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.
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
Reeves has no problem with it.. ( of couse he runs 28 psi). Good info.
Ken Adler....
Cars, A few (9)
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.Originally Posted by 8valves
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.
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!!
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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!
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.
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.
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.
Mike Marra
1986 Plymouth Horizon GLMF "The Contraption" < entertaining sponsorship offers
Project Log:
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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.
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.
Last edited by glhs875; 04-23-2006 at 07:34 AM.
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!!
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!
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.
Steve
'90 VNT competition package Shadow - T-III SC6262 conversion/restoration
'91 Spirit R/T - white
'91 Spirit R/T - white
'92 IROC R/T - red
'67 Barracuda 273 now, 440/727 awaits....
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.
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.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
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.
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