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No, If you read my post you would reaslise I didnt say that.
I said;
Yes a turbine is a restrictor.
At low engine rpm the gas volume being produced can easily pass through the turbine unnoticed.
( so at low rpm it isnt restrictive to the flow of exhaust gases )
But as engine rpm increases, this gas volume being produced is being produced to quick to pass through the turbine unnoticed.
( there fore the turbine has become a restrictor )
The gases are still passing through the turbine but because the flow is restricted to how much can pass through the turbine, the gas volume which is continuing to increase in the exhaust manifold is increasing pressure.
This pressure forces gases through the turbine. Because it is being forced, flow through the turbine is faster.
Because the gases are being forced through the turbine, the turbine begins to spin faster.

Do You Understand?

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Is it not true;
If you use a smaller turbo it will make boost at low rpm with this compromising top end power,
and,
If you use a big turbo it will make boost at a higher rpm with this compromising down low power.

If you use 2 cylinders you will need a small turbo for it to spool up at (lets say) 1200rpm.
Now if you use 4 cylinders you will need a turbo twice the size for it to only begin to spool up at 1200rpm.

Now if the turbo on the 2 cylinders becomes too restrictive and can't flow enough gases at ( lets say ) 6000rpm
You seem to think the turbo running off 4 cylinders wont be.

We are talking size for size.

Now think about what you wrote here;
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Yes the turbine can become to restrictive, this is why top end power is compromised on a smaller turbo.
Is it not true that ( lets use a workshop compressor and air blower as example ) the greater the pressure inside the compressor, the more air will flow out of the air blower quicker?

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If the short manifold starts spooling up at 1300rpm this means its creating boost from 1300rpm onwards
If the j pipe manifold starts spooling up at 2100rpm this means its creating boost from 2100rpm onwards.
I know it might be hard for you to read since its such big words and numbers but if the short manifold starts spooling at 1300rpm and the j pipe starts spooling at 2100rpm this means the short manifold had better low end response.
If you want to be stupid and get technical I can tell you in actual fact this turbo on both manifolds, was spinning at idle ( 800rpm ) but it didnt begin to spool quicker and create boost untill the engine reached the rpm figures I wrote above.

Cheerio Steve

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WOW, How about agreeing to disagree?
Its a bit like turbos vs blowers. Hell , just build whichever you prefer, and see how fast you can go.

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Quote:no, you said it restricts and INCREASES flow.

And the turbine does not remain stationary as you think until enough pressure is built up in the exhaust to turn it (

cmon guys you both know alot. phunkdocta, stop breaking his balls.

What was the original post about????????

Take it off forum guys, you two are the only ones who care now......

There is only one way to settle this now,
nine rounds of bare knuckled boxing !

hi.
n00bie here. i'm from OZDAT, but someone took my username on here, hence the dash.
i've read this thread with some interest, and have come to the conclusion that

1) geez you two have some issues. PM each other, regardless of how much you want to be a post nazi and flame each over to a crisp.

2) saying twins on a four is stupid/ ludicrous/ won't work/ won't work as well as a single is horseshit. the spooling you talk of is the same if the overall A/R of the two turbos is the same as a comparitively sized single. that is what it boils down to. if you 'halve' the exhaust ports to two, and choose a turbo to suit those 2 cylinders twice over then that will 'spool' just a well as four cylinders with a correctly sized turbo for four exhaust ports. that is just common sense, regardless of what kind of calculus you want to throw at it.

3) ever heard of a reducer fellas? it's a little cone you weld onto the manifold that reduces the diameter of the pipe, which speeds up the exhaust gasses and makes it 'hit' the turbine wheel harder, aiding in 'spool' up efficiency.

4) i dare say looking at twins, a pair of IHI-RBH4s would be ideal, with a small reducer on the exhaust 'inlet' to the turbocharger, as this turbo is more suited to a 800cc 3cyl.
however, if a single is the way to go, then a CT9 off a toyota EP11 starlet would be great, a turbo suitable for a 1300cc twin cam (that is actually quite nicely sized for a 1500cc twin cam) is ideal for an A12-A14-A15. the best bit is, they're all internally wastegated. $$$ saved there!

either way it sounds like a great little project and i wish you luck.

just a question to pro-240c.
u say that having a/c ratios of two turbos equal to that of one is in effect the same, but wouldnt the friction of two turbo shafts on their bearings, although fractional, still cause the twin turbos to spool up one billionth of an rpm more slowly?
just a joke, heh heh heh!