New TE44 turbo install. Fluttering at 12 psi, why?

[moparkid]

Just as the title says. Bison hooked me up with a new turbo for my GN, I have it installed on the car but have a couple questions:

1. I'm getting some turbo flutter at or around 12 psi. If I step into the throttle a little more I can get past it, but its present during gradual acceration.

2. My stock turbo has a vacuum port on the compressor side for boost control, but the replacement turbo does not. Do I still run a vacuum line to the wastegate actuator also? I have test drove the car both with and without, it seems a bit more lag without the vacuum line to the actuator but does create boost eventually. The flutter I previously described is present both with and without the vacuum line to the actuator installed.


Any and all help is greatly appreciated, thanks!!

 

[mgmshar]

Regarding the "flutter", my TA-49 does the same thing at almost the same boost. The TA-49 and TE-44 are basically the same turbo. I haven't found a way around it yet - when it happens, I either give it a bit more or a bit less throttle, and it goes away.

What is happening from a technical standpoint is that at that boost and throttle position, the engine is producing enough exhaust gas to spool the turbo to a high speed, but not swallowing enough air to keep the mass flow rate high enough for the boost pressure being generated. If you look at a compressor map for the compressor wheel, the turbo is being asked to operate at a point to the left of the surge line (high pressure ratio with low mass flow). So, the compressor goes into rotating stall and surges.

In the stock chip, there was some code in there that would purposely cycle the wastegate solenoid partially open under these conditions (call it "moderate throttle") so that some of the exhaust gas would bypass the turbo and keep its speed down. In most aftermarket chips, or if you use a manual boost controller, the wastegate is held completely closed to promote spool-up under these conditions, so all of the exhaust gas goes through the turbo, and it speeds up more. For those of us who have small, easy-to-spool turbos, surging at moderate throttle can be the result. Welcome to my world.

My combo (listed in my sig) is extremely conducive to spooling up the turbo - low air intake restriction, low exhaust restriction, relatively loose converter, etc. Maybe yours is the similar?

 

[moparkid]

Yeah, I have similar mods. Bison just called me a few minutes ago, I do need to have the vacuum port in the compressor housing, and he explained the flutter also just as you did. I need to remove the compressor housing and tap it, not a big job to do.

 

[camzillaz]

Had a similar problem, TA49, bought a tornado (air foil on EBay) installed it and compressor surge is gone.

Do a search and you will find a thread with many posting on this as a solution.

I was skeptical, but it works and for $30 what do you have to lose. Give it a try.

HTH.

CZ

 

[dsa87gn]

compressor surge.
some guys claimed they solved it by using a tornado pre-turbo.
mgm, i have a very similar combo to yours and havent really noticed the surge.
What are you using for boost control? I am using a ceramic ball manual boost control valve, (old voodoo boost controller) set at ~23#, I wouldn't think that has anything to do with it though

My car spools very fast with the stock converter...hmm Im going to have to find a good strech and cruise in the 10-13 lb boost range.

 

[bison]

Don't run a tornado.

 

[mgmshar]

compressor surge.
some guys claimed they solved it by using a tornado pre-turbo.
mgm, i have a very similar combo to yours and havent really noticed the surge.
What are you using for boost control? I am using a ceramic ball manual boost control valve, (old voodoo boost controller) set at ~23#, I wouldn't think that has anything to do with it though

My car spools very fast with the stock converter...hmm Im going to have to find a good strech and cruise in the 10-13 lb boost range.

I am also (currently) running a ceramic ball manual boost control valve. I had previously run the stock wastegate solenoid, but had the same flutter problem. Your combo is quite similar to mine - strange.

When I first installed the TA-49, I was running it with the stock IC and stock torque converter. I don't remember having the flutter problem, but that was about 9 or 10 years ago, so I may have forgotten. I'm guessing that my large FMIC and looser torque converter are probably why I'm getting the flutter and you're not. Just a guess. As another note, I've run the turbo with the Garret 0.63 exhaust housing and a PTE 0.85 exhaust housing (which should, in theory, slow down spool-up a bit), but I've had the flutter with both.

I've just learned that if I feel the flutter, move the gas pedal a bit, and it goes away.

 

[mgmshar]

Had a similar problem, TA49, bought a tornado (air foil on EBay) installed it and compressor surge is gone.

Do a search and you will find a thread with many posting on this as a solution.

I was skeptical, but it works and for $30 what do you have to lose. Give it a try.

HTH.

CZ

By "pre-spinning" the air so that it's rotating when it enters the turbo, I can see that it could affect the characteristic to surge. I believe that it probably does work in some cases for curing the part-throttle surging. However, there are two things I know...

1. When I'm moving enough air to make almost 500 hp in this car, any restriction pre-turbo will be compounded through the turbo and hurt the power potential.

2. When I'm moving enough air to make almost 500 hp in this car, I wouldn't feel right putting something in front of my turbo that can shed a small part and send a small piece of debris through my compressor wheel while its spinning at 125,000 RPM. I would be waiting for the small "boom" every time I got into high boost. Maybe I'm paranoid...

 

[1KWIKSIX]

This is the reason I ordered a Ported shroud when I ordered my Precision DBB5857 SP.
Heard many stories about compressor surge being experienced at low boost / modulating throttle with these small turbos when they are used with a larger intercooler. Since my car is driven on the street I figured the ported shroud was the way I wanted to go.

 

[mgmshar]

This is the reason I ordered a Ported shroud when I ordered my Precision DBB5857 SP.
Heard many stories about compressor surge being experienced at low boost / modulating throttle with these small turbos when they are used with a larger intercooler. Since my car is driven on the street I figured the ported shroud was the way I wanted to go.

I feel dumb for asking this, but what do you mean by "ported shroud"? Did they port something on the compressor cover or something?

 

[TheGovernment]

I have a TE44 and it also surges at around 12-14 psi. It only started after I upgraded to my percision SLIC. Though it's not a huge annoyance, I would also like it to be gone. I'm running a RJC boost controller.

 

[bison]

I feel dumb for asking this, but what do you mean by "ported shroud"? Did they port something on the compressor cover or something?

Look at his avatar. Surge at part throttle is of little concern

 

[1KWIKSIX]

I feel dumb for asking this, but what do you mean by "ported shroud"? Did they port something on the compressor cover or something?

Yup, means the same thing as ported compressor cover, just different terminology......as Bison pointed out, my avatar shows the ported compressor cover.
I agree that it's really not a huge concern, however I didn't want this annoying trait since I use my car on the street. I also run a Precision SLIC which tends to precipitate this phenomen when used with a small turbo like the TA49 / TE44 / 5857 which are prone to exhibiting this characteristic at part throttle / low boost situations which is commonly experienced on the street due to constantly changing traffic conditions and throttle modulations required. I did alot of research on the subject and didn't want to go the "tornado" route.

 

[Danster]

I use a Tornado as I had the surge with a TA-49. Been using it for about 4-5 years now with no issues. I can't see that breaking. I have been down the track quite a few times.

Works for me!

Dannyo

 

[mgmshar]

OK, I see it now. Your cover has the machined groove and holes that allow excess boosted air to recirculate back to the inlet side of the compressor wheel. Kind of like the bypass I had on my old irrigation pump (not the best analogy...) that allowed some of the pressuirzed water to recirculate back into the pump inlet and keep the pump from cavitating.

I can see how this would help to reduce part throttle surging. However, wouldn't allowing some air to bypass back to the inlet side of the compressor hurt the effiiciency of the compressor, especially at hight boost? Has anyone (Garrett, PTE) ever measured the compressor efficiency difference with a ported vs. non-ported shroud?

Since I'm running a TA49 with the bolt-on inlet bell, I don't think this would be an option for me, anyway.

Different Approach - As I mentioned above, the stock chip had some code in it that would leave the wastegate "more open" by scaling the amount of DC% that is sent to the wastegate solenoid. For example, let's say your wastegate solenoid is run at 90% duty cycle at WOT, which maybe gets you about 17psi of boost. The stock chip would scale that 90% by the amount you had the throttle open. So, at 50% throttle, the stock chip would only cycle the wastegate solenoid to about (90% X 50% = 45%) 45% duty cycle, which means the wastegate would be "more open", which would allow more exhaust gas to bypass the turbine, which helps to reduce the flutter at part throttle. My numbers may not be exact, but you get the idea.

Unfortunately for us small turbo guys, all of the aftermarket chip makers seem to do the opposite - they run the wastegate solenoid at 100% duty cycle at moderate throttle to promote spool-up. For large turbos, that's a good thing, but us small turbo guys get more flutter because of this. If I was a better chip programmer, I would try to re-install that wastegate duty cycle scaling code to "go back to stock", but I'm unfortunately not that smart. I would be curious to see if any chip makers out there would like to tweak one of their chips to add this feature for smaller turbos.

I think the MAFTPro can be programmed to only activate the wastegate solenoid above a certain throttle position - maybe that could be another option. I'll have to look into that.

Interesting...

 

[camzillaz]

I am new to the GN and have been changing a number of things around and none seemed to fix the compressor surge I was having until I installed the tornado. Smooth as silk from 0 boost up to 25 PSI, at part throttle, full throttle and everything in between.

I'm sure this is a band-aid fix right now, but I'm trying to dial in the rest of my combo before any more upgrades. I plan to also add a new turbo with the SP cover sometime next year, but for now it works for me.

Bison-- Any reason for not liking this as a solution? Is it the fear of it coming apart and eating a turbo? I understand this is not the fix all solution for everyone, but it seems like a common problem and somewhat common solution? Then again, it could just be my limited knowledge of these cars and how to tune / adjust for this issue.

 

[bison]

OK, I see it now. Your cover has the machined groove and holes that allow excess boosted air to recirculate back to the inlet side of the compressor wheel. Kind of like the bypass I had on my old irrigation pump (not the best analogy...) that allowed some of the pressuirzed water to recirculate back into the pump inlet and keep the pump from cavitating.

I can see how this would help to reduce part throttle surging. However, wouldn't allowing some air to bypass back to the inlet side of the compressor hurt the effiiciency of the compressor, especially at hight boost? Has anyone (Garrett, PTE) ever measured the compressor efficiency difference with a ported vs. non-ported shroud?

Since I'm running a TA49 with the bolt-on inlet bell, I don't think this would be an option for me, anyway.

Different Approach - As I mentioned above, the stock chip had some code in it that would leave the wastegate "more open" by scaling the amount of DC% that is sent to the wastegate solenoid. For example, let's say your wastegate solenoid is run at 90% duty cycle at WOT, which maybe gets you about 17psi of boost. The stock chip would scale that 90% by the amount you had the throttle open. So, at 50% throttle, the stock chip would only cycle the wastegate solenoid to about (90% X 50% = 45%) 45% duty cycle, which means the wastegate would be "more open", which would allow more exhaust gas to bypass the turbine, which helps to reduce the flutter at part throttle. My numbers may not be exact, but you get the idea.

Unfortunately for us small turbo guys, all of the aftermarket chip makers seem to do the opposite - they run the wastegate solenoid at 100% duty cycle at moderate throttle to promote spool-up. For large turbos, that's a good thing, but us small turbo guys get more flutter because of this. If I was a better chip programmer, I would try to re-install that wastegate duty cycle scaling code to "go back to stock", but I'm unfortunately not that smart. I would be curious to see if any chip makers out there would like to tweak one of their chips to add this feature for smaller turbos.

I think the MAFTPro can be programmed to only activate the wastegate solenoid above a certain throttle position - maybe that could be another option. I'll have to look into that.

Interesting...

That is a great observation and yes there is a slight reduction in efficiency with the holes but the compressor cover itself would have to have a back flow problem under power to see it and at that point the cover is a restriction itself. It does happen when you're trying to milk the compressor for all it's worth and trying to run a small diffuser. The air actually stacks up in the compressor housing and will work against the turbine that is trying to fling it. This causes a lot of heat buildup in the charge air and increases backpressure since the turbine requires energy to keep it rotating. You would need to have a normally open wastegate or bov to prevent the part throttle surge. This is not easily accomplished with the stock setup. Pro mods and other high hp big tire cars use a Technique like this to hit the suspension really hard and flat foot launch the cars. The bov's slam shut and the car leaves like a missile.

 

[bison]

I am new to the GN and have been changing a number of things around and none seemed to fix the compressor surge I was having until I installed the tornado. Smooth as silk from 0 boost up to 25 PSI, at part throttle, full throttle and everything in between.

I'm sure this is a band-aid fix right now, but I'm trying to dial in the rest of my combo before any more upgrades. I plan to also add a new turbo with the SP cover sometime next year, but for now it works for me.

Bison-- Any reason for not liking this as a solution? Is it the fear of it coming apart and eating a turbo? I understand this is not the fix all solution for everyone, but it seems like a common problem and somewhat common solution? Then again, it could just be my limited knowledge of these cars and how to tune / adjust for this issue.

Anything that is preventing surge at part throttle is definitely creating a vacuum in between the inlet and whatever restriction. If the part throttle surge was causing thrust failure then it would need to be addressed. since this doesn't happen it's a waste. The exhaust pressure is trying to push the turbine out the ex side and the compressor is trying to pull itself out the inlet. Adding a restriction on the inlet side will increase thrust load there. It's like trying to pull 600hp or more worth of air through a stock maf. Huge vacuum which is loss of efficiency and increased thrust loading. I've yet to see a thrust failure in a te44/ta49 because of part throttle surge.

 

[Pronto]

Surging is damn annoying.

 

[UNGN]

If I had my TA 49 set to "kill" (23 psi), the part throttle surge would hammer me out of the car. The car is a light switch: all on or all off. If a honda wants to race me on the street I waive him off, because I can't "take it easy" on him.

If a Tornado stops that on the street, I would recommend a Tornado. The Surge my car has would eventually break a lot more than the turbo. It can't be doing the trans, converter, u-joints, etc. any good.

The Solution for me is to turn the boost down on the street and go slower.