turbo is Loosing boost on the top end
Thread Starter
Joined: Sep 2004
Posts: 717
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From: Fairview NC (near Charlotte)
turbo is Loosing boost on the top end my car has been loosing boost on the top end ever since I finished with the Turbo install in September.
My setup is a PTS kit with a Precision T67Q trim turbo w/ .96 exhaust housing and a .70 coldside housing, PTS FMIC, stock engine W/ LS6 valve springs, Exhaust with 3 inch cutout in front of rear axle
It will bleed off around 2 to 3 pounds from 3500 Rpm to 6500 on a steady decline
It did this before the Valve springs and the cutout was installed
what can I look for to fix this problem
I have a E-Boost 2 bost controller, Mitsibushi (sp) by-pass valve, and A turbosmart 38mm wastegate
could someone please help me with this
is the turbo to small,
I have 2 settings on the Boost controller, 1 for 7 PSI and the other is around 8.5
on both settings the waste gate starts to open at 3.5 to 4 pounds
I have the syn. set on 90 on the higher boost setting
can someone please help me
thanks Darren P
My setup is a PTS kit with a Precision T67Q trim turbo w/ .96 exhaust housing and a .70 coldside housing, PTS FMIC, stock engine W/ LS6 valve springs, Exhaust with 3 inch cutout in front of rear axle
It will bleed off around 2 to 3 pounds from 3500 Rpm to 6500 on a steady decline
It did this before the Valve springs and the cutout was installed
what can I look for to fix this problem
I have a E-Boost 2 bost controller, Mitsibushi (sp) by-pass valve, and A turbosmart 38mm wastegate
could someone please help me with this
is the turbo to small,
I have 2 settings on the Boost controller, 1 for 7 PSI and the other is around 8.5
on both settings the waste gate starts to open at 3.5 to 4 pounds
I have the syn. set on 90 on the higher boost setting
can someone please help me
thanks Darren P
TECH Resident
Joined: Jan 2004
Posts: 832
Likes: 0
From: Castro Valley, CA
There's no way that turbo is too small.
Darren, sorry to hear about the problems...
Are you getting any crankcase pressure? Or are you sure that you're losing your boost via the wastegate?
Seems like one of the first things to try would be to take the boost controller out of the picture and run strictly against the ultragate (w/default 7 lb spring) with the "top" port connected only to atmosphere.
If you're still losing boost while on the dyno, are you sure that your clutch isn't slipping?
And I'll throw this in just because it happened to me: my stock bottom end was fine running 400 rwhp N/A. But as we got to final tuning with my PTS setup, it wouldn't hold higher boost levels. There was crankcase pressurization, and a compression test revealed that #7 just wasn't going to hold on for the party. Hello, forged motor. So that's going into my car as we speak. Hopefully back to tuning it next week, I will keep you posted.
Let me know what you find on your setup...
Rich
Darren, sorry to hear about the problems...
Are you getting any crankcase pressure? Or are you sure that you're losing your boost via the wastegate?
Seems like one of the first things to try would be to take the boost controller out of the picture and run strictly against the ultragate (w/default 7 lb spring) with the "top" port connected only to atmosphere.
If you're still losing boost while on the dyno, are you sure that your clutch isn't slipping?
And I'll throw this in just because it happened to me: my stock bottom end was fine running 400 rwhp N/A. But as we got to final tuning with my PTS setup, it wouldn't hold higher boost levels. There was crankcase pressurization, and a compression test revealed that #7 just wasn't going to hold on for the party. Hello, forged motor. So that's going into my car as we speak. Hopefully back to tuning it next week, I will keep you posted.
Let me know what you find on your setup...
Rich
................ It could just be boost spiking and where it settles to is actually what you boost is set for.
Originally Posted by Darren P
my car has been loosing boost on the top end ever since I finished with the Turbo install in September.
My setup is a PTS kit with a Precision T67Q trim turbo w/ .96 exhaust housing and a .70 coldside housing, PTS FMIC, stock engine W/ LS6 valve springs, Exhaust with 3 inch cutout in front of rear axle
It will bleed off around 2 to 3 pounds from 3500 Rpm to 6500 on a steady decline
It did this before the Valve springs and the cutout was installed
what can I look for to fix this problem
I have a E-Boost 2 bost controller, Mitsibushi (sp) by-pass valve, and A turbosmart 38mm wastegate
could someone please help me with this
is the turbo to small,
I have 2 settings on the Boost controller, 1 for 7 PSI and the other is around 8.5
on both settings the waste gate starts to open at 3.5 to 4 pounds
I have the syn. set on 90 on the higher boost setting
can someone please help me
thanks Darren P
My setup is a PTS kit with a Precision T67Q trim turbo w/ .96 exhaust housing and a .70 coldside housing, PTS FMIC, stock engine W/ LS6 valve springs, Exhaust with 3 inch cutout in front of rear axle
It will bleed off around 2 to 3 pounds from 3500 Rpm to 6500 on a steady decline
It did this before the Valve springs and the cutout was installed
what can I look for to fix this problem
I have a E-Boost 2 bost controller, Mitsibushi (sp) by-pass valve, and A turbosmart 38mm wastegate
could someone please help me with this
is the turbo to small,
I have 2 settings on the Boost controller, 1 for 7 PSI and the other is around 8.5
on both settings the waste gate starts to open at 3.5 to 4 pounds
I have the syn. set on 90 on the higher boost setting
can someone please help me
thanks Darren P
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Thread Starter
Joined: Sep 2004
Posts: 717
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From: Fairview NC (near Charlotte)
Originally Posted by ESR
It could just be boost spiking and where it settles to is actually what you boost is set for.
the waste gate has a 7 pound spring in it
it is peaking at around 8.5 PSI and falling off to 5.9 to 5.5 at 6000 RPM
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Maybe the turbo is NOT too small, though the turbo just might not operate well if you're spinning past 6k rpm???
Forget it... Oooops, I just read now that it starts to bleed off boost starting at 3500 rpm. There has to be something wrong maybe with a line? I changed one of my fans and I lost ALOT of boost... Later I saw a had pinch a line with a tie strap by mistake... Look for stupid things like that maybe?
Forget it... Oooops, I just read now that it starts to bleed off boost starting at 3500 rpm. There has to be something wrong maybe with a line? I changed one of my fans and I lost ALOT of boost... Later I saw a had pinch a line with a tie strap by mistake... Look for stupid things like that maybe?
Originally Posted by Sierra5.3
Doesnt sounds like floating to me since he's only getting up to 6000rpms and the boost is falling..
You sure the Turbo isnt choking out?
You sure the Turbo isnt choking out?
However, I hadn't read that the power drops off after just 3500 rpm's, Definitely something else... I rushed through reading his post.
TECH Enthusiast
Joined: May 2004
Posts: 567
Likes: 0
From: Colorado
Originally Posted by bboyferal
Valve float can occur below 6k rpm. It usually does...
However, I hadn't read that the power drops off after just 3500 rpm's, Definitely something else... I rushed through reading his post.
However, I hadn't read that the power drops off after just 3500 rpm's, Definitely something else... I rushed through reading his post.
right..
Correct... AND many have experienced valve float on stock LS1 springs starting at 5k-5500 rpm... not as high as 6k rpm... with no such contact... only a loss of power... right... Valve float is not an over-6k rpm problem. It occurs lower than that often... happened to me.
Of course, though, that is not what is happening here.
Of course, though, that is not what is happening here.
Thread Starter
Joined: Sep 2004
Posts: 717
Likes: 0
From: Fairview NC (near Charlotte)
well I just ran it with no boost referance and it shot to 14 psi
I riconfigured teh boost controller Hook up to the second method told about in the instructions and it made 11 PSI and I could not get it to go lower
the turbo is not to small for sure
it made 14.5 psi like it was nothing
but I am confused now Because Jose said that if I unhooked the boost referance it would only make about 1 pound more than the spring pressure and it has a 7 pound spring
am i missunderstanding this or just stupid
oh well back to Square one
I riconfigured teh boost controller Hook up to the second method told about in the instructions and it made 11 PSI and I could not get it to go lower
the turbo is not to small for sure
it made 14.5 psi like it was nothing
but I am confused now Because Jose said that if I unhooked the boost referance it would only make about 1 pound more than the spring pressure and it has a 7 pound spring
am i missunderstanding this or just stupid
oh well back to Square one
one this is you are running a 38mm waste gate, I have been told that the 38mm is too small of a WG to run low boost on with our engines....aka the WG can't bleed off enough exhaust to make the 7-8 LBS of boost consistant. there is a good chance you waste gate is just fighting to keep your boost at what you have you controler set at and it can't do it consistantly. if you have the ability try to run a larger WG and see what happens.
If i am way off here guys let me know, but i always thought a 38MM WG was risky and too small if your gunna run low boost on our big engines
If i am way off here guys let me know, but i always thought a 38MM WG was risky and too small if your gunna run low boost on our big engines