kj280z Posted December 5, 2005 Share Posted December 5, 2005 Check this out: http://www.sportzmagazine.com/Z_special_GTR_photos.htm I obviously zoomed right in on this part of the article: "According to reports on IGN.com, the GT-R, with tuning and engineering done by the racing experts at Cosworth, is rumored to have a positive-boost turbo system. “This means that the GT-R will never fall into negative boost and, like a supercharger, will always have boost available.†I thought it would be good to have some discussion/speculation about what they're up to... Quote Link to comment Share on other sites More sharing options...
Bernardd Posted December 5, 2005 Share Posted December 5, 2005 vatn? or a twin scroll turbine with a boost controlled bypass ala Tim Z and James Thagard? isn't boost always positive? my turbo has never boosted negatively that i'm aware of. i positively love it on boost that's all the guesses i have. Quote Link to comment Share on other sites More sharing options...
speeder Posted December 5, 2005 Share Posted December 5, 2005 I'm curious as to the definition of "negative boost" also. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted December 5, 2005 Share Posted December 5, 2005 Surge? lol Quote Link to comment Share on other sites More sharing options...
kj280z Posted December 5, 2005 Author Share Posted December 5, 2005 I found the article that they referred to... it's at http://cars.ign.com/articles/659/659646p1.html Seems like pure speculation to me, but just for the heck of it I'll check around to see what I can dig up Quote Link to comment Share on other sites More sharing options...
Guest asad137 Posted December 5, 2005 Share Posted December 5, 2005 vatn? or a twin scroll turbine with a boost controlled bypass ala Tim Z and James Thagard? Word on the street is an electric-assist turbo system. Asad Quote Link to comment Share on other sites More sharing options...
Guest Z Draci Posted December 7, 2005 Share Posted December 7, 2005 Porsche has a turbo with variable turbine geometry. They're still working on the design to fit it into the next 911. I think it's about time that engineers completely eliminated the downsides of turbocharging--lack of throttle response and turbo lag. It's been over 20 years since production road cars were first turbocharged! Quote Link to comment Share on other sites More sharing options...
kj280z Posted December 7, 2005 Author Share Posted December 7, 2005 I think it's about time that engineers completely eliminated the downsides of turbocharging--lack of throttle response and turbo lag. It's been over 20 years since production road cars were first turbocharged! yeah! what he said! Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 7, 2005 Share Posted December 7, 2005 Simple, it's similar to the CART Systems (similar, dammit, SIMILAR!). The GTR has always had ITB's and that plenum has a soft blowoff. If they modulate the plenum bleedoff, keeping the turbo spooled via a separate wastegate you end up with positive boost turbocompressor system. The plenum bleeds off to a minimum flow line based on the surge characteristics of the wheel/turbine, and the most negative pressure you will have is on total drop throttle--and that volume is probably only about 43CC per runner between the throttle plate and the back of the valve (being as close to the head as the ITB's are!). Is this a conspiracy? Someone recently hammered the idea of ITB's in turbocharged service, and "saw no reason for them but bling factor"---he obviously never heard of a positive boost turbo system---but such is par for the course for that site... Follow, Amigo? Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted December 7, 2005 Share Posted December 7, 2005 Tony, I'm curious about this. How do you keep the turbo spooled via a separate wastegate? How would it be driven when you back off? Having throttle bodies in the runners is for improved throttle response (aka, less lag). Great if you go from puttering to racing often. Dave Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted December 7, 2005 Share Posted December 7, 2005 Porsche has a turbo with variable turbine geometry. They're still working on the design to fit it into the next 911. I think it's about time that engineers completely eliminated the downsides of turbocharging--lack of throttle response and turbo lag. It's been over 20 years since production road cars were first turbocharged! Lack of throttle response and turbo lag are the same thing. Its quite easy to eliminate. Use an antilag system and replace your exhaust valves, exhaust manifold, turbocharger regularly. Or, use a VNT turbocharger and replace that regularly as the temperature at which petrol burns reduces the vains to nothing in short order. Aside from that, as Tony mentioned, having the throttle bodies as close to the head has always improved throttle response. Dave Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 8, 2005 Share Posted December 8, 2005 I would disagree that lack of throttle response and lag are the same thing. Lag is a time based phenomenon form application of full throttle to onset of full boost. If driven CORRECTLY a turbo car of modern design will NOT exhibit any noticable lag. But to the question of "how"... You use a turbine that will spool the compressor section at a very low rpm. Oversize your wastegate. Use a computer to control it that senses rate of change on throttle position to positively close wastegate (derivative action) to prespool the turbine (udersized remember). At the SAME TIME, you have another blowoff valve controlled via solenoid to control plenum pressure to whatever the minimum flow of the compressor should be. This is similar to industrial turbocompressors. If you have a VNT turbo, this would be EXCEEDINGLY easy to overfeed the plenum at even idle. You wimply blow off excess boost from the plenum so the compressor doesn't have necessarily a lot of PRESSURE at idle, but TONS of flow. Thie results in an IMMEDIATE pressure response, as you use the same throttle position rate of change derivative action to control the plenum blowoff valve. All that flow translates into pressure when you slam the blowoff shut! I hope that all makes sense. From a control standpoint it's pretty easy to understand. Quote Link to comment Share on other sites More sharing options...
mtcookson Posted December 8, 2005 Share Posted December 8, 2005 i think the term you guys are referring to is boost threshold. that is, how long it takes to see boost when you initially take off. turbo lag is how long it takes for the turbo to spool while in gear (i.e. you are going full throttle get to XXXX rpm, let off the throttle, then get back on the throttle). Quote Link to comment Share on other sites More sharing options...
savageskaterkid Posted December 9, 2005 Share Posted December 9, 2005 Can it be anything like the new VW twincharger plan. VW is comming out with a new engine design that will come stock on one of there euro cars. For low rpm it has the supercharger pushing air in the engine, and after combustion all the pressure is forced through the exhaust spinning the turbo for high RPM power. Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 9, 2005 Share Posted December 9, 2005 Thankfully you didn't call that VW system "new"! My Suzuki Alto had that back in the 80's! I think several JDM Toyotas have used that style of compound supercharging, too. No, that's not what is being discussed, it's a turbocharger only system that continually has boost on it. Thing is, with the proper VNT turbo you could actually be on boost at idle! Muahahaha! Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted December 9, 2005 Share Posted December 9, 2005 Thing is, with the proper VNT turbo you could actually be on boost at idle! Muahahaha! Yeah, for the two days until the vains burn out. Dave Quote Link to comment Share on other sites More sharing options...
kj280z Posted December 9, 2005 Author Share Posted December 9, 2005 Dave, Do you have any experience with VNT? It's a technology that has always captured my curiosity. I've always thought it would be an awesome evolution of turbocharging applications... Is there more info on the vains you'd like to elaborate on here so we can discuss it further? Quote Link to comment Share on other sites More sharing options...
myplasticegg Posted December 9, 2005 Share Posted December 9, 2005 http://thedodgegarage.com/turbo_vnt_pictures.html Quote Link to comment Share on other sites More sharing options...
mtcookson Posted December 12, 2005 Share Posted December 12, 2005 how about holset's variable geometry system instead of the vane system? http://www.holset.co.uk/files/2_5_1_5-variable%20geometry.php Quote Link to comment Share on other sites More sharing options...
Guest Z Draci Posted December 13, 2005 Share Posted December 13, 2005 Here is the article about the Porsche turbo. Quote Link to comment Share on other sites More sharing options...
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