Juddering low rpm and deceleration

[tricker_luke]

- Kpro Version 2, Serial 7158, Firmware 2.02
- Kmanager version 3.1.4.0
- Cal file

Latest map V3.1.4.kal

- Datalog

juddering.kdl

- K20 now 2.2l rebored, clockwise motion fast road cams, 410cc rdx injectors Apexi cone filter, RBC intake manifold, Buddyclub header, spoon b-pipe, spoon n1 backbox.
serial number of your K-Pro
- Kpro bought about 4 years ago from Buddyclub UK

At light throttle there is juddering up to about 2.5/3k revs. It also sometimes judders/ bucks on deceleration, more apparent when driving down a decline and either on very light throttle or no throttle.
I have tried different overrun values down to 15kpa. I have also tried different tip in values and currently at -100 through all gears. I did try disabling the overrun delay, and although this stopped 95% of the deceleration juddering, it made on/off transitions more aggressive.

I don't know if the fact a 2.0l base map being used on a 2.2l would be causing problems? I'm getting so fed up of the driveability now, it's been a year now and I want to try and get these problems sorted.

Thanks, Luke

[Spunkster]

Has this been properly tuned on the dyno for your engine?

[tricker_luke]

Yes it has been on the dyno, not tuned by myself though.

[Spunkster]

Have you contacted the tuner about this issue?

[tricker_luke]

Hi, yes I did but no real fix came of it.
He did mention another car with the same cams showed similar problems, and when changing to a different cam,the car was a lot smoother.
My cams are near enough stock on the low lobe though, so could it be due to partial throttle maps needing some work doing?
I have also seen some maps with 0 degrees cam in column 1 and 2, whereas other maps have higher values in the same columns.

[Hondata]

You need to smooth the ignition tables so there are not such a big step in values on the first couple of rows. It will also help to run more cam angle at everything above idle. If you make a datalog and see then ignition timing oscillating, then this is an area which needs smoothing. What I suggest doing is to concentrate of one narrow rpm / load range and fix that first in order to see what changes you'll need to make for the rest of the table.

[tricker_luke]

Hi,

Did you mean more cam angle on the complete low cam table? How would you determine how much to increase?

Does Kmanager use just the cam value it shows, or does it average across all tables? E.g. at a certain rev/load low cam is 20 degrees. Does this only use the 20 degree ignition values, or should changes be made throughout?

Can you briefly explain where the problem would lie on the 2 findings shown below (the 0/10 degrees looks obvious). On the same stretch of juddering, as the revs drop to <1500 it uses 0 and 10 degrees, above it is 20 degrees.
It looks like when it switches 0 to 10 degrees, the ignition is jumping from 19-21 to 34-37 degrees.
At the higher rpm of the judder, at 20 degrees, the ignition table seems to be ok?
How could I go about smoothing the massive jump from the 0 to 10 degree table, or would it be by increasing the cam angle like you said, so that I never actually hit 0 degrees on columns 3-5?
Also, would say 8 degrees cam angle use the 0 or 10 degree table?

Sorry for all the questions, I'm just trying to learn what I can! :)

[Hondata]

Before you only had about 10 degrees cam angle at cruise, which is lower than normal.

One problem is that the ignition is about 20 degrees on the 0 degree table and 40 degrees on the same point on the 20 degree table. This is the sort of thing which will cause the oscillation. Set the cam angle to 20 degrees everywhere, including idle, to fix this.

Then you will need to make sure the ignition does not increase sharply with rpm at any point. I think you've identified the step on the 0 degree table.

[tricker_luke]

Just so I am sure, columns 1-6, 750-1500rpm should all be changed to 20 degree cam angle? Would a 10 degree cam be necessary at all?
What would a big step be classed as in ignition, 5 degrees or more/less?

Thanks

[tricker_luke]

I set the cam angle to 20 degrees in the areas I mentioned above, but when pulling away slowly that 16 to 34 degree jump felt like it almost rips the engine out.
How can I go about smoothing that area, and how would I know if the new ignition value I set is safe or not?

Thanks

[tricker_luke]

Hi,

I changed the low values to 20 degrees, and have attached the kal and datalog. It was juddering quite bad, but I also changed the ignition values to some that were recommended on another forum, but no luck.

Latest map V3.1.6 20 deg low cam.kal

20 deg low cam.kdl

As a test, I then changed all the low cam values to 0 degrees, and it ran a lot smoother. There was still a bit of juddering, but overall, a lot better than the 10/20 degree cam values.

Latest map V3.1.6 0 deg all low cam.kal

0 deg low cam.kdl

Could it be more of a fuel problem, even though I'm running closed loop?

Do the 10+ cam angles need a higher ignition value at low rpm, as opposed to the 0 degree cam table which starts off low and then builds up high. I also tried copying the 0 degree values to the 10 and 20 degree tables, but this made it judder a lot more worse.

[tricker_luke]

Hi,

I have received information from the engine builder that the cams he installed are Honda OEM profile on low lobe, but different on the high lobe.

Therefore, tuning should be ok using a basemap, however, he also told me that he has changed the cam timing to 105 degrees, as opposed to standard 98 degrees (on the standard gear, I think there are dowel positions?).

He does not use Hondata to tune his engines, so does not know its features, but has tuned over 40 engines with those cams, on different ECUs and had no judder at all.
Would the 7 degree difference on the cam angle mean that cam angles on low speed would all need to be offset? Or would it be affecting ignition values??

Any help appreciated, thanks.

[Hondata]

At this point I think it is something you need to discuss with your tuner. There are too many unknowns for us to make any more suggestions.

[tricker_luke]

All I really need to know at this stage is whether a change of actual cam degree timing will mean a need to change the RSX Type S basemap ignition values?

As I've previously shown in pictures, if I'm at 2k revs, it is on 20 degree cam table, and there are no large gaps between ignition values. It is whether these actually need changing now due to the cam degree.

[Hondata]

The actual cam lobe centres do not matter - it is the relationship between the sprocket and sensor on each camshaft. For turbo cars we typically use the Honda high speed cam profile as the low speed cam profile without any problems, so I don't think it is the cams themselves unless they are off by one or more teeth.

Again, I think it is something your tuner is going to need to address.