By the way...how are the twin turbo's setup...2 cylinders driving each turbo??
And what sort of turbo's are they?

sounds like a plan

ill get pics, but yeah 2 exhausts to each turbo

they are off a diahatsu 1000cc diesel motor

When you make your exhaust manifolds make 1 for me too so I can use my diahatsu turbos too

with that setup they will both start winding at the same time, obviously, it sounds complecated. why not just run one larger turbo on all four pots?

Quote:
Simple
Its all got to do with smaller second moment of Area.
Sorry 2nd moment of area = moment of inertia of object. the smaller the value the better. = faster spool up.

Take for example two rims of exact same weight. One is a big mother alloy 15" and the other is a stock 12" steelie.
Now which can you spin up to 1000rpm easiest (freely spining). Now remember they are the same weight.

Of course its the 12" steelie. This is because of the smaller radius.
Roational acceleration = w rev/s^2
Radius of rim = r

radial acceleration ar= w^2 * r

and good old Newton's law say's
F=Ma

you need more force to accelerate the 15" alloy.

Its a little more complicated than this, but that's the basis.

Now think of the tiurbo. Instead of one big turbo with a big radius you've got two smaller radius turbos, whose impellors (that 2 impellors) have the same mass of the big turbos.

Which one you pick now.

Hmm i'll take the two please and please tell Mr Turbo Lag to got get F#cked.

I finally got my injection ready for installation. I found a tap for the M14x1.5 air temp sensor, so I did that today. I also just received some intercooler piping/connectors today for the turbo. I've run into a few problems with the turbo however (IHI RHB5 from Subaru). The first is the exhaust flange I bought doesn't seem to be allowing the internal wastegate to open very much. How far is the wastegate flapper supposed to be able to open up? Second, the turbo does have a bit of play in the bearings...it'll hold up I think, but probably not for a long time, it hasn't contacted the turbine at all yet. The other two problems are, the exhaust manifold (I have none), and fuel outlet from the tank needs to be redone 1/2". If I had a stock A14/A15 exhaust manifold I could get that going cause my friend knows how to weld, but I have none! If anyone has a spare exhaust manifold let me know!!! I will need pictures of it to ensure it's the right style as well. Then there'll be two of us with injected turbo charged and intercooled A15's! The other thing that crossed my mind is the possibility that this turbo I have is gonna be too small and that I'll be overspeeding it at the 7000 rpm's my A15 likes so much. It's from a 86 Subaru GL10 (1.8L), but in my mind it seems like the 1.5" intake and outlets won't flow enough! I guess there's only one way to find out. The engine is ready for it though, I did a compression check today #1-140 #2-140 #3 132 #4-130, it's just begging for some dense Tokyo air to be FORCED down it's runners. This weekend I'm picking up some NISMO 1.5:1 ratio rockers ($200!), should get a few ponies from that. Good luck w/your turbo 1200rallycar!

-Andy

Turbo selection is not only about the rotational inertia, (that is admittedly better with two smaller turbo's), but the turbo has to be able to operate within its designed efficiency range or you get surge or overspeeding at opposite ends of the spectrum.

"Probably the most popular notion of the advantages of two turbo's is reduced lag. This notion is generally hard to justify. Half the exhaust energy is put through two turbines, with inertia proportional to the ^2, and mass flow proportional to the ^3, is not necessarily conducive to producing less lag"
Corky Bell (Maximum boost pp34-35).

Let the debate begin

Exactly what I was gonna say Feral...

With two smaller turbo's, the turbo's are easier to spool up, but you are only using half the exhaust flow for each one.

Plus, with this setup (I'm assuming both turbo's are flowing into a single carby), will there be a lot of turbulence created when the two air flows meet each other...(if that makes any sense???).

Personally, I like the tried and true single turbo setups, but i'm all for experimenting. Good luck 1200rc!!!

I'm staying out of this one this time, remember last time Timo?

is it going to come on the mccr cruise 1200rc? i hope so. i need to check this out