speeder Posted July 10, 2002 Share Posted July 10, 2002 For those not following my earlier adventures, I lost control of boost (too much) with this T3/T4 setup (internal swing valve and dual-port actuator) when I upgraded to a 3" downpipe and straight through muffler. The compressor is a Super V. I've pulled my turbo and found that I have a .63 A/R (Stage II) instead of the .48 that I thought it was.(There are two part numbers on the flange, the one I could see was for the .48 and the other was for the .63. inside the inlet was stamped .63) Although a turbo upgrade is coming, I would like to make this setup work for when I move it (along with the 3" exhaust) to my other car. Also it may take a while to get that setup together. I can apply 10 psi to the actuator and observe the valve open fully. The actuator arm is lengthened to the point where there is minimum spring tension holding the valve closed. Opinions please: Have I missed something? Should I keep looking for some kind of problem or just assume that I need the .82 turbine housing and go for it? Thanks, Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted July 11, 2002 Share Posted July 11, 2002 Rick, I would not be too quick to jump to a .82 and you can go a long way with that turbo. IMHO, do not upgrade your turbo until you have maxed it out. I hear one of my buddies snickering . properly tuned, you can push 350hp with that turbo and an efficient I/C. I can apply 10 psi to the actuator and observe the valve open fully. The actuator arm is lengthened to the point where there is minimum spring tension holding the valve closed. Not quite sure I understand exactly what the problem is or what you are trying to say in the quoted statement. With the actuator set as described above, the boost will be limited to the rated spring pressure which sounds like it is 10#. Shortening the rod preloads the spring and increases boost. If you are experiencing spikes with this simple setup, then try various id lines and see if that makes a difference. Also look for things that would prevent the wastegate puck from fully opening (the root cause of boost spikes). Possible causes are a torn diapragm in the cannister (blow into it and listen for a leak) or something in the housing preventing the puck from opening like bent shaft, bad bushing, etc. Disconnect the rod and move the lever by hand several times feeling for smooth action. Any little hitch or resistance could be exacerbated by the spring pressure. Quote Link to comment Share on other sites More sharing options...
speeder Posted July 11, 2002 Author Share Posted July 11, 2002 What I was referring to in the quote was a test to make sure that the swing valve and actuator were working - I have an air regulator set at 10psi, hooked this to the "pusher" side of the actuator diaphram, and watched the lever move to the full open position. I listened for air leaks from the diaphram while doing this and heard none. My reasoning after this test was that if the wastegate is open fully with 10PSI on the diaphram, then I don't have enough bypass flow from the gate when fully open to control boost. Today, with the turbo off the car, I moved the lever and looked at the swing valve every way I could imagine, and could find nothing weird. This is not a very complicated mechanism! Earlier, with the car all together and running, I simplified my hookup with a single connection (about 1 foot of 1/4" id hose) straight from the compressor outlet to the "push" side of the diaphram and still have almost no boost control (Climbs right up past 20PSI) even with the actuator arm set for maximum length to give me the lowest preload/set point possible. I even pressure - tested the hose. I'll got to the shop tomorrow and double- check everything again - this has to be something simple, especially in light of many similar setups being used by others with no problems like this. It gets worse- the last time I spiked the boost like this I think the turbo went into compressor surge - I checked side play on the shaft and it's bad. Looks as if a rebuild is in order. Quote Link to comment Share on other sites More sharing options...
R0N Posted July 11, 2002 Share Posted July 11, 2002 Rick, I had my wastegate hole inlarged with a bigger flap (Internal). I don't experience any boost creeps. Here's a good article that I copied from someone. http://www.allpar.com/mopar/boost-creep.html Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted July 11, 2002 Share Posted July 11, 2002 There is nothing wrong with a little spike, especially if it is immediately as you romp on the throttle. E.g., boost is set for 10psi and it quickly spikes to 12psi when you hit the throttle but immediately comes back to 10psi. The concern, of course is the fuel is set to support 10psi not 12psi. At that point, the engine is not under a tremendous load and the concern should be 12psi at WOT in a high gear where the engine is under the most load. This usually results from "creep" as that fine article points out. As for making the wastegate hole larger, IMO really not necessary untill you are moving so much air and cannot bypass the turbine wheel quick enough to match the rod actuation. The hole in my turbo is "stock" size and I have a little initial spike, but nothing to worry about. If you end up doing it, be certain to check how much room you have outside the marked circle on the face of the puck. You might have to go to a larger diameter puck. Quote Link to comment Share on other sites More sharing options...
speeder Posted July 11, 2002 Author Share Posted July 11, 2002 Now that I've sent my turbo off for a rebuild, I've had time to think about this. A little history: When I first got the car going earlier this year, this turbo and wastegate worked well - pretty much made and held boost wherever I set it. This was with 2-1/2" dp, tailpipe, and turbo muffler, 3:90 rear, smallish intercooler, and 35lb injectors. I then went to 52lb injectors and a BIG Spearco intercooler, and tuned accordingly. Thinking back, I'm pretty sure that's when the boost creep started, but still wasn't too bad. My next round of mods was soon after, when I went to a 3" downpipe, 3" exhaust, straight- thru muffler, and 3.36:1 LSD Gears! That's when the boost started to ramp straight up out of control. The rate of rise was too fast to be called boost creep! It was way worse winding out the higher gears. In lower gears, boost would linger briefly at the set point, then start to climb. I know that the big pipes will result in more exhaust flow, but what will that big a change in gearing (and engine load) do to boost control? (I made this change after reading many posts by the big horspower guys - Scotty foremost - who discussed tall gears for best performance with a turbo - I was going to do an LSD, and had that 3.36 R200 laying around...). Thermodynamics has never been a strong subject with me... What do you guys think - will improved exhaust flow and taller gears cause my symptoms? It really seems to me that I'm simply flowing too much for the internal gate. If this looks like a good theory, I'll do a good big external gate, and stay with the T3/4 as is - for at least a little while longer. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted July 14, 2002 Share Posted July 14, 2002 I have an internally gated hybrid and I have no problems with boost creep. What you are likely experiencing is at 10 psi, you have to bypass alot of air away from the turbine in order to keep boost low. I am going to upgrade my hybrid, and wanted to go to the stage V turbine wheel, but have been told unless I run a lot of boost, I will have to go with an external WG in order to control the boost. I think you need the stage III turbine wheel. The stage II is not big enough IMO. Quote Link to comment Share on other sites More sharing options...
TimZ Posted July 14, 2002 Share Posted July 14, 2002 Like Scotty, I'm having trouble imagining that going to a 3" exhaust should be causing this much trouble. One thing that I haven't seen mentioned is the exhaust plumbing for the wastegate outlet. How big is the wastegate exhaust pipe, and where/how is it blended back into the main exhaust? Have you checked for blockages here - this would cause exactly the symptoms that you are describing. Quote Link to comment Share on other sites More sharing options...
speeder Posted July 15, 2002 Author Share Posted July 15, 2002 -I'm on the obligatory trip to the in-laws' this weekend and this is the first time I've been able to sneak off and post to HybridZ- Like I said, this is an internal wastegate, and yes, the bypass passage from the swing valve to the exhaust side of the housing is clear. I''ll be talking to my rebuilder tomorrow and will pop for the Stage III wheel and housing, staying with a .63 A/R turbine size. I've heard some people have had to go to oversized swing valves and ported passages with this T3/4 setup (mine has the ~1/2" dia. port) - indicating that what I have isn't up to the job -so I'm going ahead with the external wastegate. Thanks to everyone who has helped with this - your insights and recommendations are greatly appreciated. Probably prevented me from going to a too-big turbo at this time. I'll let you know how the bigger exducer and upgraded wastegate work. Hoping to have that done in a couple weeks. Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted July 21, 2002 Share Posted July 21, 2002 the 3.36 gears will load the motor up more and keep boost up.i have 1 of those little plastic air regulator valves on my car and i had to put another valve to bleed off some air behind it.now it works good.the air regulator valve wont work correctly with out some flow through it.i got the valve at lowe's hardware.i dont need all those riceboy electronic gadget boxes. Quote Link to comment Share on other sites More sharing options...
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