Low pressure spring on boost bypass valve on 2.9 whipple

[MalcolmV8]

So my lower pulley recently broke leaving the blower sitting still and I notice a massive difference in my car. Idle smoothed way out, pulling off, 3 point turning in the driveway etc. all smooth as can be. With the blower working I have a lot of idle surging and it's difficult to work the car in parking lots etc. I was just amazed at what a drastic difference there was. This whole time I thought it was just the characteristics of my cams in the new motor but clearly they're very street friendly without the blower making everything go crazy.

I've noticed I only have 8 ~ 10 inches of vacuum at idle with the cams so I called Whipple to see if that's an issue with the boost bypass valve working correctly. They seemed to think that's it and said they have a low tension bypass valve spring option that I should try. Unfortunately this not only requires pulling the blower but I have to disassemble it as well to get the bypass valve out and spring changed.

It'd be really nice if that makes the car have good manners with the blower like it does without. Anyone else with cams run into this?

 

[cozmo2806]

I am messing with a similar issue. I have a TVS with cams as well. My aeroforce vac/boost sensor shows I have about 7 or so inches of vacuum at idle. I removed the spring out of the bypass actuator, but haven't had any luck finding a lighter spring. Is whipple saying they have just the spring, or the whole actuator?

 

[MalcolmV8]

I'm guessing it's the whole actuator since he said it's "about" $100. He also asked about my boost levels and said I need the kevlar reinforced version because of the higher boost. This is what the follow up email said I need.

BACT-1015 Bypass actuator light spring (single port) Kevlar reinforced

 

[cozmo2806]

Ok I may look into that. I guess I wouldn't have assumed it would affect driveability as well. Hopefully you are on to something.

 

[MalcolmV8]

My other clue was just cruising around town with the KC off I'm seeing IAT2 temps of around 150F and it's only in the mid 40s to mid 50s out on our better days. Normal light cruise in mid summer heat is around 130F IAT2, usually don't see 150s + till I'm hammering on it so the 150s in cruise now also makes me think it's only partially closed.

I did try and look at the valve on the back of the blower with a flash light and mirror while it was idling and I could see the actuator rod moving back and forth some further supporting it's not in a fully closed position. I had my son turn off the car while I was watching and it looked like it moved a lot so I assumed it was OK but it must have not been.

Another thing that comes to mind is during completely steady cruising on the highway at say 70 mph we'd occasionally get this pulsing of the car, the vacuum gauge would flicker up and down and the wideband would swing from rich to lean and back and forth as well. Never could figure out what that was and could never replicate the issue on demand. I bet it was the bypass valve flickering right on the edge of in boost, out of boost, in boost etc. It would occasionally do it on back roads on very light throttle just cruising too.

I'm glad I've found this because I really thought the idle surging and low RPM manners of pull off etc. were because of the cams and I've spent a considerable amount of time tuning it out but the whole time I've just been combating the blower and the bypass valve jumping around. So I guess my lower breaking was a good thing

 

[cozmo2806]

Yes I agree that its more than likely an issue. I took an old actuator and drilled a 3/4" hole in it and took the spring out. Im trying to find a lighter spring to put back in and then tap the top of the actuator for a -10an o-ring plug. I'm just having a hard time finding a spring. It needs to be about a 4lb spring I believe.

 

[MalcolmV8]

For reference can you post a pic of the spring you have now? I won't be able to see my actuator or spring etc. till I get the blower pulled and taken apart. Kind of curious now, I can't remember off the top of my head what it looked like.

 

[cozmo2806]

I can get a pic this weekend. It's about 2.100 inches tall, 1.125 in diameter, and .065 wire diameter. I think it's about a 5.5 pound spring.

 

[cozmo2806]

Here is a pic of the spring. Disregard the end I cut off in an experiment. Both ends are supposed to be closed.

 

[01yellercobra]

That looks like a spring out of the Tial BOV I ran on my centri set up.

 

[MalcolmV8]

It does look very much like the BOV springs. I had a few of those from my turbo Honda I built a few years back. They were much larger in size though based on the dimensions posted above.

 

[cozmo2806]

I think I may have found a spring that may be what we need. They do require a $50 minimum order tho.

 

[MalcolmV8]

Oh man, I can't believe it's so hard to find a spring. I'm hoping my new valve from Whipple does the trick. Was $120 shipped and also included some replacement plugs you have to drill out when disassembling the blower.

 

[01yellercobra]

The spring in my Tial was about the same size as your measurements. They make a spring just for supercharger use. I think it's around 3psi for opening. Can't remember off the top of my head. Down side is that was $30 or $40.

 

[cozmo2806]

The spring in my Tial was about the same size as your measurements. They make a spring just for supercharger use. I think it's around 3psi for opening. Can't 3remember off the top of my head. Down side is that was $30 or $40.

Ok yes I found what you are talking about on ebay. Are you sure they are dimensionally close to what I posted? If so, I will order one and try it.

 

[cj428mach]

Oh man, I can't believe it's so hard to find a spring. I'm hoping my new valve from Whipple does the trick. Was $120 shipped and also included some replacement plugs you have to drill out when disassembling the blower.

I take it the crusher is getting cut in two? I think you told me next time you have to pull the blower its getting cut into 2 pieces lol.

 

[01yellercobra]

Ok yes I found what you are talking about on ebay. Are you sure they are dimensionally close to what I posted? If so, I will order one and try it.

I still have the old spring out of my BOV. I'll take measurements and post them.

 

[MalcolmV8]

I take it the crusher is getting cut in two? I think you told me next time you have to pull the blower its getting cut into 2 pieces lol.

I'm looking really hard as to how to do that. I could easily weld tabs at the top, tap one and drill a hole through the other and use bolts. The bottom though there's no access. I have to come up with some slick hook type setup or something. Either that or a machine shop is going to have to get involved.
I had a spare crusher intake, kicking myself now for practically giving it away, I should have cut that one in half and got it all sorted out and ready to swap.

 

[cozmo2806]

I still have the old spring out of my BOV. I'll take measurements and post them.

Ok thank you!

 

[01yellercobra]

OD- 1.869"
ID- 1.599"
Free standing height- 3.445"