2003 Honda Accord...250 Horsepower?
08-05-2002, 08:15 AM
#41
Suzuka Master
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When I re-read all of this I can't fully identify what we are debating. Yes, cars can loose power by running lower than recommended octane; the ECU can/will dial back timing. My old GTP would pull back 10+ degrees in some cases (a 3.0 Inch pulley on the blower with no added fuel can certainly induce knock).
But I do find it hard to believe that a conservative company such as Honda would rate a car at a lower HP knowing that it was truly optimized for a higher grade fuel.
I also understand you were speculating and I made an assumption about the Honda using a convention spark control method. I based this on what our cars have, a basic piezo knock sensor which does as it is named, determine knock. The ECU then calculates the severity on places this in a value labeled Knock Counts (the Knock Counts is not an OBDII mandate but it is incorporated into the standard definitions). If the new Accord has something different then until we see it we can only guess at its capability.
Will the new Accord use a ignition trim table?? That is a good possibility; many cars today have trim tables. My wife's E46 328i has had that since '99 and is intended to allow for lower grade fuel to be run when/if needed without constantly varying the timing dramatically. I was kind of surprised to learn that our cars don't have a trim table for ignition. But in the case of my wife's car, they still rated the HP based on running premium and indicate that lower grades can be used but performance and mileage could suffer.
Oh, about real-time control. I find this statement to be about perspective. In some control systems we have worked on, we had 1 kHz PID loops running for pressure control and most people would feel this is real-time. But a lot can happen in 1 millisecond...
But I do find it hard to believe that a conservative company such as Honda would rate a car at a lower HP knowing that it was truly optimized for a higher grade fuel.
I also understand you were speculating and I made an assumption about the Honda using a convention spark control method. I based this on what our cars have, a basic piezo knock sensor which does as it is named, determine knock. The ECU then calculates the severity on places this in a value labeled Knock Counts (the Knock Counts is not an OBDII mandate but it is incorporated into the standard definitions). If the new Accord has something different then until we see it we can only guess at its capability.
Will the new Accord use a ignition trim table?? That is a good possibility; many cars today have trim tables. My wife's E46 328i has had that since '99 and is intended to allow for lower grade fuel to be run when/if needed without constantly varying the timing dramatically. I was kind of surprised to learn that our cars don't have a trim table for ignition. But in the case of my wife's car, they still rated the HP based on running premium and indicate that lower grades can be used but performance and mileage could suffer.
Oh, about real-time control. I find this statement to be about perspective. In some control systems we have worked on, we had 1 kHz PID loops running for pressure control and most people would feel this is real-time. But a lot can happen in 1 millisecond...
08-05-2002, 07:41 PM
#42
Suzuka Master
Originally posted by scalbert
When I re-read all of this I can't fully identify what we are debating.
When I re-read all of this I can't fully identify what we are debating.
Yes, cars can loose power by running lower than recommended octane; the ECU can/will dial back timing. My old GTP would pull back 10+ degrees in some cases (a 3.0 Inch pulley on the blower with no added fuel can certainly induce knock).
But I do find it hard to believe that a conservative company such as Honda would rate a car at a lower HP knowing that it was truly optimized for a higher grade fuel.
As for some “anecdotal” info:
http://beta.vtec.net/articles/view-a...rticle_id=8542 (VTEC.net – some comments, tests, etc on the 2002 Civic SI.)
The part that makes me bias towards the lower fuel is this (hey, it’s inferential, but…)
EXCERPT (see the bold section near the end):
”… Not having a service manual, and looking at the 9.8:1 compression ratio, we assumed 89 octane gas would be fine. However, it appears the engine really likes premium (If you can call California's 91 octane "premium"). After refilling with premium we found a gain of more than 2 hp and 3 lbs-ft of torque. Not bad, but not quite as good as some of the 135-136 hp numbers we'd heard about for the new Civic's K20A3. However, a few hp variance is not unheard of. Note: The official specification calls for 87 Octane...."
The 87 Octane quote caught my eye along with their dyno and octane experiments. Proof – no? However, it does make me wonder. If they are really getting 2 more ponies and 3 lb-ft of torque by switching from 87- to 91-octane, then a little extrapolation might make this “possible” by scaling-up to the 240 number on the Accord. (Not a perfect fit, but…)
I also understand you were speculating and I made an assumption about the Honda using a convention spark control method. I based this on what our cars have, a basic piezo knock sensor which does as it is named, determine knock. The ECU then calculates the severity on places this in a value labeled Knock Counts (the Knock Counts is not an OBDII mandate but it is incorporated into the standard definitions). If the new Accord has something different then until we see it we can only guess at its capability.
IMO, I think you might find the detection of torque, pressure, and other information interesting – check the last listing in the posting above. There is some “compelling” research for using spark plugs to alter ignition timing (depending on humidity, octane, etc). IMO, there are some tasty morsels in there. There is one section where they turn on the “ion sensing” with “water injection” and the results are interesting…
http://www.fs.isy.liu.se/Publication...PhD_580_LE.pdf
Will the new Accord use a ignition trim table?? That is a good possibility; many cars today have trim tables. My wife's E46 328i has had that since '99 and is intended to allow for lower grade fuel to be run when/if needed without constantly varying the timing dramatically. I was kind of surprised to learn that our cars don't have a trim table for ignition. But in the case of my wife's car, they still rated the HP based on running premium and indicate that lower grades can be used but performance and mileage could suffer.
Oh, about real-time control. I find this statement to be about perspective. In some control systems we have worked on, we had 1 kHz PID loops running for pressure control and most people would feel this is real-time. But a lot can happen in 1 millisecond...
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