turbodog Posted July 2, 2012 Share Posted July 2, 2012 Can someone please offer a convincing technical explaination of why you would need a tune when installing an aftermarket downpipe. From what i have seen personally, the only difference is that reduced backpressure may result in difficulty with boost control, which can be fixed without a tune. I read for a while and ol / cl delay was mentioned. Please advise. Link to comment Share on other sites More sharing options...
Lardo420 Posted July 2, 2012 Share Posted July 2, 2012 i thought you knew everything about everything? Link to comment Share on other sites More sharing options...
cypher0117 Posted July 2, 2012 Share Posted July 2, 2012 if your car suddenly has less back pressure on the turbo you will probably overboost which can cause lean conditions and knock and then motor death. Link to comment Share on other sites More sharing options...
I Donated Too laff79 Posted July 2, 2012 I Donated Too Share Posted July 2, 2012 dammit. Lardo beat me to it Link to comment Share on other sites More sharing options...
turbodog Posted July 2, 2012 Author Share Posted July 2, 2012 if your car suddenly has less back pressure on the turbo you will probably overboost which can cause lean conditions and knock and then motor death. Correct, there is no question this can be a problem, but it can be solved by changing restricter pills, running wategate boost, an ebc or mbc. Or even porting the wastegate in extreme boost creep cases. Is there another reason? Is it a problem with boost spiking in closed loop fueling? Link to comment Share on other sites More sharing options...
GTTuner Posted July 2, 2012 Share Posted July 2, 2012 The timing needs to be backed down also. Link to comment Share on other sites More sharing options...
Mega Users paintpollz Posted July 2, 2012 Mega Users Share Posted July 2, 2012 Correct, there is no question this can be a problem, but it can be solved by changing restricter pills, running wategate boost, an ebc or mbc. Or even porting the wastegate in extreme boost creep cases. Is there another reason? Is it a problem with boost spiking in closed loop fueling? andddd how much of a pain is it to get a $100 OTS tune? "Remember Danny - Two wrongs don't make a right but three rights make a left." Link to comment Share on other sites More sharing options...
KCwagon Posted July 2, 2012 Share Posted July 2, 2012 Correct, there is no question this can be a problem, but it can be solved by changing restricter pills, running wategate boost, an ebc or mbc. Or even porting the wastegate in extreme boost creep cases. Is there another reason? Is it a problem with boost spiking in closed loop fueling? I would choose to have a $100 off-the-shelf map, rather than changing restricter pills, using a MBC and porting the wastegate. If you think all that work is worth it, and are confident that your car will operate safely, then go for it and report back. Link to comment Share on other sites More sharing options...
SeeeeeYa Posted July 2, 2012 Share Posted July 2, 2012 Can someone please offer a convincing technical explaination of why you would need a tune when installing an aftermarket downpipe. From what i have seen personally, the only difference is that reduced backpressure may result in difficulty with boost control, which can be fixed without a tune. I read for a while and ol / cl delay was mentioned. Please advise. I am curious about your thought process... what advantage to you believe an aftermarket downpipe gives that justifies a workaround, as opposed to tuning for the downpipe and reaping the normal stage2 rewards? My first mod to my LGT was to gut my stock downpipe. The second mod was to gut my uppipe. I "noticed" a difference, and a dyno said I made 230 or so AWHP... puny and insignificant for the work those actions took. Within two weeks I had a Cobb DP on and Stg2 AP tune... now THAT made a difference worth the effort and money. I still got great MPG, but the car became alive with response and power. If you have no interest in stage2, and tuning, you can get some gains out of merely gutting your stock downpipe... which is a snap to do, taking less than an hour. Edit: I don't think merely changing the pill will do what you believe. Different pills change the rate of boost development, but don't limit it, per se. And, if you chose an aftermarket downpipe without a cat, even directly connecting your compressor to the WG would still likely result in overboost under certain circumstances. Retention of the mid-pipe cat would mitigate, but not eliminate, such boost creep under all conditions. Removal of both cats would certainly be an issue. Maintaining both cats would help, but again begs the question: why the AM DP. You better have the means and inclination to maintain continuous touch with your ECU via logging. That goes without saying with even the simplest of mods, but especially those that may cost a motor. Link to comment Share on other sites More sharing options...
sumfoo1 Posted July 2, 2012 Share Posted July 2, 2012 boost comes up earlier too so timing needs to start retarding a few hundred rpms earlier. Link to comment Share on other sites More sharing options...
Qckslvr Posted July 2, 2012 Share Posted July 2, 2012 Yikes, Ive been trolling this thread because I recently purchased a Tactrix cable, and am in the process of determining whether i want to take the plunge directly to stage 2. Only now do I realize how amateur my understanding of the variables involved with forced induction tuning. I feel like I know so little that I couldnt possibly undertake this jump as of yet. If anyone wants to keep explaining some of the direct implications of reducing restriction at the downpipe, you will have an avid reader following... Link to comment Share on other sites More sharing options...
Lardo420 Posted July 2, 2012 Share Posted July 2, 2012 look at your stock downpipe and then look at the aftermarket one. if you cannot figure out what this will do, you need to immediately give up all hope of tuning your car yourself. Link to comment Share on other sites More sharing options...
manletGT Posted July 2, 2012 Share Posted July 2, 2012 OEM DP'on the left' vs CNT DP'on the right' (Gutted OEM DP, are you even trying?) I gutted my stock DP, but after installing an aftermarket CNT DP...I noticed a difference in performance and sound. (Standard Stage 2 Cobb AP map) http://i.imgur.com/O79v1.jpg Link to comment Share on other sites More sharing options...
dr_sharp Posted July 2, 2012 Share Posted July 2, 2012 Can someone please offer a convincing technical explaination of why you would need a... tl:dr Because racecar lol Link to comment Share on other sites More sharing options...
BAC5.2 Posted July 2, 2012 Share Posted July 2, 2012 Simple - Unpredictable boost control [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
joe sko Posted July 2, 2012 Share Posted July 2, 2012 BAC has spoken. You better listen. Link to comment Share on other sites More sharing options...
CapnJack Posted July 2, 2012 Share Posted July 2, 2012 Can someone please offer a convincing technical explaination of why you would need a tune when installing an aftermarket downpipe....... Please advise. Correct, there is no question this can be a problem, but it can be solved by changing restricter pills, running wategate boost, an ebc or mbc. Or even porting the wastegate in extreme boost creep cases. I believe you answered your own question. A tune does not only mean that someone waved a magic wand over your ECU, it can be any of the above you mentioned. A tune used to mean filter, plugs, wires, cap & rotor, points and condenser, carb cleaning, etc. When your car is changed from basic condition, meaning that it is not running to the same tolerances as factory condition, a "tune" is needed to make it run under the new conditions or to restore it to what it thinks is optimal condition. Whether it be an ECU tune to change boost tables or installing a MBC, something needs to be done. Link to comment Share on other sites More sharing options...
turbodog Posted July 3, 2012 Author Share Posted July 3, 2012 I believe you answered your own question. A tune does not only mean that someone waved a magic wand over your ECU, it can be any of the above you mentioned. A tune used to mean filter, plugs, wires, cap & rotor, points and condenser, carb cleaning, etc. When your car is changed from basic condition, meaning that it is not running to the same tolerances as factory condition, a "tune" is needed to make it run under the new conditions or to restore it to what it thinks is optimal condition. Whether it be an ECU tune to change boost tables or installing a MBC, something needs to be done. Completely agree. So is boost control this only real issue then? The problem I have is with people making blanket statements that "you must have a tune with a downpipe", taken to mean an ecu tune. When in fact you really just need to "tune" how boost is controlled, which can be done in several different ways. Of course, to get maximum benefit from a downpipe an ecu tune is the best choice. Link to comment Share on other sites More sharing options...
dr_sharp Posted July 3, 2012 Share Posted July 3, 2012 You should get a downpipe and control boost a different way to put all the haters in their place! Do it! lol Link to comment Share on other sites More sharing options...
turbodog Posted July 3, 2012 Author Share Posted July 3, 2012 You should get a downpipe and control boost a different way to put all the haters in their place! Do it! I've seen it done, with logs and WBO2 to prove it, but on a wrx and sti. Perhaps there is something different with the legacy, which is why I ask. If I ever get around to putting a downpipe on my car and going stage 2, I will certainly log it with a WBO2 on the stock tune, after adjusting the boost control lines to prevent spiking. Replacing the pill with a needle valve works great for that from what I've seen. Link to comment Share on other sites More sharing options...
I Donated thefultonhow Posted July 3, 2012 I Donated Share Posted July 3, 2012 Completely agree. So is boost control this only real issue then? The problem I have is with people making blanket statements that "you must have a tune with a downpipe", taken to mean an ecu tune. When in fact you really just need to "tune" how boost is controlled, which can be done in several different ways. Of course, to get maximum benefit from a downpipe an ecu tune is the best choice. Okay, so let me get this straight. You would rather change restrictor pills, port the wastegate, and install an MBC to get very little benefit over stock, than load on a tune with higher boost targets and get a huge benefit? When OTS maps are only $100? In other words, you'd rather spend a lot more effort to get a lot less in order to save MAYBE $75? If yes, I don't know what else to say. Link to comment Share on other sites More sharing options...
dr_sharp Posted July 3, 2012 Share Posted July 3, 2012 Okay, so let me get this straight. You would rather change restrictor pills, port the wastegate, and install an MBC to get very little benefit over stock, than load on a tune with higher boost targets and get a huge benefit? When OTS maps are only $100? In other words, you'd rather spend a lot more effort to get a lot less in order to save MAYBE $75? If yes, I don't know what else to say. Shut your logical pie-hole! I want to see turbodog's great idea happen lol Link to comment Share on other sites More sharing options...
turbodog Posted July 3, 2012 Author Share Posted July 3, 2012 Okay, so let me get this straight. You would rather change restrictor pills, port the wastegate, and install an MBC to get very little benefit over stock, than load on a tune with higher boost targets and get a huge benefit? When OTS maps are only $100? In other words, you'd rather spend a lot more effort to get a lot less in order to save MAYBE $75? If yes, I don't know what else to say. No, I simply have a problem with people making blanket, inaccurate statements. But I have even more of a problem with people trusting their motors to off the shelf maps without extensive logging and a WBO2. The hysterical irony here is that it's probably safer to run the stock tune (with corrected boost control) with a downpipe, than an OTS map without proper logging. IMHO. Please explain why if I'm wrong. Link to comment Share on other sites More sharing options...
dr_sharp Posted July 3, 2012 Share Posted July 3, 2012 The hysterical irony here is that it's probably safer to run the stock tune (with corrected boost control) with a downpipe, than an OTS map without proper logging. IMHO. Please explain why if I'm wrong. You are sooo right! Just do it! lol Link to comment Share on other sites More sharing options...
I Donated thefultonhow Posted July 3, 2012 I Donated Share Posted July 3, 2012 I agree completely that you should log with an OTS map to make sure you're not getting any knock. With that said, saying "if you get a DP, you need a tune" is a lot easier than saying, "if you get a DP, you need either a tune or a complex combination of boost control strategies that you're probably not interested in anyway." Link to comment Share on other sites More sharing options...
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