Boost Bleeding Off = Bent Intake Valve?
Thread Starter
10 Second Club
iTrader: (19)
Joined: Feb 2004
Posts: 2,542
Likes: 2
From: Alexandria La.
Boost Bleeding Off = Bent Intake Valve? I have been bleeding off boost and have been racking my brain trying to figure out where its going and I'm running out of ideas. After spending my weekend installing some patriot dual extreme valve springs I have now ruled valve float out of the equation.
Here's what all I have tried.
1. Bypassing the boost controller
2. Relocating the boost controllers signal to the intake manifold
3. Moving my wastegate reference signal from the turbo housing to the intake manifold
4.Pressurizing the turbo & looking for leaks in the cold side (found lots of small ones and fixed them all)
5. Double checked over the intire hotside for leaks, couldnt find any.
6. Replaced valve springs as stated above.
The car (with a 7psi spring in the gate) will make 5.5 psi pretty quick and then starts going down hill from there, its usually at 3.5 psi before I have to shift.
I have now moved on to the idea that maybe an intake valve is bent and that may be where my boost is going. The car seems to run ok, it dosent pop on acceleration, & seems to idle ok but it has always been a little lopey with the 224 cam on a 112 lsa. I plan on doing a compression test later this week when I have time, I'm sure if I have a bent valve it will show up there. Honestly I have revved the car pretty high with nitrous (before the turbo) so high in fact that I pulled all the pushrods to make sure they werent bent. They are hardened Comp Cams push rods and werent bent at all.
I just wanted to throw this idea out there and see what some of you that have been there broke that and see what anyone had to say. Anyway I'm getting frustrated and am running out of ideas.
Here's what all I have tried.
1. Bypassing the boost controller
2. Relocating the boost controllers signal to the intake manifold
3. Moving my wastegate reference signal from the turbo housing to the intake manifold
4.Pressurizing the turbo & looking for leaks in the cold side (found lots of small ones and fixed them all)
5. Double checked over the intire hotside for leaks, couldnt find any.
6. Replaced valve springs as stated above.
The car (with a 7psi spring in the gate) will make 5.5 psi pretty quick and then starts going down hill from there, its usually at 3.5 psi before I have to shift.
I have now moved on to the idea that maybe an intake valve is bent and that may be where my boost is going. The car seems to run ok, it dosent pop on acceleration, & seems to idle ok but it has always been a little lopey with the 224 cam on a 112 lsa. I plan on doing a compression test later this week when I have time, I'm sure if I have a bent valve it will show up there. Honestly I have revved the car pretty high with nitrous (before the turbo) so high in fact that I pulled all the pushrods to make sure they werent bent. They are hardened Comp Cams push rods and werent bent at all.
I just wanted to throw this idea out there and see what some of you that have been there broke that and see what anyone had to say. Anyway I'm getting frustrated and am running out of ideas.
i have the same problem, i believe mines due to a turbo that is to small, but since you have a t76 that shouldnt be a problem!.........i found this on a prior thread..
Whoa, finally an update...
Took the car to another tuner and dyno. Found out my base fuel pressure was too high and it dropped a few psi right around 4500 rpms and the AFRs were going LEAN... Also, the timing was sky high and the plugs were gapped around 38.
Retuned the car with the lower fuel pressure and tighter plug gap (32). Now, it's good until 5800 rpms. Checked backpressure and it was at 33 psi max and 11 psi on the intake side. AFRs go rich at 5800, no matter what we do to the fuel trims.
I understand that the backpressure ratio is 3:1 and it should be more like 2:1. Will exhaust pressure rise with increased boost? I was thinking of raising the boost to 14 or 15 psi to lower the backpressure ratio... Any thoughts? Will it work to see if backpressure is the issue? If not, I think I will try new valve springs next...
Took the car to another tuner and dyno. Found out my base fuel pressure was too high and it dropped a few psi right around 4500 rpms and the AFRs were going LEAN... Also, the timing was sky high and the plugs were gapped around 38.
Retuned the car with the lower fuel pressure and tighter plug gap (32). Now, it's good until 5800 rpms. Checked backpressure and it was at 33 psi max and 11 psi on the intake side. AFRs go rich at 5800, no matter what we do to the fuel trims.
I understand that the backpressure ratio is 3:1 and it should be more like 2:1. Will exhaust pressure rise with increased boost? I was thinking of raising the boost to 14 or 15 psi to lower the backpressure ratio... Any thoughts? Will it work to see if backpressure is the issue? If not, I think I will try new valve springs next...
Thread Starter
10 Second Club
iTrader: (19)
Joined: Feb 2004
Posts: 2,542
Likes: 2
From: Alexandria La.
Plugs looked good, there were 3 on the passengers side that had light black marks on the outer portion, like where the spark plug boot didnt cover. The head looked clean around the manifold, no soot from leaking. Those plugs looked like if they were leaking it would be where they seal to the head. I'm running TR6's, they dont have any kind of washer on them and those plugs were in pretty tight.
The other side had 2 that looked kind of wet, like oil, didnt smell any gas though.
If I'm bleeding boost, I dont see where a leaking ring or plug at the threads would make the map sensor see a loss of boost unless it was leaking past an intake valve that wouldnt seal up right.
What kind of wastegate? Are you 100% sure it is a 7.5psi spring? Check the BOV too.
What turbo kit? if it has a poor design, you will never be able to calm the gate down, it will just force it self open.
What turbo kit? if it has a poor design, you will never be able to calm the gate down, it will just force it self open.
Thread Starter
10 Second Club
iTrader: (19)
Joined: Feb 2004
Posts: 2,542
Likes: 2
From: Alexandria La.
The BOV is good and dosent open up under boost, untill it sees vaccum at least. I tested it by pressurizing the turbo inlet and turning up the volume on my 60gal/5hp compressor to maintain a steady 10 psi and it was air tight.
Honestly the only thing I havent done as of yet is take apart the wastegate to look for something wrong. I dont know if I could spot a problem in the waste gate if it slapped me in the face, Im not very familiar with the inside of one.
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo Thread Starter
10 Second Club
iTrader: (19)
Joined: Feb 2004
Posts: 2,542
Likes: 2
From: Alexandria La.
I don't see anything with that, that would cause a problem.
I might have missed it, but where are you picking up the boost source?
I know with my Eboost2, just by changing the arrangement on the boost solenoid, it took me from a 15 psi base with a 7.5 psi spring, to spring pressure with it zeroed out. Just by routing hoses different. I have taken mine as high as 21 psi from that same 7.5 psi spring with the boost controller.
I am guessing the engine is ok, you would have some drivability issues if a valve was bent.
Explain exactly how you have the w/g gate vacuum hoses.
I might have missed it, but where are you picking up the boost source?
I know with my Eboost2, just by changing the arrangement on the boost solenoid, it took me from a 15 psi base with a 7.5 psi spring, to spring pressure with it zeroed out. Just by routing hoses different. I have taken mine as high as 21 psi from that same 7.5 psi spring with the boost controller.
I am guessing the engine is ok, you would have some drivability issues if a valve was bent.
Explain exactly how you have the w/g gate vacuum hoses.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
As above.
Post details of how the wastegate is plumbed.
And if there is any adjustment for the w/g spring.
And how/where are you monitoring boost ? and are there definately no leaks in that pipework ?
Post details of how the wastegate is plumbed.
And if there is any adjustment for the w/g spring.
And how/where are you monitoring boost ? and are there definately no leaks in that pipework ?
Thread Starter
10 Second Club
iTrader: (19)
Joined: Feb 2004
Posts: 2,542
Likes: 2
From: Alexandria La.
I don't see anything with that, that would cause a problem.
I might have missed it, but where are you picking up the boost source?
I know with my Eboost2, just by changing the arrangement on the boost solenoid, it took me from a 15 psi base with a 7.5 psi spring, to spring pressure with it zeroed out. Just by routing hoses different. I have taken mine as high as 21 psi from that same 7.5 psi spring with the boost controller.
I am guessing the engine is ok, you would have some drivability issues if a valve was bent.
Explain exactly how you have the w/g gate vacuum hoses.
I might have missed it, but where are you picking up the boost source?
I know with my Eboost2, just by changing the arrangement on the boost solenoid, it took me from a 15 psi base with a 7.5 psi spring, to spring pressure with it zeroed out. Just by routing hoses different. I have taken mine as high as 21 psi from that same 7.5 psi spring with the boost controller.
I am guessing the engine is ok, you would have some drivability issues if a valve was bent.
Explain exactly how you have the w/g gate vacuum hoses.
Thread Starter
10 Second Club
iTrader: (19)
Joined: Feb 2004
Posts: 2,542
Likes: 2
From: Alexandria La.
I did talk to Brian @ JGS and ask if theres a diaphragm in there that could be torn and he said no just a piston and an 0-ring. I hope I get the top off and find a torn o-ring.
Thread Starter
10 Second Club
iTrader: (19)
Joined: Feb 2004
Posts: 2,542
Likes: 2
From: Alexandria La.
No sorry, no pics of the plumbing I have all the lines hidden as best as possable.
I do however have everything t-d off the brake booster line. (BOV,wastegate,boost controller, & fuel pressure regulator) If that matters.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
I would not plumb anything that bleeds off air together with items that do not, unless the supply line to all those items was quite substantial.
If you have a large manifold..say 1/2" diameter feeding all items, then it would probably be ok.
In theory...even the booster will bleed off occasionally, although it should never leak under boost.
if a diapghram or something was damaged on the cold side of the WG...you'd get too mcuh boost, unless there was no spring.
If the hot side was held open...spool could be very slow, and possible low boost available.
If you have a large manifold..say 1/2" diameter feeding all items, then it would probably be ok.
In theory...even the booster will bleed off occasionally, although it should never leak under boost.
if a diapghram or something was damaged on the cold side of the WG...you'd get too mcuh boost, unless there was no spring.
If the hot side was held open...spool could be very slow, and possible low boost available.
Thread Starter
10 Second Club
iTrader: (19)
Joined: Feb 2004
Posts: 2,542
Likes: 2
From: Alexandria La.
I would not plumb anything that bleeds off air together with items that do not, unless the supply line to all those items was quite substantial.
If you have a large manifold..say 1/2" diameter feeding all items, then it would probably be ok.
In theory...even the booster will bleed off occasionally, although it should never leak under boost.
if a diapghram or something was damaged on the cold side of the WG...you'd get too mcuh boost, unless there was no spring.
If the hot side was held open...spool could be very slow, and possible low boost available.
If you have a large manifold..say 1/2" diameter feeding all items, then it would probably be ok.
In theory...even the booster will bleed off occasionally, although it should never leak under boost.
if a diapghram or something was damaged on the cold side of the WG...you'd get too mcuh boost, unless there was no spring.
If the hot side was held open...spool could be very slow, and possible low boost available.
You could test a lot of things by removing the wastegate, capping the ends temporarily and cautiously testing. If the boost goes up then drops then, you can rule out the WG. I'd take it out and drive it and brake boost while someone else monitors. Pull some extra timing out for safety - maybe even run some race gas for insurance while you test.
Jim
Jim
Thread Starter
10 Second Club
iTrader: (19)
Joined: Feb 2004
Posts: 2,542
Likes: 2
From: Alexandria La.
You could test a lot of things by removing the wastegate, capping the ends temporarily and cautiously testing. If the boost goes up then drops then, you can rule out the WG. I'd take it out and drive it and brake boost while someone else monitors. Pull some extra timing out for safety - maybe even run some race gas for insurance while you test.
Jim
Jim
building boost on the foot brake would be awesome but my car is still a 6 speed for now.