BLKMGK Posted July 16, 2002 Share Posted July 16, 2002 Check out this guy's ride! Pointed out to me while having a discussion on SupraForums concerning cost effectiveness of doing a Supra vs a ZX TT. http://www.z32.com/readerrides/reader56.htm I was pointing out how much more expensive a TT is to modify vs a Supra since you've got to buy two of everything and have to dive into the engine sooner. Pretty neat! Quote Link to comment Share on other sites More sharing options...
mtcookson Posted August 13, 2002 Share Posted August 13, 2002 i thought the supras that were turbo (the last gen that was in the us) were twin turbo. i thought most of them jsut converted it over to single. if i ever got a TTZ i would do the same and just make it a single. Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted August 14, 2002 Author Share Posted August 14, 2002 Not that simple - the later Zs are a V type motor and to go "single" requires a great deal more plumbing than it does on the Supra which is a straight six with all of the exhaust ports on one side.... Some have done singles on the ZTT but not many it would seem. Quote Link to comment Share on other sites More sharing options...
mtcookson Posted August 16, 2002 Share Posted August 16, 2002 it shouldn't be that bad considering the earlier 300zx's wre v6 with a single turbo. you just have to have some crossover pipes and stuff. definately not as easy and efficient as an I6 but it would definately be better price wise. Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted August 17, 2002 Author Share Posted August 17, 2002 Umm, previous Zs being single has nothing to do with making the later ones single. Early ones were like the Supra - straight six. Doing a single on a V6 is a bit harder. The GNs did it but take a peek at the plumbing involved.... Quote Link to comment Share on other sites More sharing options...
Bob_H Posted August 18, 2002 Share Posted August 18, 2002 BLKMGK, The previous post was talking about the mid-late 80's 300zx's which were all V-6 motors and the turbo 300zx's,(talking about Z31 cars), were single turbos on a V6. And yes, the piping and such was a chore, but there are people out there who have gotten 400+ hp to the wheels with that setup. It is not cheap though. -Bob Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted August 19, 2002 Author Share Posted August 19, 2002 LOL, thought those were L6 too - doh! Talk about a plumbing nightmare - ick! Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 22, 2002 Share Posted August 22, 2002 WHY?!?!?! To this day, it eludes me as to why people dont seem to understand WHY on a V engine two moderatly sized turbo(one for each bank) are more efficiant than one large single turbo. There is a reason road racing cars, like the Audi LMP and other top road racing cars with turbo V engines utlise one turbo per bank...... It is 2:30 AM though, and Ich musse schlaufe, so, I will explain later. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 22, 2002 Share Posted August 22, 2002 Who's talking race cars? Yeah if you run 40 lbs of boost sure thing, but I don't see anyone saying the Buick GN's are inefficient with a single turbo running in the 9's and making over 900 RWHP in a 3500 lb car? Heres the post: http://www.hybridz.org/ubb/ultimatebb.php?ubb=get_topic;f=17;t=000200 Regards, Lone Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted August 22, 2002 Share Posted August 22, 2002 I doubt the single turbo conversion on that ZXTT is cheaper than getting two upgraded turbo's. That is one of the tightest engine bays out there. On the supra, generally, twins make slightly less power than the one single, but the one single takes longer to spool up. So it is sort of a trade off, and you have to decide what you want. I had a friend that had a ZXTT with JWT sport 550 turbo's, and all the supporting mod's, and on pump gas it was a brutal feeling car. It ran thru the gears like a motorcylce does. He ran a 12.5 at 115 or so at the strip with it. BUt he just drove it to the track, and ran it. No adjusting of the boost, no cooldown, no race fuel. Just pump gas with a hot motor on street tires. I think his 1/8th was 8.0 at 91 mph. Pretty impressive times in my opinion. The word on ZXTT's to is to have the exhaust manifolds extrudehoned. Supposed to improve flow by 40 percent. GN's just flat rock. They have good developement people working on them all the time pushing the envelope. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted August 22, 2002 Share Posted August 22, 2002 Just because I like to question commonly-held beliefs, I'd like to challenge the notion twin turbos spool faster than one. You will have half the exhaust flow through each turbo, and what I've read (sorry, this is theoretical, not actual and tested) says the turbine speed is proportional to the square of the flow. So a large single turbo has a larger wheel requiring more exhaust flow to spin at the same speed, but it has twice the exhaust available, and should be able to spin faster, or push more than twice the intake charge over what a twin can flow with less turbine speed. From the same source (Maximum Boost), Corky also states the turbine acceleration is proportional to the cube of the exhaust flow, so for a large single turbo with greater inertia, but twice the exhaust flow, it will still spool faster provided it has less than 6x the inertia of a small twin. That's my limited understanding of how I think this stuff works, but I'm sure I'm missing some insight, having no practical experience. Feel free to flame - I am always interested in learning more about this subject. [FLAME SUIT ON] The only reason they put twins on the Z32 was the tight engine bay and plumbing nightmares from routing a single. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted August 22, 2002 Share Posted August 22, 2002 No real reason to flame. Turbo's come in all different sizes. Obviously one BIG turbo should spool up faster than 2 BIG turbos. But the same cannot be said for 1 BIG turbo vs. 2 small turbo's. The early turbo Porsche 911's had a large turbo taht was set up for max top end power. That also meant you really had to get some exhaust flowing to generate boost. Massive turbo lag. From what I have read (since I have yet to own such a car) the early turbo 911's took a definite touch to drive well. Letting off the gas mid turn would put you in the ditch because the turbo would still be kicking out max boost. If you have two smaller turbos set up in a progressive arrangement, then you can have one pumping up max boost in the mid RPM band and a second open up for the upper RPM's. Quote Link to comment Share on other sites More sharing options...
Guest brad Posted August 22, 2002 Share Posted August 22, 2002 ---------------------- Just because I like to question commonly-held beliefs, I'd like to challenge the notion twin turbos spool faster than one. You will have half the exhaust flow through each turbo, and what I've read (sorry, this is theoretical, not actual and tested) says the turbine speed is proportional to the square of the flow. So a large single turbo has a larger wheel requiring more exhaust flow to spin at the same speed, but it has twice the exhaust available, and should be able to spin faster, or push more than twice the intake charge over what a twin can flow with less turbine speed. From the same source (Maximum Boost), Corky also states the turbine acceleration is proportional to the cube of the exhaust flow, so for a large single turbo with greater inertia, but twice the exhaust flow, it will still spool faster provided it has less than 6x the inertia of a small twin. That's my limited understanding of how I think this stuff works, but I'm sure I'm missing some insight, having no practical experience. Feel free to flame - I am always interested in learning more about this subject. [FLAME SUIT ON] The only reason they put twins on the Z32 was the tight engine bay and plumbing nightmares from routing a single. --------------------- There are a number of reasons they went with the twin setup. The plumbing is one of them. Also, emissions can be quite an obstacle on turbocharged cars. The key to reducing start-up emissions is getting the cat. converter hot as soon as possible. The best way to do that is to put it as close to the engine as possible. Putting a turbo in between the cat and the explosion really hurts warm-up time. The larger and more massive the turbo, the longer the warm-up time. Keep in mind that boost lag is related to flow characteristics and backpressure. The number of items to consider when comparing lag between a twin setup and a single setup is enormous. Money can overcome many problems, but as a general rule, you can assume a smaller turbo will spool up faster but be able to produce less maximum boost than a larger turbo. I don't have Bell's book handy, but that formula you reference must use a variable to modify the exhaust flow (hence the "proportional" part). That variable is not a universal constant; it will change based on the parameters of each individual system. A larger turbo will generally need larger bearings, a larger shaft, must be placed farther downstream, etc. All of that would yield a numerically lower variable. Friction and inertia are enemies of a quick spool-up time, so bigger ain't usually better when it comes to helping with boost lag. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted August 22, 2002 Share Posted August 22, 2002 Inertia and size affect turbo spool up time, but so does the design of the impeller. The exhaust turbine is definitely built with a certain exhaust flow in mind. Thus a turo for a Kenworth may produce nothing in the way of boost for an idling Z car engine. Similarly, a Z turbo may be maxed out by an idling Kenworth. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted August 23, 2002 Share Posted August 23, 2002 I think some of my point was missed. Obviously a small turbo will spool faster than a large one with the same exhaust flow. But when you deprive the small turbo of half the exhaust, the reading and physics I understand dictates that the small turbos will spool slower. This is because half the exhaust will not result in half the turbo output, it will result in one fourth the turbo output. Quote Link to comment Share on other sites More sharing options...
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