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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > N55 Turbo Engine / Drivetrain / Exhaust Modifications > Throttle closure at 2300rpm?
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      04-29-2018, 01:58 PM   #1
Lancelot
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Throttle closure at 2300rpm?

Hi

I got a custom tune 2 weeks ago from a local reputable tuner, and i've been experiencing an issue around 2200-2300rpm, where the engine would not accelerate frankly but instead behave uncertainly.

I've got this log here and the sequence from 0:00:02,057 to 0:00:02,076 for instance,
http://www.bootmod3.net/log?id=5ae60752d10b436f3d89c554

- accel pedal is steady at abt 73%
- rpm woes from 2350 down to 2200, and timing drops from 5 to 3.5 deg
- followed by throttle angle going from 74.5% down to 62%

I haven't noticed this happen at other engine speeds, it's very clearly, and repeatably so at 2200-2300rpm under load but not WOT, I've noticed it happen almost systematically at that particular engine speed.

Now I don't see anything else in those logs, what could be a cause for this?
What else would you recommend I log?
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Last edited by Lancelot; 04-29-2018 at 02:19 PM..
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      04-29-2018, 02:38 PM   #2
the dope steez
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Well it's kind of hard to tell from your logs, But throttle closures aren't much to worry about, it's a result of too much boost being generated so to protect itself the car tapers the throttle. Perhaps the tune is requesting too much boost at those RPMs?
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      04-29-2018, 02:46 PM   #3
Lancelot
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It's a custom map as the BM3 doesn't have a OTS map for ActiveHybrid 3 unfortunately

Regarding boost, it's only about 11psi so that doesn't sound like much?

I also noted on logs I have it's always on 6th speed, wondering if there is some feedback from the gearbox to reduce the load, since with the tune we're close to 600Nm it might be hitting the gearbox input limit which is lower in 6th gear and it's protecting itself? But why at 2200 rpm only then...
Need to log the engine torque too I guess.

Or could it be misfires? (no CEL to report though but it could go undetected)
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      04-29-2018, 06:52 PM   #4
bradsm87
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All of the 8HP70 N55 TCU calibrations I've seen have a 760nm torque limit so I doubt it's that.
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      04-29-2018, 11:23 PM   #5
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First, you AH guys suck with you're awesome transmissions.

Second, from what I've seen in MHD whatsapp chats, throttle closures are pretty normal even on a stock car.

I'm far from knowledgeable in reading logs so take this with a grain of salt, also I don't know BM3 logging so forgive me there too.

WGDC, maybe it's different in BM3 but that looks funky to me during the whole log.

In MHD there is a "timing correction per cylinder." Is that data available in BM3?
Also, MHD has "torque limit" field that pegs over 1,000,000 when the tranny is limiting torque, if you have that value take a look at that as well.
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      04-30-2018, 02:30 AM   #6
enemigo13
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throttle closures at low rpms are normal when throttle along with wg tries to maintain required boost. stock m2 has them even at high rpms. why you will not see it at higher rpm range with correct tune? because targets usually are higher than stock turbo can give. And throttle closure occurs when actual load is higher (or close to it) than required. So at low rpms even stock turbo is able to provide virtually any load (200%+) so if it temporary overshoots throttle keeps it down.
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      04-30-2018, 04:16 AM   #7
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Quote:
Originally Posted by enemigo13 View Post
throttle closures at low rpms are normal when throttle along with wg tries to maintain required boost. stock m2 has them even at high rpms. why you will not see it at higher rpm range with correct tune? because targets usually are higher than stock turbo can give. And throttle closure occurs when actual load is higher (or close to it) than required. So at low rpms even stock turbo is able to provide virtually any load (200%+) so if it temporary overshoots throttle keeps it down.
Thanks, most helpful, i'll datalog boost target and actual boost see how that looks
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      04-30-2018, 07:28 AM   #8
enemigo13
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yes but log boost of intake manifold not pre throttle. As throttle closes a bit
manifold pressure drops but pre throttle boost shoots up but as it does not enter engine it means nothing.

Quote:
Originally Posted by Lancelot View Post
Thanks, most helpful, i'll datalog boost target and actual boost see how that looks
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      04-30-2018, 10:55 AM   #9
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How does that explain this though?

Quote:
where the engine would not accelerate frankly but instead behave uncertainly.
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