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Upgrading from stock twins and onset of lag

480 Views 2 Replies 3 Participants Last post by  BLKMGK
Upgrading from stock twins to a small single,large single and larrge twin setup , could someone give examples of the rpm delay in attaining full boost. How much does one realy loose in response by going bigger than say an Sp63. If the response is so quick how can people tolerate the increased lag of a big single or Hks twin setup. I'm looking for mainly for a streeable setup about 85% street with some occasional autocrossing. I would really like The high power that a larger setup would afford me but I don't want to lose too much down low. By the same token it would be sad to lose too so much down low that I might be concerned about losing anything from a stop to a 20mph roll. What I would need is a comparison of the spool charactaristics of small and large singles and twins. What do the more experienced board members think would be a good comprimise. Comments please
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this is my opinion, and ive never driven nor even rode in an upgraded turbo supra, but im sure i can speak for most everyone here who has upgraded turbos. once the boost hits on upg turbos, it more than compensates for the increased lag. have you seen videos of supras running upg turbos?? watch the rpm gauge in the upper gears, see how fast they reach the redline mark, then watch your own car, and see how long it takes to redline..... remember when 2nd gear almost flew to redline in notime at wot??? imagine that in say 4th and 5th gears....

I've noticed that tooling around town I can get boost on stock twins as early as 2K right off of idle. Some of the timings that one of the guys here has done start at 2K and goto 3K with boost at 3K reported. He's done the same in the 3K to 4K range with full boost hitting by 4K on his particular setup and he's had several. He does this in multiple gears - I wish others would too please. I don't recall his name off the top of my head - Steve I think and he posts to the big list too. Look through some of the "first impression" posts and you'll probably find his posts or get a good idea from others. Steve(?) posted good information and documented things with a peak\hold boost gauge - it's invaluable information. Once the turbo spools up it reaches your set boost level quickly and by 4500RPM on most streetable setups you're flat out flying. A boost controller that can keep boost lower depending upon your gearing sounds like a better and better idea :)

I've got stock twins now but intend to upgrade to a single as soon as finances and supporting prep allows. I'll probably go smallish on the turbo knowing that I can always swap out the turbo itself for more power since the support for bigger numbers will already be there. Plan and build with an eye towards where you might want to be and keep the stock twins until the rest is done IMO. FWIW - if you read threads in the dyno perofrmance section you'll get lot's of information about this - it's a FAQ...
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