[Jhunsberger]

Has anyone with a Whipple or even Maggie ever experience like a surge around 2500 rpms, which I feel is due to the Whipple bypass valve closing? Seems to occur during normal to light acceleration/pulling out from a stop. It’s like if I gave less or more throttle or short shifted or ran thru this rpm range quicker it doesn't do it, but under light or slow driving and as the rpm goes thru the 2500 rpm range there is just this unsettledness with the engine, a rough spot, then it cleans up and the kind of takes off abruptly. It’s nothing severe or out of control, just a surge, but it hurts some of the daily drive ability.

I reached out to Whipple yesterday asking if there is a different bypass valve or spring I could try or an adjustment to be made. My tuner, CSP says they have done everything they can to smooth this out, it’s just the bypass valve closes rather aggressively. This has been the case since the Whipple was first installed, so it is not due to any recent mods, it has been my only real complaint so far with the setup. I even wondered about some sort of adjustable inline valve for the vacuum hose for the bypass. I did make my hose about 2x longer than what was supplied by Whipple, I highly doubt this would cause a problem.

I have read on the HPTuners board about some saying its in the tune related to airflow tables and others saying its just the standard bypass valve that is used. I dont know much at all about the tuning of these cars or HPTuners, but I dont see how you can tune much to affect the vaccum at a certain RPM.

[L78toLT1]

My Maggie does the EXACT same thing. I have never driven a lt4 equipped Camaro or vette. It would be interesting to know if they are completely seamless when transitioning from boost/no-boost conditions. I'm sure they perform better than my car or there would be complaints. I find this to be a fairly minor annoyance; I have learned to drive around it but it would really be nice to eliminate or significantly mitigate this issue.

[KingLT1]

I would think it could be smoothed out in the driver demand table. I haven't noticed it yet with mine but I have not had a chance to drive it much.

[L78toLT1]

Originally Posted by KingLT1

I would think it could be smoothed out in the driver demand table. I haven't noticed it yet with mine but I have not had a chance to drive it much.

I'll see what Ted comes up with when I get my motor back in and start tuning. We never really addressed the boost transition flat spot when I first installed the blower. Now that I've jerked everything apart to install the 2nd phase of my mods, we will obviously be starting over again anyway. I'm hoping if we cannot completely tune out this condition that we can at least make it a little less intrusive. I guess I will find out soon, the machine shop has finally started on my motor, I'm hoping to get it back by the weekend!

[Jhunsberger]

Originally Posted by KingLT1

I would think it could be smoothed out in the driver demand table. I haven't noticed it yet with mine but I have not had a chance to drive it much.

Yeah it would be good to know if you experience it as well. I have learned to drive around it, but it would be nice to smooth it out. It seems to be worse when it is cold, but it is always there. i would imagine if you have driven your car at least 50 miles with some stop and goes, you would experience it. It does it every time i am out in it.

[Jhunsberger]

Originally Posted by L78toLT1

I'll see what Ted comes up with when I get my motor back in and start tuning. We never really addressed the boost transition flat spot when I first installed the blower. Now that I've jerked everything apart to install the 2nd phase of my mods, we will obviously be starting over again anyway. I'm hoping if we cannot completely tune out this condition that we can at least make it a little less intrusive. I guess I will find out soon, the machine shop has finally started on my motor, I'm hoping to get it back by the weekend!

Kind of relieving you have experienced it as well, and knew right away what i was talking about. I have learned to drive around it as well. i will see what Whipple has to say. And hopefully some other experienced PD SC guys and tuners can chime in.

Good luck with your build, it is so painful waiting for stuff to get done. I am sure it will all be worth it, i am excited to see your results.

[L78toLT1]

Thanks, man. I am champing at the bit to get the car back together!
It's interesting that the Maggie and Whipple behave so similarly. I wonder if lt4's use a vacuum actuated bypass valve? While I don't have a clue, I would not be surprised if they use an electric valve with a sophisticated feedback system that gets input from dozens of sensors. I hope King is correct that it can be tuned out.

[Jhunsberger]

So this is the response i got back from Whipple:

"You can move the vacuum line from boosted operation to vacuum actuation."

"You can also put a .020” orifice inline to slow its response down."

I am willing to try them both. Might be easier to move to vacuum actuation, just need to find a vacuum line to tap into.

[L78toLT1]

Very interesting! I am very interested to see whT effect this has on your car. I imagine you could do the same on a Maggie, the valves are probably very similar.

[Chris V]

My car does the same (Whipple).

Matick Chevy did a bunch of blown Silverados and reconfigured the electronic bypass valve actuator from the LT4 to work on the Magnusson (if I'm recalling this correctly).

I'd love a good electronic bypass valve on my car.

Here's the LT4 part - https://www.gmpartsdirect.com/oem-pa...bC12OC1nYXM%3D

Anyone want to sell me a kit?

[Jhunsberger]

I found an in-line .029 orifice fitting that I am going to try. Found it here:

http://www.42draftdesigns.com/inline-restrictor/

I will let you know how it goes.

An electronic one would be so much better!

[Jhunsberger]

Just and update, the .029 inline orfice for the bypass valve did not make any difference in smoothing out the rough spot between 2500-3000 under light acceleration.

[KingLT1]

We had decent weather today so I got my car out and cycled between 25-3000rpm several times and did not notice any rough spot. I'm wondering if it has to do with how my driver demand table is tuned or is it just a Manual trans issue?

[SC88]

I have a magnuson and can't say I've experienced this issue. Will definitely be looking for it when I get it back together