I see alot of aricles about single turbo..but not twin (one for low rpm, one for higher). Is a twin setup even possible on a 225 /6?

I also hear the /6 redlines around 5k rpm? is there any way to increase the rpm redline in these engines? to make them more suitable for "racing" instead of draging?
or at least make them less 'splody?

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I like the cars that go VROOOOOM

not the new ones that go wrrrrr -.-;

I've seen a picture of a twin turbo slant mocked-up somewhere. Can't seem to find it now, but it used manifolds based on the Dutra Duals. However, it appeared that they used a conventional parallel setup where both turbos spooled at the same rate, not the staged setup you describe. Such a twin setup would certainly be an interesting possibility. I believe the Nissan 300ZX TT used a setup similar to this.

However, a staged twin turbo using turbos of unequal size is a royal pain. The setup on a Supra Twin Turbo, for example, has a set of valves in the exhaust manifold that change the amount of exhaust driving each turbo. The control system required is an engineering nightmare - even the guys on msefi.com haven't come up with an aftermarket solution for twin turbos that I'm aware of, and they've found ways to hack or reverse engineer just about every other engine control system known.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

Look at the last picture in the article.

http://www.slantsix.org/articles/turbo- ... rticle.htm

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

I think your looking for something like this

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http://www.cardomain.com/id/lncognito

That's a sequential setup for a diesel. Works great if you want 60 psi.

What he wants is two turbos, one that spools up fast but chokes at 3000 rpm where the other one takes over and makes boost up to redline. Both blow into the intake, rather than one into the other.

Seems like a common exhaust manifold would work for something like this, without the valving the Supra deals with. When the backpressure goes through the roof on the little turbo, it would force the exhaust through the big one.

Oh, wait. How do you for the exhaust through the little one before it chokes? If you don't, you might as well not have the little one.

What if you had a spring loaded valve? The spring would keep it closed until the backpressure reached the right level. Or, maybe a boost sensing valve?

Hm...

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

then get 1 turbo matched to your engine needs

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http://www.cardomain.com/id/lncognito

They have turbos that have adjustable vanes.

At low rpm/exhaust flow the vanes are close together so the exhaust flow fast between them, then the vanes open up as exhaust flow increases.

So you get quick spoolup without choking

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Until recently, VGT's have just been something that I regarded as an off the wall idea that could never be succesfully implemented in a "home brew" setup. After seeing/playing with them this summer though, they seem pretty cool; controlling them still seems to be a major obstacle though. Are there any aftermarket/home brew solutions that take care of the controls?

I would think a diaphram based on backpressure would work. No back pressure, tight vanes. As the backpressure builds up behind the tight vanes, they open up a bit to reduce the backpressure by opening up the vanes.......

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Ah, they make vacuum operated ones? The units I'm familiar with have a stepper motor that controls the geometry. Hm... now if I just had a lot of money...

Don't know what they make, I'm just theorizing............

Another possibility is a modified wastegate. Instead of opening up a wastegate, the vanes are opened up instead.............

I don't see why a simple analog/mechanical setup wouldn't work.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

yeah thats what I'm looking for.. My thinking was that it would give a smooth from lower to higher RPM transition (I'm a noob to /6s and turbos, but it seems to make sence)

If a twin turbo isn't fesible (haven't given up on it yet though )
What about a small,quick spooling turbo with a *small* blower to give a final combined boost?...it would seem to give the smooth trastion and a better full range response?

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I like the cars that go VROOOOOM

not the new ones that go wrrrrr -.-;

That's the problem. A single turbo setup is a compromise. It can work, but it's a fine line, and it's really easy to make it either laggy or lose top end power. A non-symmetrical twin setup could make it easy to get past that.

GV turbos were used by Mopar for about one year, 1990, and by Shelby in '89. They called them VNT's, Variable Nozzle Turbos. Seems to me that most people complained about them and swapped to a standard Garret because the VNT's couldn't be tweaked for more boost. I think at least one person figured out how, but don't know for sure. I think they were a combination of vacuum and computer controlled.

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

Your small turbo would limit power because of the exhaust backpressure.

If anything you would want a small blower for instant low end boost, and a larger turbo for top end boost. Not sure what a small, fast turning blower would do to things at redline, but my bet is nothing good.

Also, one of the things I like about turbos is there is very little parasitic losses when not into the boost, but a blower drags the motor down all the time. Seems to me that I've seen as much as a 100 hp loss due to the drag from the blower (at peak hp).

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

VNT's have no wastegate, at least not the setup Chrysler used. The vanes perform the equivalent function, so any control system will need to adjust their position based on the intake pressure and not exhaust pressure.

Twin parallel turbos of equal size can spool up a bit faster than one very large turbo. But any time you start playing around with spinning the turbos at different speeds or making them unequal sizes can give you all sorts of control headaches. A system that makes them perform better than a standard parallel setup - or even a large single turbo - would need to take care of all of the following functions:

* Ballance the amount of exhaust flowing through each turbo and the wastegate(s) as needed
* Prevent air in the intake from flowing backwards through either turbo
* Avoid creating restrictions (e.g. the task above shouldn't be tried with spring loaded check valves if at all possible!)
* Ideally, keep both turbos operating in the speed and flow range where they are most efficient.

That last one is the real nightmare if you have unequal size turbos. I definitely wouldn't want to try a purely mechanical control there.

There are a few examples of cars that used both a turbo and a supercharger. Usually this shows up on weird show cars. Like staged parallel turbos, though, this isn't a good area for newbies to work on.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair