Compressor Surge (Turbo sneeze)

[fatride]

Took the car out today for the first time. Getting on the highway, when the car shifts gears I'm getting (Turbo sneeze). Just 1/4 throttle when the cars shifts it surges and seems to bog then goes. Any ways to cure this issue? I have not done a full blast in the car to see if it happens......
Thanks

 

[RUQWKNF]

A compressor bypass valve will help, unfortunately, with the turbo you are running and without a ported shroud compressor cover, 1/4 throttle under boost or half throttle under boost are pretty much things of the past. What is happening is, the motor can not take the amount of air that is being thrown at it under 1/4 or 1/2 throttle, so the charge air starts to back up and causes the turbo to start surging. Once you get to the 70 series and larger turbos on 231-248ci motors, they are like light switches and don't care for partial anything throttle without a ported shroud compressor cover.
Therefore, the only real solution would be to get a ported shroud compressor cover. Your predicament is specifically what the ported shroud compressor cover was created for. Now, with that said, it's gonna come down to whose 70 P-trim turbo you have. If it is a genuine 7076H turbo, then you could purchase a CCH70P ported shroud cover with hardware from PTE and it should bolt up without any problems.
Here is a picture showing what a ported shroud compressor cover looks like on a PT70 series turbo.

If that turbo is from another turbo company that uses a different backing plate and compressor cover, you're out of luck. You could send your turbo to PTE and see if they would be able to retrofit/convert it over to their backing plate and CCH70P cover tho. If you opt for this route, Jim in repairs is the man to talk too.
Here is a picture and link that talks about the ported shroud.

TurboByGarrett.com - Turbo Tech103
Scroll 1/3 of the way down the page until you see the PS picture.
Quote taken directly from this link,
"A Ported Shroud compressor (see Fig. 2) is a feature that is incorporated into the compressor housing. It functions to move the surge line further to the left (see Fig. 3) by allowing some airflow to exit the wheel through the port to keep surge from occurring. This provides additional useable range and allows a larger compressor to be used for higher flow requirements without risking running the compressor into a dangerous surge condition. The presence of the ported shroud usually has a minor negative impact on compressor efficiency."

Hence the reason you don't see this type of cover on most Buicks, cause most people only race with this size turbo and no more partial throttle. Exactly how much hp the PS cover hurts has never been determined on a Buick. It has been determined on Turbo Supras tho. But that's another secret.

HTH

Patrick

 

[TurboBob]

try turning the boost down all the way and see if it goes away. If it does, post back.

B

 

[tbirdv6]

A compressor bypass valve will help, unfortunately, with the turbo you are running and without a ported shroud compressor cover, 1/4 throttle under boost or half throttle under boost are pretty much things of the past. What is happening is, the motor can not take the amount of air that is being thrown at it under 1/4 or 1/2 throttle, so the charge air starts to back up and causes the turbo to start surging. Once you get to the 70 series and larger turbos on 231-248ci motors, they are like light switches and don't care for partial anything throttle without a ported shroud compressor cover.
Therefore, the only real solution would be to get a ported shroud compressor cover. Your predicament is specifically what the ported shroud compressor cover was created for. Now, with that said, it's gonna come down to whose 70 P-trim turbo you have. If it is a genuine 7076H turbo, then you could purchase a CCH70P ported shroud cover with hardware from PTE and it should bolt up without any problems.
Here is a picture showing what a ported shroud compressor cover looks like on a PT70 series turbo.

If that turbo is from another turbo company that uses a different backing plate and compressor cover, you're out of luck. You could send your turbo to PTE and see if they would be able to retrofit/convert it over to their backing plate and CCH70P cover tho. If you opt for this route, Jim in repairs is the man to talk too.
Here is a picture and link that talks about the ported shroud.

TurboByGarrett.com - Turbo Tech103
Scroll 1/3 of the way down the page until you see the PS picture.
Quote taken directly from this link,
"A Ported Shroud compressor (see Fig. 2) is a feature that is incorporated into the compressor housing. It functions to move the surge line further to the left (see Fig. 3) by allowing some airflow to exit the wheel through the port to keep surge from occurring. This provides additional useable range and allows a larger compressor to be used for higher flow requirements without risking running the compressor into a dangerous surge condition. The presence of the ported shroud usually has a minor negative impact on compressor efficiency."

Hence the reason you don't see this type of cover on most Buicks, cause most people only race with this size turbo and no more partial throttle. Exactly how much hp the PS cover hurts has never been determined on a Buick. It has been determined on Turbo Supras tho. But that's another secret.

HTH

Patrick

Patrick,
I have the same housing as pictured (ported shroud,4" in/3" out)
My turbo was sold to me as a PTE67-is this possible (seller claims its approx 3 yrs old)???
I'm thinking its a 70
FRED

 

[fatride]

It just started to rain . My 70 is an older model Garret turbo. But only has a few hundred miles on it. Don't know much about it, got it from my buddy. It was one of Pete Bartons turbo's which he used on his Yellow ANS car. Would a BOV help??

 

[RUQWKNF]

Fred,
Yes, the Ported Shroud H cover for the 67 has been in existence that long. However, the H cover with the Precision logo on the discharge, has only be around for about a year, year and a half. The cover pictured above is the new style H cover. Slightly larger than the older H cover that had the raised name plate casting in the discharge, where a small name tag would be riveted to the compressor cover. You should be able to take the backing plate clamps and bolts off the compressor cover and find a CNC cut part number. Make sure you either take a digital picture of the orientation/location of the clamps before you take them off, or at least mark them with a permanent pen. This will help you put it back together if you indeed take the compressor cover completely off the turbo. There is also an O-ring on the backing plate that helps seal the comp cover to the backing plate. Try not to rotate the cover when taking it off as it can tear the o-ring. The 67 p/n would be CCH67P, the 70 p/n would be CCH70P. You can't put a CCH67P cover on a turbo equipped with a 70mm wheel unless the cover was re-machined to the correct contour of the 70mm wheel. Once you take the backing plate clamps off you will see the CNC cut part number on the backside edge of the compressor cover. The number gets covered up by the backing plate clamps. When you go to reinstall the clamps and bolts, tighten the bolts in a criss cross fashion hand tight. Putting a light dab of oil on the o-ring will allow you to rotate the cover if need be to get the proper orientation during installation. I believe there is one bolt that maybe hard to get too and might require you rotate the cover just slightly to get the bolt started.

fatride,
In this instance, I don't believe a BOV will cure part throttle surging, as the BOV will only function under positive pressure to negative pressure changes, such as when lifting from WOT. You should be able to send your turbo to PTE and see if they can convert it to a current PS H cover tho. If you are determined to run partial throttle boost, the ps cover is really the only cure.
Hope all this helps.

Patrick

 

[fatride]

Thanks!

 

[TurboBuRick]

You back from the dead or what?

 

[Brer Rabbit]

Hey Rick?

Is that Birchwood around ur gauges?

 

[TurboBuRick]

Is that Birchwood around ur gauges?

What! Thats mahoganoy. Are you jellous of my wood? :biggrin:

 

[fatride]

Yeah Rick I alive. Finally got the car up and running. Now I just need your help .......

 

[TurboBuRick]

Yeah Rick I alive. Finally got the car up and running. Now I just need your help .......

Cool Just give me a call or shoot a pm. I'm ready when you are.

 

[fatride]

Cool Rick! I just want to wait till my alky kit comes in. It's hard to find race gas this time of the season. I give you a buzz hopefully in a week or 2..... Thanks

 

[chevyII]

how about going to a larger exhaust housing?

 

[Roc87]

My PT51 did this somewhat, but my PT61 does exactly what you describe. I can't run betwen 5 and 15 pounds of boost at part throttle without the flutter.

 

[GNVYUS 1]

A blow off will not help the part throttle surge, the ported shroud would but a few are experiencing some surge with that on the import boards.

You won't believe this but the Tornado kills the part throttle surge. I have one in my 91 Talon and it worked, I can hold any psi now on the highway and pass people without being WOT.

 

[turbojimmy]

I'm confused about the difference between 'surge' and 'sneeze'. When I put my BB70 on I noticed a lot more 'sneezing' when I let off the gas even at part throttle. It will stumble unless I give it a lot of throttle, but again this is only when I've let off the gas. Steady acceleration at 'normal' throttle (1/4, 1/2, whatever) is fine.

I'm moving the MAF to the up-pipe this weekend which I'm told will help with this stumble-after-sneeze thing. What's the difference between this and 'surge'?

Jim

 

[TurboBuRick]

I'm confused about the difference between 'surge' and 'sneeze'. When I put my BB70 on I noticed a lot more 'sneezing' when I let off the gas even at part throttle. It will stumble unless I give it a lot of throttle, but again this is only when I've let off the gas. Steady acceleration at 'normal' throttle (1/4, 1/2, whatever) is fine.

I'm moving the MAF to the up-pipe this weekend which I'm told will help with this stumble-after-sneeze thing. What's the difference between this and 'surge'?

Jim

I think they are talking the same thing.
Let us know how you like the blow through thing.

Rick

 

[GNVYUS 1]

Sneeze and surge are different.

When you let off the gas you get the sneeze, surge is when you are under boost and you feel a bucking.

There are specific reasons for each but that is the quickest way to describe them for now.

 

[turbojimmy]

I think they are talking the same thing.
Let us know how you like the blow through thing.

Rick

I finished the job today. I used a 45-degree fitting from my Big Mouth kit to mount the air cleaner and the 4" clamps from the kit to mount my alky bottle (after fabricating a bracket - it's ugly but functional). So far 23 PSI and the up-pipe hasn't blown apart yet.

Coming off throttle under boost is SILKY SMOOTH now. Cured the problem I was having completely.

Pics attached.

Jim