CrunchyTaco

Hello all,

Haven't been on here in a long time but need some help with a long running problem. Truck has had some power issues and I have spent a bunch of time and money on parts trying to fix it. Not going to get into all of it but the only thing that I have found that is definitely off is that my bypass actuator is slow to close when throttle is applied.

Videos on YouTube show that the bypass valve slams shuts immediately under moderate throttle application. Mine is take just over a second and doesn't fully close unless the truck is red lined. I have replaced the actuator with a new unit from magnusson, removed the freeze plug and cleaned around the valve, and it rotates freely. The valve immediately opens upon engine start up and closes on shut down. The vacuum hose appears crack free and holds vacuum.

The truck has 100k miles. 3.4 with 4th gen supercharger. TRD 7th injector.

Any ideas on why this valve is sluggish and doesn't fully close unless under full throttle for several seconds? I believe this may be the root of my power loss problem. Any help is greatly appreciated! Thanks.


Joe

vital22re

iTrader: (2)

I have the same issue. I'm sending mine in for rebuild.

CrunchyTaco

The whole supercharger? What led you to that decision? What kind of boost are you getting? How many miles? Are you having a midrange power loss problem? Who are you sending it to? Estimated cost and wait time?

My nose cone is new but the housing, rotors and bearing have 100k on them. I can still rotate the rotors by hand. Immediately stops if I do but they will rotate. Still showing an indicated 7lbs if boost at WOT. No horrible noises coming from it.

Texas_Ace

A full rebuild sure would not be a bad idea but you could just try to get a replacement actuator. Yours is bad for sure if the hose that feeds it is good and it still takes a second to close.

Can see if you can get it from TRD but it might be pretty pricy.

CrunchyTaco

Bought a new actuator from magnusson a couple of months ago. No change. Was wondering what upstream of the actuator that could cause this. I have already dropped a bunch of money attempting to fix the power problem and don't want to foot the bill of a rebuild right now if I don't have to.

Thanks for your reply though. Your thoughts were one of the ones I was really wanting.

Texas_Ace

Well if you got a replacement already and it is doing the way thing then time to look elsewhere.

First off remove the actuator and try moving the plate manually. It should have virtually zero resistance. It is possible that gunk could build up and cause it to bind.

While you have it off check the hose for any possible leaks.

Then block the hose off and find another vacuum line you can barrow (or better yet a vacuum tester if you have access to one). Then try sticking the vacuum line to the actuator to see how fast it closes without anything else effecting it. It should snap opened/closed depending on how you look at it.

Then try putting a little pressure into it with an air compressor (~10-20psi), see what happens, listen for any leaks. Can try putting it in some water to look for bubbles as well.

With an issue like this best to break it down into the basic parts and test them individually.

ktoy4r

Hey CrunchyTaco, do you have a video of how your bypass valve actuator moves? A while back I had checked out a bunch of supercharger videos too. I noticed some where the actuator slams shut quickly:
and

and some where it moves slower (kind of hard to see):
and

How does yours compare to those? It sounds like yours might be moving extra slow, but I was just curious so I thought I'd ask.

CrunchyTaco

Mine moves like the 3rd one. Just takes a minute. Made sense to me for a power loss problem cause it seemed like it would be bypassing the supercharger.

Either way, took out the jet like thing in the actuator hose fitting. It opens instantly now but didn't really help anything. Revs quicker under no load but drives the same under

The problem is not the actuator. Hose is good. something with the supercharger? I have good vacuum but something is not taking that vacuum away quick enough under throttle to make the actuator work like it should.

Texas_Ace

Not sure I understand, if the actuator is closed then that is all it can do. Not sure why there is a restrictor in yours.

If the bypass is closed properly then next step would be a boost leak test.

CrunchyTaco

It is slow to close. I have had a long term mid range power loss problem with my truck that is becoming impossible to track down. The slow closing actuator was the only thing I could find that was out of place. My thinking was the fact that it was slow closing may reveal some other problem with boost or vacuum. Was hoping that someone brighter than me may have some ideas or someone had a similar problem and found a fix.

It is a small fitting that is supposed to be in there. My old actuator had one too and at some point the truck ran fine with it. I only took it out to try to see if the actuator would fully open.

Sorry if this seems kinda scatter brained but this truck is killing me. I have replaced about every part imaginable and haven't had any luck tracking it down.

ktoy4r

You can see the brass colored "restrictor" is the following picture:


My actuator moves slowly as well. I first thought it might be indicative of some vacuum/boost problem too, but after seeing those videos on YouTube where some moved fast and some slow I figured it was normal. But I don't really know. I sent my supercharger to Jon Bond Performance to re-coat the rotors and fix anything that was wrong. He also checked out the bypass valve and said it was fine. The actuator moved slowly before and after I got the s/c back (I had replaced the actuator too).

I don't have a noticeable mid range power loss like you, though. Do you just feel it, or can you see a change in your boost gauge or anything?

niall

I have absolutely no experience with superchargers. but Lots of Forced Induction knowledge.

For a second, omit the wastegate actuator from your power loss issue. With Turbos, the general first rule is to do a boost leak check. Essentially, Block off your intake, Pressureize the system, and listen/look for leaks, not sure on the exact method on your setup, but If Your Motor Holds Boost, it'll hold Vac, and that's not the problem.

If you have access to a different boost guage, hook it up, and confirm yours is still accurate, if it is, and you're achieving the correct psi, it's no longer a boost issue, and start looking to fuel/spark.

Just some thoughts, maybe you've already done them though.

Texas_Ace

I would leave the restrictor out of it, there is no need for it. Mine didn't have one and worked fine.

Like I said next step is a boost leak test, if that comes up clean then next most likely cause is a tune issue. Do you have a wideband?

Correct on the boost test although the better method for finding leaks is to spray everything down with soapy water and look for bubbles.

vital22re

iTrader: (2)

Well I should chime in here as I have an update on mine. Turns out the bypass valve itself was out of adjustment and the plate was slightly hanging on the side of the bore. Wade at embree specialty machine adjusted it as he was rebuilding the rest and says its good to go now. Pm me if you want to know more.