Twin Turbo Compressor Maps ?

[A. Frayn]

I have been doing a little web research, and what I am finding seems too simple.

Lets say one was looking at running twin turbos on a 3.4L DOHC engine. Just hypothetical at this point.

Most of what I see, says you can size one turbo to half the corrected airflow. Or in other words, size one to a 1.7 L three cylinder engine. Then double the result, and you have the equivalent map for the 3.4 running two.

Is it really that simple? Something tells me that it is not. I suppose in this hypothetical case, one would have two throttle bodies feeding a common intake manifold to all six cylinders. I am thinking of the twin turbo Dodge Stealth as a comparison case.

Or would the above case be relevant for one turbo, one throttle body, and one intake per bank of three cylinders?

Is anybody here able to shed some light on this?

[teamlseep13]

Sizing twin turbo's is actually pretty easy, just keep in mind what the engine and turbos are both really doing.
Your engine will be consuming a certain amount of air. If its breathing through two turbo chargers, then each turbo should flow roughly half the amount of the total air consumed by the engine.
As for the way the turbos are fed into the intake, if all of your cylinders feed from a common plenum or if they are bank seperated, you would size the turbos the same way.
Having a "loop" where a turbo feeds the single bank and its own plenum/throttle that it is attached to, actutally isn't as good of an idea as you would think it is. Most engine will actually respond well to running the turbo's outlet to the opposite bank of cylinders. Now thats not a rule of thumb, but if you look at most of the twin turbo, or even quad turbo engines throughout all of motorsports, they normally will feed across the banks if they keep the plenums seperate.
But forget all of that, because you will do a lot better with a balance tube connecting the two seperate plenums to keep things evenly distributed, like boost, temperatures etc.
Sorry for the lenghty explanation, but I am kind of a turbo junkie...

[A. Frayn]

teamlseep13:

Thanks for the insights and info on that. The "cross" feeding of one exhaust bank to the other intake bank had never occurred to me as a "system balancer".

I have Hugh MacInnes old book, but not the newer one by Corky Bell. Would you have any other good sources of information on this particular subject?

[teamlseep13]

The book by Corky Bell is a great one. Also, a great web resource if you haven't already found it is www.grapeaperacing.com
I am an old school muscle car fan, but turbos rock and twin turbo v8's are even better. Grape's web site is greating for compressor formulas.
Also, for an online turbo calc, try www.turbofast.com.au
If I think of anyting else, I will post it. Hope this helps

Hunter

[TurboGT]

The turbofast web sight also has the turbo calc program you can download, along with a few other programs. Very nice thanks for the link :thumbleft:

[Shaun41178(2)]

IMO the corcky bell book is an intro type book to turbocharging. It teaches you basics for the uninformed, but it really doesn't have much. I had to do a lot of my own research to get to where I am today.

Its a beginners book to turbocharging but there are so many holes in that book. Just dont' think of it as a turbocharging bible.

[eHoward]

I have the Hugh book (and the corky book too) and it's a fine turbo book. You don't need another on that subject.

Now, there are plenty of other engine related books you could buy.

teamlseep13:

I have Hugh MacInnes old book, but not the newer one by Corky Bell. Would you have any other good sources of information on this particular subject?

[TurboGT]

I have the book Forced Induction Performance Tuning by A.Gram Bell. Still reading it and I can see how it is missing some stuff but it has a lot of good stuff on turbos, superchargers and "boost" in general. Great book to start out with.