So, I bought and installed a ZFR 6758 and for the last couple weeks have been trying to find out why it is over boosting so bad. No matter the tune, the turbo always goes to 30 pounds of boost! I was wondering if it could be the waste gate, bpv, vacuum lines or what? I don't have any pictures currently but have no problem running out to the car and taking the pictures for you guys.

Mods
Zfr6758
ZZP upper charge pipe
Treadstone tr-12 intercooler
3-bar map
ky stage 3
turbo xs fl catback
zzp catless downpipe
powell stage 1 mounts
AEM CAI

 

It's bases off of airflow, not PSI. mines set to 33lb/min

It should be the cooler temps causing it to over boost.

 

Well, according to the log the car is trying to limit the boost but its not.

 

Verify the pre-load on your wastegate, do you have the high boost or medium boost canister?

 

What is based off airflow? If you're talking about the ECU it's based on torque, and if the car is dropping the desired boost and the boost isn't dropping it means the wastegate isn't opening enough.

 

OP are you tuning this yourself? If so what are your DAL and WGDC, and did you touch the Optimum spark and torque tables?

(sorry random additional questions popping up)

 

No I am not I have a tuner, but not for sure on the canister. Anyway I can check?

 

Stop talking



OP - There's either an issue with your waste gate, or your tuner. If you're running the high boost wg can, they can at times be tough to control at first. Have your tuner go SUPER conservative on wgdc settings to start and work your way up slowly.

 

there is 4-5 tables you need to mess with to control the boost. not just two. are you doing the tuning on it?

 

No he has a tuner

 

I was suggesting starting with the two that (to my knowledge) have the largest effect on boost.

 

Well, I'll get him on the conversation tomorrow. But as of right now I was thinking that it may be the boost canister because of that linked thread. But I can always upload logs for you guys to look at.

 

I personally agree. Ultimately, yes, there are of course many tables to address for proper boost curves and control in a "normal" circumstance. However, specifically in the case of the high boost can on a 6758, the 2 tables that have by far THE most effect on how hard a how much boost you will make are the wgdc and prop gain. Those 2 tables alone will dictate virtually all of your boost control regardless of what any other table is set at. Go even slightly too aggressive with those 2 tables and any and all other settings will straight up just get blown past.

 

wgdc
pressure limit
pressure rpm factor
DAL

Just the four off the top of my head.

 

All of which will be blasted by desired targets (short of wgdc) if prop gain and wgdc are set too aggressively with the high boost can. All the other tables will do is force the car into limp mode due to an overboost condition. Only way around it is to set the overboost limits through the roof and subsequently watch boost launch to the moon. Seen it happen in some questionable tunes unfortunately. Some of which were boosting far more than the 31psi limits of the 3bar maps and flat lining them at 31psi in the graphs.

 

there is a couple in there that are hardset limits and start the calculations for the others. One table noticeably is way too over looked by people. the one little table that makes 20+ psi capable at redline on a stock k04.

 

Is it located under the tab labeled "Magic Land"?

 

nope.

 

LNF, full bolt ons, catless dp, k04 holding over 20psi to 6500+ rpm? Excuse the skepticism but that's a pretty tough pill to swallow. I've made it happen with lnf's in otherwise stock form, but with full bolt ons.... meh idk. That's quite a bit to ask of that little guy. It's kind of a flow limitation thing we're talking here, not so much a tune thing. Ya know?

 

the problem people run into is overshooting and losing control of the wastegate. this goes back to the limiting tables and 99% of the people who dick with these cars over shoot them by a lot and don't understand the math behind them, and how the affect everything they are doing.

Say your setting a max of 270 kps to more or less get away from the codes, but you have a max factor of 3.0 and your target is 24 psi. guess what just happened. you just over shot the target by 3.9 psi. this is causing the wastegate to double its duty and slam shut and open back up causing more work on the solenoid itself. All with in a split second.

At 6300 i see an average of 21-22 psi with a commanded peak of 24 psi. it's not rocket science, people just don't understand the tables and how they work together for their own personal benefit.

I do understand the flow limitation of an object spinning at 100k rpms. Which is why i rarely go past 6100-6200 rpms on a stock turbo/stock cams as all you're doing is pissing it off and wasting time.

 

So I found out that the pre-load is set all the way out, would adjusting this help?

 

yes, i would start by backing the nuts off so you can move the WG by hand. move the WG all the way to the closed position and tighten the nut finger tight, turn the preload nut 3-4 more times then tighten the jam nut on the other side. that will give you a baseline to start from

 

There needs to be a solid amount of pressure on the rod itself when installed.

 

What do you mean?

 

he means there needs to be enough preload to stop the WG from flapping about when its supposed to be closed