NefMoto

My car currently sports Tial 770s, 4" to 2.5" super smooth y-pipe, SRM ICs, large Bi-pipes (and soon RS4 intake with Hemi throttle), 2.8 heads and I am having hard time controlling part throttle torque delivery. The ECU is using 5120 hack with real load, no underscaling (which is probably why I am having the issues, underscaled tunes are less sensitive to over-TQ situations).More specifically the initial onset of part throttle torque overshots the target value by a lot due to lack of WGDC control with high racking pressure on wastegates - tial 770s in mildest set up effectively delivers minimum of 21-22psi without any wastegate activity.

The ECU tries to moderate boost by closing the throttle which eventually settles boost/torque on the level I originally requested via gas pedal but to get there I am first hitting much more TQ.

Say I press the pedal to deliver 50% TQ and I initially hit 16psi which after some internal battling gets moderated down to 8psi and that's what the ECU rides at to red line. The whole process takes ~1-2s to settle.


What are your tuning strategies, or at least suggestions, to moderate TQ delivery in this situation without WGDC involvement?

Are there any maps that similarly to boost maps define aggressiveness of throttle activity to reach desired torque/boost or am I doomed to approach this with KFWDKSMX map and what else?


Thanks!

Are you seeing fast path torque intervention (ignition retard)?

I'm also curious how to accomplish this. Almost every "pro" tuned car i've driven with big turbos and tight wastegates suffer from very poor part throttle control-ability.

IMO the proper solution is wastegates that can open with much less pressure, but packaging restraints make that almost impossible (on the 2.7t at least).

I don't see timing retard.

I tried adjusting wastegates to something smaller but tial packages ones with spring that starts moving at about 18-19psi so it cannot be lowered below about 20psi as it needs some preload.

Are you having load intervention or just charge pressure intervention (aka overboost)?

You can use N75 and 1bar WG crack pressure if you want. Really simple and part throttle works fine with a big turbo. I've done it before.
You will have to rescale some hPa axises though.

due to packaging restrictions, any wastegate(s) small enough to fit the stock 2.7t location(s) don't seem to want to hold pressure very well with cracking at 1bar.


Not sure I follow. Rescaling hPa internally in ME7 won't change a wastegate's cracking and holding characteristics

You need to ensure you are not getting are not getting any N75 duty request on part throttle with such high WG cracking pressure.

Rick

N75 between 0 and 100% will make no difference whatsoever until 14-15 psi anyway.

You probably want to adjust FUEDK so that the ECU does not overshoot it's initial throttle control.

Have a look at BGPLGU. You have to calibrate your "base boost pressure" right to get this properly working.

Pretty sure this does not exist in 551M and plgru_w = pu_w.
Besides, even if it was there, then from a quick glance I had a while ago, I don't see how calibrating this will affect this at all. Nothing you do to LDRPID is going to make a difference in this case.

The only thing you can do is with a stiff wastegate spring to lower filling is either close up the throttle or trigger the N249's.
IMO what needs adjusting is the filling adjuster, specifically the filling at a throttle position.
The throttle oscillation is the ECU incorrectly choosing the base set point, and the settling is the P controller working to equalize rl to rlsol.

pssol higher than 95% base boost pressure will make the throttle pop open because that's the limit were the air charge is supposed to be controlled by boost control. Staying under this limit will have the throttle control things. The function is there to handle excatly these kind of problems. Even the stock cars have it especially in cold conditions.

 

So vpsspls_w?

We can talk niceties all day, fact of the matter is, BGPLGU is not used on 551M/551G and lots of other software. Code for it is missing as well.
plgru_w = plgu_w = pu_w there.

And extrapolating on that - if BGPLGU is not there, then the only thing that can be done is tweaking KFVPDKSD and KFVPDKSE.

In LDRPID, plgrus_w is KFDPLGU * KFWPLGTA * pu_w. Both maps are filled with 1's, so effectively you have plgrus_w = pu_w.


This is what I was getting at with vpsspls_w.

Yes.
If the base boost pressure is defined in BGPLGU or in LDRPID is not relevant. It's the same thing just another name.

I have successfully been tweaking KFVPDKSD/E to 1 just up over WG cracking pressure which makes it snap to WOT only when requesting base WG pressure or higher.

Then of course recalibrated KFWDKMSN to suit.

And I hope KFMSNWDK too, which is inverse.

That was what I was talking about when speaking about FUEDK correction.
If you have a stiffer spring then for certain throttle openings you will have higher airflow.

silentbob was speaking about a different thing (ECU going WOT due to pressure ratio) - I guess for correct functionality both should be tuned.

Yes, but it isnt needed unless you run CWBGMSZS.0 or if you want to be able to run it with MAF sensor unplugged.


That is exactly what KFVPDKSD/E does, I maybe misunderstanding you here though.

Or if the MAF sensor fails...I've been dealing playing around with a larger TB lately, amazing what a difference calibrating these maps properly makes.

Ok so let's get into this a little more since this is an issue that I experienced w/ my 605 setup back in the day as well. (21 psi w/ 0% WGDC).

So what the the Y-axis represent... 

FR states the following: Pressure ratio of intake air pressure to base boost pressure.

So is the Y axis just boost pressure in BAR? (ie. 1.0 = 14.5psi?)

What does the numbers in the table represent and how does it all work together?  1 is no change in boost setpoint, less then one is less req' boost for the set point?

So tweak KFVPDKSD/SE by modifying pressure ratio axis first to reflect more precisely my new high WG cracking pressure. Massage values (to under 1) in lower pressure ratio columns so that the ECU doesn't go crazy with throttle and overshoots?

I'm interested in the way of scaling TB maps. Is it ok to start with scaling by the percent of area difference like with MAF housing?
For example going from 57 mm to 64mm would give 26% difference.

Regards
Lobuziak

What you can try to do is make the airflow at throttle plate match airflow from maf.
Or tune your car with the MAF, then unplug it and tune the maps so that it runs as well as possible without the MAF with similar AFR through the range.

PRJ:

I've been toying with KFMSNWDK and the inverse, KFWDKMSN.

Adjusting MSNWDK to the point mass airflow and calculated airflow over the throttle plate matched results in a significant decrease in the values of the map (1360 was my last row). I then took the values in this map and transferred them to axis of WDKMSN. How exactly does one determine which values work well here (for the map, not the axis WDKMSN)? I notice the RS4 file ends at 52, I find it hard to believe that's as far as the TB opens, when the s4 file ends in the 90s? Any tips? Am I missing something significant? Right now with the hemi TB my calculated airmass over the throttle plate and measured airmass are fairly perfect, but I feel WDKMSN may not be correct.

Dillinger, read up on the other two maps mentioned, those calculates when WOT is the best throttle angle.

WDKMSN/inverse is on used on part throttle.