[Beas]

Recently Dyno'd and 299whp was a lot less than expected. Cobb AP says a Boost leak, but i feel like there may be some other issues. Id like to hear some of you guys' thoughts on what could be going wrong.

2008 335i
Mods: Cobb stage 2, AR catless DPs, Injen DCI, HKS SSQV. stock exhaust

side note, 335i with same mods plus intercooler and exhaust made 405whp on same dyno.

Manual tranny. Red Line is 3rd gear pull. Blue line is 4th gear. graph is power x speed.

My main concern is the ~30hp drop at about 5500 rpm and then power falls off.





thanks for reading.

[jpsimon]

did you log?

[rader1]

We'll need to see some logs to begin trying to help. However, since you're already getting a 30FF code then that's probably your issue. A boost leak is a power killer.

[themyst]

Where is the baseline on stock boost.

[Beas]

Originally Posted by themyst

Where is the baseline on stock boost.

dont have it, it was just a dyno day. 2 pulls is it.

going to open it up wednesday and try and fix the leak.

[AU335i]

I don't think the power just dropped at 5500 RPM... if the Red is a 3rd gear pull then that fall off is about right since 3rd redlines around 100...

[Beas]

the blue line, pull in 4th, was the first run and the motor was not really warm. that may have had something to do with the fall off.

Fixed the boost leak today and can feel a huge power jump. Shop said it was a bad O-ring. hopefully im closer to 350whp now.

[Ken_C]

Originally Posted by Beas

the blue line, pull in 4th, was the first run and the motor was not really warm. that may have had something to do with the fall off.

Fixed the boost leak today and can feel a huge power jump. Shop said it was a bad O-ring. hopefully im closer to 350whp now.

Bad o-ring where?

[Fundahl]

Originally Posted by Ken_C

Bad o-ring where?

Probably throttle body.

[Wedge1967]

I don't personally think it's a boost leak because it would be more consistent. Looks like your 3rd gear pull had a power drop about the same up top. With high compression / high boost / high RPM, you're plugs may not be able to keep up with the current gap. Have you replaced your plugs and did you reduce the gap from stock? I've seen 1000 hp engines on a dyno turn as little as 800 hp because of the plugs were gapped to wide. So it's not to far off the mark to say your ECU is pulling timing because you're getting a misfire at high RPM due to your plugs. I know it's a pain when you're on the dyno to make adjustments like this, but you could pick up some hp smooth out the top end of your power curve.

[Beas]

As for the O-ring, i have no idea where. i was in a rush and just picked up the car and left.

Originally Posted by Wedge1967

I don't personally think it's a boost leak because it would be more consistent. Looks like your 3rd gear pull had a power drop about the same up top. With high compression / high boost / high RPM, you're plugs may not be able to keep up with the current gap. Have you replaced your plugs and did you reduce the gap from stock? I've seen 1000 hp engines on a dyno turn as little as 800 hp because of the plugs were gapped to wide. So it's not to far off the mark to say your ECU is pulling timing because you're getting a misfire at high RPM due to your plugs. I know it's a pain when you're on the dyno to make adjustments like this, but you could pick up some hp smooth out the top end of your power curve.

thanks for the response Wedge.

I replaced the plugs about 3 months ago when i first installed the Cobb AP. As for the gap being too wide, idk its possible. i didn't put them in, shop did it along with some other installs. Maybe i can make a hard pull in 3rd then check the AP and see if im getting any misfires.

The motor def feels stronger, but that doesn't mean its not still dropping off hard at the top end.

[Wedge1967]

Yeah, a lot of times you can't tell if the engine is missing at high RPM, but it will drop power and pull timing if it does. Anytime you increase the boost with a mod, you're taking the chance it will misfire at high RPM because you're just exceeding the ability of the plug to fire under those conditions. Reducing the gap will fix some of the issues. NGK Iridium's are a good replacement if you do have issues. The finer tip the better. You can find them in .4 and .2 mm. They will last longer than copper or platinum, although copper is the best conductor. But if you go copper, you may end up changing your plugs as often as you change oil.

Good luck and hope you can fix the issue.

Originally Posted by Beas

As for the O-ring, i have no idea where. i was in a rush and just picked up the car and left.



thanks for the response Wedge.

I replaced the plugs about 3 months ago when i first installed the Cobb AP. As for the gap being too wide, idk its possible. i didn't put them in, shop did it along with some other installs. Maybe i can make a hard pull in 3rd then check the AP and see if im getting any misfires.

The motor def feels stronger, but that doesn't mean its not still dropping off hard at the top end.