NefMoto

Hello Nefmoto,

I've asked this question in various forums and PM'd various tuners all with different responses.

If I currently have a k04 tune, and change out the k04 turbos for some k24/rs6 hybrid turbos (keeping everything else the same)... will there be any significant problems?
I was under the impression that the n75 would control the boost levels, and of course there would be some power left out on the table. I am ok with that as my block is not built, and I rather not have k04's running at their limit.

What is the verdict on this?

Thanks!

Charge pressure control will not even be close.

Could you elaborate?

The PID will have to be retuned.

Will i damage anything running the k04 tune?

Depending on what K04 tune it is, absolutely. If it was tuned to ride the map the ecu won't know it's overboosting. The SRM's running K04 level wastegate duty cycle will be 30+ psi.

It is an 034 motorsports tune.

So the n75 on the k04 tune wont be able to regulate boost levels correctly?

Is there any way i can modify this tune myself for rs6 wastegate duty cycle?

you can use a manual boost controller in parallel to control over boost... its not the right way but its a cheap effective way to avoid a retune if thats what your trying to do by the sound of it.

thanks Marty.

I want to get a proper rs6 tune, but not until my block is built. I do not want to throw a rod.

When you say run a MBC in paralle, i would run it like this pic?

(http://ctny.audiworld.com/mark/s4/misc_data/mbc_parallel.jpg)

yes sir

There is no risk to your rods with a proper tune and pump gas on the SRM's.

34psi too be precis.
A friend of mine did it, and at first run he blew his clutch.
Than the tuner here in Sweden did something that is absolutely Nono.
He reached down and turned on the wg screws a couple of times, and fucked it all upp.
The car is impossible too tune now.

I would love that but due to time constraints I need to have my car running and i dont think ill know enough about nefmoto to have a proper tune. Im trying to learn as much as i can

Since the K24/26 hybrid turbos are larger machines, running on K-04 boost maps, should result in about the same boost pressure as the K-04s with slower spool up response time, not excessive boost. The boost controller is a 3 mode PID controller, (Proportional/Integral/Derivative) with actual boost pressure feedback for comparison to the requested boost, for offset/rate/reset response to drive the N75 control pressure output value accordingly. the N75 control voltage PWM duty cycle is adjusted by the PID controller output to achieve the necessary boost pressure and associated torque development.  Therefore I don't believe there is any risk of excessive boost pressure or out of control boost regulation. With torque demand base engine management two main factors are used as inputs for boost pressure control, the MAF meter output is used for engine load determination, and the MAP sensor output is used for boost pressure measurement. Boost pressure is one of the main torque control variables used by the ECU to match torque achievement with the sum of the torque demands at any instant. If the ECU uses drive by wire throttle, the engine management is based on torque demand. Mechanical  throttle control uses a different boost control model in the ECU software, but is also a PID controller  configured in software. In the specific boost pressure control  for mechanical throttle control, the larger turbos running with  K-04 tune, would most likely not boost as much as the K-04s due to the larger turbine and reduced spool up response. Given enough time, the larger turbos should develop about the same boost as the K-04s. I don't know of any way the larger K-24 based turbos could accelerate out of control, developing excess boost pressure when controlled by the K-04 tune, with everything operating normally.

Best case scenario:

Boost will overshoot, the throttle will close, you will hit limp mode. The issue isn't with the turbos so much as its with the fact that the K24's use actuators that are 2-3 times stiffer than regular K04s.

Add to that most tuners disable, or severely numb overboost detection, and the fact that you're already near the map limit so there isn't enough headroom to sense an overboost condition, let alone for the PID to work, and you are asking for trouble.

Worst case scenario (and the one that will likely occur)

Boost will overshoot. You exceed the map limit so the ecu cannot accurately detect an overboost condition. It sees 22psi and is happy. It continues to allow the N75 to run at 85 percent duty cycle (which, for the typical K04 is 21psi). 85 percent duty cycle on the K24's is closer to 32psi.

Like Daz said, the outcome will either be limp, unstable boost, or extreme overboost depending on the tune.

The torque model outputs desired torque, this is converted to desired load, and then target boost pressure. Boost pressure is tightly regulated while the previous two are not.

If DLDR was tuned tightly for the K04, then the car may go into limp due to underboost (slower spool). Otherwise depending on target boost pressure it will oscillate or overboost.

While building boost pressure, P will shoot high and easily exceed TVLDMX keeping N75 dc above 95%. During this time, I is winding up and will definitely reach ldtvmx, which for a K04 is going to be much higher than needed for the K24. Once, target boost pressure is approached, D will not be great enough to pull DC down enough to avoid overshoot because I is way too high. If boost control is closed loop at this time and target boost pressure is low enough, boost will oscillate wildy from the overshoot and different wastegate response. If the ECU is closed loop, the car will boost beyond 30 psi due to dc being locked above 85%.

Please explain how you associate the larger K-24 turbocharger response dynamics to the K-04 specific PID boost controller parameters you speculatively described above. It is not at all clear that the interaction will necessarily have the undesirable effects alleged. Specifically, the described dynamics of the controlled system imply the various torque demand/load/boost control functions are unable to control the boost pressure within allowable stable range levels, but the several codependent variables occurring need additional detailed explanation. I am not trying to be argumentative here, but these are important factors involved and the concepts are usually not fully developed on this forum, for clarity and complete understanding of the overall situation involved with this.
I don't have enough information from your comments to be able to determine the validity of the speculated response of the turbo/PID controller interaction.

A lot of long words. I'll make it short.

Between a different wg and the completely different compressor housing, for a given N75 duty cycle, the response will be entirely different.

That is to say... the PID will have to be retuned. Minimally, the I-limit will definitely have to be different.

Not sure why you are accusing anybody of speculating; this should be pretty obvious if you've tuned the PID in *any* ME7 car.