Evan Purple240zt Posted August 7, 2009 Share Posted August 7, 2009 Alright, let me back up here a bit. My car has always been a bit of a dog in 3rd. I go through 1&2 VERY fast and 3rd just never felt right. Garrett even noticed it watching my car at the track. This is an RB25DET we are talking about here.. 2.5 liters. I have always had a compressor surge (or at least it sure sounds like it) in 3rd past about 1/2 throttle in the upper RPMs. I suspect this really has something to do with it. I have tried everything I can think of to eliminate this situation. I have messed with the tune a bit, changed to new I/C plumbing etc.. thinking it was a setup problem. I am now wondering if the t3/t04e 60 trim .63ar exhaust housing is just a poorly sized turbo.... I do spin this motor to 7800 btw. Boost level doesn't matter either. I run a tial external gate and an HKS boost controller, I had a greddy and it did the same thing. I have this situation from 14 psi spring pressure all the way to 25psi. I really want to get this solved, can anyone shed ANY light? Thanks. Quote Link to comment Share on other sites More sharing options...
wigenOut-S30 Posted August 7, 2009 Share Posted August 7, 2009 Hey Evan, This turbo has a pretty small compressor map. You can use this site squirrel Performance and kinda get a idea to what you are looking at. Does the surge clear up at a certain RPM?(my guess is around 5 Krpms)? You will see the surge line to the left. If at any time you are over in that area, thats when you will get the surge. so if third gear is a really long gear and your at say 300 and nail it.. you could be over in that area until the higher RPMs to where the turbo is working for you. here is the link to the site. you can punch all of your data in and see what turbo combinations are good for you http://www.squirrelpf.com/turbocalc/index.php?version=4&target_peak_power=375&pr_ref=14.000&engine_disp=2.800&engine_disp_factor=0&target_af=12&bfsc=0.47&max_ic_loss=2&rpm_redline=6500&rpm_peak_power=5500&rpm_max_boost=3200&rpm_min_boost=2800&vol_1=75&vol_2=82&vol_3=87&vol_4=82&vol_1=75&vol_2=82&vol_3=87&vol_4=82&intake_temp_1=90&intake_temp_2=115&intake_temp_3=120&intake_temp_4=125&turbo_n=1&map_sel0=68 Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted August 7, 2009 Author Share Posted August 7, 2009 Gabe, if I pussy foot the throttle no surge, but the second I wack it wide open it goes nuts. It will even do it at lower throttle openings. Seems the turbo is just wrong at this point. Quote Link to comment Share on other sites More sharing options...
TimZ Posted August 7, 2009 Share Posted August 7, 2009 Gabe, if I pussy foot the throttle no surge, but the second I wack it wide open it goes nuts. It will even do it at lower throttle openings. Seems the turbo is just wrong at this point. Evan - I don't remember what injection system you are running - can you datalog an example of this happening? Like Gabe, I'm curious about what rpm this starts at and when (or if) it stops once you pass through a certain rpm. Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted August 7, 2009 Author Share Posted August 7, 2009 Tim, I am using an apexi' power FC. The logging is kind of granular, Ill see if I can log in some sort of graph type affair to show exactly whats happening. Evan Quote Link to comment Share on other sites More sharing options...
B00STDZ Posted August 7, 2009 Share Posted August 7, 2009 My car use to do that... Had to do with the BOV Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted August 7, 2009 Author Share Posted August 7, 2009 Yeah, time to methodically re-evaluate everything. On your BOV, what was the actual problem? Sprung too tight, too loose? Quote Link to comment Share on other sites More sharing options...
Drax240z Posted August 7, 2009 Share Posted August 7, 2009 Evan, forgive me for not following closer, but what engine are we talking about? KA? SR? Dispalcement? Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted August 7, 2009 Author Share Posted August 7, 2009 Holy brainfart! Ill update the first post. RB25DET 2.5 liters. I thought for sure I had that in there. If memory serves, I have had this problem with two different BOV's in the system. My current is a forge motorsports bypass valve that hangs open at idle like the oem unit did. Evan Quote Link to comment Share on other sites More sharing options...
Nigel Posted August 8, 2009 Share Posted August 8, 2009 So what exactly happens other than "it goes nuts"? When you floor it, does it start to build boost and then hit a wall where the boost gauge needle starts wildly swinging back and forth, the engine starts jerking, and it just won't build more boost? That would be surge, and judging by the map that wigenOut posted, you'll have it with that compressor. Strange that you say it happens in the upper rpm's though. What happens when you floor in in third from 2500 rpm? Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted August 8, 2009 Author Share Posted August 8, 2009 It builds boost, but not very quickly. It is less related to rpm as it is to throttle position. Hang tight, I am going to go do a datalog tomorrow so I can illustrate exactly what the scenario is. Thanks guys. Quote Link to comment Share on other sites More sharing options...
B00STDZ Posted August 8, 2009 Share Posted August 8, 2009 Well, when you hear the surge, can you hear the BOV too? If you cant hear the BOV or hear it very softly that means your spring is probably too tight... If the air isnt released before the throttle body when you shift or when you left off the accelerator, it has to go somewhere, which is most likely back where it came from, the turbo... Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted August 8, 2009 Author Share Posted August 8, 2009 My bov is very quiet anyway, not sure I could hear it. I can try springing it more lightly, its pretty easy to do with where I have it installed. Quote Link to comment Share on other sites More sharing options...
B00STDZ Posted August 8, 2009 Share Posted August 8, 2009 See I had the same problem but my BOV is really loud so it was quiet obvious... Quote Link to comment Share on other sites More sharing options...
e_racer1999 Posted August 8, 2009 Share Posted August 8, 2009 Hey Evan, This turbo has a pretty small compressor map. You can use this site squirrel Performance and kinda get a idea to what you are looking at. Does the surge clear up at a certain RPM?(my guess is around 5 Krpms)? You will see the surge line to the left. If at any time you are over in that area, thats when you will get the surge. so if third gear is a really long gear and your at say 300 and nail it.. you could be over in that area until the higher RPMs to where the turbo is working for you. here is the link to the site. you can punch all of your data in and see what turbo combinations are good for you http://www.squirrelpf.com/turbocalc/index.php?version=4&target_peak_power=375&pr_ref=14.000&engine_disp=2.800&engine_disp_factor=0&target_af=12&bfsc=0.47&max_ic_loss=2&rpm_redline=6500&rpm_peak_power=5500&rpm_max_boost=3200&rpm_min_boost=2800&vol_1=75&vol_2=82&vol_3=87&vol_4=82&vol_1=75&vol_2=82&vol_3=87&vol_4=82&intake_temp_1=90&intake_temp_2=115&intake_temp_3=120&intake_temp_4=125&turbo_n=1&map_sel0=68 Not trying to threadjack, but that Squirrel Performance site is very useful. Does anyone have any engine-specific.... specifications that we can plug in there? I.e. VE for stock L-series or RB? Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted August 8, 2009 Author Share Posted August 8, 2009 Its raining today, hopefully it clears up! WOT in the rain is a bad idea. Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted August 14, 2009 Author Share Posted August 14, 2009 Still no mapping yet, my boost controller crapped out so I installed my manual boost controller. No surge at 15 psi, no surge at 17 psi but the surging starts at 20-21psi. Ill get some maps tomorrow hopefully. I haven't had a place to go all the way to redline safely. The surging is very visible on my boost gauge, the bouncing needle is pretty apparent. I don't think my bov is sprung too tight because I can make it open by gently closing the throttle under 5 psi of boost or so. Car feels very slow at 20psi as well when it starts surging. Evan Quote Link to comment Share on other sites More sharing options...
Tony D Posted August 15, 2009 Share Posted August 15, 2009 Read the sticky on surge and what it is in this forum. It sounds like stated earlier, you are experiencing a minimum flow surge condition. If you bled some air off when going WOT, even though you are 'wasting' air, you will likely have less issue with the surging. When you pussy-foot it, your turbine speed (and therefore flow potential at the compressor side) is lower, meaning less flow, and less pressure. When you hammer it at lower RPMs, it indeed is possible you are overproducing air for the speed of the engine, so you get boost...but flow across the wheel is insufficient to let stable operation continue. Quote Link to comment Share on other sites More sharing options...
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