Stroked m50 dies at high RPM

[02stu]

I have a 2.8L m52 bottom end and a non vanos 2.5L m50 head with all of the m50 electronics manifold etc. It has plently of power under 4,000 rpm but after wards the exhaust note changes dramatically and it looses power. Any ideas on what could cause this? Is it fuel starvation?
Thanks

[TwoJ's]

Have you checked fuel pressure? Checked the plugs for evidence of lean or rich condition?

[gazellebeigem3]

what software are you using?

[02stu]

stock m50 software for now, according to Tree house it will run fine on m50 software. Maybe not though. Think any chip would improve power at high RPMS? Could this be a sign of a clogged cat?

[SchnellerVert]

Sounds as thou you need to put it on the dyno and get some fuel curves of what it is doing.

Which ECU are you running 402 for the NV and what chip? Are you using a hotwire mas or the later style mas?

[02stu]

Alright so after doing a little more research it seems that the fuel pressure regulator is not supplying enough pressure, 47 psi vs. 51 that the m52 requires. What is the cheapest way to increase my fuel pressure? Does the vacuum hose running to the pressure regulator have an effect, or does it just effect idle? I would rather not buy a 200 dollar BavAuto regulator. Anyone know if the m52 fuel rail will work on a m50 intake manifold?

[SchnellerVert]

You could buy an oem higher pressure regulator. You have a 3.5 bar right now correct. Porsche uses 4.5 bar that are compatable.

[matt]

47 vs 51psi is not enough to make a difference. Especially not if your oxygen sensor is working properly.

Changing your fuel pressure is NOT a good way to change air fuel ratios if you're using an oxygen sensor.

[02stu]

I don't have an 02 sensor, I was under the impression that under full throttle the engine ran open loop anyways, is that not correct? Do you know if I could use the entire m52 fuel rail?

[matt]

No, that is not correct.

At full throttle, the motor is not reading the oxygen sensor, but it is USING data collected from the O2 sensor at part throttle for fuel correction. Fuel trims are calculated at part throttle, then applied globally.

I don't know about fuel rail fitments... I know I used the whole shebang off a 95 325i and it works great.

[Mot]

I dont see why the m52 fuel rail wouldnt work, my m50 manifold all fit right into it...

[dark89e30]

No, that is not correct.

At full throttle, the motor is not reading the oxygen sensor, but it is USING data collected from the O2 sensor at part throttle for fuel correction. Fuel trims are calculated at part throttle, then applied globally.

I don't know about fuel rail fitments... I know I used the whole shebang off a 95 325i and it works great.

Nailed it. Get that check engine light OFF! Until then, this thread is useless.

[02stu]

If I am able to get my check engine light to turn off, does that mean that I don't belong on R3V anymore?

[dark89e30]

Nah, but that light should be your first priority. We all know that there will be other issues... Your ECU, at this point, has no idea where your fuel trims should be at, especially since your engine is stroked. Your computer still sees a 2.5 and after it adapts, it should provide additional fuel. The FPR will definitly help but the only way the computer can tell where the A/F ratio is, is with an O2s. Have you checked your fuel pressure? Your FPR might not even be spiking the pressure.