[hawk02]

Originally Posted by ninetres

Are you insinuating the MAP sensor can’t read the (theoretical) 1-2psi increase for some reason, and adjust fuel accordingly? Worst case scenario is those tables being extra rich for protection.

No. I'm more concerned about cylinder air mass, spark timing and knock.

[Infern0]

Originally Posted by hawk02

How do we know what the proper adjustment is supposed to be? There's been no "official" instructions for checking or adjusting the bypass valve. At least the LSA has a tool available to make the adjustment in spec. If messing with the screw adds a pound or more of extra boost as some have described, I'd be concerned that the limits of the stock tune could be exceeded, especially for those running on 91 octane.

Don't they all receive the same tune universally from the factory? They aren't tuned to what the screw is set to individually.

As mentioned above, they are simply bolted on to the car directly from Eaton.

If the above follows logic, if "you" were one of the ones who happens to be over-tightened, the correction would make it run better, as it would be corrected to what the tune assumed was in place from the start.

[Fraxum]

Originally Posted by Infern0

Don't they all receive the same tune universally from the factory? They aren't tuned to what the screw is set to individually.

As mentioned above, they are simply bolted on to the car directly from Eaton.

If the above follows logic, if "you" were one of the ones who happens to be over-tightened, the correction would make it run better, as it would be corrected to what the tune assumed was in place from the start.

What I don't get is why is that set screw there at all? Does the arm touch the screw while driving?

[Fraxum]

Reporting back on this. After 4 all out runs in 300 DA my MPH was just 125. Seems low to me. But then 1,300 miles may have something to do with it. I am very slightly off the set screw, so I will try a snug fit next.

[17CamaroZL1]

Originally Posted by Fraxum

Reporting back on this. After 4 all out runs in 300 DA my MPH was just 125. Seems low to me. But then 1,300 miles may have something to do with it. I am very slightly off the set screw, so I will try a snug fit next.

Snugging the screw shouldn't change anything unless it lowers boost a tad, right? Do you have PDR vids of your runs? I can compare them to mine and see if it is a track timing system issue. My hometown track reads 1.5 to 3 mph lower than the other 2 tracks I've ran on when crossing the line at the same PDR speedo readings, depending on which lane I'm in.

[phaedrus]

I was skeptical this would do much to the performance of my car (2018 Convertible M6) and the jury is still out in my mind, but backing mine off (counterclockwise, as was initially suggested) does repeatably increase the *peak* boost reported by my P3 gauge (details below). I don't know what it does to the boost curve, if anything. n't

I haven't been able to test it at the dragstrip, but I am getting gains of up to 2 tenths of a second in 0 to 60 MPH (don't love the metric obviously, but it's the only way I can time it, again with my P3 gauge). I know that sounds like a lot and I wouldn't bet my life on it as it's only repeatable around 2/3 of the time (the only 1/3 of the time it runs the same as the factory setting). It's further complicated by how finicky the car is to launch.

Details in the table below. Cliff notes are that with the screw in the stock position it runs in the 3.9 range (0-60) with a "good" launch and 4.1-4.2 with a bad one (bogging, if the tires light up I bail on the run). With the screw backed off a bit, I run 3.71-3.72 consistently with a good launch, 3.9 with a bad launch, and three "holy shit I wish I could do that consistently" launches that resulted in 3.53-3.54 0-60 times.

Boost Screw Position Peak Boost (via P3 Gauge) 0-60 MPH (via P3 Gauge)
Stock 10.9 PSI 3.91 seconds
Stock 3.91 seconds
Stock 4.28 seconds

1/8 Turn Counter Clockwise 11.6 - 12.3 PSI 3.53-3.54 seconds
1/8 Turn Counter Clockwise 13.5 PSI once 3.71 seconds
1/8 Turn Counter Clockwise 3.91 seconds

1/4 Turn Counter Clockwise 11.2 PSI 3.72 seconds
1/4 Turn Counter Clockwise 3.91 seconds
1/4 Turn Counter Clockwise

1/8 Turn Clockwise 10.0 PSI Haven't tried
1/8 Turn Clockwise
1/8 Turn Clockwise

1/4 Turn Clockwise Haven't tried Haven't tried
1/4 Turn Clockwise
1/4 Turn Clockwise

[Fraxum]

Originally Posted by 17CamaroZL1

Snugging the screw shouldn't change anything unless it lowers boost a tad, right? Do you have PDR vids of your runs? I can compare them to mine and see if it is a track timing system issue. My hometown track reads 1.5 to 3 mph lower than the other 2 tracks I've ran on when crossing the line at the same PDR speedo readings, depending on which lane I'm in.

Back again. I dunno if Atcos mph #s are accurate but I would suspect they are. So I snugged the screw instead of the slight gap from before. My mph was slightly under 125 as I would expect with the higher DA from my 125 runs. Stock my screw was about 1/4 turn in. This adjustment did not make any changes on my 5th gen ZL1 either for me. On that car by fooling around I did make it slower. So My conclusion so far is if your adjustment is way off you can fix that, but most ZL1s are okay. However, 3 ZL1s have run 128-129 stock, maybe those MPHes were off. I ran in over -1,000 DA and my mph only went up to barely 126.

What we need are back to back dyno runs. I will ask what Ted Jannety thinks. He has a CA6 ZL1 now.

[17CamaroZL1]

If you have PDR you can compare your speedometer to the track speeds and tell if the track is right, high, or low. Both Clay City, where I ran my 10, and Bowling Green read pretty much dead on what my speedometer does. My hometown track in London reads about 1.5 mph slow in the right lane and 3 mph slow in the left. I've ran as low as 121 in 3500 DA and as high as 127 in around 600 DA at London. I think I've always ran 125 to 127 at BG with between 1700 and 900 DA. I've only ran at Clay City once, but made 9 or 10 passes that night, and was mostly running 128 to 129.5 in -800 DA. The outside air temp and how cool you keep the blower, makes a big difference in your trap speed with these cars.

I'll probably play around with the set screw when I get the chance. I'm not really expecting it to make a difference, but it's worth a shot.

[big dave]

Since the speed at the track is based off an average between 2 points, I expect the PDR to read perhaps a couple mph higher than the mph on the time slip. I've run 128+ at 3 different tracks. I've discounted my home track because it has been proven to show a vast difference in mph between the 2 lanes. It has shown mph as high as 131. Hopefully it has been fixed by now. For me the key is that all the ets have been consistent. My quickest pass was run at Maryland International Raceway, where my mph seemed to be in line with where it should be for the given et. I think it legitimizes my 128-129 mph because it was done at multiple tracks.

I think my bypass valve must be set up the way it should be, I have no plans on touching it. Maybe I'll toss in on the dyno one day, I don't think it'll put down anything special.

[17CamaroZL1]

Exactly Dave. I probably shouldn't assume everyone knows that the track mph is an average between two timing lines at the end of the track, but that's how I verify how close the tracks read compared to the car, other tracks, and even individual lanes. For our stock cars you can basically look at the speedo mph at the finish line and subtract 2 mph and the track speed should be very close to that, because there is always a 2 to 3 mph difference in speed between the 2 timing lines and the speedo may read a tick high due to running lower than normal air pressure.

I can also say that I've never seen any evidence that one track or one lane reads a better ET than another. The times always seem consistent for the DA and my 60'.

[Fraxum]

I asked Ted Jannety on this topic. His opinion is unless it is off to begin with there nothing in it for us.

I drag race often in different DAs and fooling around with the set screw has given me nothing on 2 ZL1s in a row. Although I did make my 2015 M6 ZL1 slower for a bit. So I did test a bad setting.

This ZL1 ran almost 125 in +1500 DA and just over 126 in -1300 DA. Same track, Atco. It seems to me DA and the set screw setting do not affect this car much.

So much like dynos on the same dyno the same day being the most informative about gains, MPH on the same track I think are very comparative and the best indicator of your power if you do not spin at the line. Especially in an auto shifting for itself.

[Can'tHave2MuchHP]

Originally Posted by Lt1z350

I have had around 5 guys on here email me directly on it and all saw gains. I log 12-13 psi with mine adjusted all the way down. I was seeing around 7-9 most of the time till I adjusted it. I will say I asked a big name company about it and they said it’s now known that adjusting it will achieve about the same as an 18 percent lower. The thing is your creating the heat of 12-13 lbs even if engine is only seeing 9. So why not use what the blowe with give you on the pulley combination. Sort of stupid not to take it as it’s free hp. I also see lower manifold temps on a run with the door shut how it should be. I’m in the process of a bunch of mods so will get back to track here soon and see if car will run the same as others tuned with same mods but me with out a pulley swap. If your car is seeing pat the 3rd line already then it’s fine but most have said lucky to hit the second. Mine with the bypass solenoid vacuum line off was spiking to the bottom of the gauge so close to 15 psi before I put the 2 inch headers on the car. It gets to a point where stock is boring on any car at any power level but if leaving it stock at least get what you can from it and make it right. Bleeding boost creating heat isn’t the right way to lower the boost.

I agree with you, solid post.

When I get my car some break in miles on it, I'll see where my boost is at, log it, adjust the bypass and then log again. I won't be tuning this car, at least not yet, and I'll probably never take it to a strip either, but I'll let you know how the logs and butt-dyno compare.

Is there anything else to it other than turning that set screw out away from the plate? Should I re-apply some blue loctite or just leave it? Any positives/negatives of having it hanging way out in the air vs. barely touching the plate?

[Fraxum]

I will still wait for the back to back dyno run. I had mine all the way off so I am at max boost if I am wrong anyway. Maybe my ZL1 will loosen up with more miles, @1,500 mi. now.

I do think there is something there if you are logging and seeing something. But for me I am leaving my ZL1 alone for a while. It is so much fun just the way it is.

This is really easy to test with the simple adjustment.

[collinms]

What ended up being the verdict on this?