| efficiency should be -- I don't have the knowledge or experience to answer that. But the "vagueness" in Garrrett response has prompted me to search for more answers. This is interesting -not sure how correct it is- taken from Turbo Limits Almost all turbo compressor designs are designed to safely run at
2.6-2.8 pressure ratios for long periods at or near the mass-flow rating of
the unit. ---
"Remember, too, the amounts of time we are spending at these boost
levels. Maybe 10 seconds per 1/4 mile if it is a really good run. If we are
on the highway and decide to play around with the limits of the vehicle,
30-45 seconds if the road is really clear. Consider how many seconds/day
you spend _above 15 psi_ and I bet the time doesn't amount to much over the
course of a year. Even at 45 seconds/day, we are talking about 4.5 hours
per year above 15psi (and even then we are within the design spec of the
compressor as long as the above limits are observed). Road racing is
another issue, where a substantial amount of time is spent at max boost, as
a result they replace their turbos on a regular basis.
Let's talk efficiency: Even a 100% efficient compressor will heat
the intake air by the very process of compression. The most efficient
automotive turbocharger commercially available peaks at about 78%
efficiency, and most really good auto turbos peak out at about 72-75%.
Peaks of 65%-70% are still pretty good, and most compressor maps are drawn
out down to about 50% efficiency. The compressor still functions well as
the efficiency goes down below 50%, the air just gets heated a _lot_ more
and is less dense than it would be if the unit were more efficient.
Even when the compressor is 100% efficient, at 15+psi an
intercooler is necessary to keep intake charge temperatures below
preignition (detonation) levels. Once an intercooler has been added, its
efficiency far outweighs that of the turbocharger compressor in terms of
relative importance." ---
and more info from the Ztechz site Basically it says :
"
JWT BB-700: aka disco potato by JWT is a 62 trim, .86 a/r Garrett GT28RS turbo.
31LB/Min or 448cfm @ 2PR @ 72% efficiency.
37LB/Min or 535cfm max flow @ 25psi.
30psi max boost limited by compressor wheel speed. " I think based on what Greg is saying and Garrett is saying --that power can be made at higher than 23PSI levels , but u shorten the turbo life ...which I think is the same thing Ash was saying -- "u have to pay to play" And the part mentioned above about road racing kinda speaks to the post the other day by "I forget" about why u tuned it down for road racing conditions ... I think it is starting to sink in .. if I just can jut figure out what the desired max efficiency is .. I'll be straight .. It seems to me after 2.5 pressure ratio is it more based on intercooler efficiency than turbo efficiency ( someone correct me if I am wrong ) -- water injection and large intercoolers would have a large effect on that --more so than race gas ???? so I dare say that --we all were a little correct and maybe a little incorrect - even Garrett ??? What am I missing here ? I am not an expert -- so correct my thinking someone if I am offbase here !!!
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" .. going back and forth with you on a stupid point is like watching a retarded kid double dribble in basketball, you get tired of calling foul all day" ... Slowninja(GT28RS Inconel Z) on October 03, 2005 at 8:43 AM "the only chips you know about are Doritos. =)" ...ZEngineer on June 11, 2005 at 4:23 PM "....These posts only serve to make you look even worse, its gotten so bad it even makes me look bad to reply to you...." maglito on January 22, 2005 at 3:11 AM "What, are you afraid that only a couple of good ones have rolled off the production lines and the rest are crap?? ... Its mechanics not the stockmarket." ... ZisLuv on May 03, 2004 at 6:12 PM Z32 Power.Com Dyno Z Post 1 Z Post 2 My Project Z View Me! |
