Words to wise on SC6152 turbo

[glhs875]

If you have a SC6152 turbo, and your planning on using an internal waste gate, you might want to reconsider or at least do some research. I have got MASSIVE boost creep with mine!! I don't know how high it will go, I haven't had it wide open and when it hits 18 to 20 psi I have been getting out of it. The waste gate is opening around 10 to 12 psi, but it's useless after the R's come up!! DAMN! A whole lot of work to fix the problem. Other than that, I like the turbo so far. It's on an 8V 2.2.

[Speedeuphoria]

Yeah I wouldn't run internal on anything even clost to that large 50trim hybrid would be the largest internal I would mess with. But then again just turn up the boost and you won't have a problem(or not as much, you may still have creep since its an 8valve)
I got a 38mm tial and the same turbo but haven't got it runnning yet to see if it will hold low boost

[GLHSKEN]

Reeves has no problem with it.. ( of couse he runs 28 psi). Good info.

[8valves]

That's interesting that you're having a creep issue, what size is the WG puck? Espescially since you're using a 4" exhaust, I wouldn't forsee it being a problem.

It shouldn't be the lower boost level that will be the problem, plenty of people run those turbos at 13 psi or so with no issues, albeit both cars I'm thinking of are on TiAL 38's.

I would say divorce the WG outlet from the normal DP, but since you're at 4" there shouldn't be an issue once again. I'll have to think about this for a while.

Aaron Miller

[glhs875]

That's interesting that you're having a creep issue, what size is the WG puck? Espescially since you're using a 4" exhaust, I wouldn't forsee it being a problem.

It shouldn't be the lower boost level that will be the problem, plenty of people run those turbos at 13 psi or so with no issues, albeit both cars I'm thinking of are on TiAL 38's.

I would say divorce the WG outlet from the normal DP, but since you're at 4" there shouldn't be an issue once again. I'll have to think about this for a while.

Aaron Miller

The internal wastegate hole is only around 20mm!! The boost holds fine at around 1/3 throttle or less all the way up in the rpms's. But go 1/2 throttle or more and things go wild! Starting at about 5500rpm, the boost starts climbing and seems to keep climbing (?) all the way till the engine slams against the rev limiter (6650rpm). The engine feels like a 2 cycle dirt bike with a power band!!! Iam going to have to get some race gas so I won't damage anything till I get this crap sorted out. I may have a quick fix for the problem Iam going to try out to try out and hopefully make the car streetable and more controllable. Iam going to take all the shims out of my BOV and try to make it bleed off the excess boost. It may not work I don't know. Then if that works, when I want more boost capabilty, just put shims back in the BOV.

[glhs875]

Yeah I wouldn't run internal on anything even clost to that large 50trim hybrid would be the largest internal I would mess with. But then again just turn up the boost and you won't have a problem(or not as much, you may still have creep since its an 8valve)
I got a 38mm tial and the same turbo but haven't got it runnning yet to see if it will hold low boost

I can't keep the boost level down as it is!! I sure don't want to try and make the boost level higher, at least for now. I guarantee that the turbo would make boost in the upper R's with the waste gate can loose and with the waste gate puck flapping in the wind!!
You should be okay with the 38mm Tial.

[mech1nxh]

glhs875...
intreeging thought process...
super efficient (73%) turbo.....
and control the cold side instead of the hot....
the mind races..a PWM solenoid on the BOV.....
the program could use t/p rate of "drop" v/s rpm (with map)
to still function as a BOV, then rate of "rise" to function
as a boost limit device...and with a good I/C......damn!!

[glhs875]

glhs875...
intreeging thought process...
super efficient (73%) turbo.....
and control the cold side instead of the hot....
the mind races..a PWM solenoid on the BOV.....
the program could use t/p rate of "drop" v/s rpm (with map)
to still function as a BOV, then rate of "rise" to function
as a boost limit device...and with a good I/C......damn!!

Using the BOV as an adjustable boost bleed as well as for it's normal function WORKS!!! I can control things now! I'm starting to like this turbo even more now!:thumb:

[glhs875]

My BOV is before the intercooler as well, so bleeding the BOV doesn't overheat the intercooler for no reason. With things the way they were, the turbo was feeding upon itself. Boost creep equaled more exhaust volume which would equal more boost creep etc, etc.

[Ondonti]

some of the most powerful cars out there use multiple bov's to control boost instead of a wastegate. Not a good idea on a street car or a car with a small inefficient turbo.

[contraption22]

Use the BOV to control boost? Isn't that extrememly inneficient? The turbo is going to continue to spool faster... creating generating more heat. Doesn't make sense.

[glhs875]

Use the BOV to control boost? Isn't that extrememly inneficient? The turbo is going to continue to spool faster... creating generating more heat. Doesn't make sense.

Maybe not, by bleeding off the boost with the BOV there is less air to burn and that means less exhaust volume to make boost with. And the BOV bleed is only coming into effect from 5500rpm up on my combo, that's when the internal wastegate starts to get overwhelmed. During light to moderate throttle and below 5500 rpm it bleeds off nothing. And it will only be used mainly on the street, at the strip it will be disabled, with the BOV used as normal. I agree it's not the best thing in the world, but for now, until I build a new header with an external wastegate setup, it works. I'm still using the internal wastegate as a main boost control, the BOV is only controlling the boost creep above 5500rpm on the street.

[glhs875]

On a side note along with the boost creep problem, the turbo is a little laggy on my 2.2 8V w/ Taft S3 cam and with an auto with a 2.78 final drive. With some tuning I have cut some of the lag time down. Iam also going to change the .91 transfer gears with some 1.06"s and make my final drive a 3.22 again. That should help as the lag is defintely rpm related. I don't want to put in a smaller cam, because with the S3 cam, the turbo, and with all the port work I've done, this thing pulls VERY VERY hard up top, from 5500rpm all the way to the rev limit of 6650rpm. Iam going to have to raise the rev limiter to get the full potential from this combo. If I get the response up some more I defintely will have the most powerfull engine I have ever built. Well it already is, it's just a little lazy down low right now, but not really to bad, I can make 5 psi from power braking, but then it climbs slowly from there until some revs are made. Iam just use to having to take power away from the combo down low to maintain traction, along with trying to add some power up top, intead of trying to add some power down low with out taking it away up top. If all else fails along with the final drive change, I'll have my torque converter loosened up a little.

[glhs875]

I may have cured the boost creep problem. I possibly installed the cam 1 tooth retarded from at least where I had it installed on my other engine. Maybe even 1 tooth altogether, it's hard to tell with my adj. pulley. Any way, I already had the cam sitting 4 deg adv. according to the pulley (which if it was 1 tooth retarded it would still be 5deg retarded), and it still felt like it was still retarded to much. It's sitting at 8 deg adv. on the pulley now, and the car feels more normal. It will still keep pulling harder & harder to my 6400rpm shift light and has more bottom end torque. I closed the bleed on my BOV to make it hold more boost then made a 2nd gear blast. The boost didn't continously keep climbing like it did before. If the cam timing was the cause, I'm confused, I've never ran into anything like this before. I still think that with a larger waste gate, the problem would have never shown up in the first place. But I don't know!! And Iam going to keep a close eye on things, because this engine is wierd, and has a tendency to try and run away. I may have to perform an exorcism on it!!

[Directconnection]

Using the BOV as an adjustable boost bleed as well as for it's normal function WORKS!!! I can control things now! I'm starting to like this turbo even more now!:thumb:


It may be working, but it is a very in-efficient means of controlling your problems. Your manifold is seeing "X" amount of boost, yet the turbo is working overtime at "Y" amount of boost. Uneccessary shaft speeds = higher backpressure and higher charge temps as well. You may know this... but pointing it out in case you didn't.

[glhs875]

It may be working, but it is a very in-efficient means of controlling your problems. Your manifold is seeing "X" amount of boost, yet the turbo is working overtime at "Y" amount of boost. Uneccessary shaft speeds = higher backpressure and higher charge temps as well. You may know this... but pointing it out in case you didn't.

I agree with you, but that is keeping me from blowing up a fresh engine until I get things sorted out. And I don't plan on leaving the BOV as a boost limiter. Like I said playing with the cam timing may have cured the problem. I still have to do some futher testing to find out for sure. On a side note, I wouldn't want a larger turbo on a 2.2 for the street. It's spooling up fairly soft from a dig. It doesn't have the boost hit like a hybrid or smaller turbo has and that Iam used too. But that really helps launching on street tires. I can lean on it hard and still maintain traction. The turbo is working more like a supercharger from a dig. Of course a little looser converter would spool things up more quickly Iam sure. Because by raising the final drive to 3.22 from 2.78, and by advancing the cam timing from where I originally had it set, made the engine come alive much more quickly. The turbo definitely likes the R's. But Iam going to run it like this for now, because I want to try and beat my best street tire time of 8.59 (300 treadwear tires). I have gone 8.22 on DR's in a Daytona. I still have alot of sorting out to do on this combo.

[gasketmaster]

Are you running the E or S compressor cover?

The wastegate hole in the turbine housing is 20mm but what size is the wastegate puck that covers the hole?

Just curious :)

[glhs875]

Are you running the E or S compressor cover?

The wastegate hole in the turbine housing is 20mm but what size is the wastegate puck that covers the hole?

Just curious :)

Iam running the S cover. The puck is only about the size of a quarter, which is just big enough to cover and seal the hole. The internal wastegate hole as delivered clearly does not flow enough, or at least on my combo. The internal gate can control the boost just fine until 5500rpm & up. Then it is out of control. How high will the boost creep up without bleeding it off with the BOV for now, I don't know. I have seen it hit 25psi + by mistake, and I immediately got out of the throttle. That was starting with the boost set @ 10psi where I can control it. I think what I will end up doing is add an external gate to control the high boost, and use the internal gate to control the boost to start with. In other words use a 2 stage wastegate. The reason I may want to do that is, with the way the internal gate is working, I can have the boost come in so easy and progressive in 1st gear that it keeps the tires planted real well. Once I get everything tuned in, I should be able to ET real well, even on street tires. That remains to be seen. I will probably make some runs at low boost with the combo set up like it is just to help me see how the combo can ET. But to get the full SAFE potential out of things, I will have to make some changes, being the torque converter, rev limiter, and of course the wastegate. I know that much already.

[SCalder]

You can bore out the wastegate opening to almost 1" and still use the internal flapper. This will eliminate most of the boost creep.

Steve

[glhs875]

You can bore out the wastegate opening to almost 1" and still use the internal flapper. This will eliminate most of the boost creep.

Steve

That's definitely an option. But I think I'll just add an external wastegate setup to the combo so I can adjust how high the creep will go. Iam really liking the power curve the creep is giving. And I don't want to loose that. Even with the internal gate only, I can still have the boost ramp up very quickly if needed just by upping the base boost pressure. I just can't limit the boost in the upper R's.

[GLHNSLHT2]

what SV are you using??? Maybe TU can weld on one of their huge flappers. I have the older Turbonetics flapper that is 1.125". I bored out my hole to 1" even. with .062 around the edge it seals fine. The new turbonetics SV comes with an even larger flapper and the TU piece is bigger than that. Port that sucker! easier than coverting to an external.

[glhs875]

what SV are you using??? Maybe TU can weld on one of their huge flappers. I have the older Turbonetics flapper that is 1.125". I bored out my hole to 1" even. with .062 around the edge it seals fine. The new turbonetics SV comes with an even larger flapper and the TU piece is bigger than that. Port that sucker! easier than coverting to an external.

It might, but after I have been mulling over things, I seriously doubt a 1" hole (25.4mm) will be even close to big enough to cure the boost creep. The boost was still climbing quickly when I noticed it was already @ 26psi, with the 20mm wastegate that's on the car now, with it able to control the boost in the lower revs @ 10psi!!! And I don't mean to brag, but this combo is capable of making some serious HP! And that's where the flow problem with the small wastegate comes in. I could be wrong, but I think it will take a wastegate with an opening of at least 40mm (about 1.6") to cure the creep without having to possible redue things again if I were to go smaller than that.

[4sfed4]

I suspect the boost creep problem may only be applicable to the 8V cars. I ran the standard fare internal gate/flapper on the SC6152S with a TIII and was able to hold 10-11 psi (maybe less...never tried) all the way to 7500 rpm.

[glhs875]

I suspect the boost creep problem may only be applicable to the 8V cars. I ran the standard fare internal gate/flapper on the SC6152S with a TIII and was able to hold 10-11 psi (maybe less...never tried) all the way to 7500 rpm.

That maybe the case. I don't know. But I do know that at least part of the reason is from how well my combo is breathing up top. With the massive amount of port work that I have done (ports as large as a 16V) along with the S3 cam, the powerband on this engine has me in amazement!!! It pulls great off boost and in the lower revs, but once the engine hits 4000rpms it starts to really come to life, and by 5500rpm, it's ripping all the way to the rev limit of 6650! I know it will make power at an even higher rpm. And I know that a 16v breaths well also. The boost creep is not from the compressor outdoing the engine that I can tell. Now if the engine didn't have the upper rpm power that it has, I would think that might be the case. But at this point, I don't know all the details of what is going on yet. All I really know is, I like how it runs so far. But the track will tell the tale.

[4sfed4]

I will confess to not reading this whole thread.

Have you tried running the car with the flapper completely loose (i.e. wide open)?

[glhs875]

I will confess to not reading this whole thread.

Have you tried running the car with the flapper completely loose (i.e. wide open)?

No I haven't. But I'm tempted to try it. This situation has caught me by surprise.

[87csx2.4]

I will confess to not reading this whole thread.

Have you tried running the car with the flapper completely loose (i.e. wide open)?Good idea at least it will give you an idea how much bigger the hole needs to be.I ve ran mine at 6 psi no problems but I have a 40mm wastegate.

[glhs875]

Good idea at least it will give you an idea how much bigger the hole needs to be.I ve ran mine at 6 psi no problems but I have a 40mm wastegate.

I'm thinking that's what size Iam going to use. I feel it's better to be a little too large than too small for the wastegate. But I'm going to make some runs with it like it is first, with using the BOV to limit the boost creep. I want to enjoy the car for awhile before I tear it back down. I will probably wait to do the external waste gate after I get my common block built for this thing with a steel crank and custom rods. Iam a little worried about an 87 block with a cast crank grenading with this combo if I were to really turn up the wick! And I will probably only run a max of 15psi on the bottom end I have now. This combo is capable of making way more power than I expected!! BTW Kevin, are planning on going to the track this weekend?

[87csx2.4]

I know exactly what you mean about some enjoyment time you know what Ive been going through with the converter but I believe its good to go now.Im going to the track for sure weather permiting.

[glhs875]

I know exactly what you mean about some enjoyment time you know what Ive been going through with the converter but I believe its good to go now.Im going to the track for sure weather permiting.

I smell a new personal record!! GOOD LUCK:thumb:

[4sfed4]

I would try that soon as it will tell you whats going on. Sometimes one can get boostcreep due to the actuator arm running out of travel.

Of course...easy for me to say as on a TIII it takes about 10 seconds to remove the wastegate arm.


No I haven't. But I'm tempted to try it. This situation has caught me by surprise.

[glhs875]

I would try that soon as it will tell you whats going on. Sometimes one can get boostcreep due to the actuator arm running out of travel.

Of course...easy for me to say as on a TIII it takes about 10 seconds to remove the wastegate arm.

Well I've already tried 2 different waste gate cans. First one I had on there had a very stiff spring. It would only allow a minimum of 18psi before the creep. And using regulated pressure going to the can to check how it was opening, that's about the amount of pressure (18psi) it took to make the arm start to move. So I then installed a can with a much weaker spring, and also checked for operation with compressed air. It has full wastegate can travel. On the weaker can, it will allow a minimum of 8psi before the boost creep, and with the vacum line on the can going straight to the intake.

[4sfed4]

What happened to me once was that, although the wastegate arm was moving through its full amount of travel, due to the orientation of the can and the flapper, the flapper was not actually moving through its full "arc". So, even when the actuator arm had reached its limits of extension, the flapper itself was not maxxed out rotationally (so the door was not open 100% as far as it could have given no actuator arm limitation).

That doesnt mean this is happening to you, only that it can happen and gives the same symptoms as a wastegate hole that is too small.

Thats why the most definitive way to assess things is to just let the flapper be completely loose and see if the boost creep is still massive.

[glhs875]

When I have time (soon) I will unbolt the actuator and see what happens. It just seems apparent to me that two different cans had the same problem occuring at the same rpm level no matter what the base pressure was set at. And with the actuator loose, if the creep is still present, what does that mean other than the hole is too small?

[Boost_Virgin]

When I have time (soon) I will unbolt the actuator and see what happens. It just seems apparent to me that two different cans had the same problem occuring at the same rpm level no matter what the base pressure was set at. And with the actuator loose, if the creep is still present, what does that mean other than the hole is too small?


But if the travle of the arm is the same distace on both cans you would have the same problem with both WG cans. Did both cans get mounted in the same place? Before you do a bunch of work it would be a cheep test.

[glhs875]

But if the travle of the arm is the same distace on both cans you would have the same problem with both WG cans. Did both cans get mounted in the same place? Before you do a bunch of work it would be a cheep test.

Trust me, there is alot of travel capability on both of the cans. They can open up far enough that the WG puck can turn side ways and kind of hang up. Iam sure (I hope) it doesn't have to open up that far in operation.

[4sfed4]

Trust me, there is alot of travel capability on both of the cans. They can open up far enough that the WG puck can turn side ways and kind of hang up. Iam sure (I hope) it doesn't have to open up that far in operation.

Not to hang onto this idea ad nauseum, but if my puck didnt swing open all the way (i.e. until the side of the puck actually hit the casting of the swingvalve), I got boost creep.

Again...perhaps not the cause of your boost creep, but when trying to ascertain the causes of something like this, one has to start eliminating variables. Simply letting the puck flap in the breeze and noting the results will give you direction as to how to attack the problem.