[17CamaroZL1]

I just recorded a quick pull yesterday to see what mine is making stock. It was right in the middle of the 2nd and 3rd lines, which equals 9.375 psi. So it's pretty much dead on the factory rating. Guess I'll have to check the bypass butterfly to see if it looks like it's sealed shut. If not, I may try to set it and retest for a gain in boost. It'll be a while though. Weather is showing rain for the next several days.

[VAZL1]

Originally Posted by Lt1z350

Stock boost hp rating is 9 lbs. Seems most cars don’t even see that until this has been done. There is a guy on the corvette side running a 18 lower and 2.38 upper on stock tune. He claims it is seeing 14 lbs on the stock tune which is possible but sure he gets tons of throttle closure. It really doesn’t matter wht psi it makes as once reaching the limit of torque it will pull it back some through the solenoid unless you block it off like I had done. I assume why I see spikes to 14 at shifts or I was on the stock tune. If you find my logs posted you see though I was at 185-190 kpa or 12+ lbs it was closing the throttle to keep torque in check.

Saying all that then why bother??? Some that have been to the track multiple times only seeing high 11s @ 119-122 over and over I am sure that car isn’t near the limit in the tune. My car Dave with blue zl1 big Dave and very few others have seen 128-131 mph trap speeds this I believe it the total limit on the stock tune with decent traction. So all the cars should be able to achieve this with variables like incorrect boost bypass settings. So on a 1.70-1.80 60 foot any of these cars auto or manual should be able to make 127-131 mph. If it’s hotter and higher da it will just hold the throttle 100 percent open and achieve the max boost set by the door. I ran 126 mph in the heat of summer in Florida at Gainesville so all the other cars should reach that. I see a lot on the list at 120-122.
As for lean I just did a full tune with e85 so more boost more timing and I am still pulling more fuel out of the tune then was set stock. So no way in hell any one can go lean. When cat over temp kicks in the commanded can drop to a horribly pig rich 10.8 I have seen it in logs and why stock cars have super dirty tail pipes. This in no way will do any adverse affects. I’ve seen videos on line of guys runs just pouring black smoke all the way down the track. These cars make the most power from 12.0-12.4 on the street I like safe and around 12.0-12.2 peak dyno will be closer to 12.6 from what I have seen on most di some run n/a combos to 13.0 which is crazy to think as normal port engines always liked 11.7-12.0 ball park n/a and 11.4-11.7 boosted.
EVERYONE should check this setting if you care about your car being right. Every single pd supercharger that runs a bypass like this has some sort of instructions stating this door should be sealed when under boost. If this was ok to do then all cars would be pulleyed way down then just bleed off where you want the boost. Problem is your creating the speed and heat no matter of boost is going into the engine or out the bypass. Life would be much easier as just go with the smallest pulley possible and back it down. Seen some guys buy 3 uppers in the past trying to hit a certain psi as went too small and made more boost then liked for that combo. Changing stuff in front of and after blower like long tubes and no cats affects boost. Boost is just a measurement of restriction so when boost goes up it is more push back of air. Why when you go from stock exhaust and cats to long tubes no cats a blower car can lose boost due to less restriction. Another reason why to recover that boost from a good exhaust some will then go to smaller pulley get the boost back that was lost from less restrictive parts. The big thing on this smaller blower is the efficiency range is low so when try to speed it up you get tons more heat. Right now on my combo it’s the coolest it has ever been in my logs and I see a drop in manifold temp over a full run rather then it climbing through 180 degrees as it did when car sat bone stock. By GM doing this if they did on purpose all they did was creat a bunch of heat to deal with and the guys it will affect the most is road course racers as it can’t recover from that heat in stock form. Another reason I guess why GM says it’s ok to modify anything with heat and not affect your warranty. I have seen this posted over and over with the z06 crowd. On stock cars GM will not void a warranty if trying to reduce heat. Bigger radiator heat exchangers trans coolers why ever it is you go with to try to help keep car coolest in your conditions.

Thanks for the detailed response. I agree the car is pig rich from the factory. I guess it's time for me to give this a shot. I'll report back my before and after findings

[Blackdevil77]

This thread and little procedure should be a sticky

[BMWM.D.]

I’m going to see what this does on mine. I have a real boost gauge (P3 vent gauge), and also have logs showing my boost. Trying to determine boost based on the vague factory gauge isn’t the best test IMO.

I’m sure it’s been mentioned here, but throttle closure is the main reason for boost lower than the ~9 psi specification. Mine was bad after installing a Roto-fab. After dialing in some tables with HPT, I was seeing close to 11 psi. This was a result of keeping the throttle open, and likely some boost gains from reduced intake restriction. Now I have headers, and it’s close to the stock number — as the gain from the intake and loss from the headers have more or less cancelled each other out.

[Boosted4life]

Originally Posted by Lt1z350

Stock boost hp rating is 9 lbs. Seems most cars don’t even see that until this has been done. There is a guy on the corvette side running a 18 lower and 2.38 upper on stock tune. He claims it is seeing 14 lbs on the stock tune which is possible but sure he gets tons of throttle closure. It really doesn’t matter wht psi it makes as once reaching the limit of torque it will pull it back some through the solenoid unless you block it off like I had done. I assume why I see spikes to 14 at shifts or I was on the stock tune. If you find my logs posted you see though I was at 185-190 kpa or 12+ lbs it was closing the throttle to keep torque in check.

Saying all that then why bother??? Some that have been to the track multiple times only seeing high 11s @ 119-122 over and over I am sure that car isn’t near the limit in the tune. My car Dave with blue zl1 big Dave and very few others have seen 128-131 mph trap speeds this I believe it the total limit on the stock tune with decent traction. So all the cars should be able to achieve this with variables like incorrect boost bypass settings. So on a 1.70-1.80 60 foot any of these cars auto or manual should be able to make 127-131 mph. If it’s hotter and higher da it will just hold the throttle 100 percent open and achieve the max boost set by the door. I ran 126 mph in the heat of summer in Florida at Gainesville so all the other cars should reach that. I see a lot on the list at 120-122.

So this brings up an interesting question for me. I only see 7.5 to 8 psi of boost BUT I am at 7200 feet elevation. I did the bypass adjustment with no change. I feel that the car can only make that much boost due to the elevation. So my question is could I get away with doing a pulley on the stock tune since it will just compensate back to what the car would make at sea level anyways?

[NicD]

Adjusting this is only going to make boost go up if it was set incorrectly from the factory or if somebody had it off and was screwing with it. Boost is also relative to your elevation and density altitude so it's a variable. For 99% of the people this will do nothing for you.

[Bill_76]

That's mine any way to know with a picture if it is ok?

[Can'tHave2MuchHP]

Originally Posted by Bill_76

That's mine any way to know with a picture if it is ok?

Not really as the ultimate adjustment is to have that set screw hardly touching that "plate" if at all, as noted some users just leave it hanging in the air.

[hawk02]

The problem with threads like this is that they give the impression that 90% of the bypass valves come mis-adjusted from the factory.

If you think about it, all GM does is bolt the supercharger to the block. Adjustment of the bypass valve is done by Eaton when they assemble the SC. This would explain why there are no instructions for adjustment in the GM service manual.

I've seen boost as high as 9.4 psi through the P3 gauge on my car so I'm confident my boost bypass valve is adjusted to spec.

[Can'tHave2MuchHP]

Originally Posted by hawk02

The problem with threads like this is that they give the impression that 90% of the bypass valves come mis-adjusted from the factory.

If you think about it, all GM does is bolt the supercharger to the block. Adjustment of the bypass valve is done by Eaton when they assemble the SC. This would explain why there are no instructions for adjustment in the GM service manual.

I've seen boost as high as 9.4 psi through the P3 gauge on my car so I'm confident my boost bypass valve is adjusted to spec.

I agree it does create that mentality just like it did for the LSA. But at the same time, why not check it and adjust it? It's not going to hurt anything, worst case scenario you don't gain any HP. Best case though is your car happened to be the one with with the set screw screwed into the plate and bleeding off all your boost.

[Gunkk]

Originally Posted by Can'tHave2MuchHP

I agree it does create that mentality just like it did for the LSA. But at the same time, why not check it and adjust it? It's not going to hurt anything, worst case scenario you don't gain any HP. Best case though is your car happened to be the one with with the set screw screwed into the plate and bleeding off all your boost.

[hawk02]

Originally Posted by Can'tHave2MuchHP

I agree it does create that mentality just like it did for the LSA. But at the same time, why not check it and adjust it? It's not going to hurt anything, worst case scenario you don't gain any HP. Best case though is your car happened to be the one with with the set screw screwed into the plate and bleeding off all your boost.

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.

[ninetres]

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.

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.

[Krypton1le]

I imagine there could be some concern with the actuator bottoming-out repeatedly or the bypass throttle blade over rotating and contacting the seats (not sure if that term is correct)?