![]() ![]() We were running a huge boost spike (22 psi ?) going down to 16 psi at redline. ((We were able to make more power on my gf car with the stock turbo with a modified manifold using an external wastegate and plenty of porting/modification. That regardless of the tune boost will not remain constant at 14-20 psi range. What I needed is confirmation from the members that you all have the same experience:-īecause of the small turbo in the N55 the turbo run out of breath and boost will tapper in the top RPM. At that point, the turbo was way past its efficiency range, would not last very long (who cares right ?) and we were running in the high 13's AFR (not recommanded).Īs for the cam phasing, we discovered that on a friends car who was able to hold 16 psi at redline with his stock manifold, only to discover, when tuning his bigger turbo setup, that he was one or two teeth off on the exhaust cam. Results were 340 whp and 400wtq on a stock turbo, while the same car without these modification was doing 300whp 320wtq at 20 psi falling to 14-15 psi at redline. ![]() We were able to make more power on my gf car with the stock turbo with a modified manifold using an external wastegate and plenty of porting/modification. OR the pcm might do nothing and just add the right amount of fuel and DO more power (as long as the air is not getting super hot and the engine not knocking). Depending of the computer algorithms, it might pull timing, reducing power, or go into limp mode or whatever. porting the exhaust manifold (if there are any bottlenecks)Īnything else will results in big boost spikes. You might be able to hold more boost doing some modifications, but never in a significant mater. This is typical of small turbo running out of breath. Running 16psi at 6500rpm would be a whole other story. To be fair, sometimes it is fueling system limitations, but even when the fueling system is up to task you'll see this happen. Tunes gain huge percentages of torque or horsepower in the midrange, but less so at higher RPM. You'll find the same thing going on in other aftermarket tuned turbo cars. a stage 1 tune may show fains of +80-100 ft-lbs with 16psi midrange, but only +50-60hp up top at 10-12psi. That's an indication they are running out of flow. Outlet temperatures start to raise drastically with more boost. But at 6500 RPM the turbos seem to start to choke around 10-12 psi. The turbos are probably fine midrange and fairly high boost. The nature of how turbos work with regards to efficiency and spindle speed means running tons of boost midrange is generally no more dangerous to the turbos than moderate boost a higher RPM. You should spend less time worrying about what boost level is safe and more time worrying about what flowrate is safe. I wonder could 12 PSI be the maximum the N55 turbo? Did anyone actually run 16-18 psi on N55 and stayed constant at higher RPMs? Would I typically more boost with downpipe ( how much)? Will rotating the wastage rod 3 to 4 turns help increasing boost? I use AEM methanol injection to be safe and always careful!!!. I have tried different trick to manipulate the wastegate but my problem is -boost spikes!!! Sometimes boost peaks to 25 psi at lower RPM but still drops drop to 12 PSI above 5000!. Vacuum at the wastegate will increase to 20hg at high RPM but boost (still) decrease to around 12 psi. I have used a vacuum gauge at the wastegate line to read the vacuum single. I want boost to be constant at 15-18 PSI. My car runs 373 HP at the wheels ( Mustang Dyno). Boost will tapper to 12 psi from 5800 RPM. My setup include pp-performance tune which would allow boost to raise to 15psi. I have 2011 BMW 135i and I wonder can the N55 single turbo maintain 15-18 psi above 5800RPM and up to the rpm limit. ![]()
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