Turbo Flutter

[tmsbuic]

I have a TA-49 from PTE and a 3"THDP with a RJC Boost Controller on a internal wastegate. Everything works great under power, what I notice is under light throttle and then letting off a little, I can hear and feel a flutter.
Do you think I need to tighten up the wastegate rod and little(I have it set where it will just slip on the wastegate) It seems like the wastegate puck is bouncing open and close just for a few seconds and only after letting off the throttle. Or, could it be the size of the THDP puck compared to the PTE housing?

 

[XLR8]

A turbo "flutter" or sneeze, etc. is normal when lifting the throttle after building a little boost. People with the stock air box may not hear it.

 

[Ormand]

The wastegate rod should be set so that you have to pull it a little- like about 1/8 of inch- to slip it on the wastegate arm. So if yours will slip on easily, it's too loose, and could cause the waste gate to "chatter", before you get to boost.

 

[turbopete]

My 49 flutters too

At part throttle and WOT I get the flutter. It sounds like boost is being "blown off" like from a poppet valve. I could just be hearing things due to the open K&N filter. Could also be due to a still kinda restrictive exhaust. I did change to the Hooker cat-back style and took off the stock flowmaster, but still have the stock downpipe. I did check for turbine wheel play and exhaust oil smoke and all looks to be OK.
Thoughts?

 

[wiked87gn]

Thats normal pete dont worry about it..

 

[turbopete]

Normal? Good

I was wondering about that. But since I haven't broken the turbo in about 3 years, it must be happy.

 

[evil666]

My car does the same thing when I want to accelerate at part throttle, this happened since I put in the 3 inch thdp. It never did this before so I quess it has to do with the puck on the thdp because the wastegate rod was never touched. When I floor the car it runs great, but sometimes 1/2 thottle accelerations could get a bit annoying with boost flutter. I was told by Jason Cramer from RJC that this was normal, but if someone has a solution to get rid of this problem please tell me. I was told once by porting the hole of the turbo housing it might get rid of this but I don't know if this is correct.

Marco

86 Grand National t-top (59900km)
stock long block,stock suspension, red stripe convertor, te44, smc alk injection, 24lbs boost, 94 octane, hooker cat back with dyno max ultra flow muffers, tomco 30lbs injectors, dynotech stage 4 street chip, thdp, mease 24 row IC, Ron Custom max boost brake module, MT drag radials (275/50/15) 3800lbs race weight with driver.
BEST E/T
60FT=1.52
1/8= 7.38
I/4= 11.74
MPH=113 Best MPH=114

 

[FiveOhSlow]

evil, I have a very similar problem. Mine flutters at part throttle mostly between 10-20lbs of boost. You can see the boost gauge needle fluttering itself and it is very annoying. slight throttle and full throttle are usually fine. I would love to solve this problem




TE44, homemade cold air induction, RJC boost controller, 42.5 injectors, alky injection

 

[Mad_Trbo]

Just out of curiosity is this the system trying to relieve itself after the throttle plate has been shut or partially shut. If so isn't this creating a surge of sorts on the turbo. The only way I see it is the boost created has no where to go so it backs up into the compressor housing and then forces it's way through the air filter. The fact that it is backing up seems similar to another issue.

Imports use blow off valves, especially on those cars equiped with manual transmissiosn. With each shift of the gear the throttle plate is typically slammed shut. The system needs to relieve itself and this is done through a blow off valvle.

Isn;t a similar type system needed on these buick's? More so at higher boost levels perhaps?

 

[FastTurb]

may just have been my problem

I always had a little flutter with the open K&N, THDP, PT54 and 3 inch open exhaust but it recently got a lot worse. I found the screens in the OEM MAF had come unattached and were laying sideways in the inlet of the MAF. I put them back in right and I am back to a little flutter.

Bill

 

[Mad_Trbo]

My honest opinion this flutter is bad for the car.

 

[buickturbo-t]

I’ve got a similar problem, say I am merging onto the highway and step on it a little bit to bring the car to 10-12 lbs of boost about the time the ALKY kicks in, I will get tones of KR enough to peg the knock gauge, while this is going on the turbo will flutter and the car will jerk. If I just step on it to WOT I get very little knock if any at all and the car pulls great. I do have exhaust leaks at both of my headers from cracks but I have not yet pulled them off to weld them again, I'm thinking about getting a set of TA header. I don't know if this is because of the leak or something else or if it is just normal. I have turned off the ALKY and still get the same response from the car. IF anyone has any ideas please let me know.

 

[Ormand]

My honest opinion this flutter is bad for the car.

I'm sure you are right. My turbo with 180,000 miles on it may not last to 200,000, and I'm sure if I had a blow off valve, it would go 300,000. But who wants a turbo to last that long, except on truck? Seriously, on a turbo Buick with stock or near-stock turbo, a blow off valve is NOT needed. With a bigger turbo, maybe. You have to be careful when you try to take lessons from a chebby or a stang or a ricer and apply them to a turbo Buick, because the same things don't always work.

 

[corsair231]

The flutter/surge is caused by the compressor coming off of it's efficiency range (map). The turbo spools and boost builds but at part throttle the compressor is trying to shove more air into the engine but because the engine cannot handle the flow the pressure builds until the excess has to go somewhere. The compressor is still flowing more than the engine/throttlebody can handle but not enough to keep building boost so the higher pressure air flows back past the blades into the intake tube. Excercise: Take a garden hose and put it in your mouth. Wrap your lips around the hose and turn it on very slowly. You can swallow enough water to keep up. Now turn it on wide open. What happens? (Caution perform this excercise only with adult supervision)
If you go full throttle the compressor speeds up enough to start building additional boost and eventually everything smooths out enough that flow, boost pressure, and speeds even out as it moves away from the edge of the map. Anything that changes the engine's ability to flow air can alter the map's orientation. A larger down pipe may make the turbo spool faster building boost faster, lower in the rpm range where the engine can't use it. A larger wastegate hole may help because it allows more flow to bypass the turbine and slows spool. But with a larger hole the wastegate does not have to be opened as much to control boost which is why it may help with creep. Air intake mods are like putting a megaphone on what is already happening. Making the surge more noticeable.
As far as the blow offs. Slamming the throttle closed causes the turbo to stop spooling and quickly fall off of the map. This is harder on the turbo because the air does not just simply slip past the blades, it acts as an airbrake because driving it against the thrust bearings. In our cars the automatic lessens this because the throttle is not closed between shifts. Manual trans cars shift at least 4 times on acceleration and again on deceleration. This happens on every acceleration not just wot runs. The wear is just greatly accelerated on manual transmission cars.

 

[Blazer406]

Anybody ever heard a loud thump when you have a water faucet wide open.. and quickly close it....... the thump is called "water hammer". The sudden stoppage of water spikes the pressure against the closing valve.... causing the thump you sometimes hear.

The same concept is happening when the turbo has built up pressure in the intake tract... and intercooler... and up-pipe..... then you slam the door (the closing throttle blade) on all this pressure... and spinning compressor wheel..... causing the flutter you are referring to.... much like the "water hammer" I mentioned above. This also IMHO causes the compressor blades... when confronted with a massive pressure spike in the compressor outlet....cavatates..... causing the compressor impeller to rapidly loose speed (along with some speed fluctuation)and thrust toward the exhaust side.

That's about as good as I can explain it.... as I understand it.

HTH

 

[turbopete]

OK then

Thanks for the explanation.
So, I guess the reason some of us experience this more than others is due to intake set-up, turbo size and the exhausts ability to pass air.
Since this is hard on the turbo internals, I don't see any way to avoid it except to try and open the exhaust enough to minimize the flutter. To try and figure out the airflow on my combination without just swapping parts would take more engineering knowledge than I have.

Hey, it goes fast and is reliable. Nuff said...

 

[Blazer406]

Thanks for the explanation.
So, I guess the reason some of us experience this more than others is due to intake set-up, turbo size and the exhausts ability to pass air.
Since this is hard on the turbo internals, I don't see any way to avoid it except to try and open the exhaust enough to minimize the flutter. To try and figure out the airflow on my combination without just swapping parts would take more engineering knowledge than I have.

Hey, it goes fast and is reliable. Nuff said...

The real solution is to put a blow off valve on the compressor side... it acts as a pop-off to purge unused boost when the throttle blade closes rapidly.....
downside to this is if it leaks... you are loosing boost when you don't want to......

Most turbo buick people live with the "sneeze" and just try to not close the throttle rapidly too often..... I personally like the sound.... but I know it is not too good for the turbo internals.....

 

[PHANTASM]

mounting a blow off valve?

how would you mount a blow off valve set-up? (drawing)

i spent alot of money on this car and don't want to buy another turbo.

thanks
i get a massive flutter with my pt61 when at part throttle if you close the throttle to fast from accelerating.

 

[evil666]

In my case I get boost flutter at part throttle acceleration and when I release the the gas. I know it is bad for the turbo to release the gas quickly when you are at full throttle. What I want to know, is for someone to tell me if the flutter at part throttle is bad for the turbo or not?

Thanks Marco

86 Grand National t-top (59900km)
stock long block,stock suspension, red stripe convertor, te44, smc alk injection, 24lbs boost, 94 octane, hooker cat back with dyno max ultra flow muffers, tomco 30lbs injectors, dynotech stage 4 street chip, thdp, mease 24 row IC, Ron Custom max boost brake module, MT drag radials (275/50/15) 3800lbs race weight with driver.
BEST E/T
60FT=1.52
1/8= 7.38
I/4= 11.74
MPH=113 Best MPH=114

 

[corsair231]

From the way that I understand it the flutter at part throttle comes from the compressor side losing its ability to move the air. It is still being driven by the turbine side but it is at the point that it cannot pack any more air into the engine. Sort of like my garden hose example. Air is still flowing and the engine is still drinking but the hose cannot put more into the engine so the excess comes back out around the hose. The air slips back out at the tips of the compressor blades or either the blades just cannot pull more air in. I don't think it is as bad on the turbo because the turbo is still being driven at approximately the same speed.
When the throttle is slammed shut the engine is no longer drinking air and the exhaust is no longer driving the turbine and you get the water hammer effect. The air that was already compressed has no where to go and since the turbo is now pretty much freewheeling the principle of differential pressure comes in to effect and the higher pressure air tries to expand to fill the low pressure area in front of the turbo (and outside the low restriction air filter ). To do this it now tries to turn the compressor backwards, or at least almost stops it, to let so much pressure escape at once. Think of blowing up a balloon and then letting it go. That maybe why front mount i/c's can be so bad about surge, more volume filled under pressure (bigger balloon). Think of the compressor blades as being a prop on a shaft. When it is buiding boost it is grabbing air and pushing it out behind it and in effect pulling itself toward the air source. If you reverse the direction it turns it is then pushing itself in the opposite direction which shoves it against the thrust bearing, causing the most wear.