TimZ Posted July 10, 2001 Share Posted July 10, 2001 quote: Originally posted by Z_Ferrari: the wastegate actuator vacuum line i have is hooked up to the turbo inlet. So...its seeing NO boost, but its still functioning fine. How is this happeneing? 7psi in first, 11 in 2nd, 16 in third, off the map in 4th? How exactly is that functioning fine? Sounds to me like your turbo is running open loop, and is only being limited by the amount of time it spends in each gear. It doesn't sound like the wastegate is doing anything. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted July 10, 2001 Share Posted July 10, 2001 I apologize, but I am only understanding part of this. I just want to add my 0.02, then I'll go away. IMO, the best place to reference the wastegate is the compressor housing -- the nipple poking out the side of the compressor snail. When you reference the point where the boost is generated, you have the least lag and the best control over the wastegate, and consequently the most stable boost level. Also, Scottie GNZ's method of raising boost by shortening the rod SHOULD only work to a point (I know it's working well for you ), but by removing travel from the actuator, there will be a point where the actuator cannot open the wastegate all the way as the internal spring will go solid. My idea, and what I will implement soon, is just to add spring tension to the wastegate externally, which will not limit the travel. If your boost is uncontrolled at higher power levels and RPMs, this could be the problem. Once again, I know I didn't directly address the problem, but I hope the input is well taken. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted July 10, 2001 Share Posted July 10, 2001 I'm confused. Too many scotts. The external spring one is a nice solution. You could take off the old wastegate rod, and thread it. Then put on 2 nuts/washer to act as an adjustable spring perch, so you could vary the effect of the spring. Woohoo, coilovers for your turbo! Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted July 10, 2001 Share Posted July 10, 2001 There is indeed a bit of confusion in this thread. Let me see if I can help clarify some of it. Z_Ferrari When I referred to the ID of the line being the problem I had, I was referring to line that is the source for the wastegate actuator, not the I/C pipes. IMO, the pipes you have are a bit small considering you are running an upgraded turbo. I will repeat what both Tim and I have said about what we think is the problem. Based on the symptoms, it appears the wastegate is not functioning, ie, it is staying shut. I already gave you 3 reasons why that could happen and I caution you to find the problem before you continue running the car. The kind of boost you could potential see in 3rd or 4th with stock injs and pump gas is asking for trouble. Shortening the wastegate rod is a tried and trued method of adjusting boost, but there are some caveats. Do not use it to get more than about 6# boost increase. 1 full turn usually equates to 1# boost. When you shorten the rod you are preloading the spring in the wastegate cannister. The stock spring pressure and the length of the rod are the keys to the pre-set wastegate actuation. Pre-loading the spring by shortening the rod requires more boost against the diaphragm to move the rod. The more you shorten the rod, the more you have pull against the spring to put it back on the lever. Shortening it too much will reduce the rod travel and worse, cause the spring to bind. ANOTHER CAUTION, do not turn the rod while it is still connected with tension on it as that will destroy the diaphragm. SleeperZ I use a combination of a bleeder valve and an adjustable wastegate rod to go from the stock 12# wastegate setting to the 23-24# I run at the track. This is my latest procedure. I use the bleeder valve to go from 12# to about 20#, then the adjustable rod to go above that and do any adjustments at the track. When I am on the street, I disconnect the bleeder valve, and cap the line , and have about 15-16# on the street. DRAX Yes, the spring method is pretty neat also and puzzled why others do not try it. Hope I did not throw more mud in the pond. Quote Link to comment Share on other sites More sharing options...
TimZ Posted July 10, 2001 Share Posted July 10, 2001 quote: Originally posted by SleeperZ: IMO, the best place to reference the wastegate is the compressor housing -- the nipple poking out the side of the compressor snail. When you reference the point where the boost is generated, you have the least lag and the best control over the wastegate, and consequently the most stable boost level. Okay, the reference can be placed anywhere between the compressor outlet and the intake manifold. It's largely a matter of personal preference. Placement does make a difference in the response characteristics, though. Placement at the compressor outlet, as SleeperZ suggests will definitely give you the most stable boost response. However, it does not give the least lag - actually this setup will give the most lag, due to the fact that the wastegate gets it's control signal sooner. The upside to this is that this setup generates the least heat, since the turbine is well controlled. The further downstream you go with placement, the more delay there is in the boost signal that gets to the wastegate. Consequently, the turbo runs open loop until the boost signal arrives at the diaphragm. This results in a faster boost rise time, but the intercooler has to dissipate more heat, since you are making the turbo work a bit harder. Also, you can expect a bit of a boost spike (1 or 2psi) at the onset of boost with this setup. If you have an efficient intercooler, this isn't much of a problem. If you are an engineer, this is a very good example of an overdamped vs. underdamped controller. Like I said - this is largely a matter of personal preference. I suggested moving the reference after the IC, since the original post complained about decreased boost levels after installing an intercooler. [ July 10, 2001: Message edited by: TimZ ] Quote Link to comment Share on other sites More sharing options...
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