Power Cutting out under Full Boost

[Robo's]

Im getting Power Cut for a split second between 3500/4500 rpm under full throttle. If i wind down the boost (below 15psi) i dont get it but over that i get this power cut. From 5000rpm to redline i dont get it at any boost.

I am thinking its the AFM maxing out, but reading from the SAFC i dont get 100% Air Flow until about 5000prm, so why would it do this below 5000rpm with Air Flow between 80/90%.

Is it Boost Cut, do the Series 1 R33 GTST have boost cut???

Its quite temperamental, sometimes i get it and sometimes i dont but its always in the midrange where boost is at its peak.

Im running a HKS 2530 too.

[RB30-POWER]

Well the factory torque peak figure for the rb25det is at 4400rpm (295nm)

Generally where peak torque is, this is where the motors volumetric efficiency is at its greatest (where it can take in maximum air per cycle)

Thats basically what cams do, they move the peak volumetric effiency point around the rev range. And where the rev point that the motor can use maximum air is, you are going to get maximum torque.

So anyway, back to the point, around 4400rpm is where the RB25 cams allow the motor to take in maximum air.

So my guess would be that is why its cutting there. (Thats the point where the motor makes peak torque and uses maximum airflow it can, which must be just tripping the Air Flow meter cut)

You could always get a fuel cut defender, this holds the air flow meter voltage as high as it can without actually cutting.

Some more info on VE here.

http://www.epi-eng.com/ET-VolEff.htm

[RB30-POWER]

And remember if you only get it sometimes, I bet its on the cooler days that it cuts out because the air is more dense. Which will cause the AFM to read more air, naturally.

[Robo's]

And remember if you only get it sometimes, I bet its on the cooler days that it cuts out because the air is more dense. Which will cause the AFM to read more air, naturally.

Yes generally get it on cooler days.

Looks like its time for a Z32

[devious17]

Hey Robo's, I had the same problem too after installing my Profec B. Everybody is either telling me this or that but no one can give me a good solution to this cutting off problem, I paid a visit to one of our tuning shops and the mechanic listened intently to what I had to say then he walks over to my car,popped the hood and unpluged the MAP sensor driving the stock in dash boost meter. Then he said " Now take it for a spin and see if it's still happening" . Took it out gave it a good wallop and NO MORE CUT OFFS! Everytime!

Now I gotto go get me a boost meter.

[Robo's]

Z32 fixed it

[bangahh]

Hey Robo's, I had the same problem too after installing my Profec B. Everybody is either telling me this or that but no one can give me a good solution to this cutting off problem, I paid a visit to one of our tuning shops and the mechanic listened intently to what I had to say then he walks over to my car,popped the hood and unpluged the MAP sensor driving the stock in dash boost meter. Then he said " Now take it for a spin and see if it's still happening" . Took it out gave it a good wallop and NO MORE CUT OFFS! Everytime!  

Now I gotto go get me a boost meter.

Where abouts is the map sensor driving the indash boost meter ?

[devious17]

It a small black box near your brake's master pump. a hose going tothe intake plenum and a plug underneath the MAP sensor. Hope that helps