Contour Enthusiasts Group Archives Forums Modifications Duratec Performance Twin Turbo?

But I corrected my statement, still immature statemets were made....

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.

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.

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...

That's all......

Single turbo will beat twin turbo on most conventional engines.

Efficiency rules.

I thought we both agreed a single turbo setup was more efficient???

I was just refering to Chris pulling out the "Book of Corky" line...

My turbo experience is with early chrysler 2.2's, Garret T3 and T3/4's, and nearly every turbo Mitsubishi has made. Designed and tested many setups.

I have little experience with the variable vane turbos beyond understanding how and why they work & rebuilding a few for the 2.2 R/T engines.

my $.02...speaking as a guy who actually HAS applied forced induction to his 2.5L motor..


My vote, in this application goes for Single Turbo. In fact, in MOST applications.

Here's why...

Less heat...less complexity.

The subject of Lag has been brought up a bit. My answer? "Who cares?". Lag is GOOD for a FWD car...if I hit my 8psi at 1500 rpms, I'd be going thru tires left and right.
As is, with boost coming on ~2000 [How much lower do you want boost, anyway?] and maxing by 3000, my car spools soo fast traction is always a concern. Some of the things you can do to help (reduce) spool time is, use stock exhaust manifolds...MAYBE slight porting, but not much. Its all about heat and velocity to get that sucker moving....A little lag allows the car to get rolling. 1st gear is a joke. I need a much taller 1st gear.

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.

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.

now, for subjective remarks that I cant explain:

-Show me one of the Pro-Import guys using twin turbos?
-As mentioned before, show me one 700hp+ TT supra?

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.

Yes...corky's book Maximum Boost, I assume your speaking of is an excellent book...also find the technical guides from the makers of the turbos and read about what they designed the turbo specifically for, and hpw the designed them...it's kinda cool.

lol... a conversation turned deadly once again.

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:


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."



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?



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)



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)



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)



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? 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.



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.



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.



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.



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.

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 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

Ok well ther is always one good thing about flaming. it sure does bring out soem good details and facts. rara wins the prize for the most quotes ever used. well i think i will do what was said earlyer. i will wait till chris's turbo comes out. the whole idea on the twin was one per manifold. well i think i will go out and by a T25 or some thing nice. and mess with it.

I don't think there has been any flaming at all in this thread! though I am surprised but as a moderator it makes me happy

ahhh...that's the response type I like...

Personally I test drove the BMW's...I have driven many many BMW's...The only one I have not driven is the Z8, as we got one, and the senior techs got to drive it. I have driven many M5's (my favorite), M3's, all of the 3 series, 5 series, 7 series including the 750, nd only one 8 series since they no longer make it, and all Z3's. I love those cars. I worked with the techs to find otu what is wrong, or what isn;t wrong with the cars. What an awesome job I had. Too bad I had to go back to school.


I can pretty much drive anything...I actually find it hard to drive the cougar since the clutch is soooooo short, and I got used the excess clutch pedal play of german engineered cars. Oh well...

Since I don;t feel like copying and pasting everything you said, cause it'll take too long, but I feel you contradicted something you said.

I was saying in most cases a single turbo setup will be optimal, and your examples of twin setups are in 100,000+ cars, porsche and Ferarri. I'm talking about pretty much every other car. And if every car used porsche's twin setup, I'd completely change my view and say single or twin would be great. But on pretty much all cars you see on theroad every day, they would benefit from a single set up over a twin setup. It is true with the Supra, if you want to break the 1000hp barrier, the single turbo setup is the way to go...if you wan a nice mediocre 650hp...the single turbo is still the way to go...ha, only 650hp

About a twin turbo making more heat...unless you are using a ****ty and massively huge single turbo, two 16/18/20g or 2 T25's will need to be run at higher boost to make equivalent power compared to let's say a nice Garrett T3/To4e hybrid at a lower psi...therefore creating more heat, both in the intake charge, and in the engine bay itself. Making power is all ablout CFM...the more you flow the better. The lower psi you run, the less heat you make, so if you can flow (these are just made up numbers)...1000cfm at 8psi or 1000cfm at 12psi...which setup is more efficient? The twin smaller turbo setup will need to run at higher psi, therefore making more heat. It's true running 2 smaller turbos may have a smoother curve, with more power down low, but still, I thing the extra low end will be negligeable to the extra power made by the single larger turbo...also as already said by myself and BigProbe, that extra bit of lag from using the larger single turbo will really help with the launching of a FWD car. A supercharger is great since it produces power from low to high RPM's...the problem is down low where you may have too much ho and torque to get traction, and the same I feel would occur with low end power from twin small turbos.

About VATN turbos having problems...my info comes from sources from a Mercedes tech I know, along with many people I've been talking to since the idea of a VATN turbo kit has been announced on these boards. SOme of my info is hearsay, and other is actual hands on. Most believe it will be easier and cheaper to run a nice T3 Super 60, and forget about that low end power, since, heck we never had it to begin with. I agree with that. I hate to be limited, and I feel a standard Garrett T3 or some variation, will be less limited than the VATN...

I think I covered all I can cover. I'm typing out of memory of the previous long post, and the more I type, the more I forget.

On thing I'd like to add to anyone who wants to turbo a car. My belief for modding a car when a turbo will be involved. Optimize the engine and transmission for NA setup at stock compression ratio, then introduce forged low compression pistons and forged rods, and then the turbo. Get everything out of the engine first, and then turbo it. Also, if you do that, you can have 350hp with a turbo running at 5psi, compared to another guy who has 280hp running at 15psi, and causing damage to the engine. If Leo capaldi (sp?) gets 323 NA hp out of a stock duratec, someone else with head work can make some nice power, then turbo the car. Too many people go about it the wrong way. And people like that anger me, especially when they complain that the duratec engine sucks cause they are only making 250hp@12psi, and someobe else had 280hp all NA...

That's all...My goal is to run a consistent 13.9 or better in the 1/4 mile in my cougar all NA, and street legal. Also on the 2.5L block. I want to modify everything else other than the block it self, and see what I can do. Then from there I'll run a 3.0L setup or stico with the 2.5L, cut compression, make the engine as unbreakable as possible, and throw a turbo on then...

Right...the heat I am talking about is from the HOT side of the turbo...not the compressor side. The turbos will have to spin FASTER (due to smaller fans) to pressurize a manifold with the same volume of air, compared to a larger fan. Spinning faster = hotter

Boost Threshold?...hmmm I see your point, but it has no validity vs. Lag. When I put the pedal to the floor, I hit full boost within about 1-2 seconds regardless of what rpm/gear I am in. Lag is nonexistant, for all practical purposes.

In order for a twin set up to provide the kind of response you want (even though I have no idea what you are looking for), a sequential set up is best, but then you go back to cost and completity...(one oil line, one return line, one manifold, that sort of thing)
no matter how you stack it, it will be more than a single turbo set up, 9.5 times out of 10.

We can talk about the advantages on different applications until we are blue in the face, but the fact remains, The guy who started this topic prolly doesnt give a rat's ass how twins work on a 78 Fairmont...he wants to know how they work on HIS 2.5L V6. For OUR purposes, a twin turbo set up provides MORE disadvantages thand ADvantages.
So, the advantages over a TWIN set up are clear: