Recent Topics
Pennzoil Platinum 5w30 vs 10w30
by Snagglefoot
40 minutes 31 seconds ago
LM MoS2. Honest, if not appropriately tested?
by wemay
46 minutes 31 seconds ago
Brisket flat on charcoal
by 04SE
Today at 08:45 AM
Weird Oil level question
by audia6
Today at 08:27 AM
DNA test and opening a can of worms
by WhyMe
Today at 08:11 AM
Ghetto testing a wheel speed sensor
by Nayov
Today at 06:23 AM
dash cam
by DAC2018
Today at 05:08 AM
WoO driver Jason Johnson injured
by bdcardinal
Today at 01:08 AM
Plastic burning smell when WOT
by Jaha24k
Today at 12:57 AM
Duckham's 15w50 Oil 12 one liter bottles
by Lolvoguy
Today at 12:00 AM
Ruger LCP .380
by PW01
Yesterday at 11:24 PM
Launching boat with stick shift
by troutfisher
Yesterday at 11:22 PM
Free oil
by Spitter
Yesterday at 10:53 PM
Porsche Panamera buying advice
by CharlieBauer
Yesterday at 10:04 PM
RC cars
by red7404
Yesterday at 09:36 PM
Any Good 4K Movies ?
by Warstud
Yesterday at 09:06 PM
Gray on Oil Dipstick?
by chinee
Yesterday at 08:41 PM
Clear plastic scratch remover?
by Quattro Pete
Yesterday at 08:15 PM
Parking wars show.
by Chris142
Yesterday at 08:15 PM
set for years
by 93cruiser
Yesterday at 08:07 PM
Newest Members
bwechols, bowupid, pod423, lemaitrix, azzid0906
65303 Registered Users
Who's Online
87 registered (87sammy, 2015_PSD, 2004tdigls, 04SE, 14ecocruze, 9 invisible), 1331 Guests and 48 Spiders online.
Key: Admin, Global Mod, Mod
Forum Stats
65303 Members
67 Forums
285897 Topics
4771175 Posts

Max Online: 3590 @ 01/24/17 08:07 PM
Donate to BITOG
Page 1 of 3 1 2 3 >
Topic Options
#4473480 - 07/28/17 10:20 PM Variable Ignition Timing Based on Knock Sensors
john_pifer Offline


Registered: 07/08/12
Posts: 1971
Loc: Nashville, TN via Memphis
So, my question is really, how long is the cycle.

Let's say it's late July in Tennessee, almost 100 outside. I'm driving my Tacoma down a highway at 55 mph in high gear. The road grade starts to go uphill and I tip into the throttle a little bit, just to maintain my speed, but not enough for the automatic to downshift. I hear some light pinging, which is pretty normal. I've spiked cylinder pressures by cracking the throttle open even more at a not-very-high RPM.

SO, let's say I had been burning 93-octane fuel, but, on my last stop, I filled up with 87-octane pee water. Presumably, the knock sensors would detect any knock (how sensitive they are, I'd also like to know - will the sensors pick up pinging, or, would it have to be an actual knock event?) and pull the timing back a little bit.

OK, let's say, 300 miles down the road, I fill up with 93 again. How long does it take my ECU to re-advance my ignition timing and give me back my few extra HP & LB/FT? If I floor it and redline my engine through the first 3 gears as I'm merging back onto the highway, does the ECU then detect the fact that there was no knock, and advance timing again? Or, is there a timeframe that it has to get through with no knock, in order for the timing to be re-advanced?
_________________________
16 WRX - PPPP
07 Tacoma V6 - M1 EP 5W-30, Fram Ultra, 10K OCIs, 198K
07 Yamaha R1 - Rotella T6 5W-40, Bosch 3300
07 Yamaha YZ-250, Klotz, Rotella


Top
#4473567 - 07/29/17 12:40 AM Re: Variable Ignition Timing Based on Knock Sensors [Re: john_pifer]
LvR Offline


Registered: 09/19/09
Posts: 24
Loc: SA
There is a whole set of "War and Peace" like novels to be written on the subject ................... so imo its too manufacturer specific, model specific, and engineering approach specific to make a "generalized" statement.



Edited by LvR (07/29/17 12:42 AM)

Top
#4473623 - 07/29/17 05:13 AM Re: Variable Ignition Timing Based on Knock Sensors [Re: john_pifer]
GMBoy Offline


Registered: 11/22/04
Posts: 7705
Loc: Texas
In the case of GM vehicles the PCM's fuel trim and timing "maps" are always the same. This means the vehicle will always attempt max timing advance/fuel trim every time - the knock sensors pull timing back but next full throttle or other load event will have the car again attempting full advance.....the knock sensors control how much advance is allowed. This is the short version of a long and complicated strategy. Hopefully this will explain it a little.

Top
#4473627 - 07/29/17 05:38 AM Re: Variable Ignition Timing Based on Knock Sensors [Re: LvR]
SteveSRT8 Offline


Registered: 10/10/08
Posts: 18958
Loc: Sunny Florida
Originally Posted By: LvR
There is a whole set of "War and Peace" like novels to be written on the subject ................... so imo its too manufacturer specific, model specific, and engineering approach specific to make a "generalized" statement.


Exactly, wildly platform specific.

Our sig car's knock sensors are so sensitive that you never hear knock even when premium is not used. Our newer fleet trucks are GM and I've never heard any audible knocking there either.
_________________________
"In a democracy, dissent is an act of faith."
J. William Fulbright
Best ET-12.79 @ 111 mph
4340 pounds, Street tires
Just like we go to Publix

Top
#4473708 - 07/29/17 08:23 AM Re: Variable Ignition Timing Based on Knock Sensors [Re: john_pifer]
Excel Offline


Registered: 12/25/15
Posts: 148
Loc: Memphis TN
I have noticed in TN that our 87 pings way more than in other states
I would say what gas we buy is not the same state to state .

After multiple road trips from TN to Florida and other places I ping the most
in my home state,no matter what brand . I think we are not getting what we expect
at the pumps
_________________________
2015 Ford F150
2015 Ford Mustang GT,Whipple powered
2017 Yamaha FZ09


Top
#4473721 - 07/29/17 08:38 AM Re: Variable Ignition Timing Based on Knock Sensors [Re: john_pifer]
HerrStig Offline


Registered: 08/24/11
Posts: 9560
Loc: Boston, MA
What octane does the manual stipulate?

Top
#4473755 - 07/29/17 09:35 AM Re: Variable Ignition Timing Based on Knock Sensors [Re: john_pifer]
Johnny2Bad Offline


Registered: 05/20/13
Posts: 1810
Loc: Saskatchewan, Canada
Knock sensors are notorious for being ineffective, I wouldn't rely on one to keep detonation at bay. Think about the job they are asked to do ... decide which engine noise is knock, and which is some other normal engine noise/vibration. Nearly impossible. I would keep a can of Octane Boost in the truck instead, using it when you are stuck with a grade lower than you need. Much safer procedure.
_________________________
'57 FL Straight 50 wt
'90 Miata 1.8L w/Rotrex Supercharger [Mobil1 0W-40]
'96 Ram 1500 [3.7L Mobil1 0W-20 / 1L 15W-50]
'01 PT Cruiser [Mobil1 0W-40]

Top
#4473759 - 07/29/17 09:45 AM Re: Variable Ignition Timing Based on Knock Sensors [Re: Johnny2Bad]
Brad_C Online   content


Registered: 07/27/12
Posts: 617
Loc: Perth, Western Australia
Originally Posted By: Johnny2Bad
Knock sensors are notorious for being ineffective, I wouldn't rely on one to keep detonation at bay. Think about the job they are asked to do ... decide which engine noise is knock, and which is some other normal engine noise/vibration. Nearly impossible. I would keep a can of Octane Boost in the truck instead, using it when you are stuck with a grade lower than you need. Much safer procedure.


Que? What tripe. Knock sensors have been installed for decades because they work. Do you really thing manufacturers would take the time to design and tune them on a system if they were ineffective?

If you actually understood how they worked, and how the algorithms in the ECUs very effectively mask out the mechanical noise you refer to, you might have a better understanding of just how effective they really are. Once you've put a scope/logger on a vehicle and seen the ignition retard individually on single cylinders to cope with anomalies you'd be blown away at how "effective" they are.

Don't let the facts get in the way of a good conspiracy theory though. Much better to add some "miracle in a can" to the tank. Oddly enough, if your miracle in a can is any good (and again you were actually watching the ignition) you'd see the ECU slowly advance the ignition to actually take advantage of the extra octane your elixir bestows upon your chariot.

Top
#4473764 - 07/29/17 09:48 AM Re: Variable Ignition Timing Based on Knock Sensors [Re: john_pifer]
Ducked Offline


Registered: 10/25/12
Posts: 4388
Loc: Taiwan
Originally Posted By: john_pifer
Presumably, the knock sensors would detect any knock (how sensitive they are, I'd also like to know - will the sensors pick up pinging, or, would it have to be an actual knock event?)...


Doubt that's an "officially" defined distinction, which it would need to be before the question could be answered by anyone.

Top
#4473773 - 07/29/17 10:01 AM Re: Variable Ignition Timing Based on Knock Sensors [Re: Johnny2Bad]
LvR Offline


Registered: 09/19/09
Posts: 24
Loc: SA
Originally Posted By: Johnny2Bad
Knock sensors are notorious for being ineffective, I wouldn't rely on one to keep detonation at bay. Think about the job they are asked to do ... decide which engine noise is knock, and which is some other normal engine noise/vibration. Nearly impossible.............................


Well - read my first post again and then realize this is in fact the only instrument/sensor found on most current engines that allow the ECU to actually cope with the garbage fuel found in some places ............................... without it EVERYBODY would ALWAYS have to drive on a pre determined fixed (read expensive) RON/MON fuel in order to allow ALL ECUS to manage combustion effectively.

Top
#4474107 - 07/29/17 07:43 PM Re: Variable Ignition Timing Based on Knock Sensors [Re: john_pifer]
Silk Offline


Registered: 07/26/03
Posts: 4566
Loc: New Zealand
The Mitsubishi MUT III factory scanner shows knock learn - how much it is retarding from the 100% standard setting. Something we always look at with a GDI, normal engine shows nothing, as they are made to run on our fuel. My Volvo should run on a premium fuel, but I run it on the low octane, on a trip I put in premium, and fuel economy comes up a few kms later. I guess it remaps, but haven't bothered to watch ign advance on the scanner...a bit dangerous.
_________________________
1987 BMW R65 - Penrite V Twin 20/50
2005 Nissan Expert - Gulf Western 10W-40
1996 Volvo T5 - Penrite HPR15 - 15W-60. Ryco syntec filter.

Top
#4474169 - 07/29/17 09:21 PM Re: Variable Ignition Timing Based on Knock Sensors [Re: john_pifer]
OilSwag Offline


Registered: 07/02/17
Posts: 43
Loc: Tennessee
I agree with the above about each manufacturer being different. It all depends on ecu programming along with the sensitivity of the knock sensor. Sme more so than others. The ultimate goal is the ecu adjusts before there is knock. I went from a Ford modular 2valve to a Infiniti VQ engine. I swear I can't make that car knock. Even with 87 octane at low rpm high load. So the ecu is pulling time before there is a chance at a audible knock. You can get knock and not notice it in sound. So in Infiniti's scenario the car has timing being pulled before there is an audible knock. In my opinion the knock sensor is doing it's job and the ecu was programmed well. My Mustang would knock like [censored] with less than 93 and not adjust to it. I think it's best to not let knock happen. Use an octane booster that works if you need to
_________________________
03 Infiniti G35 209K, Castrol Edge 5W30 topped with Edge HM, Fram Ultra Filter, Berryman/MMO fuel maintenance in 93 E0, all synthetic fluids

Top
#4474173 - 07/29/17 09:26 PM Re: Variable Ignition Timing Based on Knock Sensors [Re: john_pifer]
eljefino Offline


Registered: 06/15/03
Posts: 32659
Loc: ME
Saturn S-series was quick to pull and slow to give back.

Mine would drink a slug of oil after coasting down hill in gear, knock, and get a "flat spot" in acceleration that took ~200 miles to work out.

That car took very well to water decarbonization.

Top
#4474287 - 07/30/17 12:46 AM Re: Variable Ignition Timing Based on Knock Sensors [Re: eljefino]
john_pifer Offline


Registered: 07/08/12
Posts: 1971
Loc: Nashville, TN via Memphis
Originally Posted By: eljefino
Saturn S-series was quick to pull and slow to give back.

Mine would drink a slug of oil after coasting down hill in gear, knock, and get a "flat spot" in acceleration that took ~200 miles to work out.

That car took very well to water decarbonization.


Ha! That's interesting!

My WRX, being a 2016, and TGDI, and, being prone to LSPI, you would think it would have the most sophisticated anti-knock programming, that would keep it from knocking at all, right? Wrong. Must be a hard engine to keep from knocking, because it will knock from time to time. And I'm not talking the light pinging I get from the Taco on [censored] 87 fuel going uphill in hi gear in 100 heat. The WRX will knock hard enough that it actually momentarily loses power. This is if I'm in high gear at, say, 65 mph and I open the throttle to, say, 50-60% to pass someone. Classic LSPI. And I only use Top-Tier 93 in that car. Usually Shell. Must be hard to account for. But...then again...they didn't do a great job of EFI tuning in that car anyway.
_________________________
16 WRX - PPPP
07 Tacoma V6 - M1 EP 5W-30, Fram Ultra, 10K OCIs, 198K
07 Yamaha R1 - Rotella T6 5W-40, Bosch 3300
07 Yamaha YZ-250, Klotz, Rotella


Top
#4474328 - 07/30/17 03:44 AM Re: Variable Ignition Timing Based on Knock Sensors [Re: john_pifer]
bbhero Offline


Registered: 03/20/15
Posts: 4630
Loc: Virginia
Isn't 87 octane more volatile than 93?? Would the ECU actually advance timing for lower grade 87 due to it being more volatile?? And pull back timing for 93 being that it is less volatile?? Therefore the ECU would take more advantage of the 93 by pulling back timing and actually compensate for 87 being advancing the timing.
_________________________
Nissan Altima 3.5 Coupe Valvoline Advanced Full Synthetic 5w30 Federated Auto 4612ex
"Treat your family like your friends and treat your friends like your family."

Top
Page 1 of 3 1 2 3 >