Question about boost spike just after throttle lift - BMW 1 Series Coupe Forum / 1 Series Convertible Forum (1M / tii / 135i / 128i / Coupe / Cabrio / Hatchback) (BMW E82 E88 128i 130i 135i)

Neon01 · 11-23-2012, 02:54 PM

I assume this is normal, but just wanted to make sure. Car currently has Cobb AP stage 1+FMIC aggressive (93oct) linear throttle map. Did some logging today and pretty consistently find that my boost is peaking around 16.5-17 psi @ 4200 RPM, then tapering to about 12-13 psi @ 6200 RPM - about what I would expect. Except one or two data points after I lift throttle, at which it spikes to maybe 19-20psi, but only for a single data point. The extremely transient nature of the data there makes me believe it's not even accurately reading pressure, but I thought I would make sure.

Should I be concerned about this? The car has a ER charge pipe with Synapse BOV.

Also, what does the torque data actually tell me, if anything? I assume this is a calculated number, so I'm dubious about it's accuracy (I'm seeing peaks of close to 800 N*m, which is ridiculous, of course).

Stohlen · 11-23-2012, 08:44 PM

Thats just the pressure build up before the BOV is overcome and vents the pressure. Your system is functioning normally.

Tee-Dub · 11-23-2012, 10:20 PM

Pretty sure I've read this is normal on manual transmission cars. How do you like the COBB? I'm debating over tunes and am leaning towards the COBB although it is the most expensive I like the idea that it isn't a piggyback.

Neon01 · 11-24-2012, 02:08 PM

That's really what I like about it - the ease of use. That's worth a bundle to me, and if I were buying a tune myself I probably would go with the Cobb. My car came with it when I bought it used recently, so that decision was already made for me anyway.

Just the ability to data log and check codes so easily is worth something to me. The only thing I do wish it had that the other piggybacks give you is the ability to switch maps on the fly. Still, it's easy enough that I don't mind doing it with the Cobb.

Sauce · 11-24-2012, 04:03 PM

Back in the day when I had a Subaru and was a ricer, you could adjust the spring on the BOV to make it open quicker. Like someone said it is just the pressure before the bov is releasing. I don't know about Synapse specifically, but I'm sure there is some sort of adjustment, I'd look into loosening it up a tad. I don't think it's something to be super worried about but..

11-23-2012, 02:54 PM	#1
Neon01 BMW Nut Drives: 10 135i, 04 S2000 Join Date: Jun 2007 Location: Forest Hill, MD Posts: 413 iTrader: (5) Garage List 2004 Honda S2000 [0.00] 2005 BMW M3 - Retired [0.00] 2009 BMW M3 - Retired [0.00]	Question about boost spike just after throttle lift I assume this is normal, but just wanted to make sure. Car currently has Cobb AP stage 1+FMIC aggressive (93oct) linear throttle map. Did some logging today and pretty consistently find that my boost is peaking around 16.5-17 psi @ 4200 RPM, then tapering to about 12-13 psi @ 6200 RPM - about what I would expect. Except one or two data points after I lift throttle, at which it spikes to maybe 19-20psi, but only for a single data point. The extremely transient nature of the data there makes me believe it's not even accurately reading pressure, but I thought I would make sure. Should I be concerned about this? The car has a ER charge pipe with Synapse BOV. Also, what does the torque data actually tell me, if anything? I assume this is a calculated number, so I'm dubious about it's accuracy (I'm seeing peaks of close to 800 Nm, which is ridiculous, of course). __________________ SOLD 9/22/12 - 09 M3 Sedan \| Space Gray/Ext Fox Red/Carbon Current - 10 135i \| Alpine White* \| Coral Red \| M Sport \| Premium \| Cold \| iDrive \| 6sp \| BMW Performance 04 S2000 \| Berlina Black \| Black \| OEM Front Lip \| Pioneer HU \| K&N Intake \| Rays G-Games 77S 18s
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11-24-2012, 02:08 PM	#4
Neon01 BMW Nut Drives: 10 135i, 04 S2000 Join Date: Jun 2007 Location: Forest Hill, MD Posts: 413 iTrader: (5) Garage List 2004 Honda S2000 [0.00] 2005 BMW M3 - Retired [0.00] 2009 BMW M3 - Retired [0.00]	That's really what I like about it - the ease of use. That's worth a bundle to me, and if I were buying a tune myself I probably would go with the Cobb. My car came with it when I bought it used recently, so that decision was already made for me anyway. Just the ability to data log and check codes so easily is worth something to me. The only thing I do wish it had that the other piggybacks give you is the ability to switch maps on the fly. Still, it's easy enough that I don't mind doing it with the Cobb. __________________ SOLD 9/22/12 - 09 M3 Sedan \| Space Gray/Ext Fox Red/Carbon Current - 10 135i \| Alpine White \| Coral Red \| M Sport \| Premium \| Cold \| iDrive \| 6sp \| BMW Performance 04 S2000 \| Berlina Black \| Black \| OEM Front Lip \| Pioneer HU \| K&N Intake \| Rays G-Games 77S 18s

11-24-2012, 04:03 PM	#5
Sauce Lieutenant Drives: Montego 135 Join Date: Aug 2011 Location: Studio City Posts: 515 iTrader: (1)	Back in the day when I had a Subaru and was a ricer, you could adjust the spring on the BOV to make it open quicker. Like someone said it is just the pressure before the bov is releasing. I don't know about Synapse specifically, but I'm sure there is some sort of adjustment, I'd look into loosening it up a tad. I don't think it's something to be super worried about but.. __________________ KW V3's, Sparco Pro2000's, Vorshlag CP's, JB4, Heat Wrapped Raceland DP's, aFe stg. 2 Sealed Intake, Miro 111's, Hankook RS3's 225/245 (for now), Seibon M3 CF Hood, Turner Motorsports Alum. Radiator, Big Tom IC, BMW Performance bumper.

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11-23-2012, 08:44 PM	#2
Stohlen Lieutenant Drives: AW 135i Join Date: Aug 2012 Location: Waterford, Mi Posts: 542 iTrader: (1) Garage List 2008 BMW 135i [5.00]	Thats just the pressure build up before the BOV is overcome and vents the pressure. Your system is functioning normally.

11-23-2012, 10:20 PM	#3
Tee-Dub Captain Drives: 2008 135i Join Date: May 2009 Location: Vancouver, WA Posts: 754 iTrader: (9)	Pretty sure I've read this is normal on manual transmission cars. How do you like the COBB? I'm debating over tunes and am leaning towards the COBB although it is the most expensive I like the idea that it isn't a piggyback.