Gazboy Posted November 16, 2006 Share Posted November 16, 2006 Blowing the paper ball is not very comparable, is it? Also remember that lag is only measured over the boost threshold. Just using it as an illistration. Quote Link to comment Share on other sites More sharing options...
Gazboy Posted November 16, 2006 Share Posted November 16, 2006 Gaz, this 2 vs 1 argument has been around for years. It is based on the incorrect assumption that the 'big' turbo will be twice as big as any of the 'small' ones. The argument goes that inertia forces in centrifugal assemblies tend to increase by the square/cube of diameter, so the 'big' turbo that is twice as big will have to overcome resistance that is 4/8 times as much, hence the disproportionately larger lag. In real life it ain't so because other manufacturing parameters get in the equation. Also a turbo that is twice as big will flow a lot more than the two 'half' turbos, so the comparison is flawed anyway;) So, to answer why Nissan fitted the GTR with twins... Quote Link to comment Share on other sites More sharing options...
M4RK RZ Posted November 16, 2006 Share Posted November 16, 2006 I understand what you mean by the assumption of one larger turbo being twice the size of the small ones. So let me ask a simple one, TT supra/stock turbos - Single turbo supra - with a comparable compression output to the twin turbo on full tilt. on the line - ready to set off - which is the fav? - the twin turbo must be off and gone first!? Quote Link to comment Share on other sites More sharing options...
bondango Posted November 16, 2006 Share Posted November 16, 2006 Dont forget toyotas turbo design principals have changed too....take for instance The twin-turbo 1JZ-GTE. it was rated at around 280 hp at 6200 rpm. On the newer model 1jzgte (with VVT-i) Toyota dropped the twin setup and went single turbo. which produced well more than 300 hp andTorque was rated at 268 ft·lbf at 4800 rpm. Quote Link to comment Share on other sites More sharing options...
Chiefgroover Posted November 16, 2006 Share Posted November 16, 2006 How about a well built short motor with all the right bits, 264 cams, this seq. setup and an 8000rpm red line. Thats 6000rpm window of boost, thats gotta be NICE to drive. Quote Link to comment Share on other sites More sharing options...
Wez Posted November 16, 2006 Share Posted November 16, 2006 So let me ask a simple one, TT supra/stock turbos - Single turbo supra - with a comparable compression output to the twin turbo on full tilt. on the line - ready to set off - which is the fav? - the twin turbo must be off and gone first!? Its already been shown that a well setup single can spool just as good if not better than a bpu stock tubbied motor. Whats the argument here Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted November 16, 2006 Share Posted November 16, 2006 I understand what you mean by the assumption of one larger turbo being twice the size of the small ones. So let me ask a simple one, TT supra/stock turbos - Single turbo supra - with a comparable compression output to the twin turbo on full tilt. on the line - ready to set off - which is the fav? - the twin turbo must be off and gone first!? Terry S's black car was making positive boost before 1500rpm, and full boost before 3000. Thats much quicker/more power than the sequentials can produce, not to mention that the single could reliably carry on up to 1.6 bar before coming out of its efficiency range. Edited: Doh! Replied before reading Wez's reply Quote Link to comment Share on other sites More sharing options...
M4RK RZ Posted November 16, 2006 Share Posted November 16, 2006 Its already been shown that a well setup single can spool just as good if not better than a bpu stock tubbied motor. Whats the argument here there is no argument, im trying to learn something here I must had missed the post clarifying what you just stated ''Don't fall for the theory that two smaller turbos have less lag than a big one. This argument is flawed, and it usually comes from the same people who advocate that a big intercooler will increase lag'' thats what im trying to get my head round !! Quote Link to comment Share on other sites More sharing options...
Wez Posted November 16, 2006 Share Posted November 16, 2006 Post 39 in this thread shows BPU vs Single clearly. http://www.mkivsupra.net/vbb/showpost.php?p=1088949&postcount=39 Quote Link to comment Share on other sites More sharing options...
Chiefgroover Posted November 16, 2006 Share Posted November 16, 2006 Anyone seen or heard from Terry S recently? Quote Link to comment Share on other sites More sharing options...
Wez Posted November 16, 2006 Share Posted November 16, 2006 Anyone seen or heard from Terry S recently? I heard he was really busy with work, although he does still pop on here occasionally. Quote Link to comment Share on other sites More sharing options...
Gazboy Posted November 16, 2006 Share Posted November 16, 2006 Anyone seen or heard from Terry S recently? Yeah, he's snowed under with work I believe. Edit- sorry, didn't see Wez's comment. Quote Link to comment Share on other sites More sharing options...
JohnA Posted November 17, 2006 Share Posted November 17, 2006 Terry S's black car was making positive boost before 1500rpm, and full boost before 3000. Thats much quicker/more power than the sequentials can produce, not to mention that the single could reliably carry on up to 1.6 bar before coming out of its efficiency range. ...and I bet that it was from a later design generation than the CT12 units;) ... As you know there are several factors involved when manipulating boost threshold/lag/off-boost response in general. Also the design briefs can be different: OEMs would tend to play it very safe with ignition advance for example, while a one-off can be mapped under the assumption of a minimum fuel quality. Toyota did a good job out of squeezing the maximum out of the turbocharger technology they had at the time, and creating a very flat torque curve as well. Let's not forget that while this is good for driveability, it makes the car feel bland and uneventful. An enthusiast's car is unlikely to have a flat torque curve, isn't it? Quote Link to comment Share on other sites More sharing options...
Wez Posted November 17, 2006 Share Posted November 17, 2006 Toyota did a good job out of squeezing the maximum out of the turbocharger technology they had at the time, and creating a very flat torque curve as well. How is the torque flat when the 2nd turbo comes online at 4000rpm, that is not giving it a smooth drive, unpredictable sounds closer. Quote Link to comment Share on other sites More sharing options...
JohnA Posted November 17, 2006 Share Posted November 17, 2006 http://www.max-boost.co.uk/stuff/supra/2JZGTE_powergraph.gif Quote Link to comment Share on other sites More sharing options...
Ark Posted November 17, 2006 Share Posted November 17, 2006 How is the torque flat when the 2nd turbo comes online at 4000rpm, that is not giving it a smooth drive, unpredictable sounds closer. How can it be unpredictable if you know it's about to kick in? Quote Link to comment Share on other sites More sharing options...
Wez Posted November 17, 2006 Share Posted November 17, 2006 That does not look like any torque curves I have seen from stock tubbied cars. Quote Link to comment Share on other sites More sharing options...
Wez Posted November 17, 2006 Share Posted November 17, 2006 Well my second turbo had a mind of its own, depending where you were in the rev range sometimes it came online sometimes it didnt. This did improve when running the AEM though. Quote Link to comment Share on other sites More sharing options...
JohnA Posted November 17, 2006 Share Posted November 17, 2006 That does not look like any torque curves I have seen from stock tubbied cars. It looks very similar to mine when it was stock. It also felt flat as feck. Uninspiring. Quote Link to comment Share on other sites More sharing options...
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