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Messages posted by: subgenius
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thanks again. i'd just like to clarify that the 2400rpm stall speed of the "hemi 5.7" that i reported earlier was actually an aftermarket TC. based upon feedback from a knowledgeable/reliable source, it appears the stock stall speed of the 07+ hemi 5.7l TC is in the neighboorhood of 1700-1800rpm. the best estimates by a few people on lostkjs indicates that the stock stall speed (flash stall) is somewhere around 2200rpm.

i guess now the question becomes what would be the best stall speed for the CRD. as you are aware there is a 20+ page thread on lostkjs discussing the issue. just brainstorming on the issue, it would seem that you would want a sufficient amount of "slip" to allow the turbo to spool quick, or have a good compromise between rpm and load in order to spool fast. on the other hand, ideally you would want full lock at peak tq. aftermarket manufacturers blanketly suggest a stall speed 500-700rpm lower than the stock TC for diesel engines. so given the fact that the engine supposedly peaks at 1800rpm (supposedly because we are using reference material from the POS stock TC), we would want full lock at 1800rpm. ergo, the best solution seems to be the hemi 5.7 TC, or the suncoast if you just have to have the billet case.
great! i hope these questions aren't coming across as being flippant. hopefully they will be beneficial to other customers as your company grows.

what would you suggest for optimal torque converter stall speed? some have suggested going with a 5.7l hemi TC with a stall speed of ~2400 (IMO far too high for the crd), others have suggested a suncoast TC with user definable stall speed (1500-up), yet still others have suggested the euro unit, which presumably has similar stall speed to the pre-f37 TC.

by the way, do you know the stall speed of the euro tc? i have heard that post f37 stall speed is ~1800, but since peak torque occurs at ~1800rpm, i am guessing it is much later.

thanks again.
i was under the impression that it was the TCU's duty to decide how much to lockup the transmission (how much to let it slip). you make it sound like its the ECU's job. can you only specify full lock for a certain rpm/mph/gear, or is it a table where you can set lock-up points? reason i ask is it would be awesome to lockup in certain gears at certain rpm's in order to help in-town mpg.

can the customer specify what boost he wants? i am thinking more along the lines of setting WOT around a PR of 3 instead of 2.5. i am at a high altitude and would like every last bit i can muster out of the turbo.

i am not sure why you say the best zones for economy. the adiabatic efficiency of the turbo is not proportional to mpg. even if it was, the difference between a PR of 2.5 and 3 is 3%, and from 2.5 to 3.25 is 5%. ok, sure, you might not want to REALLY overdrive the turbo into the PR 3.7 zone in fear of really heating the air up, but certainly the intercooler was designed with a safety factor better than 1. IMO, they had to have oversized it by at least ~10% just for the differences in climates that the liberty would come into contact with.

also, have you guys installed the euro TC? if so, were the results positive?

thanks!
Hello,

I am looking at purchasing either the stage II tune or the "HOT" tune. First, I am wondering, does your tune override (or ignore) signals sent from the TCU to reduce power output / let the transmission slip as is the case with the F37 flash? I am guessing there are two different answers for the two tunes, but I would like your clarification on the matter.

second, and semi-related, will the transmission fully lock in the top gear / low rpm for max economy? or again, is this controlled differently in the two tunes?

also, how do you guys control boost pressure if the vanes are controlled by the vacuum signal? Is their a bleeder type solenoid somewhere in the system?

last question -- what pressure ratio are you guys targeting on the HOT tune? I am hoping for a peak of 3 to really let this thing loose. also, do your fuel timing tables and boost tables have sufficient resolution / range to address higher loads of PR's close to 3? i know you guys are aware but here is the compressor map for others http://www.turbobygarrett.com/turbobygarrett/catelog/Turbochargers/GT20/GT2056_751578_2.htm

Sorry for the rather pointed questions. I come from the open source wrx tuning community and am wondering how many parameters you guys have access to.

Also, if you could provide the PN for the "euro" TC i would appreciate it.
 
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