fattymcgee Posted February 23, 2012 Share Posted February 23, 2012 I have seen people cut the bottom row of the RT table, which closes the throttle body part way above XXXX rpm. I like your boost target approach a little better--in theory--because it keeps the requested torque value high. The TCU reads the RT value, so you want it to be as high as possible (on AT cars). You would time the drop for around 6475 rpm or so. Not a bad idea. Turbo will spool right back up when the RPMs drop, so that's not an issue. It might hit max boost again before the shift is even over. It's standard issue with Cobb ATR. I have not directly compared the logged timing drops to logged EGT from aftermarket gauge, but it would be very nice to publish that data for the benefit of all 5EAT tuners/owners. Yes, it has been done on turbo cars, and it has been discussed many places on the net. I have seen a before/after dyno of a R34 or so showing the curve shifting left by around 1000rpm. The Subi crowd hasn't jumped on that wagon, otherwise I bet it would be done by many. The wiring is easy, just use basic open or closed switching with a couple of the aforementioned sensor switches in series. The cost is around $750 to do it, but you can easily spend double if you want. Plus tank fills. If people truly cared about shifting the curve left significantly, they would do it. Thus it must not be too big of a driveability problem for most. It's amusing, people use spark cut antilag probably more than nitrous spool assist, probably because it went mainstream. Yet big boom in exhaust is known to be hell on those parts (namely the turbine). Just goes to show the importance of what is "in" when someone makes an upgrade decision. I personally am 'downgrading' from TD06-20G to VF37-PE1825 twinscroll. Boost threshold should not be a problem anymore. I don't like my 20G on city streets. Check you pm's. I need to pay for the VB mod so it can be sent ASAP. Link to comment Share on other sites More sharing options...
05COLEGGT Posted February 24, 2012 Share Posted February 24, 2012 Porting your exhaust manifolds, crosspipe, uppipe and turbine inlet are easy free ways to help get more gas into the turbine which will help it spool earlier. Link to comment Share on other sites More sharing options...
ClimberDHexMods Posted February 24, 2012 Share Posted February 24, 2012 Porting your exhaust manifolds, crosspipe, uppipe and turbine inlet are easy free ways to help get more gas into the turbine which will help it spool earlier. You may be right, but there are some very knowledgeable members here and elsewhere who say the difference is minimal or sometimes even a little counterproductive. I'm not looking to start a big debate on porting, just saying it's a very big to-do in the car enthusiast world, to the extent it may well be overdone in many instances. [CENTER][B][I] Front Limited Slip Racing Differentials for the 5EAT now available for $1895 shipped, please inquire for details! [/I][/B][/CENTER] Link to comment Share on other sites More sharing options...
Mega Users seabass07 Posted February 24, 2012 Mega Users Share Posted February 24, 2012 Funny thing is, I have a friend with a TD06SL2-20G 8cm2 on ELH and a lighter car, not even trying a 4D spool strategy, and he still sees full spool at 3k6... I didn't see ELH listed in his mods. That might be the way to go. Link to comment Share on other sites More sharing options...
bmx045 Posted February 24, 2012 Author Share Posted February 24, 2012 oem headers help with quicker spool but leave a little bit to be had on the top end... Link to comment Share on other sites More sharing options...
fahr_side Posted February 25, 2012 Share Posted February 25, 2012 I didn't see ELH listed in his mods. That might be the way to go. I mention that my friend's car has ELH precisely because OP doesn't, and ELH is generally accepted to slow spool (especially if cold) while improving top-end. My friend's car still spools a full 1,000rpm before OP's, and I'm sure changing the manifold out will only make it worse. Case in point; I have tuned two '08 STis, both with stock fuel, intake and turbo. Both have full TBE and 3-port BCS. One has an ELH and the other the stock manifolds. The ELH car spools about 400rpm after the other no matter how I tweak the tune, and I can barely come up with a difference at top-end with the same boost curve... 3g/s maybe. That difference would however be more obvious with a turbo that doesn't fall on it's face past 5k5 rpm... Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs. Link to comment Share on other sites More sharing options...
ClimberDHexMods Posted February 25, 2012 Share Posted February 25, 2012 I too had late spool with ELH. But man did it make the car quieter Geoff at full race uses primaries somewhere in the 1.4X" ID range. I have it written down somewhere. Much smaller than most, yet can make excellent top end. I bet the tubes volume and material thickness has a lot to do with it. JDM Spec Cs are twinscroll ELH. I have a kit in the garage. Speaking of quicker spool, there is also afterburner nitrous. The guy on the net and YouTube with the 3.8L and S510 (BIG turbo) uses two stage, where first shot of wet nitrous is intake manifold, used largely for EGT. The second wet shot is at the turbine inlet. Hits the extra heat, combusts, spools up the S510 before the car is even launched. Its kibd of a big deal Only done for brief periods of time and is a small shot. Sounds very effective if great care is taken to isolate the wet supply from the exhaust heat. Probably not the best DD idea. But if no one is willing to do a basic nitrous shot, then no one is going to do the advanced. [CENTER][B][I] Front Limited Slip Racing Differentials for the 5EAT now available for $1895 shipped, please inquire for details! [/I][/B][/CENTER] Link to comment Share on other sites More sharing options...
ericem Posted February 25, 2012 Share Posted February 25, 2012 should have left the stock headers and you have the boost tapering for the auto anyway so why the need for the tiny top end increase. Link to comment Share on other sites More sharing options...
ClimberDHexMods Posted February 25, 2012 Share Posted February 25, 2012 He has stock headers... a 20G isn't a small increase, at least it doesn't feel small. On MT it can do 330 pump / 395 E85, WHP. The taper is not like what tuners do normally across the powerband especially with smaller turbos. It would only be done for a brief moment to help the longevity of his transmission (though even at 15psi on a 20G a stock 5eat will not shift nicely for long). He has it handled. [CENTER][B][I] Front Limited Slip Racing Differentials for the 5EAT now available for $1895 shipped, please inquire for details! [/I][/B][/CENTER] Link to comment Share on other sites More sharing options...
bmx045 Posted February 26, 2012 Author Share Posted February 26, 2012 it cuts to wg boost starting at 6k, it just happens to be 16psi with 0 wgdc, lol. either way i let off once it does that and manually shift to 4th then get on it again. we will remove this once the vb mod comes so it will hold 20psi throughout the gears. Link to comment Share on other sites More sharing options...
ericem Posted February 26, 2012 Share Posted February 26, 2012 oh i thought you had el headers you said when i meant top end comparison was not talking about the 20 g haha. Link to comment Share on other sites More sharing options...
ChefRacer Posted February 26, 2012 Share Posted February 26, 2012 Why doesn't anybody mention relocating the turbo to the 5th gen location. With 5th gen headers, custom oil/coolant lines and maybe spal fans to make room, it should increase spool time drastically and increase the effectiveness of a tmic at the same time. Link to comment Share on other sites More sharing options...
Mega Users seabass07 Posted February 26, 2012 Mega Users Share Posted February 26, 2012 It will be part 5th gen though. Not worth it. Link to comment Share on other sites More sharing options...
ChefRacer Posted February 26, 2012 Share Posted February 26, 2012 Who cares if its part 5th gen, I thought the whole point was to make the car as fast and efficient as it can be. That was the general creedo for the DSM crowd and I joined the Subaru b/c I thought that it seemed very much the same (even if subaru guys seem a bit more obsessed with looks) Link to comment Share on other sites More sharing options...
ChefRacer Posted February 26, 2012 Share Posted February 26, 2012 If anybody made a hybrid 4th gen/5th gen system that would give me pre turbo exhaust headers similar to every other factory turbo setup that isn't subaru, hence less than 3 feet of exhaust manifold piping before the turbo, I would be glad to be a guinea pig. Link to comment Share on other sites More sharing options...
fahr_side Posted February 26, 2012 Share Posted February 26, 2012 Why doesn't anybody mention relocating the turbo to the 5th gen location. Pretty drastic step there. While a 5EAT does load the engine differently than the 5MT does, I don't think it can be responsible for 1,000rpm difference in spool. If there are no leaks or other mechanical issues then I think the answer lies in the tune. Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs. Link to comment Share on other sites More sharing options...
ChefRacer Posted February 26, 2012 Share Posted February 26, 2012 I'm not talking about the transmission at all, I'm talking about the way that the turbo was relocated to the front/bottom of the motor in the 5th gen LGTs Link to comment Share on other sites More sharing options...
fahr_side Posted February 26, 2012 Share Posted February 26, 2012 I'm not talking about the transmission at all, I'm talking about the way that the turbo was relocated to the front/bottom of the motor in the 5th gen LGTs I got your point, I just chose to ignore it. Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs. Link to comment Share on other sites More sharing options...
ChefRacer Posted February 26, 2012 Share Posted February 26, 2012 Thanks, I feel the love Link to comment Share on other sites More sharing options...
fahr_side Posted February 26, 2012 Share Posted February 26, 2012 Thanks, I feel the love Get over it! This is the tuning forum eh? Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs. Link to comment Share on other sites More sharing options...
Mega Users seabass07 Posted February 26, 2012 Mega Users Share Posted February 26, 2012 How does the torque converter effect spool? Since the engine will jump to ~3500 rpm, it has to change the way it spools. Anyone have experience with same setups with larger turbos on auto vs manual? Link to comment Share on other sites More sharing options...
fahr_side Posted February 26, 2012 Share Posted February 26, 2012 How does the torque converter effect spool? Since the engine will jump to ~3500 rpm, it has to change the way it spools. Anyone have experience with same setups with larger turbos on auto vs manual? Simple. While the converter is slipping and grudgingly allowing revs to climb it's not presenting that much load to the engine or (indirectly) to the turbine. Remember how the bigger turbos with higher boost threshold show a bigger difference in boost threshold between gears (on manual cars) than the smaller ones do? The answer back in the day for the 4EAT bugeye guys was a high-stall converter. Take a look at this FXT pull with similar mods to the OP but with the addition of a high-stall converter. I know a lot of people with only a TD05H-18G on a 4EAT FXT that cannot stand the gap between the converter stall and spool point, it's horrible in traffic. This dead-spot can however be improved to a degree by a different approach to the tune. Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs. Link to comment Share on other sites More sharing options...
Mega Users seabass07 Posted February 26, 2012 Mega Users Share Posted February 26, 2012 So it will spool significantly less while the stall speed is pegged than a manual trying to spool the turbo? Im only referring to maybe 2000-3500 rpm on a manual vs when the stall speed is pegged. Link to comment Share on other sites More sharing options...
fahr_side Posted February 26, 2012 Share Posted February 26, 2012 So it will spool significantly less while the stall speed is pegged than a manual trying to spool the turbo? Im only referring to maybe 2000-3500 rpm on a manual vs when the stall speed is pegged. Well, you have to consider total gear ratio really, including the TC factor. If you're in that spot where your vehicle speed is low, converter is not yet stalled, and the load on the vehicle is enough to keep engine revs below the boost threshold of your turbo, then yes you are going to wait a while before much of anything happens. At those sort of engine speeds where the TC hasn't stalled, a manual should be putting more load on the engine and therefore there's more energy in the exhaust to spool the turbine, though this will depend on gear ratios, final drive ratio, vehicle weight etc. This is a really good example of a setup with probably a stock TC plus a large turbo with higher boost threshold. As he goes WOT you can count a lot of time between revs reaching the TC stall-point and boost threshold. It's probably more extreme in every way than what OP is facing, but it's a good example nonetheless. [ame=http://www.youtube.com/watch?v=rmNy-ajRV0U]Supra From Hell - YouTube[/ame] Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs. Link to comment Share on other sites More sharing options...
bmx045 Posted February 26, 2012 Author Share Posted February 26, 2012 I dont even know. Link to comment Share on other sites More sharing options...
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