Overboost limp mode?

[AugustusCaesar]

Hey guys, I'm having a weird issue. I need some help.
I have a 2024 Nissan Z with 2,900 km on it.
Stock, aside from a muffler delete.

Car has run amazingly up until now.
I have no codes, no DTCs, no discernible leaks.

The car seems to be building boost too quickly, and too much or something. I'm hitting 20psi of boost at like 4,700 rpm I'm third gear. And then I get an insanely aggressive power cut that jerks the entire car immensly. I don't know if it's spooling too quick, and there is an overboost failsafe that kicks in? But I try to do a pull and each time I'm getting this aggressive, lurching, power cut. And each time, I think I'm hitting 20psi of boost.

I don't know what in the heck!
And I want to try to see if someone has had this issue and if I can fix it without having to go to the dealer.

 

[VR30Infection]

That does sound like over boost protection. That is weird for a car that still has all its cats and no tune.

 

[offizial]

If you’re hitting 20psi with only a muffler delete, and no tuner boxes, then technically you’d have a boost leak.
We should look at this in the simplest way possible. I doubt this is true that you have an active boost leak. If your intake
had a hole/was disconnected, the MAF sensor would notice this and throw a code. After the intake are the turbo impellers. These are driven from the exhaust side of the turbo (from my knowledge) and then the flow goes into the intercoolers then into your intake manifold.

Perhaps your boost pressure gauge is faulty, or your turbo speed sensors. The turbo speed should hit 25k RPMs at full throttle and sit there, and then the highest boost I have seen stock is 17-18psi in 2nd (MT) around 5k rpm then dropping back to 15psi where it tops around 14psi from 3rd gear up. This is where a tune would help this car, I don’t know why Nissan capped the boost after 2nd gear, but I can only guess for longevity as the higher gear you are in, the longer the boost is active. This is tough to fix on your own, but I can only guess it must be your boost pressure gauge. (Technically)

However, while you would probably be the first one to experience this, your muffler delete could cause too much flow on the exhaust side of the turbo, and having a stock intake would limit the airflow. So while you do not technically have an engine code error, your car isn’t getting the air it needs for the boost it is achieving. Without going to the dealer, try an aftermarket intake, this will up the overall air your car will be able to suck in, I can only guess the limp mode is from the car pouring in too much fuel for the boost it thinks it’s making, and not enough air. Try disconnecting your battery for 30 mins to reset the ecu also. This may just fix the issue. Your ecu could be compensating for the exhaust (which it was made for) but is being restricted on the intake side.

 

[ZMidlife]

I would ask one of the primier tuners that sees thousands of VR30s or Nissan.

 

[FSUZ33]

Could it be a wastegate issue?

 

[AugustusCaesar]

Could it be a wastegate issue?

I'm thinking it must be. But I don't know how to diagnose that, and fix it. I'd rather avoid the downtime and potential for the dealer to mess up more stuff.

 

[offizial]

Have you tried resetting the ecu by unplugging the battery? I’m aware that the waste gate is calibrated to the ecu, it might just need a recalibration. Whichever way you go please keep us updated.

 

[AugustusCaesar]

Have you tried resetting the ecu by unplugging the battery? I’m aware that the waste gate is calibrated to the ecu, it might just need a recalibration. Whichever way you go please keep us updated.

Reset ECU, still does it. I made a video this time.

 

[offizial]

it’s picking up boost like crazy!

 

[AugustusCaesar]

This video shows it too, but less aggressive.

 

[AugustusCaesar]

it’s picking up boost like crazy!

So what do you think then? Surely it cannot be a product of the muffler delete? A simple axle back cannot mess with anything to that degree?

 

[offizial]

So what do you think then? Surely it cannot be a product of the muffler delete? A simple axle back cannot mess with anything to that degree?

If you reset the ecu then it can’t be the exhaust. Do you feel the extra boost in performance? This could determine electrical (boost gauge) vs waste gate issue

 

[offizial]

It doesnt do this 1-2? It’s weird. I’d be taking off my intakes as I’ve got the nismo cai and driving to the dealership!!

 

[AugustusCaesar]

It doesnt do this 1-2? It’s weird. I’d be taking off my intakes as I’ve got the nismo cai and driving to the dealership!!

It can do it 1-2.
But the lurch is so much more, I felt is safer when trying to replicate the issue, to do it in the higher gears. I think I can feel the extra performance. What bothers me, is that hotbox or whatever basically adds boost to get to where my car is. So is the lurch a failsafe? Or am I destroying my engine by trying to replicate the issue?

 

[offizial]

It can do it 1-2.
But the lurch is so much more, I felt is safer when trying to replicate the issue, to do it in the higher gears. I think I can feel the extra performance. What bothers me, is that hotbox or whatever basically adds boost to get to where my car is. So is the lurch a failsafe? Or am I destroying my engine by trying to replicate the issue?

For real, I was going to install my tuner box and now I’m thinking not to. Bc they send the boost to 20psi no problems. Whatever it is the car doesn’t like it, but it seems like it’s just cutting fuel, no real problem for the engine to take. I think the wastegate may need to be recalibrated or turbo replaced. Which is confusing to me bc it should not be happening in the first place!