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RB25det Power FC cut

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Hi there,

I d like to ask if anybody could help me diagnose my issue. My R33 S2 runs beautifully on stock 7psi hitting the 6800 rev limit and everything. After i installed the Turbosmart boost tee and raised the boost... at WOT the engine just cuts out about 6000 rpm like into a limp mode. When this happens my boost gauge is showing about 11 psi, the AFM reads 4400 mV and my AFR is 10.75 while desired is 10.95. Is it normal that my AFM voltage is raising like that with RPM (see pic)? could be that my AFM is faulty? I tried to scale the maf more precisely but there s just no change at all...

I already smoke tested the whole intake system...fixed heaps of small leaks but it s till happening... I m even thinkin about if my turbo doesnt have an internal air leak or something...

Setup: Power FC, stock turbo, 550cc Sard injectors, Z32 MAF, 2 years old Splitfire coilpacks, standard spark plugs gapped to 0.8mm, brand new Turbosmart blow off valve, Bosch wideband O2 sensor

Thank you guys

well, what is your rev limiter set to in the power FC?

G'day David.

How are you tuning the Power FC? With a commander, or a PC interface at all?

It's not unusual for your actual AFR to be a little off from the target, you need to tune the base map in the PowerFC to get these to match up.

Can your PowerFC do any boost control at all?

Does your power FC have the boost pressure sensor kit installed and active? If it does the system has a boost cut built into it based on the selected target boost level. If i remember correctly it is .25 bar above the target boost level.

Arghx7: the rev limit is set to 6750rpm

Zac.Perston: yeah i ve got the datalogit software to it I ve tried to tune it by changing the airflow data at the MAF settings and get the same as the target but still cuts out... I took off the turbo though and i found out that it s not the stock one...looks like a Garrett GT28 but i m not really sure see pic

RBS14: I heard about that cut but i have the boost control switched off... the boost is set through a turbosmart boost tee

Can u guys see the pictures I m attaching?

I can't

I know you've mentioned you have 2 yo splitfire coils, however I'm still wondering if you are perhaps running into a misfire situation rather than a limiter? It might be worth trying a tighter plug gap to see if this helps. The coils tend to bake in the valley between the cams, particularly if you're still running the standard cam cover and this drastically reduces their life.

when the cut happens it s like hitting the wall... doesnt feel like a misfire thing at all :/ I m holding full throttle....boost cuts out...revs holding 6000rpm like in a limp mode...its really strange... Last week put on new plugs 6x NGK BCPR7ES...they came with 0.8 gap...

here s the chart again whats happening:


Tomorrow I m getting rid of the boost tee and installing a new wastegate actuator to 11psi lets see what happens...yeah and thats my unknown turbo:


Just to be sure, even though you've got it turned off, set your boost control settings in the power fc well out of the range you could ever hit, just to rule out that being a possible issue.

Post screenshots of all your tables and settings. Also, you need to set all your boost settings to max to make sure it's not doing a boost based fuel cut.

Hey guys... so the thing is that to run on 12-13psi I needed a 25psi wastegate actuator spring...like, is it normal? anyway, here s the boost cut what I was talking about:


and here are my power FC settings...



In settings 5 set all your "boost" values to 2.0 to raise the fuel cut. That's probably not going to fix it (doesn't look like you have a boost sensor hooked up) but do it anyway just to eliminate it as a possible cause. Is the boost tee still installed? Are you sure you pressurized the whole system to check for leaks? Smoke tests don't put the piping system under boost.

sry did you mean in the setting 1 right? yeah I removed the tee and changed the actuator for a bigger one... yeah like the pipes and intercooler are good I put pressure on them separately and they are holding pressure... but if I pressurise just the turbo inlet and block the compressor house outlet from it... everything comes out from the disconnected inlet manifold and the crankcase house... I wish I could try another turbo just like that

Yes settings 1

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