Thanks for the measurements. Unfortunately its too big to fit in our little actuators. Ill keep hunting.
Low pressure spring on boost bypass valve on 2.9 whipple
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Thanks for the measurements. Unfortunately its too big to fit in our little actuators. Ill keep hunting.
Yea true. Let us know what you find with the different vacuum readings.
Subscribing.
Been fighting surging idle with cammed 4v's. If i disable the bypass the idle cleans up similar to what OP was describing.
Been fighting surging idle with cammed 4v's. If i disable the bypass the idle cleans up similar to what OP was describing.
I have the 2.9 with Crusher and have idle surging issue real bad at start up...and for the first couple of minutes.
Can you describe the process for disabling the bypass so I can see if it cleans mine up?
Can you describe the process for disabling the bypass so I can see if it cleans mine up?
OK so Whipple off lower and intercooler removed
My boost bypass valve is sandwiched between the lower plate and the elbow
Have to drill out a couple plugs to access all the bolts to remove the lower plate. I ordered two replacement plugs from Whipple along with new o-rings and the new low tension bypass valve.
Here's the valve on the plate
Had to undo a locking tab here and pull this assembly apart to get the valve off
Some testing of the stock bypass valve. 11 inches of vacuum to be in the fully contracted or bypass valve pulled all the way open. I repeated the test a few times, sometimes only 10 inches but most times 11 inches.
The replacement valve is fully open at only 4 inches. On some tests only 3 inches but most commonly at 4 inches.
After the bypass valve was installed into the lower plate and activating the actual valve I re-tested and found still 4 inches of vacuum and it was fully opened.
Since my car would idle between 8 ~ 10 inches of vacuum, mostly around 8 inches of vacuum, I can see how this was a problem. The bypass valve was flapping back and forth and only partially activated causing the surging idle.
The new valve should hold nice and solid since it only needs 4 inches of vacuum. Can't wait to try it. I have a few other issues to sort out so it'll be a few days but I'll report back.
My boost bypass valve is sandwiched between the lower plate and the elbow
Have to drill out a couple plugs to access all the bolts to remove the lower plate. I ordered two replacement plugs from Whipple along with new o-rings and the new low tension bypass valve.
Here's the valve on the plate
Had to undo a locking tab here and pull this assembly apart to get the valve off
Some testing of the stock bypass valve. 11 inches of vacuum to be in the fully contracted or bypass valve pulled all the way open. I repeated the test a few times, sometimes only 10 inches but most times 11 inches.
The replacement valve is fully open at only 4 inches. On some tests only 3 inches but most commonly at 4 inches.
After the bypass valve was installed into the lower plate and activating the actual valve I re-tested and found still 4 inches of vacuum and it was fully opened.
Since my car would idle between 8 ~ 10 inches of vacuum, mostly around 8 inches of vacuum, I can see how this was a problem. The bypass valve was flapping back and forth and only partially activated causing the surging idle.
The new valve should hold nice and solid since it only needs 4 inches of vacuum. Can't wait to try it. I have a few other issues to sort out so it'll be a few days but I'll report back.
That's the one that came in my brake bleeding kit.
It has a catch can for the brake fluid.
I'm very interested in this....I am seeing unusually high IAT2s like you mentioned earlier in the thread. Also before my whipple install my cruise control didn't work. The shop that put my blower on managed to fix the issue (not sure what it was) and now when I have the cruise on, any little deviation in loss of mph will cause a hard surge to maintain the mph that the cruise is set to. Do you think this could be the issue? I just hate to pull the blower and get the spring installed.
*edit*....what are your IATs looking like now that you have the new spring in there?
Jr.
*edit*....what are your IATs looking like now that you have the new spring in there?
Jr.
Do you have aftermarket cams in the car? What specs? How much vacuum do you see at idle?
Stock cams....cant remember the vacuum at idle but it seems pretty normal for stock. I was just curious about this due to my high IATs and the surging while having the cruise set.
Jr.
Jr.
The problem I was reporting is a low vacuum condition caused by different cams. The low vacuum can't fully open the bypass valve. The lower tension spring allows the bypass valve to fully open with minimal vacuum to get around this issue.
If you have stock cams this is not your fix, you have something else going on. You'll need to look at the usual stuff, intercooler fluid full? IC pump working and running? good heat exchanger that's clean and not damaged, intercooler under the blower in good shape.
Surging could be your tune, something wrong in the MAF area, plugs or maybe something wrong with your cruise control if it only happens there.
Well Update: - the low pressure spring bypass valve allows the car it idle out of boost and not be surging but it has a horrible side affect when driving.
As you accelerate and vacuum reduces the car starts to run out of air as it passes the 10 inches of vacuum point. I can see why the stock bypass valve would open at this point. So what happens is the car runs out of air and when it hits the 3 ~ 4 Hg point the valve opens and it gets a sudden rush of air and the car jerks or lunges as it gets a sudden rush of air. A lean spike is seen on the wideband too right as it snaps open. It is extremely annoying to drive with. I'm not sure what a good fix to this is.
I've since swapped cams and went to slightly milder cams and now have 11 ~ 12 inches of vacuum at idle. I'm thinking of switching back to the prior bypass valve and if the valve still flaps or it surges at idle then adding a mini vacuum helper pump to pull on the bypass valve when idling.
Open to ideas?
As you accelerate and vacuum reduces the car starts to run out of air as it passes the 10 inches of vacuum point. I can see why the stock bypass valve would open at this point. So what happens is the car runs out of air and when it hits the 3 ~ 4 Hg point the valve opens and it gets a sudden rush of air and the car jerks or lunges as it gets a sudden rush of air. A lean spike is seen on the wideband too right as it snaps open. It is extremely annoying to drive with. I'm not sure what a good fix to this is.
I've since swapped cams and went to slightly milder cams and now have 11 ~ 12 inches of vacuum at idle. I'm thinking of switching back to the prior bypass valve and if the valve still flaps or it surges at idle then adding a mini vacuum helper pump to pull on the bypass valve when idling.
Open to ideas?
Interesting, my car drives really good with the low pressure spring. It does have a tiny bit of what you are taking about, but with the stock spring it did it way worse. I am going back to my tuner on Friday to play with this. He was very confident he could tune it out by playing with what he called pump shot.
My car actually had it a little bit on the stock spring too but its way more pronounced and annoying on the new low pressure spring setup. I'm not sure how you'd tune that out? It's a physical surge of air happening right as that valve closes (not open as I was incorrectly saying above). I can see using the accelerator pump logic in the tune to try and tune out the lean spike but it won't stop the surge which is a physical blast of air. Even tuning the accelerator pump logic seems worthless to me. Unless you stabbed into the gas pedal triggering it you wouldn't even hit the exact point of the valve opening. Keep us updated on how you attempt to tune that out goes.
I've been thinking about this a lot and something I want to experiment with is a restrictor in the line slowing down the valve operation. If the valve closed slowly instead of just snapping instantly you wouldn't have that jerk. The only side affect I'd have to see is when you're attempting to move out fast and nail WOT will the valve still move quick enough or will it cause a hesitation?
I have to pull the blower to replace injectors anyways so I think I may just tear it all apart and go back to the stock bypass valve. Perhaps I'll try the restrictor idea before doing that.
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