wastegate actuator???

[96atgsx]

I have a 96 at gsx with a jdm motor that i bought from a guy who had installed a t-28 turbo w/17lb wastegate actuator. I didn't realize at the time that it meant i couldn't run less than 17lbs, so now I am trying to figure out what to do. Last night I installed my stock wastegate actuator and set my MBC down all the way, but after doing a quick test drive it would still boost up past 15lbs. Right now I have no fuel mods or tuning software/logger and am looking to run at a safe boost lever(13-14psi). So am I just doing something wrong that I couldn't get the boost to be set at a lower level? I am kind of new to most of this, so I am just trying to gather some more info.

Thanks!

 

[jjrock5]

He may have done the boost solenoid mod on the car. This gets you 1 to 2 psi. The car is already set up to run 13 to 14 lbs stock so ~15 lbs doesnt sound TOO unreasonable.

 

[96atgsx]

Ok, so with that being done it would make sense that I wouldn't be able to turn the boost down past ~15? I guess I just figured I could turn it down as low as I wanted.

 

[jjrock5]

If you have the stock T25 actuator, and youve turned your boost conroller down all the way COUNTERCLOCKWISE then you've done pretty much all you can do. At this point, it's the actuators spring tension thats letting the turbo boost to that level. So you can consider this normal. As long as you stay in the 15 range, you are still safe.

 

[kenamond]

Try connecting a vaccuum line from the compressor housing nipple straight to the WGA nipple. That's as low as you can go. If it still boosts to 15psi, you probably have a WGA with a higher actuation pressure.

Stock T25 actuator will give you about 9psi boost.

 

[srpjosh]

JDM engine?

 

[wondersb]

I have the same problem with my 16g. I am now pulling it apart and porting the waste gate side. Could that be a bit of his problem.

 

[EclipticalGS]

well a lot of ppl make the common mistake of putting their MBC either off of a vacuum line on the intake manifold and even sometimes ive seen T-d off with the BOV, its like, come on. The WGA needs the quickest source of boost from a nipple on the turbo or make a new nipple in your j pipe (tap a hold and buy a screw in nipple, then jb weld to seal it or loctite.) you BOV needs that vacuum when you shut your Throttle body, your wastegate doesnt. The reason for this is say your turbo reaches the boost you have your mbc set too, but the Wastegate doesnt get the boost signal till like a second after your turbo reaches the boost you desire because it has to go through your intake mani and then down that vac line. Thats called Creep. Hope this helps a bit

 

[kenamond]

well a lot of ppl make the common mistake of putting their MBC either off of a vacuum line on the intake manifold and even sometimes ive seen T-d off with the BOV, its like, come on. The WGA needs the quickest source of boost from a nipple on the turbo or make a new nipple in your j pipe (tap a hold and buy a screw in nipple, then jb weld to seal it or loctite.) you BOV needs that vacuum when you shut your Throttle body, your wastegate doesnt. The reason for this is say your turbo reaches the boost you have your mbc set too, but the Wastegate doesnt get the boost signal till like a second after your turbo reaches the boost you desire because it has to go through your intake mani and then down that vac line. Thats called Creep. Hope this helps a bit

Although I agree that you tap the WGA signal off the compressor housing, the delay that you see from doing it the wrong way is not creep. Creep is when the WG doesn't flow enough exhaust around the turbine (at 12psi boost, the exhaust would rather go through the turbine than out the restrictive internal WG passage), so the turbine gets more flow than you want, and boost goes up until the increased backpressure through the turbine eventually forces enough exhaust through the WG to stabilize boost.

The dude with the 16g might have a creep problem, though. They're notorious for it when you have a big exhaust. I used to recommend porting, but I think it's the best bang for the buck to just go for an external WG either off the mani or built into an aftermarket O2 housing (where you'd remove the internal WG flapper and use a tial or similar on the O2 housing). Either that or get mods to run 20psi. But porting has been proven to work...if you do it right.

 

[EclipticalGS]

I agree 100% but that delay of signal from the boost having to travel all the way through the IC piping and manifold and through the long boost line rather tahn going 5 inches from j-pipe to WGA does make creep. We had this in my friends Tsi, and i fixed it. ### think about it, your turbo could be pushing 18psi but your wastegate will still see 15psi for a second or two from the long delay. A turbo can spool to 18psi faster than the boost difference going through the 10 feet of piping and 6 feet of vac line. But i agree if your still haveing creep issues even when your running J to WGA, then you need to port or go external WG

 

[kenamond]

I agree 100% but that delay of signal from the boost having to travel all the way through the IC piping and manifold and through the long boost line rather tahn going 5 inches from j-pipe to WGA does make creep. We had this in my friends Tsi, and i fixed it. ### think about it, your turbo could be pushing 18psi but your wastegate will still see 15psi for a second or two from the long delay. A turbo can spool to 18psi faster than the boost difference going through the 10 feet of piping and 6 feet of vac line. But i agree if your still haveing creep issues even when your running J to WGA, then you need to port or go external WG

But that's not creep. That's a really bad boost spike or a decreased boost signal. If the pressure 100 feet down wind of the compressor is 5psi lower than at the compressor outlet, then you're feeding your WGA a 5psi-lower signal which means you'll boost 5psi higher than if you tapped into the compressor outlet. Creep is related to the inability of the WG passage (not anything to do with the WG actuator) to flow enough exhaust around the turbine. The b16g actuator only opens maybe 30 degrees, not 90 (there's not enough throw in the actuator to rotate the lever 90 degrees), and the turbine flows a lot of air easily, so it's just a poor setup for running much below 20psi. This is usually only a problem when you have a large exhaust, because the pressure just downwind of the turbine exit is much lower with a big exhaust, and that makes it even easier for the turbine to flow air.

Creep, spikes, and bad WGA signal location all lead to higher boost levels than you intended, but they are all different phenomena.

 

[Bluefire16]

Or a real easy thing is staying off the gas pedal... Sorry just had to throw that in there...

 

[kenamond]

Or a real easy thing is staying off the gas pedal... Sorry just had to throw that in there...

Yep...cheapest manual boost controller on the market!