OK I know this is long, but its worth it! its a thrill a minute! 
Well, I get frustrated when people insist something is the ultimate de-facto standard, when it clearly is not, and many more factors are involved; so, here goes
CV6MTX said:
BTW...your wonderful VATN turbo...you speak of it as if it's great, but how come all I keep hearing about them is they are very limited in power making ability, and they break very often. Also, have a short live even if taken care of...sounds wonderful
Hmm, limited power making ability, could it be because aerodyne doesn't make any extremely large turbos? The largest single unit they make is rated for 540cfm. This company concentrates on Motorcycles and snowmobiles for crying out loud. This in no way limits the potential of a larger size of VATN turbo. Durability? do you have any data to support your claim that they aren't reliable? Aerodyne claims they have run them reliably over 100k miles, also w/ 1000 hour endurance runs, and a design life of 5k hours. I bet they could back that up with data, could you back up your failure claims? Prolly not with much more than "There was this guy, that told me his aerocharger didn't work very good, so they suck."
Oh well...I'll leave quietly. Cause i's worthless to continue. If you care I used to work for BMW, so my car knowledge is not short lived. My engine builder is a Ford Engineer I met. So, before you start saying things, think first please. That's all I ask.
You're giving up??? why? why is it worthless to continue? "Iron sharpeneth iron. . ." as long as tempers don't flare, its all good. Is your engine builder still a Ford engineer? what did he do there? As to thinking first, I whole heartedly agree, and would ask the same. On a message board such as this, we have many people that have little knowledge of cars, and come here for advice; problem is, we do have many people that will make a statement out of ignorance, or many other reasons, and mislead someone just trying to learn. (perhaps my ignorant statement was somewhat uncalled for, but I wholeheartedly stand by the stubborn comment) btw, what did you do w/ BMW?
Overview...On the duratec, in the cpntour/cougar engine bay...it'll be more optimal, cheaper, easier, in general better to use a single turbo then a twin setup, unless sequential twins could be made. Using a nice T3 Super 60 which will reach max boost at around 3000...that allows for a great ability to launch, and minimal lag if you launch from a dead stop.
I have no doubt that a good single turbo can be setup for a contique/cougar, that was never in question. The real difficulty in a TT for this application is packaging, a single could probably be done much easier in that regard. The Duratech, especially the SVT variant, lays right on the threshold of where a twin can show benefits over a single (Bell puts this threshold at around 300cfm, ironically, the ideal flow of an N/A 2.5L engine)
There are very few cases where twin turbos will be the better, optimal, cheaper, etc apporach, since the twin turbo idea is a very old one.
I beg to differ, twin turbo systems often offer a better balance throughout the rev range over a larger single turbo. Many OEMs seem to believe this as well, including vaunted automakers such as Porshe, and Ferrari. Again, I hold that it depends more on the application, its use, and the equipment being considered, than a stubborn belief that a single turbo is always better than two (or more for that matter)
It's ok if you disagree with me, but you don;t have to attack me personally. I'm not making any on this up...it's coming from years of research...
Thanks for the ok on disagreeing
Seriously though, I did not attack you personally, nor did I see anyone else attack you. While my "ignorant" comment may have been shortsighted, stubborn and blind still apply, and are in no way a personal attack, but more of a commentary on my view of your stubborn stand that a single turbo is always better. As an automotive engineer myself, I enjoy debating subjects such as this, and many times a discussion like this comes up, and people make claims they cannot back up, or will not back up. When a good-natured, but thourough discussion/debate occurs, truth is often found, and all the parties involved can learn great things. Just don't let things get ill-tempered (darn those moderators! :D)
on to DemonSVT
Most of the time, yes it does (occasionally, peak efficiency is not a prime concern, but we aren't talking about that)
I thought we both agreed a single turbo setup was more efficient???
but where does a particular turbo's efficiency lie? It depends on the PR and flow for a given turbocharger, not on whether there is one or two of them.
BigProbe's turn
Less heat...less complexity.
Less heat? where? in the intake charge? that depends on the compressor efficiency of the particular turbo (which, as I said above, depends on the PR and flow of the turbo, not how many turbo's there are) Less complexity? most of the time yes, but not always; sometimes exhaust piping to put a single turbo on a V or Flat engine can be pretty crazy.
The subject of Lag has been brought up a bit. . .if I hit my 8psi at 1500 rpms
you aren't describing lag here, but boost threshold. lag relates to a delay in boost response on throttle tip-in at an rpm above the boost threshold. Boost threshold is the lowest engine rpm where boost becomes positive at WOT.
Also mentioned was the "blow 8psi thru a straw!" etc. That is the argument that I used to take. But we are not pressurizing the piping, we are pressurizing a small paint jar at the end of the straw...in that jar, to pressurize it to 8psi (over atomospheric pressure), it would take the same amount of air volume, regardless of what is supplying the air (t25 or t88). The issue is, the larger blower will be working MUCH easier to do it.
You are somewhat correct here. the actual boost pressure is the RESISTANCE to the incoming air charge from the turbo, and if more air volume is forced at the same resistance, the boost pressure will increase.
BUT,I am still not at all clear on how a larger compressor will be working MUCH easier to do it; Like I have said twice before, the efficiency is based on the PR (pressure ratio) and the airflow for a particular compressor rather than the number of compressors involved.
Its mostly for that reason a single turbo will out-perform twins, in most applications....in order to keep the pressure up, the twins will be working much harder (read: hotter?) to provide similar gains. Not to mention, most turbos small enough to work would be way out of breath as you reach the top of the powerband.
Well, since I have already shown that your logic is flawed I won't say much here; except that, a properly sized twin setup will not run out of breath before the rpm the designer intended it to run up to. Remember, in a twin setup, each turbo only needs to flow HALF as much air as a single for the same setup.
-Show me one of the Pro-Import guys using twin turbos?
Umm, show me one that is larger than 3L and/or not an inline engine that is concerned about anything other than Peak hp numbers. Come on, most of these guys choose front wheel drive as the configuration of choice for drag racing! It isn't always about what is ideal with them.
show me one 700hp+ TT supra?
Again, not many 700hp+ Supras that are concerned about more than peak hp numbers.
How about the road racing Skylines? Most of them retain a twin setup for even high hp cars because they are concerned about a setup that is USABLE, not just a dyno queen or a drag strip wonder.
If a guy here wants to turbo his contour, use a well-designed SINGLE turbo set up. A single turbo set up will be cheaper, more simple, and out peform a tt set up in 9 out of 10 cases.
If I were turbo-ing my contour (I may someday, but the Cobra is going first) I would honestly pursue a single turbo setup, but to say it would be cheaper no matter what is a little shortsighted. Simpler? More than likely, yes. Out perform? it would depend on a lot more than the # of turbos to determine this one, and I bet a TT could win more than 10% of the cases
