Cannonball89 Posted December 20, 2011 Share Posted December 20, 2011 (edited) This is a follow-up to my Divorced Port thread: http://forums.hybridz.org/index.php/topic/99036-3-downpipe-38mm-divorced-port-wastegate/ I'm trying to eliminate the boost creep I'm seeing by enlarging the internal wastegate hole and also making the path leading up to it easier for exhaust gases to flow into. While I was at it I also gasket matched the inlet of the Turbine housing to match the T3 gasket because their was a lot of room between the edge of the gasket and the edge of the inlet, which probably was creating some turbulence at the inlet of the Turbine. I used a Rotary Rasp in an electric drill to do this. It wasn't too hard, but I did destroy the drill LOL. This is the size of the wastegate hole as it came originally. About 3/4" diameter I enlarged it to about 1" diameter Internally the hole was simply drilled in at a 90 degree angle and the internal casting was not molded to divert flow into it. I removed a lot of metal to direct the exhaust gases into the hole easier. The casting left a lot of room between the the inside of the Turbine housing and the edge of the gasket. Now it is matched nice and tightly to a T3 gasket. Hopefully this will eliminate my creep, if not then I will be drilling the exhaust manifold and going to a regular External Wastegate and ditch the Divorced Port design. This was still a good thing to do because the turbo should theoretically spool faster with the inlet of the turbine housing gasket matched. The exhaust manifold needs to be gasket matched now too though, I am debating if I want to pull it off now or just do it some other time. Edited December 21, 2011 by Cannonball89 Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted December 20, 2011 Share Posted December 20, 2011 Very interested in your results. I did the port match to the turbo, but that was it. Since I don't boost much over 15psi, I haven't seen any creep issues, but once I get my motor back together I should have the capacity to run more boost. Quote Link to comment Share on other sites More sharing options...
Cannonball89 Posted December 20, 2011 Author Share Posted December 20, 2011 Very interested in your results. I did the port match to the turbo, but that was it. Since I don't boost much over 15psi, I haven't seen any creep issues, but once I get my motor back together I should have the capacity to run more boost. If your not seeing creep at 15psi then you should be fine if you turn the boost up. More boost means less gas has to go through the wastegate. In my case I was trying to run 10psi initially but saw creep up to 20psi. My goal is to get my setup to hold around 15psi, and I might run 20psi down the road. But if I can get it to hold 10psi then I know ill be safe at higher boost levels. Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 20, 2011 Share Posted December 20, 2011 You can dump excess boost overboard from a mismatched compressor to accomplish this as well... Quote Link to comment Share on other sites More sharing options...
Cannonball89 Posted December 21, 2011 Author Share Posted December 21, 2011 You can dump excess boost overboard from a mismatched compressor to accomplish this as well... Not sure if I follow... Can you elaborate a bit? Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted December 21, 2011 Share Posted December 21, 2011 Not sure if I follow... Can you elaborate a bit? Sounds like a pressure relief valve on the intake to control boost creep. Recirculate if you are using a MAF. Quote Link to comment Share on other sites More sharing options...
Cannonball89 Posted December 21, 2011 Author Share Posted December 21, 2011 Sounds like a pressure relief valve on the intake to control boost creep. Recirculate if you are using a MAF. Oh ok, like the factory relief valve on the rear portion of the intake that I removed! Yeah that would work as an emergency overboost protection (as the factory Nissan part was designed for) but I wouldn't want to rely on that as part of my boost control system. I know that people on here have relied on that to help regulate boost but I'd rather control boost entirely from the exhaust side. Seems like making the turbo produce all of that excess airflow that will be dumped before it reaches the combustion chamber would result in more heat for less boost (I.E. out of the ideal effeciency islands on the T3/T04E compressor maps). Still not sure what Tony means by "mismatched compressor" Are you saying my compressor is too big/small? I have a T3/T04E with a .63AR turbine and .50 compressor which I though was ideal for my setup which is a stock F54 bottom end with a stock non-ported P90 head with the stock ZX turbo cam. The only real modifications are an intercooler, full 3" exhaust from the turbo back, and megasquirt. Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 21, 2011 Share Posted December 21, 2011 (edited) No, not at all like that, the ERV is a dumb valve meant as emergency relief, not process control! You are very incorrect about your thoughts on heat production and flow. This is extensively discussed, and I'm not going to repeat it. Please refer to the archived section of posts at the top of the board, you will find it there. Surge Explained If a compressor is producing more boost than it's supposed to at one RPM but not another...it's going on and off it's curve. The engine's consumption is linear. The turbos is not unless regulated. If you have creep, your compressor section is oversized the turbine section is undersized, or there is another mismatch somewhere given the design point on the engine. As to this: "I'd rather control boost entirely from the exhaust side. " You are trying to control the boost with the 1960's Era design paradigm... Alas killing dinosaurs is more difficult than it appears. Come into technology from the 1990's at least. As I said, this is all extensively discussed and I've repeated far too much as it is. Edited December 21, 2011 by Tony D Quote Link to comment Share on other sites More sharing options...
Cannonball89 Posted December 21, 2011 Author Share Posted December 21, 2011 Very interesting. That is definitely something to consider if my creep continues, or even if it doesn't, bleeding off flow could make the turbo pull harder at low RPM. I have to go to work now, but later tonight I will continue researching and learning about this, and look into the controllers. If they could write some code to enable Megasquirt to control a bleed valve that would be perfect... Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 22, 2011 Share Posted December 22, 2011 You have hit on the biggest advantage of the boost bleed. Lower RPMs at higher boost outside the minim flow surge line. You will never get that with "wastegate only control"! Quote Link to comment Share on other sites More sharing options...
litch Posted January 17, 2012 Share Posted January 17, 2012 So what, and where exactly can I get a device that bleeds boost? Im confused as to exactly what you are referring to. Quote Link to comment Share on other sites More sharing options...
Cannonball89 Posted January 17, 2012 Author Share Posted January 17, 2012 So what, and where exactly can I get a device that bleeds boost? Im confused as to exactly what you are referring to. Read the "Surge Explained" sticky. Your just "wasting" energy on the compressor side rather than the turbine side. The operation is essentially the same as that of a conventional wastegate except that opening the valve at low RPM, before a conventional wastegate would open, will keep the compressor to the right of the surge line, and in a more effecient flow area. The trick is to have a BOV that can flow the proper amount of air, and I believe that the larger the better. The smaller the BOV, the more of a "hissing" sound you will get. And the biggest thing is the controller. Tony knows where to get them, ask him nicely and he will probably give a hint. I know Megasquirt has the capability to accomplish this, I just don't think the code is written for it. If I ever actually do this I will post a thread detailing it all, but for now it's just one of those things to keep in mind. How soon I do it will depend largely on the success/failure of my porting at controlling boost. Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 19, 2012 Share Posted January 19, 2012 (edited) Actually you have just promoted me to send yet ANOTHER e-mail to our IT department to recover those controller manuals Cannonball! Something ELSE that doesn't 'auto migrate'... man, I wish these guys used "Ghost" like the last company. Yes, remember that a wastegate only controls the SPEED of the wheel based on the pressure you are seeing. it's trying to move you (in a hamfisted way) vertically on the compressor plot while your engine flow is moving up and to the right as RPM's rise. Wastegates only give 2D control because it's controlling SPEED which controls FLOW without regard to where the efficiency curve is. Really, if you have the BOV setup as suggested, with the Wastegate set not to a PRESSURE setpoint, but to a peak efficiency island SPEED (or a 2D algorithmic approximation of that area of the map) you then control pressure to the engine solely through overboard bleed of boost. Basically, you turn it into a CVT of sorts. Your turbo is always trying to sit in the most efficient area it can operate and just dumping excess air overboard. There is no downside to the engine for this, though turbo longevity may be an issue due to running at peak RPM's all the time. But this would be marginal IMHO as the 'new' control scenario would totally eliminate OVERSPEED of the turbo as happens with wastegate-only control. Edited January 19, 2012 by Tony D Quote Link to comment Share on other sites More sharing options...
Cannonball89 Posted January 19, 2012 Author Share Posted January 19, 2012 (edited) So... If I understand this, one way to set this up would be to have a turbine wheel/shaft speed sensor feeding turbine RPM (not engine RPM) data to a controller, and the controller would modulate a conventional exhaust-side wastegate to maintain the RPM of the turbine at whatever RPM the turbocharger is most happy in, with a hysteresis of a few hundred or a few thousand RPM. Basically just use a solenoid like this one: http://www.diyautotune.com/catalog/ebc-electronic-boost-control-solenoid-kit-p-285.html , but have it referenced to turbine speed rather than pressure, by way of a controller. Then the BOV on the compressor side of the system would be setup identical to how a conventional exhaust side only wastegate would be setup, opening at a given manifold pressure. Since a conventional BOV operates by way of vacuum, you could simply mount a regular wastegate in your I/C piping that would bleed off excess flow, in addition to a conventional BOV that opens on lift-throttle. So this is not really that complicated. The bleeding off from the intake side should be as simple to rig as installing a conventional wastegate. Controlling the speed from the exhaust side is a little more complicating, but just because it's kind of "uncharted water". When you think about it, the software in the control module would be very simple, the kind of thing that could have been done 40 years ago probably. Does this sound right? EDIT: I suppose you could also use a mass air meter before the turbocharger to measure how much air the turbocharger is flowing, and reference the exhaust side wastegate to that in order to keep the turbocharger in it's peak effeciency island. The engine ECU could be operated on speed density or you could mount a second, blow-through mass air meter downstream of the compressor-side bleed valve to feed data to the ECU. Edited January 19, 2012 by Cannonball89 Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 19, 2012 Share Posted January 19, 2012 (edited) Uncharted water? Dark Secret: Check out what Electromotive still sells that's Automotive Related. Turbocharger Tachometer, anybody. Well, why on earth would you ever need one of those? (Even if you are making 1100HP...) Many ways to do it, but rudimentary PID loops to unified valves would do it. No need for two different function valves on the inlet rate of change of TPS in a negative value would work on a derivative action to drop flow overboard as the TB was closing instead of waiting it to close and trying to react to the rapid rise in pressure... Not that I got like 20 hours on pacific flights to ponder the control scenarios... Edited January 19, 2012 by Tony D Quote Link to comment Share on other sites More sharing options...
Cannonball89 Posted April 9, 2012 Author Share Posted April 9, 2012 Just wanted to update this thread, I tested the car with a 15PSI spring in the wastegate, and saw a maximum boost of 17PSI at the top end of 3rd gear. I will probably be at the dragstrip next Saturday and be able to datalog a run through 4th gear, but for now I am calling this a success, because before I ported the wastegate opening, I was seeing over 20PSI at the top of 3rd gear with a 10PSI spring in the wastegate. One other thing I changed was to move the source for the vac/boost line going to the wastegate from the manifold to the compressor outlet. I might move it back to the manifold in the future though, I have noticed that it keeps the wastegate open on lift throttle (no vacuum pulling the wastegat shut) and that cracking pressure seems to be much lower, I can hear the wastegate start to open by about 5PSI. In regards to the control methods we have been discussing above, this product from Turbosmart seems to be the closest thing to what we were discussing, but it isn't quite the same principle: http://www.jscspeed.com/catalog/Universal_Parts/Universal_Blow_Off_Valves/Turbosmart_Electronic_Blow_Off_Valve_Controller.html This allows you to open the blow off valve as a part of the boost control scheme, opening at a certain pressure to prevent overboost, which is in keeping with what we have been discussing, but it doesn't seem to offer the ability to open the blow off valve at low RPM surge conditions to help the turbocharger spool faster and keep right of the surge line on the maps. Basically the only controllers I have been able to find on the web from industrial compressor companies that are advanced enough to do that cost between $5,000-$10,000 and are as big as a suitcase. Tony, did that guy with the Z32 ever tell you what kind of controller he is using? I am really curious to know. Quote Link to comment Share on other sites More sharing options...
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