Hi all, My RB8 has not been boosting correctly for a while and so far none of my local Renault specialists have been able to successfully diagnose the issue. It reaches around 0.5-0.6bar, where it then surges/fluctuates by 0.1bar until redline. This surging is clearly audible and is confirmed by the RS monitor. Some time later the check injection warning comes up and "DTC226322 Boost Pressure Circuit" error is logged. The issue started a few days after installation of a catless downpipe along with a tune, however that same code had come up a few months prior, with no noticible (to me) symptoms and was simply cleared. I have since tested with the stock map again and the issue still occurs. After looking for any boost leaks and swapping various sensors around, it was initially diagnosed as the turbo - the compressor wheel blades were damaged. (Air box had not been tightened at some point so we believe this is the cause) I then had the turbo rebuilt (into a hybrid) and the DV and actuator were tested and working. This did not solve the issue, but given the damage, it had to be done so I wasn't too worried. The n75 valve, boost pressure regulator and map sensors were swapped with known working ones, which yielded no change. Next suspect was the actuator, even though the turbo builder did test it, the workshop that removed and refitted the turbo used an air compressor and found the wastegate opened at around half the pressure of a Meg 3 GT in the shop at the time, so we were pretty confident that the actuator was leaking. After searching for one locally I eventually just ordered a Forge actuator from k-tec. My Renault specialist installed it and set the preload to the same as that of another RB8 in the shop, also with a Forge actuator. Again, no difference. I then left it at the workshop for a week him to take his time and go through everything, vacuum hoses, wiring and software configuration. He compared the configuration with that of his own 265 and made some changes. It is now boosting a bit more smoothly, but still only around 0.7bar and fluctuating a little. Any insights or ideas anyone can give would be appreciated
assuming had good look at plugs (correctly gapped) injectors (one weak one will do it) and coils again one weak one id be looking at mapping after that
Thanks for the reply. Plugs were checked last service, a couple months before issues started, though they are high on my to do list. I was going to have injectors tested/cleaned when the turbo was being done, but then I ordered the 630cc injectors from K-tec so I didn't bother. The problem is that I need to do a remap with the bigger injectors, which I can't really do if the issue still persists as we won't be able to log it properly. So they are still waiting to be fitted. Can't remember if my coils were ever checked, but my #4 coil is loose as the thread for the coil bolt is worn. My local workshop ordered the necessary helicoil. Haven't felt any misfires, though I wouldn't be surprised if I missed some. Given the "Boost pressure circuit" dtc, surely that rules out anything related to ignition/fueling? Ofcourse an issue there could definitely cause my symptoms, but would it not log a different error :?
So still few things not properly checked here, plugs should be .6mm also why fitting 630 injectors ? Another classic is fuel pump if weak will deffo give these symptoms
Injectors are because of the hybrid turbo. Fuel pressure is apparently perfect. I'll see how it goes after doing the plugs and fixing the coil
A local tuner here in South Africa. I did test again with the stock map though so the map shouldn't be the culprit
And it was still the same? I had similar issues and chased then for ages and it was down to a really poor map, Had it tuned by EFI and it disappeared
Yeah, initially it would audibly fluctuate between 0.6-0.7bar Then when we tried the stock map again, it would fluctuate between 0.5-0.6bar. The surging wasn't as noticable, especially in normal mode, but I think that's because it was boosting less
Clearly there is still something wrong if it only boosts at 0,7bar, these do around 1 bar standard! Not much we can do or say over the internet really. Do you have an aftermarket intake fitted? I’ve had a car with Injen hardpipe kit on the dyno which would surge like mad, removed the N75 dump port from the intake kit and it solved it. Apparently some kind of swirl caused inconsitent ambient conditions for the N75 valve
@tutuur Yeah, hence the post I had an intake made earlier this month, but the issue started in September. Interesting about the possible effects of the intake though!
Got the car back from Renault this week with new plugs, fixed coil threads and some other maintencance items. Technician said he needs more time to go through the whole boost circuit. In the mean time I'm going to take it to a specialist who is willing to swap parts with his own 265 and get him to test with his sound generator pipe(incase the diaphragm inside is torn), primary o2 and then probably coils and injectors.
Really weird issue I have never encountered before! Normally through logging on the dyno I can pretty much diagnose any fault in seconds. If you want me to have a look over there are options
Any help or suggestions would be appreciated. The cost of all the diagnostic labour is adding up Sadly I don't have any logging tools that work nicely on this car, but I can try find someone who has
