03-20-2018, 12:59 PM | #43 |
Drives: none Join Date: Nov 2012
Location: Dallas, tX
Posts: 248
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I couldnt get traction today and didnt feel like heading out to the highway. Anything north of 65mph around me will get you a fat ticket so doing 100 on side roads wasnt in the cards today.
It was well north of the 2nd line approaching the 3rd line, but that wasnt on a long, stable pull since I couldnt get enough traction to get a clean pull off. BUT I dont really remember where the boost was at before I backed it out 1/4 turn. Im really guessing I didnt gain anything. |
03-20-2018, 01:23 PM | #44 | ||||||
Cal
Drives: 2017 6th Gen Camaro ZL1 Coupe M6 Join Date: Sep 2013
Location: Newport, NC
Posts: 779
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Based on other posts, it seems there is a wide variation between "stock" pre-load settings. Lt1z350 had 2 1/2 turns - others had barely 1/8". I wonder why? Quote:
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I'm sure you can understand the scepticism, though. These are very dramatic changes for such a seemingly minor adjustment. Not that I don't believe you - you obviously have the logs to backup your words - but the boost increases showing in your logs do not seem possible without a pulley upgrade. Using a Google search for [convert kpa to psi] 130 kpa = 18.8549 psi 170 kpa = 24.6564 PSI 190 kpa = 27.5572 psi Could the pressures recorded in your logs be sampling from a different point than the boost gauge on the instrument panel? Hell, even if you half these numbers it's remarkable. I'm guessing the "other trick" you mentioned in your first post is some kind of solenoid adjustment or mod. This is truly a remarkable revelation! Like you said earlier, though, the power management system is likely to reduce much of the benefit for those of us maintaining the stock ECM tune. Please keep us posted on your progress. If you open another thread please reference it here so we can follow. [Questions] That much of a performance difference makes me wary. Several questions come to mind. -- Why would you not want throttle response to be as quick as possible from the factory? -> Could it be to meet EPA MPG/Air Quality targets? (yes) -> Could it be related to torque management? (yes) -> Could it be an assembly line QC issue? (yes) -- Are power increase claims universally true among other stock ECM ZL1's and due solely to preload adjustment? -> If so, at what cost? In other words, what else could be affected? --Would GM consider this a "modification" to deny related or unrelated warranty claims? Based on results of some Google searches, I believe that completely removing the preload is not a good thing any more than excessive preload. From what I've read, it seems pretty common that throttle response increases with less preload. Thanks to Lt1z350's explanation I can see how it makes more power with less bypass air. The only things I have concerns about are stuck bypass valve and possible heat build-up from too little bypass at idle and low RPM. Some of my references seem to indicate that zero preload risks stuck bypass valve (as 2017-ZL1 indicated) that could result in increased IAT (possible timing retard) and wasted fuel economy as the bypass would never open. On the other hand, too much preload allows too much air to bypass, resulting in lower boost / less power. I don't think this is something your dealer will adjust for you since they may view it as a "modification". If you're not worried about this then checking and adjusting preload seems like a relatively low-risk adjustment, provided you do it when the engine is hot and don't go with zero preload. I'd be very interested to see more hard numbers, though. Anyone else going to post logged boost, IATs, and other parameters before and after to compare? --Cal References: PROPERLY mounting your Boost Bypass Valve Super Charger Bypass Valve Adjustment. (posts 20858 & 20867) |
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03-20-2018, 01:27 PM | #45 | |
Cal
Drives: 2017 6th Gen Camaro ZL1 Coupe M6 Join Date: Sep 2013
Location: Newport, NC
Posts: 779
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03-20-2018, 01:41 PM | #46 | |
Drives: 18 ZL1 A10 Join Date: Nov 2008
Location: South East, FL
Posts: 3,024
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2017 ZL1 M6 Bog City, 2013 ZL1 M6, 2010 2SS M6
ZL1::J-E-T-S JETS JETS JETS |
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03-20-2018, 01:52 PM | #47 |
Cal
Drives: 2017 6th Gen Camaro ZL1 Coupe M6 Join Date: Sep 2013
Location: Newport, NC
Posts: 779
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03-20-2018, 02:05 PM | #48 |
Drives: 2018 Camaro ZL1 (A10) Join Date: Apr 2017
Location: Las Vegas, NV
Posts: 51
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“Unfortunately” (lol) for me, mine was set correctly from the factory. So no free gains for me. Dang.
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03-20-2018, 03:25 PM | #49 |
Drives: 2018 ZL1 M6 Join Date: Dec 2017
Location: CA
Posts: 301
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How do you know it is correct? What is “correct”?
Last edited by Boost or bust; 03-20-2018 at 07:35 PM. |
03-22-2018, 08:09 AM | #50 |
Drives: Red hot ZL1 A10 2017 Join Date: Nov 2016
Location: MS Back to France (29)
Posts: 804
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Same for me!
How do you know if it’s Correct ? Unscrew until there is a very little space... Then screw to barely touch I did less than a 1/8 of a turn It was correct, no change :-( |
03-22-2018, 09:43 AM | #51 |
Drives: 18 ZL1 A10 Join Date: Nov 2008
Location: South East, FL
Posts: 3,024
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Why can't it be a consistent 11.6 lbs of boost at 6000 rpm on every run? Why does it have to dip lower?
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03-22-2018, 10:01 AM | #52 |
@zle_blackwing
Drives: 2018 ZL1 1LE Join Date: Mar 2017
Location: S OC
Posts: 1,390
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Is there a reference in the service manual for this adjustment?
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2018 ZL1 1LE - Red Hot, Nav, PDR
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03-22-2018, 10:12 AM | #53 |
Drives: 2018 ZL1 M6 Join Date: Dec 2017
Location: CA
Posts: 301
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Because of the torque control protocol in the computer. Throttle opening is not directly corresponding to your gas pedal. All of the sensors are constantly providing feedback to the computer. The computer then commands an acceptable throttle opening and allowable boost pressure. It can reduce the psi up or down regardless of where your right foot is. Welcome to Big Brother. You can massage some of this out with a custom tune.
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03-24-2018, 01:34 PM | #54 |
Drives: Crush ZLE M6 | 2000 Corvette FRC Join Date: Jun 2010
Location: Cencal
Posts: 1,659
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Only glanced at the boost gauge once on a quick drive this morning. Boost was PAST the third line, with a small amount of real estate between the needle and third line.
Theoretically the third line is 11.25psi so I figure I was in the ballpark of 12psi. What is the car supposed to boost to stock? I’ll try to do a few more pulls this afternoon. I’m going to do a good rinseless and Reload process here shortly. |
03-24-2018, 01:47 PM | #55 |
Drives: Crush ZLE M6 | 2000 Corvette FRC Join Date: Jun 2010
Location: Cencal
Posts: 1,659
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^^^Answer to my question: 9.4psi according to this GM presser
http://media.gm.com/media/us/en/chev...owerhouse.html |
03-24-2018, 01:55 PM | #56 |
Drives: 2018 ZL1 A10 Join Date: May 2017
Location: Wyoming
Posts: 106
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I only see the needle go barely past the 3rd mark so my calculation 8psi but I'm also at 7200 feet elevation so I would guess due to the air density it would be normal to be a few psi under sea level.
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adjustment, boost, bypass, lt1z350 |
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