Question about dyno and motor

autoart · 03-21-2013, 01:33 AM

Almost all n54 hp dyno graphs drop or flatin-out after about 5,500 rpms. My question is why? Are the turbo's to small? or is it somthing else? I guess I should be shifting at 5,500 rpms and not letting it go to 6500 rpms when I want to go fast. Thanks.

georgelb · 03-21-2013, 07:30 AM

Yeah, they're too small to keep increasing boost up to redline, or even holding the same as in the midrange. On your shifting...if you shift at 5500 to go faster, you're going to have a bad time.

AK 335i · 03-21-2013, 08:10 AM

shift around 6100-6300 rpm if you want to go fast in a 6AT on stock turbos

TTurbo335 · 03-21-2013, 09:59 AM

+1 I shift around 6k

Jeff@TopGearSolutions · 03-21-2013, 12:03 PM

5500 would be too low.

To really understand your shift points you need to dyno your own vehicle then calculate based on gear ratios your highest average HP at what RPM.

Torque is important too. Remember, shifting at peak power is not always the answer, sometimes you want to shift a little after peak power so on the next gear change it drops you into the meat of the powerband.

On average, shifting at 6100-6300 is usually the sweet spot for stock turbos.

Wedge1967 · 04-08-2013, 09:54 AM

Run'm out and run'm hard. Alpina AT shifts at 6800 and for a track flash I would think they probably did a lot of research as to where the best shift point was for the AT. Now that might be a little different for the MT as the gearing is different, but I've always found my 1/4 mile times suffer if I try to short shift. Just my opinion.

BEAR-AvHistory · 04-08-2013, 11:31 AM

With a light tune JB4/ISO + FMIC on 40% E85 I have my shift lights set for 6000, reaction time, mine not the DCT, adds a few hundred RPM to that. Based on my dynos & traps its the best place for me.

03-21-2013, 01:33 AM	#1
autoart Colonel 347 Rep 2,281 Posts Drives: 2009 335i e90 M/ 22 X3 Join Date: Oct 2010 Location: socal iTrader: (8)	Question about dyno and motor Almost all n54 hp dyno graphs drop or flatin-out after about 5,500 rpms. My question is why? Are the turbo's to small? or is it somthing else? I guess I should be shifting at 5,500 rpms and not letting it go to 6500 rpms when I want to go fast. Thanks.
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03-21-2013, 07:30 AM	#2
georgelb nsomneeak 39 Rep 501 Posts Drives: E92 RB 335i Join Date: Apr 2010 Location: DFW, TX iTrader: (3) Garage List 2007 335i [8.00]	Yeah, they're too small to keep increasing boost up to redline, or even holding the same as in the midrange. On your shifting...if you shift at 5500 to go faster, you're going to have a bad time. __________________ RB Turbos w/ N20 TMAP Sensor \| 93 Octane Protune by Cobb Plano \| xHP Stage 3 \| BMS DCI \| STETT CP \| Forge DVs \| RB PCV \| Helix FMIC \| CP-E Catted DPs \| Walbro 450 \| Bilstein B12 \| M3 Control Arms \| Defiv Lockdown Kit \| BBS CH \| Michelin A/S 3+ Hixson BMW of Monroe, LA - Shady Dealer \| Last edited by georgelb; 03-21-2013 at 07:31 AM.. Reason: they're their there
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03-21-2013, 08:10 AM	#3
AK 335i Major 48 Rep 1,290 Posts Drives: black 335i E90 Join Date: Sep 2012 Location: boynton beach iTrader: (0)	shift around 6100-6300 rpm if you want to go fast in a 6AT on stock turbos
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03-21-2013, 09:59 AM	#4
TTurbo335 Second Lieutenant 21 Rep 200 Posts Drives: BMW 335i Join Date: Nov 2012 Location: So Cal iTrader: (2)	+1 I shift around 6k
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03-21-2013, 12:03 PM	#5
Jeff@TopGearSolutions 3441 Rep 79,211 Posts Drives: C6 Z06, 09 335i, 10 335xi Join Date: Dec 2008 Location: www.TopGearSolutions.com iTrader: (37)	5500 would be too low. To really understand your shift points you need to dyno your own vehicle then calculate based on gear ratios your highest average HP at what RPM. Torque is important too. Remember, shifting at peak power is not always the answer, sometimes you want to shift a little after peak power so on the next gear change it drops you into the meat of the powerband. On average, shifting at 6100-6300 is usually the sweet spot for stock turbos.
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04-08-2013, 09:54 AM	#6
Wedge1967 Banned 125 Rep 2,172 Posts Drives: '07 e92 AT Sport Montego Blue Join Date: Sep 2011 Location: Portland, OR iTrader: (3)	Run'm out and run'm hard. Alpina AT shifts at 6800 and for a track flash I would think they probably did a lot of research as to where the best shift point was for the AT. Now that might be a little different for the MT as the gearing is different, but I've always found my 1/4 mile times suffer if I try to short shift. Just my opinion.
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04-08-2013, 11:31 AM	#7
BEAR-AvHistory 2020 Z4 M40i - 2022 M4C Convt 3129 Rep 5,264 Posts Drives: 2020 Z4 M40i - 2022 M4C Convrt Join Date: Jun 2011 Location: Raleigh, NC - OIB, NC iTrader: (0) Garage List 1965 COBRA (FFR rep ... [8.57] 2023 Jeep Wrangler ... [9.50] 2009 Yamaha V-Star [0.00] Cars 2-BMW, 2-FORD, ... [0.00] 2023 Ford Expeditio ... [0.00] 2020 Z4 M40i [10.00] 2022 BMW M4C [7.25] 1998 FORD Ranger 4X4 [0.00]	With a light tune JB4/ISO + FMIC on 40% E85 I have my shift lights set for 6000, reaction time, mine not the DCT, adds a few hundred RPM to that. Based on my dynos & traps its the best place for me. __________________ Kevin Dravit Gray, Black Leather, Moonlight Roof, Red Calipers 2022 M4C - 2020 Z4 M40i - 2023 FORD Expedition XLT Max 4X4 400BHP - 2009 V-Star - 1998 Ranger 4X4 5MT - 1965 Cobra (R) 5MT - 2023 Jeep Wrangler Sport S 6MT
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