New turbo project direction

[yodabiri]

Since I am not likely to get my t4 turbo, I am thinking of going in a slighntly different direction. What do people think of a twin turbo setup with a couple of tiny t3 or maybe even smaller turbos on a 250 ci engine? Would this type of setup be plausible? Would it be too hard to tune? I think i can manage the fabrication of the header (kinda have it planned out maybe I will post a sketch of it when i can) and the intercooler lines.


Thanks in advance for your responses!

 

[Bort62]

I think that twin turbos is twice the work for the same end result.

 

[wallaka]

Me too.

 

[yodabiri]

Hehe I kinda thought so too, but it would be wicked cool to see two "hairdriers" under the hood. Plus I was onto the idea because there are a bunch of thunderbird turbo coupes at my local junk yard, and their turbos are still there and look pretty good as far as i can tell. They are also way to small to be used on a 250 in a single turbo application, but I was curious about a twin application. Ok well I got a fairly unanimous answer. Thanks! I will save up the money to get a t4 turbo or something similar

 

[Does10s]

If you get the smaller A/R turbine housings (.43 I think )then you may be able to make that work. (on a 250) For those turbo's a 200 will take forever to spool them.
A twin turbo setup has it's benefits.
Smaller turbo's = quicker spool.
Two of them = same or greater ending airflow.

The downside is obvious. Just about twice the plumbing.

Later,
Will

 

[InlineUK]

Hi there,
I am currently working on a twin turbo 250 for my 68 Mustang. I'm using a pair of small turbos from a nissan skyline, T25s i think they are. I looked at the T3s from the ford 2.3 turbo engine, but i think they might be a little on the large side for what i want.
I think a twin turbo six wll definitely turn some heads! 8)

I agree with Does10s; there will be a lot of plumbing!

These are my turbos, picked them up off ebay.

 

[XFlow_Fairlane]

I would look at the T3's used on a 2.2L mopar from the 80's.

like a .42 compressor.

 

[Bort62]

Smaller turbo's = quicker spool.
Two of them = same or greater ending airflow.

The downside is obvious. Just about twice the plumbing.

Later,
Will

Small turbo = quicker spool given a constant exhaust volume flow.

But if you've got two of them, then you have half the gas flow...

 

[XFlow_Fairlane]

they have a lower mass and are more efficent at lower impler speeds.....so faster spool. but they will max out sooner and generally will not support as high as a boost level as a single turbo will

 

[wallaka]

I'd say a well-sized single will beat doubles anytime. But, if you are going with junkyard parts instead of new, it might be better to work with what you have.

A lot of the 5.0 guys use two T-bird T3's, they are sized exactly right for that application. Not so much for a 200, I'd say. Now, a T04B or -E, that's a different story.

 

[addo]

I will say that the lack of space will cause more issues than any benefits gained. You'd have to convert to a subframe front end just to get clearance around the twin manifold.

 

[Bort62]

they have a lower mass and are more efficent at lower impler speeds.....so faster spool. but they will max out sooner and generally will not support as high as a boost level as a single turbo will

The lower mass is going to be approximately linearly proportional, so the same applies as above.

I think that a properly sized single makes more power, every time. There are situations where a twin is appropriate (V engines) But I don't think it is in an inline.

Unless you do funky sequential stuff like some OEM's going for a particular power curve.

 

[yodabiri]

Wow I never expected to open up this big of a can of worms. Thanks everyone for your responses. I will calculate my funds and see what I will get. By the way does anybody know how those sequential turbos work? I will look those up in a bit.

Thanks again for you inputs!

 

[wallaka]

Depends. A couple of setups are called sequential. The one on the RX-7 and Supra had two turbos and a complicated exhaust manifold with diverter doors and servos to move them. At low RPMs, all of the exhaust goes to one turbo. At a certain RPM, exhaust is diverted to the other turbo.

It was designed right before the efficient turbine wheels and housings were availible. From what I've seen, installing a modern, single turbo inevitably gives as good response and supports more power. Plus the rat's nest of vacuum hoses, sensors, servos, and wires is no longer an issue. This setup would be next to impossible to duplicate by a home fabricator.

I have seen similar strides with turbos that have a divorced housing, I think that the latest Powerstroke turbos feature this along with the variable geometry vanes on the compressor. I'm not too sure, though.

I've heard series or staged turbo setups called sequential, this is where a large turbo feeds into a smaller one. This results in very, very high boost levels: over 50 psi easily. Usually used by tractor pullers and the like.

 

[yodabiri]

The one I was thinking of is more along the lines of a small quickly spooling turbo used in low RPM when the exhaust flow is minimal. When the RPMs increase the exhaust is diverted to another turbo that is larger and would provide the necessary top end. I am guessing that this setup is very complicated and would require cervos to divert the flow.

 

[Bort62]

Yeah, you don't wanna get involved in that...

 

[Bort62]

On a V engine, Twin turbos can actually simplify the installation. Otherwise, you end up making a lot more work for yourself.

 

[yodabiri]

Yea I wasnt planning on it, that would be too complicated especially for me.

 

[SR_Crewchief]

Sequential or Compound setups are moderately common on Cummins Turbo Diesels. They are 2 different sized turbos (ie 1 big and 1 small). On the hot side the small is fed from the manafold and feeds the large, and reverse that for the cold side. Depending on which pairs you go with the target is either higher low rpm boost or very high high end boost. Keep in mind that CTD's are designed from the ground up for very high compression compared to our inline gas engines.

 

[JGTurbo]

they have a lower mass and are more efficent at lower impler speeds.....so faster spool. but they will max out sooner and generally will not support as high as a boost level as a single turbo will

The lower mass is going to be approximately linearly proportional, so the same applies as above.

I think that a properly sized single makes more power, every time. There are situations where a twin is appropriate (V engines) But I don't think it is in an inline.

Unless you do funky sequential stuff like some OEM's going for a particular power curve.

Lower mass is a linear proportion? Hardly. It's the moment of inertia that matters anyway and it isn't linear either.

I=mr^2 The moment on inertia varies as a SQUARE of the radius.

Two smaller turbos will spool quicker than one larger one.