Observation while datalogging: unidirectional KR

[dale_gribble]

I have recently noticed my car has different behavior depending on the direction I am going when I make 4th gear WOT runs at the frontage road I run at. It took me a while to finally nail it down what the hell was going on.

From a road perspective, it is perfectly flat, in decent repair, and only has an 3' elevation over a .4 mile stretch of road. It runs north and south along a major freeway with posted 50mph speed, no driveways or cross-streets and perfect visibility. The road would seemingly provide consistent north to south or south to north datalog runs.

I always noted some kr (~1.5) on the NB runs and never on the SB runs. I always chalked this up to different elevation resulting in different calculated load or something similar in the tune resulting in some true KR. Tonight, I stacked up a bunch of NB and SB logs and found something pretty interesting:

The KR had a very unique characteristic on ALL of my NB runs. It would hit ~0.5kr @ ~3000, and then hit 1.4 @ ~5,000 and peak again at 1.4 @ 5200 with one little kr blip @ ~6200. The SB runs on the same road yielded none of these KR blips but had some characteristics of their own (0.5kr @ a few distinct RPMs).

I started going through past months' logs and I'll be damned if this almost EXACT KR profile wasn't exhibited on a bunch of past months' runs. I traced it back to summer months even. I could tell which direction the run was simply by looking at the KR profile.

The KR was due to bumps and/or noise from the road, not to my car. After studying the stretch of road on Google Earth, it confirmed what I saw. The road has very few repairs southbound and a bunch of patches northbound.

So, kids, the moral of the story is, you may want to run a conservative tune and baseline a datalogging road before doing tuning runs on it. Otherwise, you end up fighting the road and not tuning your car. Now that I understand my road, I will only make runs southbound from here on out.

Here are some examples. You can see what I am talking about; these are runs months apart from one another across different tunes. Again, none of these KR blips happen when travelling the road southbound.

[dale_gribble]

I kept trying to dial the timing back to see if these blips would ever go away and they never went away which is why realized it probably wasn't the tune and finally gave up and started looking over the logs...

[amggilly305]

these cars are very sensitive when it comes to reading kr.

[dale_gribble]

Ya, I agree completely. I think my aftermarket motor mounts play their part too... I think I am going to dump my AWR trans mount and just stick with the PMM and RMM. The NVH on the trans mount is pretty bad and that can't be good for KR.

[amggilly305]

i have all 3 awr mounts and don't have an issue with kr at wot. find a smoother road

[dale_gribble]

Originally Posted by amggilly305 find a smoother road

Ya, i got that... For the record, its a pretty damn smooth road overall, it isn't some beat up road in the sticks. Its good for others to read this so they don't tune phantom kr... I am sure i am not the only one.

Originally Posted by amggilly305 i have all 3 awr mounts and don't have an issue with kr at wot. find a smoother road

By the way, which duro bushings you running in the trans mount?

[amggilly305]

@dale_gribble; 70 for all 3

[dale_gribble]

Originally Posted by amggilly305 @dale_gribble; 70 for all 3

Ya, i need to go 70 maybe on the tmm... The 88 is pretty harsh.

[mituc]

Definitely the motor mounts + road noise (even stiffer dampers/springs may result in false knock). I've seen this before several times.

[kgb]

Originally Posted by amggilly305 i have all 3 awr mounts and don't have an issue with kr at wot. find a smoother road

I see your Stratified Tuned....Doesn't the AP allow the adjusting of the knock sensors sensitivity? If so, could you adjust that accordingly and retest?