COBB Tuning Posted June 6, 2011 Author Share Posted June 6, 2011 Launch Control, on an automatic, is effectively controlled by the transmission or more precisely, the stall speed on the torque converter. LC as we have enabled it here, is only for manual cars. The stock transmission may not be ideal for drag racing and if you are looking for better drag-launch performance, you may want to look into a built transmission, valve body, high-stall torque converter and a line lock! Someone had mentioned not having enough time to build boost at the staging lines. You might consider "late staging". That is, line up to stage and trip the first light and build boost, then as your opponent get's staged, inch forward and trip the second light. You get about 7 seconds after the pre-stage before you red-light. Travis COBB Tuning Link to comment Share on other sites More sharing options...
iNVAR Posted June 6, 2011 Share Posted June 6, 2011 Could've sworn I said basically what COBB just said regarding the TC. See? I do sort of know what I'm talking about... Thanks for the expert voice. Maybe that will give me some "forum cred" from now on. Link to comment Share on other sites More sharing options...
cholmes1 Posted June 7, 2011 Share Posted June 7, 2011 No one except NSFW seems to acknowledge the core of the problem/question. I am aware that the TC will allow only a spectrum of RPM's before it allows engagement. What my respondents don't seem to understand is that the TC is not designed to be used as a rev limiter you would burn up parts quickly if you used it that way. Line lock on our cars would be most easily duplicated using the brakes and e-brake in conjunction. However, same problem in using them to repeatedly hold an engaged transmission which will result in failure sooner rather than later. A torque converter is nothing like a dedicated rev limiter or launch control. This is why Mercedes, Lamborghini, and others who use automatics, still use a LC function. The goal would be to have a device, like the Cobb AP, to set an RPM where I would not need to late stage or purchase a high-stall and could simply set it, floor the throttle, and hold a pre-set RPM... ** FYI: A Legacy GT with a high stall TC would be basically useless unless you have a track only car or a massive turbo. A high stall TC on a daily driver would be a PIA since the stock will already allow stall around 3000rpm which is more than I would need on the street** The other upgrades (VB, etc) are in the works. LOTS of info here if someone has further interest in how these things work and what their limits are... http://legacygt.com/forums/showthread.php/5eat-pride-120921.html This could also be helpful for those who have never owned an auto trans or are still confused on how a TC works. http://auto.howstuffworks.com/auto-parts/towing/towing-capacity/information/torque-converter.htm Thank you for the response Travis (Cobb Tuning) maybe you can think about mentioning it to the programmers at Cobb. We have plenty of 5EAT members that are always looking for tuning options. FWIW iNVAR I never doubted your 'cred' simply answered your question(s). Best, C.H. Link to comment Share on other sites More sharing options...
YN-TGL Posted June 7, 2011 Share Posted June 7, 2011 What about if I have a protuned map? Can I add this feature or would I need to get a new tune and have the tuner use an updated base map to tune from. TIA Link to comment Share on other sites More sharing options...
iNVAR Posted June 8, 2011 Share Posted June 8, 2011 No one except NSFW seems to acknowledge the core of the problem/question. I am aware that the TC will allow only a spectrum of RPM's before it allows engagement. What my respondents don't seem to understand is that the TC is not designed to be used as a rev limiter you would burn up parts quickly if you used it that way. Line lock on our cars would be most easily duplicated using the brakes and e-brake in conjunction. However, same problem in using them to repeatedly hold an engaged transmission which will result in failure sooner rather than later. A torque converter is nothing like a dedicated rev limiter or launch control. This is why Mercedes, Lamborghini, and others who use automatics, still use a LC function. The goal would be to have a device, like the Cobb AP, to set an RPM where I would not need to late stage or purchase a high-stall and could simply set it, floor the throttle, and hold a pre-set RPM... ** FYI: A Legacy GT with a high stall TC would be basically useless unless you have a track only car or a massive turbo. A high stall TC on a daily driver would be a PIA since the stock will already allow stall north of 3000rpm which is more than anyone would need on the street** The other upgrades (VB, etc) are in the works. LOTS of info here if someone has further interest in how these things work and what their limits are... http://legacygt.com/forums/showthread.php/5eat-pride-120921.html This could also be helpful for those who have never owned an auto trans or are still confused on how a TC works. http://auto.howstuffworks.com/auto-parts/towing/towing-capacity/information/torque-converter.htm Thank you for the response Travis (Cobb Tuning) maybe you can think about mentioning it to the programmers at Cobb. We have plenty of 5EAT members that are always looking for tuning options. FWIW iNVAR I never doubted your 'cred' simply answered your question(s). Best, C.H.I believe those cars aren't like the 5EAT version of our cars. You are talking about cars that have clutch based automatic transmissions. A 5EAT is torque converter based. Here's a list of some cars with LC: http://www.automotiveaddicts.com/2486/cars-with-launch-control-houston-we-have-lift-off Audi R8Audi TTBMW M3BMW M5BMW M6Bugatti VeyronChevrolet Corvette/ZR1Ferrari 360csFerrari 599 GTB/GTOFerrari F430/ScuderiaFerrari 458 ItaliaLamborghini Gallardo/LP560Lamborghini Murcielago/LP640Lexus ISF ??Lexus LFAMercedes Benz McLaren SLRMercedes Benz SL63 AMGMercedes Benz SLS AMGMitsubishi Evo Lancer Evolution/MRNissan GT-RPorsche 911/Carrera/S/GT2Volkswagen GTI/Golf/Rabbit/R32 I got your point about using a LC feature as a rev limiter. MY point, which you're still missing, is that you're NOT preventing damage to a 5EAT by using any sort of LC feature. Your TC is still going to be engaged to the engine, even if you were to use a LC feature to limit the revs. This is why I mentioned the thing about a neutral drop... that is the ONLY way to disengage the TC from your LC. You could have a LC feature limit your RPMs to say.... 2500 (assuming the stall on the TC is high enough) and you could hold your pedal down all the way and the LC would keep it at that rev. But you are STILL putting stress on the TC because it is still engaged! Link to comment Share on other sites More sharing options...
cholmes1 Posted June 8, 2011 Share Posted June 8, 2011 Valid points iNVAR, but our auto trans' (at least 08+) do have clutch packs. The TC is the primary connection, yes, but we do have them and upgrading them is a stronger solution to the 5EAT problems than a higher stall TC. PICS: http://legacygt.com/forums/showpost.php?p=3363968&postcount=1669 You are also correct on the fact that the LC would be placing added strain on the trans just by the very nature of holding revs and not moving, BUT if it were at 2500-2800 which is below our stock stall speed then the ends, in this case consistent launches, would justify the means. Also, a TC does not feel strain as you implied, it is simply a series of spinning fins pushing trans fluid through the VB. The clutch packs are what burn up and the connected drive train bits are what suffer the shudder. A neutral drop, as you cited, would certainly disengage the trans, but that is not a true or consistent LC methodology. You would be taking the full potential of the engine and then slamming it through the TC, clutch packs, VB, axles, driveshaft, etc. By the very nature of fluid there would still be a slight delay compared to a manual clutch setup and you would cause untold damage to the drive train if done with any consistency. As you stated prior... I don't understand how this could even work on a 5EAT. The torque converter has a stall speed. When you hit that stall speed, you will not rev any higher ( why do you think this? The car will not just bounce off the TC stall if that is what you are implying ), not without physically replacing the torque converter... or putting your car into neutral and performing a neutral drop which in our cars would destroy your transmission. The revs that people plan on using here for LC are going to be far above the stock torque converter's stall speed ( Very true, but my inital question and continued discussion is on the basis of consistency ). Yes, it's adjustable, but a stock torque converter's stall speed is usually pretty low... under or around 2000. ( It is closer to 3K around 2850 before creep ) Someone else chime in here please. Maybe I'm completely mistaken here. If I gave you or anyone the impression that a launch of any kind, regardless of the transmission, did not place added strain on components then that was my error and I apologize. I was simply saying that a TC is not a rev limiter as was suggested and should not be used as such. An LC set at 2500 would be below stall, not cause any additional damage than a 'power brake' launch, and would be FAR more consistent in any racing application. I believe this discussion has reached an impasse iNVAR. I appreciate the links you provided above and will continue to search for a launch solution. If I come upon one I will be happy to return with my findings. Best, C.H. Link to comment Share on other sites More sharing options...
iNVAR Posted June 8, 2011 Share Posted June 8, 2011 I know they have clutch packs, but it's not the same function as a traditional clutch. I believe all of those cars in the list have the ability to completely disconnect the engine from the drivetrain through the use of a clutch system. (e.g. DSG) Again, I could be mistaken. I don't understand how this could even work on a 5EAT. The torque converter has a stall speed. When you hit that stall speed, you will not rev any higher ( why do you think this? The car will not just bounce off the TC stall if that is what you are implying )My last car was an automatic, but a very old one from 1990. When you held the brake down and floored the gas, the revs would jump to about 2500 and hold steady there until backing off the gas or releasing the brake. Link to comment Share on other sites More sharing options...
YN-TGL Posted June 8, 2011 Share Posted June 8, 2011 Bump for an answer from the gentlemen at COBB... What about if I have a protuned map? Can I add this feature or would I need to get a new tune and have the tuner use an updated base map to tune from. TIA Link to comment Share on other sites More sharing options...
COBB Tuning Posted June 8, 2011 Author Share Posted June 8, 2011 Bump for an answer from the gentlemen at COBB... Check out the "protuned map conversion" web form described in the first post of this thread. You'll be able to convert your protuned map (assuming you have a manual transmission). Bill Link to comment Share on other sites More sharing options...
YN-TGL Posted June 8, 2011 Share Posted June 8, 2011 Yes, 5MT here. I'll look into it, thanks man. Link to comment Share on other sites More sharing options...
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