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Boost is lower than it should be - Boost Bypass? Belt Slip? Magic?

TurboJuice

Regular
Mar 30, 2011
119
0
I got barely any help on SVTP, so lets see if you locals can come to my rescue. I also always have a fridge full of cold beer if anyone wants to lend a hand or check it out!

Ok I have a BF 2.93 upper and a Metco 4lb lower with a complete BF idler kit. This is all on a stock eaton. I have changed belts a few times with the same results. Gates and gatorbacks.

I am only seeing 14psi from 5k up on a cool night. All my searching shows I should be at 16-17psi. Correct?

I dont think it is belt slip anymore and now I am thinking something is up with how my vacuum lines are routed or the Boost bypass solenoid?

Thoughts?

photo.JPG

photo-1.JPG

photo-2.JPG


Previous owners vacuum work...
Vacuum%20Lines.JPG



I have also seen this newer method of boost bypass. Is this something i should do?
http://www.svtperformance.com/forum...-boost-drop-off-eliminate-boost-solenoid.html
 

Zack

4 Doors 4 Life
Mar 21, 2004
6,297
20
NW Indiana
Whether its right or wrong, leave it be.
14+ psi on an eaton makes it very inefficient and produces gobs of heat.
Get it ported or get a twin screw.


....and throw away all that trash on the drivers side.
Your boost bypass valve needs to have a boost line hooked to the top port. Leave the bottom port open to athmosphere.
 

TurboJuice

Regular
Mar 30, 2011
119
0
Whether its right or wrong, leave it be.
14+ psi on an eaton makes it very inefficient and produces gobs of heat.
Get it ported or get a twin screw.


....and throw away all that trash on the drivers side.
Your boost bypass valve needs to have a boost line hooked to the top port. Leave the bottom port open to athmosphere.
I have a ported eaton sitting on my self, but that doesnt change the fact that my set up should be making 17psi as is.

I would like to ditch all the EGR components, but i will do that with the blower swap. Is there a diagram of how i should set up the vacuum lines. Can anyone confirm the how to i have listed in the first post.

From what i can tell most people have varying opinions about doing a boost bypass.
 

Zack

4 Doors 4 Life
Mar 21, 2004
6,297
20
NW Indiana
I have a ported eaton sitting on my self, but that doesnt change the fact that my set up should be making 17psi as is.

I would like to ditch all the EGR components, but i will do that with the blower swap. Is there a diagram of how i should set up the vacuum lines. Can anyone confirm the how to i have listed in the first post.

From what i can tell most people have varying opinions about doing a boost bypass.

Its simple.
The only thing that needs a boost reference is the Bypass, FRPS and line to the dash gauge.
Everything else gets regular vacuum.
When you swap blowers, take the fitting out of the lower manifold and plug it...then throw the hoses that were attached to it in the TRASH.
 

dun4791

gypsy is a whore!
Mar 2, 2004
4,536
4,257
What ain't no country I ever heard of
I know some of the earlier differences we were seeing is the lower 4 pound pullys actually differered in the od...Metco made a few different size 4 pounders. Maybe thats the issue? Or try marking the upper hub, see if it is slipping on the shaft some? Where are you referencing the boost from? Try to find a better tensioner, and get ALL of the vacuum lines ziptied right away.......good luck.
 

TurboJuice

Regular
Mar 30, 2011
119
0
I know some of the earlier differences we were seeing is the lower 4 pound pullys actually differered in the od...Metco made a few different size 4 pounders. Maybe thats the issue? Or try marking the upper hub, see if it is slipping on the shaft some? Where are you referencing the boost from? Try to find a better tensioner, and get ALL of the vacuum lines ziptied right away.......good luck.

I think this 4# lower has been on the car a long time from the original owner.

I am T'd into the stock boost gauge from behind the cluster. It is going to an AEM digital gauge.

What is a better tensioner? This ones appears to be working well.

I do need to do some vacuum line clean up. But i want to know if the link i posted in the first post is a good idea.
 

FuelSlut

FK RED STAR
Nov 9, 2005
1,969
0
OMG 4# lower. Well thats the problem! Youre setup is designed to push 21 psi! Thast the same pulleys I run 2.93 and 4# lower but on a kenne bell pushing 20.8 psi on a 100 octane lol.

You should swap your upper pulley to a 3.5 and do a 2# lower and retune that thing asap. Or try porting the Heatin but thats even pushing it.
 

FuelSlut

FK RED STAR
Nov 9, 2005
1,969
0
I think this 4# lower has been on the car a long time from the original owner.

I am T'd into the stock boost gauge from behind the cluster. It is going to an AEM digital gauge.

What is a better tensioner? This ones appears to be working well.

I do need to do some vacuum line clean up. But i want to know if the link i posted in the first post is a good idea.

Roush Tensioner I just swapped due to a bent stock one.
http://store.roushperformance.com/detail.aspx?ID=1271

By the way I just saw your other post, if you throw on the ported eaton you will still have to retune the car.
 

TurboJuice

Regular
Mar 30, 2011
119
0
OMG 4# lower. Well thats the problem! Youre setup is designed to push 21 psi! Thast the same pulleys I run 2.93 and 4# lower but on a kenne bell pushing 20.8 psi on a 100 octane lol.

You should swap your upper pulley to a 3.5 and do a 2# lower and retune that thing asap. Or try porting the Heatin but thats even pushing it.

I will let someone else chime in here and back me up, but i am pretty sure that is wrong. Pulley combinations are different for kenne bell's and eatons. A 3.5 SC pulley is barely smaller than stock.

My combination I have is good for 17psi.

Roush Tensioner I just swapped due to a bent stock one.
http://store.roushperformance.com/detail.aspx?ID=1271

By the way I just saw your other post, if you throw on the ported eaton you will still have to retune the car.

My stock tensioner is fine. And I have no idea what other post you are talking about, but I know this.




Anyways, I am not sure there even is a problem with my boost level anymore. I made it out to the track and pulled a couple decent passes. So it seems like the power is there. I cant complain about that.
 

FuelSlut

FK RED STAR
Nov 9, 2005
1,969
0
I will let someone else chime in here and back me up, but i am pretty sure that is wrong. Pulley combinations are different for kenne bell's and eatons. A 3.5 SC pulley is barely smaller than stock.

My combination I have is good for 17psi.



My stock tensioner is fine. And I have no idea what other post you are talking about, but I know this.




Anyways, I am not sure there even is a problem with my boost level anymore. I made it out to the track and pulled a couple 11.7 and 11.8 passes at 117-120. So it seems like the power is there. I cant complain about that.

Im talking about the post where you said you have a ported Eaton on the shelf and I was implying if you put that thing on you will need to retune the car. The stock tensioner will not hold up for long, its too weak and it will bend under load especially running a 4# lower. Most of ud on here have been through this.

Yes the 4# lower and 2.93 is set up for around 20-21 psi its just that the Eaton will never ever see that type of boost. Pushing 17psi out of that thing is not efficient doesent matter wich way you look at it. What I was implying you do is leave the stock 4# lower and do a 3.4 3.5 upper with it and that should be around 14-15 psi and you should be fine. But being that you just went to the track and pulled 11's everything sounds on par (great job by the way) so Id leave everything and enjoy the car.
 

hj16

Tasty!
Mar 1, 2004
9,788
21
I am only seeing 14psi from 5k up on a cool night. All my searching shows I should be at 16-17psi. Correct?

Does it hit 16-17psi around 3-4K then fall to 14 above 5K? Or does it just stay at 14?

If it is dropping it could be due to the natural inefficiencies of the Eaton. Or if you are only seeing 14 everywhere it could either be shaft slippage like Lyle mentioned or you could have one of the 3psi 4lb lowers from Metco.

Do you have a restrictive intake setup? If so that could also be a cause for low boost readings.



But ultimately, if it runs hard and puts up good numbers dont worry yourself about it.
 

TurboJuice

Regular
Mar 30, 2011
119
0
Does it hit 16-17psi around 3-4K then fall to 14 above 5K? Or does it just stay at 14?

If it is dropping it could be due to the natural inefficiencies of the Eaton. Or if you are only seeing 14 everywhere it could either be shaft slippage like Lyle mentioned or you could have one of the 3psi 4lb lowers from Metco.

Do you have a restrictive intake setup? If so that could also be a cause for low boost readings.



But ultimately, if it runs hard and puts up good numbers dont worry yourself about it.

Nope, it doesnt spike. It just hits 14 and stays there.

It might be the pulley slipping on the shaft, is that common?
I might have one of those old Metco lowers, but my belt is the right length for my set up...

And my intake set up is good. C&L pipe with 95mm maf housing.
 
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