sgt Posted October 19, 2007 Share Posted October 19, 2007 Mickey Could you go into more detail about the aem intake resonance? Link to comment Share on other sites More sharing options...
bugblatterbeast Posted October 19, 2007 Share Posted October 19, 2007 good to see you back MickeyD Link to comment Share on other sites More sharing options...
mickeyd2005 Posted October 19, 2007 Share Posted October 19, 2007 Mickey Could you go into more detail about the aem intake resonance? I only have one chart that shows it, but I have a couple of datalogs. This one is the SPT intake. It shows up in 4th gear as well on the SPT. The boost is stable but the MAF just starts oscillating wildly between 2400 and 3000 rpm. It smooths out at high rpm. http://i141.photobucket.com/albums/r69/mickeyd2005/untitled-15.jpg As you know load is proportional to MAP and load is related to rpm and MAF so if the boost is stable then the MAF should be stable, but it isn't in the chart above. On my AEM, 4th gear is fine, but 5th gear isn't. If I target 14 psi at 2400 rpm (I can achieve this in 5th gear), it oscillates pretty bad. I don't know if it is turbulence or an actual air pulse in the intake. It could have to do with the length of the pipe. I can definitely "feel" a low frequency air pulse in my ear drums if I have the windows rolled down. I'm going to try the stock air box with resonator and see if that changes anything. I don't see this in datalogs of large turbos. It's probably because they can't build that much boost at 2400 rpm. Link to comment Share on other sites More sharing options...
2005garnetGT Posted October 19, 2007 Author Share Posted October 19, 2007 perhaps its compressor surge Link to comment Share on other sites More sharing options...
mickeyd2005 Posted October 19, 2007 Share Posted October 19, 2007 perhaps its compressor surge Very possible except it occurs at a lower PR with the SPT. Also, I have looked at the compressor map for the RHF55 and the VF23. Granted these are not VF40 compressor maps, they should be close. For a 2.5liter engine, it looks like we should be well clear of the surge line at 2400 rpm. A 2.0 liter enginer would be pretty close. Link to comment Share on other sites More sharing options...
mickeyd2005 Posted November 3, 2007 Share Posted November 3, 2007 OT update. The person who owns the SPT intake in post #53 replaced his SPT intake with his stock intake. Boost is approximately the same but the MAF no longer oscillates wildly. There is still two bumps but it is no where near what it was like with the SPT. I think the resonator does help reduce the MAF oscillations. I get similar (but not as bad) oscillations with the AEM at 2400 rpm and 14 psi. With the AEM, I can feel the pressure waves in my ear drums if I have the windows rolled down so I think it's a real pressure wave oscillation in the intake. http://i141.photobucket.com/albums/r69/mickeyd2005/stockintake.jpg Of course, this only affects people with the stock turbo. Any turbo larger than the VF40 will not be able to create enough boost at 2400 rpm to cause this oscillation. Link to comment Share on other sites More sharing options...
NSFW Posted November 3, 2007 Share Posted November 3, 2007 Do you have a graph like that with time on the X-axis? Anyone know how to figure the resonant frequency of the intake system? Could you model it as a simple tube running from the air filter to the compressor inlet, and still get a reasonable approximation? Link to comment Share on other sites More sharing options...
Deer Killer Posted November 3, 2007 Share Posted November 3, 2007 http://www.legacygt.com/forums/showthread.php?t=34405 TD tuned very badly from cobb, they did a much better job in 1.16 which they release after a few posts I made here But regardless, I don't think this thread has cleared anything up, just overcomplicated matters. Especially because the tables are incorrectly labeled in Enginuity. Proportional = initial wastegate DT. What they are calling TD proportional = deriviative. But initial/course/fine is also an accurate description, as long as you understand what "dynamic system" means, the whole PID subject is just intellectual snobbery IMHO. Very important calculations for engineering large expensive projects, but not here. You will never practically get the sensor resolution you need or expect people to be able to do the math. Anyone with enough brain cells to figure out how to get warm water out of shower and not burn themselves can tune this. Learning how this system behaves is part of the fun, no? Unless you just want to make noise and go fast, get a V8 and a carb. Link to comment Share on other sites More sharing options...
LittleBlueGT Posted November 3, 2007 Share Posted November 3, 2007 Especially because the tables are incorrectly labeled in Enginuity. Proportional = initial wastegate DT. What they are calling TD proportional = deriviative. You are wrong. Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and ID1000s................by the DataLog Mafia!!! Link to comment Share on other sites More sharing options...
mickeyd2005 Posted November 3, 2007 Share Posted November 3, 2007 Especially because the tables are incorrectly labeled in Enginuity. Proportional = initial wastegate DT. What they are calling TD proportional = deriviative. Proportional is based off boost error and is definitely NOT initial wastegate. http://en.wikipedia.org/wiki/PID_controller The proportional term makes a change to the output that is proportional to the current error value. Cobb did not tune turbodynamics in their OTS stage 2 tune. They use max wgdc to control boost. Link to comment Share on other sites More sharing options...
bugblatterbeast Posted November 3, 2007 Share Posted November 3, 2007 But regardless, I don't think this thread has cleared anything up, just overcomplicated matters. Especially because the tables are incorrectly labeled in Enginuity. Proportional = initial wastegate DT. What they are calling TD proportional = deriviative. But initial/course/fine is also an accurate description, as long as you understand what "dynamic system" means, the whole PID subject is just intellectual snobbery IMHO. Very important calculations for engineering large expensive projects, but not here. You will never practically get the sensor resolution you need or expect people to be able to do the math. Not according to my datalogs. Try zeroing out the coarse gain tables and see what happens to the residual boost error. it never goes to zero. if you try the experiment, you will find that the boost error is used to index the fine gain table to look up a correction value which ends up added to the WGDC low value. if you now zero the fine gain (proportional) table and put a non-zero value in the coarse gain tables, force a boost error by choice of boost target, you will find that the WGDC starts at the WGDC low value and continue to accumulate more WGDC. the problem with the definitions is that they are not entirely accurate. When I dial in a PID for accurate tracking, I tend to make proportional non-linear to speed up the transients and use the integral term to remove residual errors. others use different approaches. when you look at the descriptions, fine gain is described as the table used to remove fine boost ripple during tracking and the coarse table is used for spool-up. you can actually use both tables either way, but it would be hard to get the system running right unless you actually know which one is making a proportional correction and which one is feeding the integrator. I wouldn't be so quick to dismiss something as intellectual snobbery. A combination of practical experience and understanding always works out better than just one of the two. the best engineers I've worked with all have both a strong theoretical background and many hours on the bench. the worst I've worked with have the theory and no practical and the average ones seem to have the practical but lack the theory Link to comment Share on other sites More sharing options...
Infamous1 Posted January 25, 2008 Share Posted January 25, 2008 Bumping a good thread link to merchgod's explanation of the TD system... http://forums.nasioc.com/forums/showthread.php?t=1433698 Link to comment Share on other sites More sharing options...
mickeyd2005 Posted January 25, 2008 Share Posted January 25, 2008 Not according to my datalogs. Try zeroing out the coarse gain tables and see what happens to the residual boost error. it never goes to zero. if you try the experiment, you will find that the boost error is used to index the fine gain table to look up a correction value which ends up added to the WGDC low value. +1 to the above Coarse Gain High = TD Integral Positive Coarse Gain Low = TD Integral Negative Do NOT zero these tables out. For some reason, some people have zeroed one or two of these tables out. It effectively changes boost control from closed loop to almost open loop. Boost control then becomes controlled only by the WGDC tables. This can result in weird boost curve in 3rd gear and overboost in 4th or 5th gear. It can also result in overboost when shifting quickly at WOT. I would never recommend zeroing out these tables but some people have sent me logs with it zeroed out. It's already proven that it's a bad idea. The WGDC Initial and TD Integral are the most important parameters to control boost. TD Proportional can affect a transient boost especially if you have a restrictor pill, but it's minor compared to TD Integral. Link to comment Share on other sites More sharing options...
Infamous1 Posted January 25, 2008 Share Posted January 25, 2008 So eccientally the WGDC Initial and TD Integral will be your WGDC with the boost error calculation added also? Then what purpose does the proportional adjustments serve? Link to comment Share on other sites More sharing options...
mickeyd2005 Posted January 25, 2008 Share Posted January 25, 2008 TD integral takes time to wind up. While it is winding up, use the TD proportional to hold the WGDC high so that you keep the door closed during spoolup. Once you hit target boost, boost error = 0, TD proportional goes to zero and you rely upon TD integral to stabilize your WGDC. Link to comment Share on other sites More sharing options...
Infamous1 Posted January 25, 2008 Share Posted January 25, 2008 TD integral takes time to wind up. While it is winding up, use the TD proportional to hold the WGDC high so that you keep the door closed during spoolup. Once you hit target boost, boost error = 0, TD proportional goes to zero and you rely upon TD integral to stabilize your WGDC. OK I see now thanks. Link to comment Share on other sites More sharing options...
Deer Killer Posted March 8, 2008 Share Posted March 8, 2008 The TD integral is the most important component of boost control. The proportional can be fairly far off and still have little impact. It takes a very small change to the integral to make a difference. I noticed that most people tune their boost using one gear (usually 3rd gear) and they control boost using the max wgdc table. That may be very easy to do, but it is not a good idea. It will restrict boost in the lower gears. The max wgdc table DOES NOT protect against overboosting in the higher gears because the engine will overboost before being clipped by the max wgdc table. I did notice that if you use a CONSTANT 10% between max wgdc and initial wgdc table that it will protect against overboosting. It was always a mystery to me how this worked, but once you log TD integral you will understand. Also, capping the WGDC by using max wgdc table takes TD out of the picture. You could put random numbers into the TD tables and it would still work because the WGDC would be clipped. Also, try to not overboost. If negative boost error is sustained, it will wind down the integral and prevent hitting target boost later. In a boost vs rpm plot of each gear, I divide the graph into two regions. One region is rpm > peak boost and the other is rpm < peak boost. In the high rpm region, the turbodynamics will behave similar to mos theoretical PID models. In the low rpm region, PID won't work normally because too much time is spent spooling the turbo. Different strategies have to be used. Here is an example of a boost response with all 5 gears. The tune is not complete but it shows how it works and how it doesn't. http://i141.photobucket.com/albums/r69/mickeyd2005/boost.jpg 5th gear - I purposefully capped boost in this gear. I had to lower boost between 2400 and 3000 rpm because my AEM intake was resonating. I notice this resonance in Legend's SPT intake in 4th gear but it shows up at a higher boost level on the AEM. Larger turbos won't have this problem. I'm going to buy a new stock filter and put my stock air box plus resonator back on and see if that helps. If I only had a place to take 5th gear to 140! Link to comment Share on other sites More sharing options...
mickeyd2005 Posted March 8, 2008 Share Posted March 8, 2008 I don't know if you're joking, but I'll answer it anyway for those who don't know. You don't need to tune boost in 5th gear above 4000 rpm. If boost is tuned correctly in 3rd gear, the boost will be stable in 4th and 5th gear from 4000+ rpm. We tend to look at boost plots with rpm on x-axis but if you plot time on x-axis, you'll see that 5th gear has plenty of time to stabilize in the 4000+ rpm range. The key is to tune boost during the pre-boost threshold range in all gears. Link to comment Share on other sites More sharing options...
Deer Killer Posted March 8, 2008 Share Posted March 8, 2008 Relax, it's a joke. Link to comment Share on other sites More sharing options...
LittleBlueGT Posted March 8, 2008 Share Posted March 8, 2008 Relax, it's a joke. MickeyD2005 doesn't joke. Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and ID1000s................by the DataLog Mafia!!! Link to comment Share on other sites More sharing options...
mickeyd2005 Posted March 8, 2008 Share Posted March 8, 2008 I was fairly sure it was a joke (read first sentence). However, I want to make sure noobs don't think they need to do top gear logs at high rpm. Link to comment Share on other sites More sharing options...
rao Posted March 8, 2008 Share Posted March 8, 2008 If you don't do logs in top gear at high rpm then how do you KNOW there isn't a problem? Rob IF YOU CARE ABOUT YOUR CAR YOU SHOULD NEVER DRIVE IT Link to comment Share on other sites More sharing options...
mickeyd2005 Posted March 8, 2008 Share Posted March 8, 2008 Funny guy. Actually, several people have sent me logs in 4th gear to redline and that's one of the reasons I posted the message. I was really surprised that they did it and told them not to do it anymore. I did look at the logs. They don't tell you anything that you won't see in 3rd gear. However, people should log in the regions that they drive in. Most people only log 3rd gear but forget to log 4th and 5th gear in the 2000 to 3500 rpm range. I'm fairly certain that most people drive in 4th and 5th gear between 2000 and 3500 rpm. Almost ALL the OTS stage 2 tunes that I have seen do not have boost set up properly for 4th gear between 2000 and 3000 rpm. And that's not even a PID issue. Link to comment Share on other sites More sharing options...
rao Posted March 8, 2008 Share Posted March 8, 2008 But how do you KNOW? and what about 5th? Rob IF YOU CARE ABOUT YOUR CAR YOU SHOULD NEVER DRIVE IT Link to comment Share on other sites More sharing options...
mickeyd2005 Posted March 8, 2008 Share Posted March 8, 2008 Sometimes I wonder about you. Log the areas in which drive in. If you drive in 5th gear at 6000 rpm on your way to work then you should log it. Come to think of it, I've never seen you post a log. Why don't yo log 4th and 5th gear from 2000 to 3000 rpm? Link to comment Share on other sites More sharing options...
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