Low pressure spring on boost bypass valve on 2.9 whipple

[MalcolmV8]

Bringing this back,

Malcolm I know you dont have the 2.9 Whipple anymore but what was the end solution with this experiment.

Did you leave the .030 jet in there or end up doing something different?

I noticed with my new 2.9 whipple and stage 3 comp cams the idle is better with blower belt removed. Curious what you ended up doing..

Thanks,

I ended up re-degreeing my cams to fix the problem. The nitrous jets are a partial "hack" that improve the situation but don't fix it. There is no cure to that problem short of re-degreeing the cams.

Pretty much no matter what you do you're fighting the issue of the bypass valve transitioning or closing while the rotors have air in them. It's going to cause spikes, lean issues, hesitations etc. due to that sudden rush of air as that happens.

The cure is to improve vacuum at idle. The bypass valve needs 11 inches to hold it fully open. I got my idle around 14 inches and went back to the stock bypass valve actuator and spring. Now when I pull off the stock bypass closes at 11 inches of vacuum like it should and the blower rotors come into action right before they're flooded with air (IE still in vacuum).

Now the car drives like stock, pulls off like it should and is how it should be.

 

[MineralCobra]

Thanks for quick response,

unfortunately re-degreeing the cams is out the question for me...

If you had to pick between the 2 bypass valves stock and lowe pressure unit ( both having their own issues) which one is "less of an issue" and could be dealth with in your opinion?

Also any info on the L&M bypass valve like what vacuume is opens up etc? I cant seem to find much info on it

 

[MalcolmV8]

In your situation the low pressure spring bypass valve is the best option. Play with nitrous jets to get the results you like. The smaller the jet the lesser impact it has when the valve transitions but it also delays the power with sudden and rapid WOT.

Most low vacuum bypass actuators I tested open around 3 inches of vacuum. I don't remember the L&M specs specifically off hand.

 

[MineralCobra]

Interesting enough I took my blower off today after work and checked the bypass valve.. it's fully open at 3-4" of vaccume.

Did whipple ever make these standard with the low pressure bypass valve?

 

[MineralCobra]

Just to update if anyone comes across this thread with same issue.

Spoke to Whipple this morning and it seems like the 2.9 comes with the low tensiom bypass valve now standard. Opens up at 3" vacuume same as Malcolm's test above.

 

[usmcah-1w]

Just to update if anyone comes across this thread with same issue.

Spoke to Whipple this morning and it seems like the 2.9 comes with the low tensiom bypass valve now standard. Opens up at 3" vacuume same as Malcolm's test above.

So did you have the surging idle with the low vacuum bypass valve before removing?

I am reading 7-10 in vacuum at idle with it surging between 700-1000 rpm and sometime stalling. I removed the blower belt and the idle smoothed out like mentioned in the thread. I got my 2.9 Black Friday and installed it couple of months ago so I'm not sure which bypass valve I have, but the actuator is not moving back and forth when idling.

 

[usmcah-1w]

In your situation the low pressure spring bypass valve is the best option. Play with nitrous jets to get the results you like. The smaller the jet the lesser impact it has when the valve transitions but it also delays the power with sudden and rapid WOT.

Most low vacuum bypass actuators I tested open around 3 inches of vacuum. I don't remember the L&M specs specifically off hand.

Did you ever look at the bypass valve and see it fluctuating?

My bypass valve stays open during idle and closes when shut off without fluctuating with the idle. The idle does smooth out with the blower belt removed like you originally stated. I would think you could see or feel the bypass opening and closing which would cause the idle surging.


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[MineralCobra]

So did you have the surging idle with the low vacuum bypass valve before removing?

I am reading 7-10 in vacuum at idle with it surging between 700-1000 rpm and sometime stalling. I removed the blower belt and the idle smoothed out like mentioned in the thread. I got my 2.9 Black Friday and installed it couple of months ago so I'm not sure which bypass valve I have, but the actuator is not moving back and forth when idling.

I got the blower last year when Lethal had the sale during Christmas. My idle did surge a little and did work smoother when belt removed. But not sure if it bypass related or tune needs slight adjustment. I just installed my new engine so engine injectors cams and everything needs to be dialed in for break in.

I ended sending the whipple back for inspection it was making a weird noise and had a little play at pulley which I didn't like. I should be getting it back in few weeks and I'll test again.

As for your bypass if it's not opening and closing during idle I doubt your surging idle is from that.

 

[tjpinkston]

subscribed for updates

 

[IgorT]

This was a great read.
I have an issue with mine after pulley down where the car stumbles leaving in first or when you tap into the trottle hard off idle. Boost jumps instantly. Or when at wot and you let off fairly quick but not instantl . The car surges.

I was thinking about a bypass valve to try and play with it.