Effects of timing retard

[Gary Allan]

Quote:
If it were dilution then it should work the same way when I start using premium again - i.e. a slow come back.


Not if you were routinely filling up at 1/2 full ..but got so annoyed with the decay that you said "DARN IT - I'M GETTING ALL OF THIS X(*#@$ out of HERE!!" and made sure it was close to empty

Now we know that this isn't the case.

Sounds almost like a short term fuel trim reaction broadening into the longer term adaptives. That is, you end up inputing more TPS, lower MAP, blablabla under the same usage ..and the PCM adapts accordingly.

That wouldn't explain the quick return, though

 

[mechtech2]

Knock sensors retard a lot for a very short time.
No codes should be thrown for a disconnected one.
Honda may have shown an improvement with a new knock sensor design because they were the worst to begin with.
Honda tuners online have discovered this years ago.
BTW, Ford had service bulletins that recommended unplugging the knock sensor for certain complaints. This was done at dealerships on some cars, so it is not a far out totally unsafe thing to do.
[If you get your fuel in foreign countries of questionable grade, then leave it in.]

 

[BuickGN]

Originally Posted By: youdontwannaknow
Originally Posted By: BuickGN
I think it would be safe to assume any car puts the timing back in after a second or so of no knock.


I'd imagine the same too, but my experience with the Acura (mdx) has been different. When I switch to low octane fuel, it pretends as if nothing happened - for about half to full tank of gas, you wont feel any loss of power or mileage. But by 2 or 3 tanks it has degraded slowly to a point where I can easily tell. Then as soon as I switch to high octane again, in about 10 miles or so, it's as if it sprung back to life! The difference is very noticeable, and that too almost immediately.

Just trying to figure out why it does what it does....



I quit trying to figure it out. My TL requires 96-97 octane to not ping. It's actually more expensive to run than my Buick that sees 100LL for street use. I'm actually starting to hate this car. The dealer says nothing is wrong, yet I can hear the pinging, see it on the scan tool, and it goes away with high octane.

 

[ikeepmychevytoo]

Less native advance specification for the station wagon version on my GM HEI. (12btdc vs. 7btdc if I'm not mistaking.) I also can't comprehend this.

 

[youdontwannaknow]

Originally Posted By: eljefino
Recently though honda was bragging about squeezing a few more HP from some accord, due to an improved knock sensor.


eljefino,
can you confirm the source of this information ? I can't seem to find anything. Where did you hear about this ?

 

[RD400]

Originally Posted By: mechtech2
Knock sensors retard a lot for a very short time.
No codes should be thrown for a disconnected one.


On my '96 A32 Nissan Maxima, it records a code but that does not light the CEL. You can feel surging during acceleration when the piezo knock sensor is adjusting.

If the sensor fails, the ECM thinks detonation is occurring and defaults to a retarded ignition setting. Some guys have removed it (which then necessitates premium fuel) and replaced it with about 550K resistor because they are prone to failure and cost around $150.

 

[mechtech2]

The computer does not default to a retarded setting when the KS is disconnected
On a Nissan, a code may be thrown, but not an engine light.
Th computer relies on it's timing map, with the sensor as a safety from poor fuel.
Use good fuel, unplug the sensor, and it will run better.
If your car needs premium fuel, use it. Why suffer loss of power and economy with a wavy powerband, bu using regular and a KS??

 

[SHOZ]

With the newer PCM controlled motors the timing retard will not go to a point of damaging the engine. I can tune mine and set the timing retard/advance rate and any particular load or rpm I want. Ford OEM is not that great of a change in either direction per clock tic of the processor.

It is not unusual for engines today to have timing ranges of -10 to 60 degrees. Timing is used almost exclusively to control idle speed fluctuations.

A modern engine with well designed combustion chambers does not need a lot of timing. But it generally will be higher at the extreme ends of the rpm range with it being the lowest near peak torque.

 

[BuickGN]

Originally Posted By: SHOZ
With the newer PCM controlled motors the timing retard will not go to a point of damaging the engine. I can tune mine and set the timing retard/advance rate and any particular load or rpm I want. Ford OEM is not that great of a change in either direction per clock tic of the processor.

It is not unusual for engines today to have timing ranges of -10 to 60 degrees. Timing is used almost exclusively to control idle speed fluctuations.


A modern engine with well designed combustion chambers does not need a lot of timing. But it generally will be higher at the extreme ends of the rpm range with it being the lowest near peak torque.


Try driving a TL with knock issues. I can hear it very well with my ears and it's showing up to 15 degrees of retard on the scanner. This is more than enough to hurt the motor. Because of this I have to run a mix of 100 octane for daily driving.

 

[JHZR2]

100 (US average type valuation, not the European style RON number only) octane???!!!??

Something is wrong with that TL... or did you make a significant change to it somehow???

JMH

 

[eljefino]

http://www.hondanews.com/search/release/952

Quote:

Several factors work together to help the V6-powered Accord achieve improved fuel economy in both EPA City and Highway cycles. A new and more precise electronic knock control system permits the boost in compression ratio. The wider gear ratio range of the new 5-speed automatic transmission boosts operating efficiency and also reduces internal friction. Improved aerodynamics also contributes to improving fuel economy.

...

To help accomplish this goal, the a new sensor determines the onset of engine "knocking" and modifies spark timing before this potentially troublesome detonation can do any damage. The system allows the engine to run with a greater amount of spark advance and a higher compression ratio than the previous V6, increasing efficiency.



It was about the same year they were bragging about HP too, though this article discusses efficiency.

 

[BuickGN]

Originally Posted By: JHZR2
100 (US average type valuation, not the European style RON number only) octane???!!!??

Something is wrong with that TL... or did you make a significant change to it somehow???

JMH


Seems to be common. There's a 10+ page thread over on acurazine. Acura denies there is a problem. I've run the car on a dyno to use the wideband and confirmed it's not running lean or rich at partial and WOT. It takes roughly 96 octane to stop the pinging. It's as expensive to run as the GN since I can't use the cheaper leaded gas. Seems to go away when I reset the computer and slowly returns as it "learns".

Car is stock with the exception of eliminating the mile or so of intake plumbing.

 

[BuickGN]

Originally Posted By: eljefino
http://www.hondanews.com/search/release/952

Quote:

Several factors work together to help the V6-powered Accord achieve improved fuel economy in both EPA City and Highway cycles. A new and more precise electronic knock control system permits the boost in compression ratio. The wider gear ratio range of the new 5-speed automatic transmission boosts operating efficiency and also reduces internal friction. Improved aerodynamics also contributes to improving fuel economy.

...

To help accomplish this goal, the a new sensor determines the onset of engine "knocking" and modifies spark timing before this potentially troublesome detonation can do any damage. The system allows the engine to run with a greater amount of spark advance and a higher compression ratio than the previous V6, increasing efficiency.



It was about the same year they were bragging about HP too, though this article discusses efficiency.


What I get from that is it's supposed to continually advance timing until the detonation threshold is found. That's a seriously messed up way of doing it. What's bad is I get better gas mileage on a steady state 70mph trip with 100 octane than 91. This tells me the car could potentially be detonating for the entire trip on 91.