Knock counts, Knock retard...

http://www.thirdgen.org/techboard/di...-reported.html

neat topic.... it's actually something i encountered a lot when first getting into tuning... i could never figure out why knock retard would sometimes just jump up to 2* or so and decay out without a count being registered... i think it's actually one of the first things that got me into reading/understanding assembly.

appears to effect 8D and probably a lot of other masks as well.

BTW, displaying the full 16 bit value instead of the MSB is scary.... having 300 knock counts appear instantly where you are used to 1 or 2 is alarming to say the least.



another situation somewhat like this(GM displaying only half of a 16 bit value) is MPH.... a lot of programs actually go so far as to define MPH as a 16 bit value with a 0-255 range, with only the MSB reported... you could have the full 16 bit value reported and then be able to see MPH difference of 1/256th of a MPH... that kind of resolution is totally unnecessary for anything the average person would deal with, but it is possible to display/track.

Quote:

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Originally Posted by RobertISaar

http://www.thirdgen.org/techboard/di...-reported.html

neat topic.... it's actually something i encountered a lot when first getting into tuning... i could never figure out why knock retard would sometimes just jump up to 2* or so and decay out without a count being registered... i think it's actually one of the first things that got me into reading/understanding assembly.

appears to effect 8D and probably a lot of other masks as well.

BTW, displaying the full 16 bit value instead of the MSB is scary.... having 300 knock counts appear instantly where you are used to 1 or 2 is alarming to say the least.



another situation somewhat like this(GM displaying only half of a 16 bit value) is MPH.... a lot of programs actually go so far as to define MPH as a 16 bit value with a 0-255 range, with only the MSB reported... you could have the full 16 bit value reported and then be able to see MPH difference of 1/256th of a MPH... that kind of resolution is totally unnecessary for anything the average person would deal with, but it is possible to display/track.

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I read that topic awhile ago, he's a sharp guy!

The only time I have experianced knock retard without a knock count was with Burst Knock Enabled. Some masks define this as knock before coolant temp allows, but all my findings are it is an anticpated Knock and has nothing to do with temp. Turn it off and the Knock Retard with out knock count goes away. The Burst Knock enabled is a good thing in a tune with high spark advance, most newer calibrations use a lot more spark advance so when cruising down the freeway and then accelerate you will get crazy knock counts along with retard, with it enabled you just get retard.

Another spark retard that shows up without knock counts is from Tourque Management! WOW! Turn that off and what a difference in driving.

to some extent, torque management is a necessary evil... not as extreme with the RWD vehicles, but some of the FWD transaxles(and AWD derivatives of FWD transaxles) are just weak. most, if not all, of the manual transmissions are fine, but the autos are scary when you have no torque management and a torquey engine.

the supercharged 3800s? those kill 4T60E and 4T65Es all the time.... even stock engines with torque management to try and save them.
the LS4 (FWD LS engine as in certain high-end W-bodies)? kill their specially modified 4T65Es easily.
the Northstars? the 4T80 fare pretty well behing them, but they have plenty of torque management as well. probably not too many people abusing their Cadillacs though.

usually, i don't hear about too many 4L60/4L80 failures until putting some significant power through them compared to what they were paired to.

now with the 6-up speed autos around... i have no idea how well they're holding up.

Lots of 4l60E trans are smoked shortly after a mass produced mail order tune to remove tourque managment etc... I've had a theory but until last week it was just that. Guy here in town just replaced his trans and wanted the Tourque Managment put back in so I read the tune and sure enough engine tourque managment was taken out, then I went and looked at transmission and sure enough they pulled the tourque managment from shifts points as well... I knew that was a bad thing...

Back to spark retard, on my truck I did lots of logs from a normal drive I do several times a week so I had a good baseline. Cruise on highway and note spark advance, MAP and TPS position. Spark advance does not match what is called for in calibration? Remove tourque managment and do same data log. Spark advance is where it should be but the kicker is TPS position is lower and MAP is higher! Had to triple check that and results were accurate. I think I found my missing MPG! All masks are differant and this one did not show spark retard, but it was there.

The spark timing value is another where an 8 bit handling of a 16 bit value caused problems. The DIS conversions I do require setting the min and max values to negative values which requires access to all 16 bits. Additionally, the spark advance values then become inverted. The correct math (IIRC) adds reference angle to ALDL spark value before displaying it but popular ALDL software written for distributor calibrations simply displays LSB. Whoops!

Older cals sometimes incorporated torque management into spark tables. It's the upshifts that kill the trans when torque management is disabled. Ford and Chrysler actually kill the engine during an upshift. Some of the GM cals were reported to do this as well but I haven't noticed it. When watching mismatched AFR and / or timing, keep in mind that cat overtemp modeling is another source of "override tuning" events. If the pcm thinks the cat is too hot it may richen the mix or retard timing. Disabling cat overtemp protection *for test purposes* can help diagnose this but leaving it disabled frequently leads to melted converters (another thank you to generic mail order tuning).

Thanks for reminding me!!! I better turn the CAT protection back on... :rolleye:

It sure messes up data when doing a tune...

the later MPFI V6 masks can run spark down to the minimum allowed spark value in the calibration... with the older non-E transmissions, it would wait until TPS and RPM passed a threshold, then wait for the RPM to start dropping due to the shift, then cut out a specific amount of advance for a predetermined amount of time or until the D-RPM ceases to be above a threshold(whichever happens first), then it adds all of the spark back in....

it actually works pretty well, since if the settings are aggressive enough, it feels like you ran into the rev limiter during the shift.