How to, The Correct Boost Bypass Mod

[metaman]

EDIT: Please read through to the end of the thread, I did this mod 3 different ways. The final way version 1.3 was the cleanest looking under the hood.

While doing research through the forums about the boost bypass actuator I discovered some things that are important for terminator owners. It has been debated over and over about the boost bypass modification that prevents the boost bypass actuator from bleeding off extra air when not in boost. I actually drove around with the modification done for 4 years thinking the whole time that it was not causing any performance issues.

I recently found out through reading through threads about this, that disabling the boost bypass actuator actually causes the blower to build up to much heat when not in boost. Apparently when not in boost the Eaton blower, especially with a pulley, moves more air than the engine can take at low throttle rpm. The result is air turbulence called cavitation which causes friction and heat.

So last week I switched the two vacume lines back so that the actuator was functional again. The result was that the air intake temps dropped about 20 degrees when just driving around not in boost. However, with the canned predator tune I have, the boost bypass solenoid solenoid still caused the boost bypass actuator to bleed off boost at wide open throttle. The car did not pull as good as it did before I reversed the boost bypass mod. I wanted the boost back, but I did not want the high intake temps that go along with disabling the actuator.

I kept on reading old threads and came across a post by RWTD the tuner. He mentioned a rerouting of the vacume lines that he does that prevents boost bleed off at wide open throttle, while at the same time enabling the boost bypass actuator to continue to function while not in boost. Here is how to do this mod.

First remove the two vacume lines that attach to the top and bottom of the boost bypass actuator. Then remove the two vacume fittings from the ends of the hard plastic lines and replace them with the correct size caps.

The two vacume fittings that are removed

The two vacume line caps that replace them

Pic of the two lines after they caps have been installed

All that is left to do now is remove the vacuum line from the FRPS sensor at the end of the fuel rail. After this you install a Y vacume fitting between the FRPS and the vacuum line that was attached directly to it.

Now you just attach a 10-11 inch section of vacuum line from the Y fitting and run it over to the top fitting on the actuator.

The lower fitting on the boost bypass actuator remains vented to atmosphere.

Now the boost bypass actuator works as designed and is no longer effected by the boost bypass solenoid and the computer never knows the difference. Another way to accomplish the same thing is to unplug the boost bypass solenoid. However, this causes the computer to throw a soft code.

 

[black 10th vert]

very cool! thanks for posting!

 

[LS1PUSSOUT]

so that wont affect the functioning of the fuel rail sensor? looks good thats all im thinking about

 

[KILRSVT]

thanks for posting....neat

 

[metaman]

Nope, it wont effect the FRPS negatively. You still have a closed system. People who delete the EGR actually remove all of the stuff on the side of the blower and run one line to the boost bypass and FRPS from the bottom of the blower. This does the same thing, just much easier than removing all of the EGR stuff. If this was a show car then I would have gone the EGR delete route. However, I do not show the engine off so I could care less.

 

[Robertp]

My car has and 8 lb lower so it has 14 psi and goes down to high 12 will this fix this? Or is this normal I'm assuming since my car is tuned this want help let me know guys

Robert

 

[metaman]

My car has and 8 lb lower so it has 14 psi and goes down to high 12 will this fix this? Or is this normal I'm assuming since my car is tuned this want help let me know guys

Robert

yes

 

[Robertp]

so this is normal?

Robert

 

[DaveMan]

I have the SCT pro racer package with the boost bypass disabled in the tune and the boost still drops off at high RPMs. I get around 12psi dropping to 10psi by redline. I'll try this and see if it works...

 

[Tractionless1]

Better zip tie those vac. caps to your hard lines. I had mine done as directed in this post and boost response was faster, happened earlier in the rpm band, required less throttle, was more solid, and did not bleed off up top. I have since reversed it back to stock for S. Florida summer time driving, IE the jungle.

 

[metaman]

Better zip tie those vac. caps to your hard lines. I had mine done as directed in this post and boost response was faster, happened earlier in the rpm band, required less throttle, was more solid, and did not bleed off up top. I have since reversed it back to stock for S. Florida summer time driving, IE the jungle.

Good point, I actually bought the zip tie gun yesterday. I am only running 14lbs of boost and the end caps are really on there solid, however better safe than sorry.

Why reverse it back to stock for summer driving? If you do the mod the way it is described in this thread instead of the way that RPM outlet says to then AIT2 temps are not going to be negatively effected.

 

[96lowbra]

Whats a boost bypass what does it do and how can this
help when can u do it more info please??????

 

[metaman]

Version 1.2

So even though the chances of any of the lines blowing off was slim at 14 PSI, I had the tie straps and the tie strap gun.

So I decided to go ahead and tie strap all of the connections. I went out to do this and found that the hard vacuum line that I had capped and had been attached to the lower port on the actuator had come into contact with the EGR pipe. This melted this line in half.

I decided to find out where it went to so I tugged on the end that goes up towards the back of the blower. I found that it actually ends up at the intake tube. It is the one on the left side of the intake tube in the center of this pic up near the connection to the throttle body.

Since it would be so easy to get rid of this line, I went back to the auto parts store and got a cap that was big enough to go over that vacuum nipple on the intake tube.

Then I started thinking about what to do with all of this hard line that I just pulled off of the car. I decided to use it in place of the larger diameter vacume hose that I had put between the FRPS and the boost bypass actuator previously. So I got out those two factory vacuum couplers that I had removed from the lines going to the boost actuator.

Then I took the hard line that I had just removed from the car and trimmed it to about the same length as the vacuum tubing that I had previously installed. I then put the two factory connectors onto the ends of this peice of hard line and tie strapped the connections with the tie strap gun. You pretty much have to do this because there are not any nipples on the ends of the custom length hard vacuum line.

Now I just removed the larger diameter vacuum tubing from the previous install and replaced it with the new custom hard line piece. After this I went ahead and tie strapped all of the connections. This is to prevent them from popping off during wide open throttle. Again, at my boost level it is probably not going to happen, but better safe than sorry.

Now the finished product matches up better with the rest of the birds nest of vacuum lines on the side of the blower. It also takes any possibility that the larger diameter line could somehow negatively effect the response the boost has on the FRPS and the boost bypass actuator. It probably wont make any difference, but it might. This was my other motive for swapping out the larger diameter vacuum hose for the hard line.

Finished Product

 

[metaman]

Oops, looks like I missed one of the connections where the 90 that used to be directly attached to the FRPS attaches to the hard line.

 

[metaman]

Whats a boost bypass what does it do and how can this
help when can u do it more info please??????

Here is a pic of the stuff on the side of the blower all labled.

The boost bypass actuator bleeds off excess air compressed by the rotors of the blower while not in boost. This is nessesary for the blower to run cool. It is a double edged sword because when hooked up the factory way it bleeds off boost at high RPM's. This mod is to prevent the motor from loosing boost at high RPM's.

 

[Tedisky]

I know this may seem like a dumb question, but, did you get all the needed caps & tubing from a parts store?

 

[68_GT]

is this better than just having the boost bypass done in the tune ?

 

[metaman]

Ah, thats better

 

[metaman]

is this better than just having the boost bypass done in the tune ?

Someone asked the same thing over on mod fords, I will just copy and paste my response from there.

Link To the Tread Where RWTD give the instructions for this mod

Quotes from RWTD from that thread

Good point. The factory bypass vacuum setup is not good for high boost, as it has pre-boost vacuum lines going to it. Trey, you need to re-route what you have from the factory. Route the boost gauge / FRPS port to the top port on the bypass and leave the lower open to atmosphere. This will prevent the bypass from opening under high boost. This is how both KB and Whipple does it, and trust me, it does and will work

Trey, there's two ports on the factory bypass valve, just like Whipple has. Look in the picture that Allen (broke7) put up above.

#1: Cap BOTH factory lines going to the boost bypass.
#2: Take the same line that goes to the FRPS, which also goes to your factory boost gauge, and "T" into it, then run to the top port on the boost bypass, and leave the bottom port open to atmosphere.

You're done!

P.s. I believe the factory line going to the bottom port on the bypass valve goes over to the factory inlet tube pre-TB. For neatness, you can just pull this completely out and cap the nipple on the inlet tube, or just leave it there in case you want to put it back to the factory method later on.

So apparently even if the boost bypass solenoid is turned off in the tune, because the factory vacuum line routing has some pre-boost lines going into the solenoid which leads to the actuator, the actuator can still creep open under wide open throttle. And apparently, the higher your boost is the more likely it is that it will happen.

 

[Jomo1994z71]

There's such a thing as a a zip tie gun? wow...
Great thread...subscribing...