below the spec power output, not above.

The higher the octane the lower the BTU content which correlates to the power potential of the fuel.

The only way this would be true in the Accord would be if Honda designed their engine with such a wide range of timing that when using 87 octane they will get, and expect, a certain amount of knock. Which after backing off the timing you end up with 240 HP. Now if you run premium the timing will be further advanced giving more power. But this seems absolutely ridiculous especially for Honda. Knowing knock will occur on the recommended fuel???

Pappy

I sure would like some of what that Honda engineer is drinking.

jts1207

they said the same thing when the Odyssey came out.......i forget the exact numbers but it was like a 5-10hp bump for premium gas

typeR

MMII comes to mind

EricL

I direct you to the present (not even the future):

Link: http://www.honda.ca/models/civic_sed...escription.asp

EXCERPT:

"1.7 Litre Engine (return)
For 2002, all Civic engines have been designed, with a 1.7 litre displacement. DX, DX-GOP* and LX engines produce more horsepower and torque than in previous generations, while Si engines provide increased torque. Civic Si models feature Honda's VTEC technology for greatly reduced emissions and higher fuel economy. Employing many refinements in the interest of cleaner combustion, VTEC technology is based on Honda's VTEC variable valve-timing system, which promotes efficient, lean combustion at mid- and high-swirl intake tract designed into the cylinder head. It creates a greater swirl effect in the combustion chamber, which improves combustion-chamber turbulence, resulting in more complete combustion, better mileage and lower emissions. A sophisticated knock-control ignition system is part of the electronic control module. It continually determines the octane rating of the fuel being used and then adjusts the ignition timing for optimum performance with that fuel. On Si models, an electronically controlled exhaust gas recirculation system helps to lower nitrogen oxide (NOx) emissions, and more precise fuel injection and air-fuel ratio control further clean up emissions. Many enhancements in these engines are focused on the reduction of internal friction. By applying proper surface treatments to high-friction areas, dramatic reductions were found. Honda uses a "micro-dimpling" process to create a microscopic texture on the piston skirts and top piston ring. Doing so minimizes the potential for metal-to-metal contact between the piston and cylinder wall, and also improves the oil film stability in these highly stressed locations. And VTEC engines (Si models) feature roller cam followers, which further reduce valve-train friction...."


IMO, the whole notion that an engine controller MUST wait to see the KNOCK and then retard the timing, on each and every cycle, is outdated. There are a number of pre-existing strategies that allow a "trend" to be developed -- and this allows a less than optimal compression to be "available" for the 87-octane fuel, but it in NO way dictates that a knock must be detected on a cycle-by-cycle basis.

Look, the current systems are smart enough to figure out how to control fuel-air with a arguably slow 02 sensor (real-time – I don’t think so). As you have pointed out before -- the purpose of the short-term fuel trim (STFT) and long-term fuel trim (LTFT) tables are to "bring" the car's fuel-air mix into line with the narrow band required from the 02 sensor. If the car had to bounce off the reading of the O2 sensor, we would all be riding bikes.

I don't see why the notion of a "sentinel" and continuous and/or adaptive control (as used in the case of the fuel-air system and fuel tables) cannot be applied in an analogous fashion to the knock sensor (as closed loop sensor) and thus having the ability to "remap" the timing curve for the "current" batch of fuel. IMO, it would be stupid to NOT adopt the strategy as currently used in the 2002 Civic (see above). IMO, timing “re-map” would make “knock detection events” the exception rather than the rule (this after the new map had been established and/or loaded).

Example: A driver (who was using 91-octane) switches to some cruddy 87-octane camel piss. The car’s computer senses knock event corresponding to various points in’s 3-D map. Each time a "knock" is detected within a "expected" knock zone, it is "marked" as a KNOCK_FOUND event. It is logged for the current TB/MAP/Temp 3D map setting and the "current ignition" timing map is "altered" (by decrementing the advance value) or "moved" to a "I've-got-cheapo-gas map (either will do). Once the CPU has "adapted", the knock events should be "exceptional" events (not the rule). When the user tanks-up with some 91-octane (or higher), the computer can restart the test. (I don't know too many people that fill-up gas while moving, so it is quite easy to have a "sentinel" in the form of a ignition on or gas flap open/gas flap close cycle to "trigger" or "force" a ignition map recalibration. This would make for a brief “adaptive” or “adjustment” period in lieu of your “knock killer strategy” (as used in most older OBDII vehicles).



Finally, I hope that there isn't any confusion regarding octane vs. BTU content -- the two are not related.

None of this is "new" stuff -- it's just old stuff with a twist. Dual/Multi-fuel vehicles have been around and running fine for quite a while. Example LPG/Petrol & Methanol/Petrol, and so on...

scalbert

The BTU value is definitely correlated to the power output when based on the manufactures claims. Octane is simply the fuels ability to resist detonation and/or preignition. Whereas, BTU is the energy value of the fuel which is an expression of the potential energy. Increase the octane, this slows the burn and reduces the BTU content.

Currently the knock sensors are piezo sensors which basically detect sounds (or vibrations or force, etc depends on the application). Based on the signal conditioning they can determine normal or abnormal combustion. In addition, the abnormalities can be used to determine the severity. This is expressed in Knock Counts in the ECU. These Knock Counts can determine a fuel quality or an engine issue but are not specific. But it will result in reduced timing advance or rather KR (Knock Retard). In the end there is reduced power. But these abnormal detections are pre-ignition, albeit small but still mild detonation. Even though you don't hear it is still detonation. But the manufacturers claim it is just octane monitoring.

Now if Honda is making an engine that can provide greater power at a higher octane I would suspect the EPA and the other FEDs would mandate they state that the engine requires that grade of fuel... This is how all other engines sold work. Try putting a Z06 on 87 octane and see if it puts out 405 HP...

As for engine really determining true octane levels, it is getting closer but not in full production. We are working with a company, and there are others, to produce reliable in-cylinder pressure sensors which could determine octane levels to a point even before there is mild detonation. This is when there can be true octane monitoring or at least monitoring before pre-ignition occurs.

BTW, nothing copied and pated in here...

scalbert

In addition, there is no control system in the world, whether that is a nuclear power plant temperature control, that doesn't look to some sort of feedback to base a reaction decision. As quoted "IMO, the whole notion that an engine controller MUST wait to see the KNOCK and then retard the timing, on each and every cycle, is outdated. There are a number of pre-existing strategies that allow a 'trend' to be developed". A trend is developed based on the output from monitoring devices. If you are referring to calculated control limits then yes, this is being done. But this is still based on the reaction to live inputs such as the current knock sensor which is, in essence a sound sensor and detects deto after it has already occurred in a small amount. So it is not pre-emptive such as fuel control.

If a rich/lean condition occurs it is corrected without any issue (within limits). But knock control is different. If the engine hears knock, which it does well before we do, if backs off timing to eliminate it. But the small amount of damage has already occurred.

Pappy

So...I guess it's the opinion of the majority that the Honda engineer is full of shit?

JagV12

The same way that the 6th gen Accord V6 loses horsepower and torque with premium fuel according to the Car and Driver test. Its all about the ECU!!

EricL

I had a buddy with a Ford Bronco with a dual-use fuel system. It ran on LPG (liquefied petroleum gas) and/or premium pump gas (around 93 octane at the time). This is like dredging-up distant memories, but the car always had more push when it was running on LPG. (This was before there were electronic boxes controlling all the cars). As a side note, when the car ran on the LPG it got the best mileage, most power, and never fouled a plug. Granted the LPG was already in a gaseous state, and the droplet size of an atomized fuel has a large impact on how much energy can be extracted from a “liquid” fuel during combustion

So, it’s interesting to note the LPG has somewhere around 19,000 BTU/LB with an “equivalent” octane near 104, and the 93-octane gas was probably closer to 18,000- to 19,000 BTU/lb. So, if you want to just compare BTUs by weight (not volume), the LPG’s got around 10 more points of octane, with similar BTU/weight contents. (Sure, it takes more room to store it, but… I think I’ve made my point).

Ok, so perhaps this is just a lack of qualification and we can all think GAS, GAS, GAS for now until the pumps run dry… But, I content that the statement you promoted is again “true in general”, but without qualification is highly misleading.

Gas is composed of a witches-brew of petroleum fractions, additives and oxygen content; you can easily end up with a 100-octane gas with higher energy content the 91-octane available in California. (Hey, sorry I can only offer anecdotal evidence, but I’d hope a few people would keep an open mind about this and do a little experimenting .)

Hey, if had to “slurp” some of the 91-octane “eco” gas that is being sold around here (in California), you would know what I’m talking about from first hand experience. (The addition of “some” 100-octane, from 76, makes the car feel like its on “uppers”.)


I’ve been looking around at “interesting” fuel articles and keep running into similar commentaries (for-fun tests have a way of become less than fun at times):

ONE OF MANY LINKS: http://www.faqs.org/faqs/autos/gasol.../preamble.html

"The addition of additives such as alkyl lead and oxygenates can significantly affect the pre-flame reaction pathways. Antiknock additives work by interfering at different points in the pre-flame reactions, with the oxygenates retarding undesirable low temperature reactions, and the alkyl lead compounds react in the intermediate temperature region to deactivate the major undesirable chain branching sequence [21,22].
“The antiknock ability is related to the "autoignition temperature" of the hydrocarbons. Antiknock ability is _not_ substantially related to:-
1. The energy content of fuel, this should be obvious, as oxygenates have lower energy contents, but high octanes.
2. The flame speed of the conventionally ignited mixture, this should be evident from the similarities of the two reference hydrocarbons. Although flame speed does play a minor part, there are many other factors that are far more important. ( such as compression ratio, stoichiometry, combustion chamber shape, chemical structure of the fuel, presence of antiknock additives, number and position of spark plugs, turbulence etc.)
Flame speed does not correlate with octane.”




The main issue is the “post event” signaling. You seemed to have a tremendous dislike for using a “conventional” knock system to detect or control combustion timing.

From my own ruminations and talks with my “buddy”, there are some detonation signals that don’t get identified by the peizo sensors…

It is a method to detect octane by “indirect” means. A quick walk into quantum mechanics will quickly kill any infatuation with direct measurements. IMO, we are heading into uncertain times (as far as long term fuel sources go), and carmakers would be foolish to even consider developing an “octane” sensor for “conventional gasoline”. Even if someone did so, I’m not sure that it would be of much use, as compared to the less-than-perfect knock sensors in use today (regardless of number, configuration, and or signal processing and adaptive strategies).

There is a simple open-gas door and close-gas door sentinel that is available on the car, and I don’t have a clue why this couldn’t be used to “help” “formulate” the car’s timing map. If you look at our car, for example, we already have a signal that is available for use in detecting a “gas” change. If carmakers can use 3D maps, why not move to 4D/5D maps with the ever cheaper CPU, DSP, and memory that become available.

The direct pressure sensing you speak of is more direct and will probably correlate to some ignition timing vs. pressure curves, but once an detonation event happens, the conditions are altered, and one is back to using an inferred and/or adaptive strategy to get an optimal spark.



Well, check out the specs on the TL and CL. The TLS wants 92-octane and the CLS wants 91-octane. Interesting note: both cars are specified with 260HP… Hmmm… different/same/specs/???

Are you so sure that there aren’t many political, managerial, and other criteria being used to specify the output? What about just making this a “half-empty” vs. “half-full” proposition and state figures in a way that has a positive psychological effect on people.

What would Joe Average want to hear?. Hmmm… “Sorry, on 87-octane you will lose 10-HP. Or: “Put in some 91-octane and you’ll get a 10-HP boost….”

I could ramble on for days about what is correct and what I think and what I think the feds think, but what it the significance? Come on, our car is rated at 260HP, yet it puts out around 200-208HP on a Dynojet dyno (when equipped with an automatic transmission). Hmmm… it’s not like a number of “visitors” haven’t asked about this…

As for the Z06, they show-up at the Canyon station (with that yummy 100-octane) along with E46 M3s, Cobras, Ferraris, and other exotics. IMO, a Z06, on 87-octane, would still kick the shit out of 98% (or so) of street-legal vehicles. The more I look at various dynos, the more I wonder if were heading back into the 70s with HP and TQ rating being moved up and down for insurance, political, and other reasons…

Perhaps you can find more info, but my browsing and experience with low-emission vehicles (do not assume internal combustion) have shown the federal government much more interested in gas mileage and emission figures

Steve, I can tell that your very interested in sensors – it is your “thing”. However, even if you detect an overpressure that needs correcting, you still need a way to “determine” the optimal timing for a given setting. Considering that the very “event” creates its own “local” conditions (piston heating, valve heating, etc), the direct pressure measurement method that you are working with still has to “adapt” to find optimal timing. And isn’t that the goal? (Or tell me how and why I’m wrong… if you don’t mind)
.

Disclosures and disclaimer city – boy, what next?

God help anyone who has multiple interests…

scalbert

See Eric, this is why I like having these conversations with you, you don't take it personally... You truely realize, as opposed to others on this forum, that it is just a discussion.

But related to the above, the cylider pressure monitoring is not to determine over pressure, but to constantly monitor actions within the cylinder. This would allows for pre-emptive control similar to the current fuel control. Not a post active issue like the current knock control.

As for the rest, it is a very debatable issue and not solved until a scan tool or laptop is hooked up to the ECU to read the actual parameters. In our cars there is a direct knock sensor which controls timing. If no knock is 'heard' we get full timing...

I haven't detected any knock on the fuel I use...

Zapata

Wow these are the types of conversations that Einstein, Max Planc, Oppenhiemer must have had while sitting around the table.

EricL

The fact that the knock signal (and related DSP) gets its input (trace) on the previous "combustion cycle" is a line that you seem to be drawing (I understand that clearly – OK?).

As for cycle-by-cycle activity, if the control system takes an action at t-1 (where t is the time of the last combustion event, it's still operating in a cycle-by-cycle mode (what if a minor correction is input to see how severe the event was?). The basic fact that the "feedback" is delayed by a single cycle is of minimal importance -- in most time domain filtering and control systems, the operation is predicated on a delay.

And, the O2 sensor is sitting pretty far down stream, please don't tell me that it is getting a "real time" signal (or go ahead and move the line back and forth as much as you like -- this can get pretty silly and the next step will be to pull out all the DSP and control theory handbooks...)

Both systems ARE CONTROL SYSTEMS -- and the algorithms are different and varied from manufacturer to manufacturer.

I'm going to toss this out for the nth time --- the main point is the stupid gas-door sensor that is sitting on the car. We have it, and its cheap and it's easy to use.

Hey, if you want to run this off-line, we can get into how the very detonation event will alter the advance required and it goes without saying that some type of adaptive strategy, averaging, and/or feedback system is required.

What's the problem of adding one more strategy and/or “map” that uses the gas filler door open/gas filler door closed event to "differentiate" and enhance the ability to optimize or "find" a one of a many baseline maps?

From here, this becomes a communications issue, and if I haven't made my point, then so be it...

EricL

I would love to know more about the "constant/continuous pressure monitoring"...

AS to the 2nd -- you're so lucky you're out of California... CO2 limits coming....

Pappy

Ok guys, lets try to get to the bottom of this. This Monday I'll fax off a letter with a copy of the engineer's quote from USA Today to American Honda and let's see what they have to say about it.

JRock

Whatever, it's rated at 240hp and that's all that matters. Any other bullcrap about using Super grade vs Regular grade is a waste of time. Either way it's 10hp. Who cares.

scalbert

I do feel a hint of hostility??

The more control the better. I was basing things on what is currently OBDII mandated in ignition control. There might be a communication issue going on here. You seem to be speculating on what can be done, and I can be incorrect. I am trying to state what is currently used.

There is a difference between fuel mapping and ignition mapping. Fuel mapping uses a feedback loop to determine the control issue in, what I would term, moderate steps. Ignition uses larger steps, waiting for an issue to react.

No control system is real-time. But there are differences in the types of response signals. Fuel control can be trended, but current ignition control is reactionary based on event.

scalbert

As more information becomes available I will present it. But in-cylinder pressure monitoring is a big area in the engine development and should provide great improvements.

But as you could expect, it is hard to constantly measure pressure in a 1500+ F enviorment.

Pappy

The article about the 2003 Accord in this month's Motor Trend doesn't mention anything about any horsepower and torque gains by using premium fuel.

EricL

No, just a moderate dose of annoyance and exasperation…


1. More control – yes. I have no problem with that.
2. I don’t see where OBDII says, “you must use one, two, or n sensors” or “you must use the following control strategy” or so on…
3. I think I made it very clear that I was speculating – in an informed fashion -- on what is being done and what could be done. You say, “I am trying to state what is currently used” IMO, not speculating would mean having an in circuit emulator and/or proprietary information for every “engine controller” in use, being assembled, and/or being designed).
4. OK, just to be clear, are you saying that you “think” or “know”, from your experience, that each and every manufacturer from 1996 to today uses the exact same strategy and algorithm for controlling the spark advance based on a “knock” trace? And, then since we never specified “what” vehicle, does this mean that all cars (weather for race and/or road use the same exact system of control)? So, when you comment on how a timing system works – you seem to be saying that the OBDII standard dictates how timing control must be accomplished (hence, my comment about “communications” issues.).
5. Or, do you mean that you are very familiar with a particular system and that system controls timing in one way. I’ve talked to and read enough information to “gather” that there seems to be a variety of ways to “process” the knock signal…

.


1. There is “lag” (a delay) in both systems. And, the “prediction” is going to be less then perfect from a number of perspectives. The last sample from an O2 sensor is going to be delayed (I’ve already said this).

2. So, you differentiate the two systems by “step size”: “Moderate steps” for the fuel control, but “larger steps” for timing control.

3. I would be more interested in the timing knock event’s perturbing the current (and future) combustion chamber’s environment more than a “moderate” and/or small change in fuel injection pulse width. However, this is a matter of degree, and both systems are using “adaptive” strategies. In a controlled and static environment, the “predictability” is not going to be perfect in either case (notice I said perfect).

4. There is case that can be made for predictor-corrector modeling and feed forward control systems.

As for “no control system is real-time”… Well, here comes communication again. Over and over people use the following phrase is help wanted ads: “Looking for expert with experience in ‘real-time” OS and control systems….” If you are referring to relativistic considerations that there is always going to be a small time lag – sure (On the other hand, Bell and Bohm might disagree )

“Fuel control can be trended, but current ignition control is reactionary based on event”

Steve, when I look at this, the whole issue seems so arbitrary.

EricL

The following is an excpert from the C&D article on what good is higher octane titled --> "Regular or Premium?"

LINK to C&D article:

http://www.caranddriver.com/xp/Caran...ne.xml?&page=1


"The results were more dramatic with the test cars that require premium fuel. The turbocharged Saab's sophisticated Trionic engine-control system dialed the power back 9.8 percent on regular gas, and performance dropped 10.1 percent at the track. Burning regular in our BMW M3 diminished track performance by 6.6 percent, but neither the BMW nor the Saab suffered any drivability problems while burning regular unleaded fuel...."

So, a little walk through the web turns up some interesting tidbits on that are varying interest about getting (and predicting) accurate spark advance data…

Spark-Advance Control by Ion-Sensing and Interpretation


Spark Advance Control by Interpretation of Ionization Currents

Signal Interpretation and Control in Combustion Engines


(VERY LONG)

Spark Advance Modeling and Control


EXCERPT REFERING TO THE SAAB "TRIONIC" SYSTEM:

AND LINK: http://www.saabnet.com/tsn/models/1999/9995pr5.html

"...The microprocessor is programmed with complex algorithms and theoretical models of the engine to be able to monitor and simultaneously control the Direct Ignition timing, fuel injection rate and intake air flow. Saab's Trionic engine management control system is capable of adapting to always optimize engine performance based on driver demands and the quality of fuel being used.... "