Strange peaks in power curve??

AW128i · 01-25-2011, 08:56 PM

I've notice on full throttle runs from a stop that the engine (N51) has two very distinct areas of the RPM range where the power delivery changes. I think it's around 2500 RPM and then again around 4000 RPM. When running at WOT from idle to redline, at those two aforementioned points, it's like the engine switches to a different cam or something. Could this be the 3-stage manifold that the N51 is rumored to have??

e90pilot · 01-27-2011, 10:10 PM

The 3-stage manifold in your N51 is not really a rumor, I can tell you it's a fact. Your observation on power is 100% correct. Those power peaks are the different stages where the intake resonates. You should feel it at 2750, 4000 and 6200. The one at 6200 is very subtle though. Check out the link in my sig. It has dynos from my 3-stage manifold swap. You'll really see the peaks there.

Evice · 01-28-2011, 06:01 AM

I do not feel that on mine with N52....and I thought N51 1 stage like N52? thought they are very same engines with different compression ratios for emission reasons.

AW128i · 01-28-2011, 07:43 AM

Quote:

Originally Posted by e90pilot

The 3-stage manifold in your N51 is not really a rumor, I can tell you it's a fact. Your observation on power is 100% correct. Those power peaks are the different stages where the intake resonates. You should feel it at 2750, 4000 and 6200. The one at 6200 is very subtle though. Check out the link in my sig. It has dynos from my 3-stage manifold swap. You'll really see the peaks there.

Good to know I'm not imagining things! I'll check out the dyno info when I get home.

e90pilot · 01-28-2011, 08:04 AM

Quote:

Originally Posted by Evice

I do not feel that on mine with N52....and I thought N51 1 stage like N52? thought they are very same engines with different compression ratios for emission reasons.

You don't have a 3-stage intake manifold so you're power curve is smooth. Lower compression means less power and torque so BMW slapped the 3-stance manifold on the N51 to make it equal to the N52. The N52 low output has a single stage manifold. In the US, the high output N52, which has a 3-stage manifold, is still found in the Z4 30i, the old X3 and X5, and of course the 2006 530/330. All those engines display the same power peaks.

amancuso · 01-28-2011, 04:06 PM

Looks like I've got an N51 as well. Was hoping for the N52 just because in the long run it will be cheaper to service. Oh well, I still love my car.

01-25-2011, 08:56 PM	#1
AW128i Major 44 Rep 1,003 Posts Drives: E82 N51 Join Date: Nov 2010 Location: Southeastern, PA iTrader: (1)	Strange peaks in power curve?? I've notice on full throttle runs from a stop that the engine (N51) has two very distinct areas of the RPM range where the power delivery changes. I think it's around 2500 RPM and then again around 4000 RPM. When running at WOT from idle to redline, at those two aforementioned points, it's like the engine switches to a different cam or something. Could this be the 3-stage manifold that the N51 is rumored to have??
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01-27-2011, 10:10 PM	#2
e90pilot Freight Dawg 102 Rep 2,103 Posts Drives: E90 325i Join Date: Jul 2005 Location: Oakland, CA iTrader: (3)	The 3-stage manifold in your N51 is not really a rumor, I can tell you it's a fact. Your observation on power is 100% correct. Those power peaks are the different stages where the intake resonates. You should feel it at 2750, 4000 and 6200. The one at 6200 is very subtle though. Check out the link in my sig. It has dynos from my 3-stage manifold swap. You'll really see the peaks there. __________________ --Marcelo '06 Arctic Metallic 325i \| Sport Package \| 6MT \| Dinan Stage III suspension \| Dinan exhaust \| 330i manifold swap! Click here! \| Active Autowerke tune \| 135i Brake Calipers \| Deiselboost caliper brackets \| E46 M3 front rotors
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01-28-2011, 06:01 AM	#3
Evice Major 194 Rep 1,457 Posts Drives: E92M3 Join Date: Apr 2009 Location: Somewhere here iTrader: (1)	I do not feel that on mine with N52....and I thought N51 1 stage like N52? thought they are very same engines with different compression ratios for emission reasons. __________________ My Track Videos
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01-28-2011, 04:06 PM	#6
amancuso Lieutenant Colonel 724 Rep 1,756 Posts Drives: 330it, 428ix, 430i Join Date: Oct 2008 Location: Lawrenceville, GA iTrader: (1)	Looks like I've got an N51 as well. Was hoping for the N52 just because in the long run it will be cheaper to service. Oh well, I still love my car. Last edited by amancuso; 01-28-2011 at 04:34 PM..
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