How best to spool a turbo, exhaust design question

Suppose you've got two, maybe three exhaust pipes a reasonable distance from the exhaust manifold (over 3 feet) with which to spool a turbo. There are three 4-cylinder banks of pistons involved. The total engine displacement represented is 6.6 liters. The pipes are all 3" in diameter. Would it be best to combine the pipes like a "Y" to one 3" pipe that then enters the turbo with a somewhat straight-line flow? Or would it be better to combine them angled as to create a swirl in the pipe in the direction of the turbine spin? Or even swirl opposite the direction of turbine spin? Or would it be better to just use two or three smaller turbos in parallel instead (I thought no, assuming that the one bigger turbo is more efficient and simpler)?

I'm contemplating a meager 8-10lbs of boost, and want to run on pump gas with stock (non turbo) motor internals except for a maybe a doubled up head gasket, cam, and maybe some bigger injectors. Hoping to boost the output 15-20%.

I think that car in particular needs 3 turbos. One for each bank of 4.

The best way to "collect" before the turbo is with a collector. Ideally they'd meet pretty much at the flange.

If your original thought is what i think it is (combining all 12 cylinders and two engines flow into one turbo), i'd say that would actually probably be more complicated than just creating 2-3 complete turbo setups.

I think 3" wouold be way laggy. Can you go smaller?

Matt on the theturbofourms.com makes big power with his crossover at this 90 angle. He does not care about the angle.

It seems to be about the pressure created in the exhaust pipe and not the flow angle. I wish he could compare the benefit of a better flow angle.

The build: http://www.theturboforums.com/threads/360606-82-Fairmont-5-3-zr1cam-80mm-4l80e-9-95-141!

You have to stop thinking about pre-turbo exhaust flow anything like n/a exhaust flow. The restriction(turbo) causes the exhaust to react more like a liquid. There is a balance of pressure and flow needed to spool a turbo. I would drop the pipe size from 3" to 2.5, or even as small as 2". I have more thoughts but I'm at work and don't have a ton of time. Just think of it as water flowing through a pipe spinning a wheel inside the pipe.

I want to see this car. I have no idea how to spool the turbos, but I want to see what this thing is.

psteav wrote: I want to see this car. I have no idea how to spool the turbos, but I want to see what this thing is.

It's this thing.

http://grassrootsmotorsports.com/forum/build-threads-and-project-cars/1986-ford-escort-dual-engined-challenge-car/52523/page1/

+1 for triple turbos.

How are you going to plumb the intake side?

If you are not combining the intakes into one source, I would think you would far out-do your 8 to 10 psi that you are targeting.

How do you even size a turbo that would have 6.6l flowing into it and supplying boost to only 4.6l?

That sounds like a good problem to have!

wvumtnbkr wrote: How do you even size a turbo that would have 6.6l flowing into it and supplying boost to only 4.6l?

HUGENORMOUS.

If you go with a combined setup between the two engines into one turbo, you're going to need some fun flex-pipes as the engines move so the pipes don't break. There's lots more I could add but I'm more curious just to see it work. Worry about optimizing it after it's in place, that way you can figure out where you want to go with your setup...

What in the world are you building a turbocharged setup for?

OK, smaller tube feeding the turbo, use the giant 3" stuff (which I already have on the shelf) as intake and post turbo stuff.

This is my current CAD model. Marvel at the detail and forethought.

It'll work. In theory. It's also about the most complicated way you could possibly do this.

So naturally, considering the car it's going in... GO FOR IT.

the region in front of the V8 is about the only place left to stick stuff and keep a passenger seat.

edit: well, there is a little room in front of the rear tires in the fender flares, but I was reserving that for junkyard intercoolers.

I've ditched the $400 transmission controller, so I've got $401.05 worth of budget burning a hole in my pocket.

That's a good way to run two engines off one turbo if you have to do it that way, you'll have to choose your turbo very carefully to keep lag down, especially with all that piping. It'll also force you to settle on running the same amount of boost in both engines.

Not running any intercoolers?

By "front" of the V8, you mean towards the back of the car, right?

Do you have a turbo already picked out or something that you're trying to use?

I REALLY think you could get one turbo for each bank of 4 on there, without really running into space constraints with the "rear" of the V8. Turbo setups don't necessarily take up more room.

Or at least just go ahead and do what you laid out there, but make it two turbos, one for the Zetec, and run the other one the way you've got on the V8. That way you don't have these ridiculous loops going on under the car, you don't have to worry about sizing a turbo that's taking in the exhaust gases (far downstream of the motors) of a 4 cylinder and half a V8, but still having to feed 12 cylinders, and you bypass any potential wastegate issues from the setup you've got laid out there.

Plus.... MOAR TURBOZ!!!!

My vote still remains with: 3 Saab/Volvo junkyard turbos, and 2-3 Saab/Volvo junkyard intercoolers.

Alternatively, i know i have one MX6 GT intercooler laying around, and might have two. If i can find the second one, come up and get 'em. Yours for $40.

I would have one turbocharger for the I4 and one (or two) for the V8.

In reply to GameboyRMH:

I've got several probe intercoolers, so maybe. I've not sourced the turbo yet, so we'll see if I can get it in budget.

no, by "front" of the V8 I mean between the V8 and the backseat firewall. When I originally designed the car I was going to put the radiator here, but I couldn't get any airflow and had to move it to above the engine where they sits now. So that is my biggest empty space right now, in front of the V8. It is also right at the COG of the car, so adding weight there is the best place to add weight.

The driver that started me thinking about this was re-routing the exhaust so it's not sitting directly under the fuel cell (which is between the V8 and the back bumper)

Oh for some reason, i was dumb and didn't realize that in your detailed CAD illustration, the V8 was on the left side.

Probe intercoolers are good.

I have to say it, with 2 engines of different sizes, flow rates, VE, etc, I'm thinking something along the lines of a compound turbo charging setup, only instead of one engine feeding 2 turbos, maybe the smaller engine feeds a smaller turbo that feeds another larger turbo on the larger engine, it's like compounding the turbocharging across engines as well as between turbos, it's actually insane now that I think about it...

edit: I should clarify that feeding is on the exhaust stream side as I have it called out, the bigger turbo's compressed air would actually go into the inlet of the small turbo which would then get split out to both engines' intakes. This would get the desired result, what would be strange here is the multiple exhaust path, you could have each turbo run off its own engine, share it, or force feed one and the the other. The last would be insane because you'd be spooling a tiny turbo with 6.6L of displacement, think instant boost just like the tractor pullers...

You know the more I think about this, wouldn't it be better to do a mix of supercharging and turbocharging, I mean that's the only logical conclusion for a Twin-Engined-AWD-Night-Visioned-LED-Lit-80s-Econobox-of-Doom...

In reply to Raze:

Yeah, but superchargers are so much money. Budget is $401.50, remember. So I'm pretty well limited to stuff I might find on the floor of the garage or rummage up at a junkyard with 16VCorey's help. Maybe Craigslist.

The VE is comparable close 125bhp/2l=62.5hp/L for the Zetec, 260/4.6=56.5hp/L for the mod motor in stock California legal trim.

For as little boost as I want, a tiny (relative to 6.6 liters) turbo might do it fine.

All I have to say is...I LOVE THIS FORUM!

Where else would you find people competent enough to build and then boost (maybe) a Twin-Engined-AWD-Night-Visioned-LED-Lit-80s-Econobox-of-Doom?

My ideas tend toward the simple end of the spectrum so my ideas might not be appropriate here.

If it was me I would pick one of the oil cooled Holset turbos off of a Dodge pickup. They are cheap, very common, and you dont have to run coolant lines. I would run it off the v8 alone. The exhaust flow wouldnt be out of the ballpark compared to the diesel so I dont think you would be too far out of the efficiency range for the turbo. I would run a bov or bpv for each engine of course. And it may not be "ideal" but an electronic boost controller in combination with a manual boost controller set at a relatively low maximum boost would give you okay control of boost for the differing combination of engine sizes. The long intake runners and intercoolers are going to give some crazy part throttle issues, but compared to making a twin engined car work I'm sure that will be nothing.

In reply to sporqster:

For Superchargers, think M62 or M90, many show up in the JY, or on FI forums where someone's 'project' never happened, I've seen some go for less than $50...

I was wondering how close the VE was, I should have realized but I wasn't thinking of the 2.0L as a Zetec, that's my bad, DOHC is great, so in other words you have 3 matched banks of 4 bangers (approximately).

A tiny turbo won't have the flow rate required to drive all of those 6.6L, that's your real problem, sure 8-10psi sounds easy, but not with enough flow rate from a tiny turbo, sizing is going to get complicated very quickly. The simple answer is 3 small turbos, or 2 turbos (one for each engine) sized for the boost, VE, and flow rate of each. This applies equally to superchargers. The complex and ridiculous answer is to either mix and match, size multiple turbos compounding, or generally figure out some silly combination, because you can.

Ojala wrote: My ideas tend toward the simple end of the spectrum so my ideas might not be appropriate here. If it was me I would pick one of the oil cooled Holset turbos off of a Dodge pickup. They are cheap, very common, and you dont have to run coolant lines. I would run it off the v8 alone. The exhaust flow wouldnt be out of the ballpark compared to the diesel so I dont think you would be too far out of the efficiency range for the turbo. I would run a bov or bpv for each engine of course. And it may not be "ideal" but an electronic boost controller in combination with a manual boost controller set at a relatively low maximum boost would give you okay control of boost for the differing combination of engine sizes. The long intake runners and intercoolers are going to give some crazy part throttle issues, but compared to making a twin engined car work I'm sure that will be nothing.

That's the 'best' solution, you will need an external wastegate, we overflow our stock internal one on a 9cm housing HY35w with a 2.3L SOHC. Controlling boost spikes are going to be a big issue as well.