probems holding steady boost
#1
11 Second Club
Thread Starter
iTrader: (13)
Join Date: Dec 2004
Location: NYC
Posts: 355
Likes: 0
Received 0 Likes
on
0 Posts
![](https://ls1tech.com/forums/images/ranks/ls1tech10year.png)
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
I have been having this issue for some time now, previously had a 6speed in the car and currently have a th400
however I noticed throughout my pull my map kpa bounces between 166 - 180
that seems like a big difference to me
i have boost leak tested my system from the filter inlet of the turbo to the manifold and found no leaks
this is me running off the wastegate, the boost controller is turned all the way in
here is my log file from hptuners , at the very end of it you can see how I make a clean wot 3rd gear pull and how it jumps around
however I noticed throughout my pull my map kpa bounces between 166 - 180
that seems like a big difference to me
i have boost leak tested my system from the filter inlet of the turbo to the manifold and found no leaks
this is me running off the wastegate, the boost controller is turned all the way in
here is my log file from hptuners , at the very end of it you can see how I make a clean wot 3rd gear pull and how it jumps around
#3
11 Second Club
Thread Starter
iTrader: (13)
Join Date: Dec 2004
Location: NYC
Posts: 355
Likes: 0
Received 0 Likes
on
0 Posts
![](https://ls1tech.com/forums/images/ranks/ls1tech10year.png)
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
Its a iron block 370 with a truck manifold pt88, 50mm jgs wg, i dont think its a wg problem though cause when it had he lighter spring in it , it would keep boost down to 5psi, i havent leak tested the hotside yet but not sure if a hotside leak will cause my issues
I also have a 4inch downpipe and it dump at the back of engine so its no very restictive
I also have a 4inch downpipe and it dump at the back of engine so its no very restictive
#4
TECH Addict
iTrader: (16)
Join Date: Jul 2005
Location: Anchorage, ALASKA
Posts: 2,899
Likes: 0
Received 0 Likes
on
0 Posts
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
When you say you pressure tested the whole cold side to the manifold, did you also test the manifold?
Sounds like an exhaust leak, wastegate leak, cracked intake manifold, or bad intake manifold gasket. You would be surprised how a little exhaust leak will cause all kinds of boosting issues.
Sounds like an exhaust leak, wastegate leak, cracked intake manifold, or bad intake manifold gasket. You would be surprised how a little exhaust leak will cause all kinds of boosting issues.
#5
11 Second Club
Thread Starter
iTrader: (13)
Join Date: Dec 2004
Location: NYC
Posts: 355
Likes: 0
Received 0 Likes
on
0 Posts
![](https://ls1tech.com/forums/images/ranks/ls1tech10year.png)
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
I pressure tested the manifold as well so i know there is no leaks, but i remember seeing a little water from my wastegat and one of the crossover pipes, so its a small leak bust i didn't think they would cause such an issue boosting, i gues ill grind them down and weld them tomorrow and see what happens
#6
11 Second Club
Thread Starter
iTrader: (13)
Join Date: Dec 2004
Location: NYC
Posts: 355
Likes: 0
Received 0 Likes
on
0 Posts
![](https://ls1tech.com/forums/images/ranks/ls1tech10year.png)
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
I did notice that when i was pressurizing the intake system i was bleeding off boost out of the oil cap, but i just figured the engine was cold and its a forged motor so it must be normal, unless it was leaking through a rocker bolt, cause i think some of them go through to the intake ports
Trending Topics
#10
11 Second Club
Thread Starter
iTrader: (13)
Join Date: Dec 2004
Location: NYC
Posts: 355
Likes: 0
Received 0 Likes
on
0 Posts
![](https://ls1tech.com/forums/images/ranks/ls1tech10year.png)
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
I dont have a boost gauge, i go by my scanner using the map sensor
however i just got finished leak testing the cold side again and found a big leak that i musta not checked b4
does something look like its missing here?
![](http://i1180.photobucket.com/albums/x404/4cefed370/IMG_20110329_120504.jpg)
so hopefully ill make some solid power gains and hold steady boost once i recieve the oring from precision, because i remember previously on the dyno my power started falling off after 5500rpm's, and then ill find and fix my minor exhaust leaks ( one fix at a time )
however i just got finished leak testing the cold side again and found a big leak that i musta not checked b4
does something look like its missing here?
![](http://i1180.photobucket.com/albums/x404/4cefed370/IMG_20110329_120504.jpg)
so hopefully ill make some solid power gains and hold steady boost once i recieve the oring from precision, because i remember previously on the dyno my power started falling off after 5500rpm's, and then ill find and fix my minor exhaust leaks ( one fix at a time )