Fun Police Cutting The Boost At 4000Rpm Wot

[bugeyedcreepy]

Yep, a thousand people have all had this problem and none of them thought to post their definitive fix. AAAAaaaanyway, As described, I have an issue where at full-song the ecu seems to be cutting the fun when I reach 4000rpm. My car is a Mk1 BA XR6T with the 6 speed manual, X-Force Exhaust, Upgraded valve springs, uprated in-tank fuel pump, bosch 968 Injectors, big intercooler, and a 14psi tune that was getting 315rwkw for an aeon (I.e. 5 years give or take...) before this started happening. The car is normal in every other respect, doesn't miss under load, idles normally, no leaks, gets to full boost before 4k and manages boost rock solid no worries and nothing changed around the time this started happening (October 15th while trekking about in Sydney actually...) and since this issue started, I've changed out both the wastegate actuator and the wastegate actuator solenoid with no effect. Doesn't matter what gear I'm in it's steadfastly stops the giggles at 4000rpm on hard stomped acceleration.

Some more info, I have a boost guage fitted and I know for a fact that the boost dies abruptly at 4k. When I wind out the revs in the taller gears, the boost gets to the limit and stays there perfectly until 4k where it reduces to little over atmo, no spikes, no creep, nuthin'. The engine is happy to spin to wherever I want so long as I don't anchor the right foot to the firewall. I've taken it to the local (but non-tunable) workshop who were able to ask the ECU what it's problem was but it did nothing more than whine about mismatched diff ratio and wheel rotation differentiation because I have split tyre sizes front and rear but this is all stuff that's been that way since it was pumped up five years ago so it isn't the cause of the issue I have now. I've also tried the other tunes I have but they all have the same net effect, it's been near on two months without my speed fix and I'm starting to get cold sweats.

Since this has started happening, I've also rebuilt the engine's bottom end with CP Forged Pistons and dirty great girder looking conrods. I'm all but ready to take it to a local Tuner to get extra huff but I Really want this issue sorted before I take it somewhere to get more herbs up it... Is there somewhere I could take my car to in Canberra that could both find/fix the issue and pump up the volume??

Please help this forlorne T owner!

;(

[bugeyedcreepy]

Before anyone asks, Traction control on/off makes no difference. Likewise, cruise control, set/unset/off also makes nary a difference... Stupid Cars, why do they torture me so??

[ratter]

data log it and it should tell you what's going on, but it sounds like torque management, but unless something has been changed it does not add up

[JVK]

Certainly entertaining little read.Ratter is right,you need to data log or your gonna be chasing your tail.

[MX Dave]

I'm eager to hear what's wrong, best of luck mate :(

[bugeyedcreepy]

Okay, More info:

These are my fault codes,

P0236 - Turbocharger Boost Sensor A Perform

P0238 - Turbocharger Boost Sensor A Circuit High

P1635 - Tire/Axle Ratio Out of Range

....What is it Telling Me??

[bugeyedcreepy]

Well finally got myself a generic ELM 327 OBDII connector via USB but not sure what the best software is to use in getting into my XR6T. Any suggestions? Just after the simple things like data loggiing and fault code analysis.

[Adam]

Gentech it Canberra are a good workshop.

Not the best time of year for something to go wrong though. A lot of places are probably shutdown over the holidays.

[ratter]

Not the best time of year for something to go wrong though. A lot of places are probably shutdown over the holidays.

Correct, but most would have been able to help at the time of the original post, probably out of luck for a little while now