zx_drift Posted May 31, 2011 Share Posted May 31, 2011 So the description isn't exactly right, but it had to be short. Here's the deal. I have a 280ZX turbo, and this past week I put in a large intercooler. After the install, the car dropped from stock (7psi) to about 5 psi of boost. I figured this is just because of the long tubes and the giant intercooler. So I installed this manual boost controller I have, turned it out a few turns, and the boost barely comes up. After messing around for a little bit, I take the boost controller off, but leave an open vacuum line tee'd inline to the wastegate. This was just a test to see if there was some problem with the controller. After doing a run, the car only boosts to about 8 psi. It should have been a lot higher seeing as how pretty much all of the pressure going to the wastegate was being bled off. Needless to say, I'm a little stumped right now. If anybody has any ideas, or has had the same situation, please give me a shout. Your help would be greatly appreciated. Quote Link to comment Share on other sites More sharing options...
billseph Posted May 31, 2011 Share Posted May 31, 2011 I haven't run into this but I'm in the process of upping the boost of my L28ET right now and you can't forget to plug the factory pop-off valve at the rear of the intake manifold or put a tighter spring in it. This is supposed to be set from the factory to vent excess of 9 psi. I know it's obvious but I'm throwing it out there. Quote Link to comment Share on other sites More sharing options...
zx_drift Posted May 31, 2011 Author Share Posted May 31, 2011 Yeah, I did think of that, so I welded it shut (I have a spare). Quote Link to comment Share on other sites More sharing options...
Tony D Posted May 31, 2011 Share Posted May 31, 2011 Where is the wastegate reference point and vacuum/boost gauge reference point...if the WG still at the turbocharger, and the BG at the intake plenum any piping or volume change will result in less observed boost. You have the same at the turbocharger, but the piping losses are greater. As for boost controller, a bit too vague to diagnose as we don't know how it was hooked up, what you EXACTLY did, or anything other than to say "the boost controller is the issue" and possibly "your boost gauge is reading wrong"... More specific information would help to pin it down more... Quote Link to comment Share on other sites More sharing options...
zx_drift Posted May 31, 2011 Author Share Posted May 31, 2011 (edited) Maybe a couple of pictures will help, I'll try and take some later today. I'll try to explain everything without them. My boost gauge is hooked up to the intake manifold. It is a brand new autometer, not some off-brand. The wastegate is getting its reference from one of the ports on the compressor side of the turbo. (right near the outlet) The boost controller is tee'd in to the line going from the turbo to the wastegate actuator. Let me know if you need any more info, and I will take some pictures tonight. Edited May 31, 2011 by zx_drift Quote Link to comment Share on other sites More sharing options...
letitsnow Posted May 31, 2011 Share Posted May 31, 2011 What kind of boost controller? A ball and spring? EBC? Bleed? By your description, it sounds like a bleed. Quote Link to comment Share on other sites More sharing options...
zx_drift Posted May 31, 2011 Author Share Posted May 31, 2011 What kind of boost controller? A ball and spring? EBC? Bleed? By your description, it sounds like a bleed. It is a bleed type. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 1, 2011 Share Posted June 1, 2011 Open bleeder to atmosphere only resulting in 8psi of boost in the plenum signifies to me a weak spring in the wastegate and the inability for it to close and direct exhaust flow through the turbine instead of around it... Have you done anything like the redrilling of the actuator arm to tighten up the spring preload yet? I mean if you outright disconnect the thing it should boost, but a 't' may still allow boost to blow through and displace the wastegate diaphragm. Quote Link to comment Share on other sites More sharing options...
ovenfood Posted June 1, 2011 Share Posted June 1, 2011 My mate had boost issues and I added a washer under each of the bolts where the WG attaches (to space it out) and it worked fine after that (his waste gates gate was just flapping around before I did that). Other than that I have almost no experience with car turbos so I'm not sure if I can help. Quote Link to comment Share on other sites More sharing options...
zx_drift Posted June 1, 2011 Author Share Posted June 1, 2011 I had a suspicion that it might be the spring in the actuator, I will try to completely disconnect the wastegate and see what happens. I'm also going to try swapping it with another one if I can find it... Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 1, 2011 Share Posted June 1, 2011 disconnecting it will let the gate flap wide open and you will get no boost. Add tension to the rod, or wire it shut and make a quick burst of WOT...by 2200 you should have boost, and by 3000 you should likely surge the compressor at over 21psi (if the turbo is working and the wastegate is truly shut)... A restrictive exhaust may be causing some issues, no information on that end (stock, modified, potatoes stuck in the outlet, etc...) Quote Link to comment Share on other sites More sharing options...
zx_drift Posted June 1, 2011 Author Share Posted June 1, 2011 I meant disconnecting the vacuum/boost line to the wastegate, not the rod haha. My exhaust is a "catback" and thats in quotes because its been cut and clamped together and there are some crushed spots :/. It still flows ok though. Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted June 2, 2011 Share Posted June 2, 2011 I would think about moving the wastegate boost reference to the manifold too... Quote Link to comment Share on other sites More sharing options...
zx_drift Posted June 2, 2011 Author Share Posted June 2, 2011 So the theory is that the boost pressure inside the turbine is higher than the pressure inside the manifold because of the drop, correct? So as an arbitrary number, the manifold pressure is 8 but the turbo is actually boosting around 10 or so, which would be enough to force the wastegate open. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 2, 2011 Share Posted June 2, 2011 Yep... For antisurge control, taking DPT (Discharge Pressure directly off the final stage discharge scroll) is the preferred metholodgy, but for PRESSURE control in a process, taking SPT (System Pressure, from a point downstream of all pressure losses) is preferable. With a properly sized blowoff/unload control valve surge should not be an issue as long as you stay within reasonable limits of the compressors surge map. Where they reference is at compressor discharge...You will see some that have TWO sensing lines one at discharge and one at the torroidal portion of the turbine wheel diffuser section which will have even HIGHER pressure...the result is the wastegate opens even quicker. Now, on the bleeder styles, if it's a simple bleeder, you will still get the same mushy on-boost response as the wastegate actually starts opening around 4psi and it can open as low as 3psi. Using a poppet-bleeder will keep all pressure off the wastetgate until actual FULL pressure has been reached, THEN apply pressure to the wastegate diaphragm Your boost comes on much harder, and sooner with this setup. If you reference the manifold instead of the discharge, you will compensate for line loss. With a poppet-bleeder you will come on harder, earlier, and since you are in the manifold plenum when you Drop-Throttle you apply actual VACUUM to the actuating side of the wastegate SUCKING THE WASTEGATE DOOR CLOSED FASTER. This helps keep turbine speed up and helps with on-boost resumption. In reality the stock system is very low boost. 10 is a good number. I've run 10psi manifold referenced for quite some time on my red 260ZT. For a 'wife's car' that's O.K. Quote Link to comment Share on other sites More sharing options...
Ben's Tuning Posted June 12, 2011 Share Posted June 12, 2011 (edited) Here is the next question... Have you checked your new intercooler for leaks? I dropped a new turbo on my dsm, and didn't tighten down one of the corner clamps tucked inside my bumper all the way... turbo was screaming, yet I was only getting 15 psi at the manifold. two turns of the clamp, and I was boosting 35 psi (i too had thought it was the boost controller, so I had moved it up). Check for leaks around the stuff you just touched, then look around from there. If the turbo's yelling, she's producing airflow. The question is, where's it going? Edit: The simplest answer is usually the right one. : ) Edited June 12, 2011 by Ben's Tuning Quote Link to comment Share on other sites More sharing options...
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