Okay so I'm fairly new to this all but have definitely looked into building an iron block 5.3 once or twice, the application would be for a prerunner truck so I'm trying to think of a way to beat eliminate turbo lag but still keeping high hp numbers. Has anyone ever tried a twin turbo with one small and one large turbo? I know this idea is implemented in newer more modern cars these days and I'm just really curious if it's an option for this engine because I would definitely be interested in that route. The engine itself will be built with forged internals and all those goodies. 😁

 

It's called compound...

And is absolutely pointless at typical low PRs of an Ls

 

A decently put together system, is not going to have significant "lag" these days, a good ball bearing turbo sized for the power band you require, should hit hard enough to scare your ancestors.. Defintalely in the "hold my beer and watch this" zone.

Most N/A pre-runner tucks with V8's are already in the 600+ HP range,, gotta believe 8 or 9 hundred should "do ya" You don't mention the specifics of what you want so we are all throwing darts.. just to see what sticks..

 

Yea thats what I was going to say. A decent setup twin turbo setup is going to make more torque then you could ask for... My single setup makes all the torque I could ever need...

 

There are people spooling 50+ psi off the two step with compound turbos. I don't see any possible need to do that on a 5.3L motor unless you are talking diesel tractor pull competitions.

 

Hi Jesse, YES it was the FHI EJ-20 TT JDM.

I have fitted this engine to Sand Cars, it ran well.
One small turbo the other much larger, ported with butterfly valves.
NOT COMPOUND, the way as you state.
Today, 20+years later, the more common method is VNT.

My latest customer is AJ, the owner of the BAJA Shop.
We have fit the Ford Truck VNT turbos.

There are other manufacturers of VNT, one such is Schwitzer. (Porsche)
There are other methods if you fit a "divided" housing.

Would you like my help ?

Lance

 

take two tubos and build a sequential setup, which on a v8 is very easy. you can then still switch to parallel e.g. for racing, by keeping the valve open.

 

I would only really consider a compound setup in 3 situations:

1. A Diesel engine with very high boost numbers/pressure ratio

2. A smaller displacement gas engine that runs high boost numbers/pressure ratio

3. A larger displacement engine 4L to 6L that runs a very large turbo, and a smaller turbo. And in this instance, it would be for driveability, throttle responce.

What you're looking at can be acheived with an exhaust valve in a split T6 housing, Exhaust housing ratio's, a trans brake, or a 2 step.

That being said...it's feasable as follows:

Say on a stock LS, you could run a 66mm turbo paired with a large frame 80mm+ turbo.

 

I did it with a 4.8 and a 60mm turbo being feed with an 80mm turbo. We really liked it. The truck had great spool and still had top end. Made 650 on just 12psi of boost on the dyno but cranked it to 18 at the track and ran mid to low 10's in a 4000lbs truck. Not bad out of a little sbe 4.8. Street spool was amazing!

 

It would be interesting how close you could get the low end power of a screw or roots blower with the top end of a turbo. I really like the power of a turbo but miss the grunt of my old roots blower.

 

I'm actually considering something similar. I have a Gt4088R (64mm) that I'm thinking about compounding a BW T6 unit, like an S480 off of.

What did you waste gate the smaller unit at?

I was thinking I'd run 7-8 lbs on the smaller unit, and then limit the large one to 15 lbs.


Then again, a spool valve does the same thing.

 

So the question I have to ask is. Do you really feel all the extra work and cost is worth the small bit of extra spool time? I'm no physicist so I may be wrong but in my head by pulling your 80mm turbos worth of air through a restrictive 64mm turbo is going to slow things down. That air will be heated as well from already being compressed. It seems like a well set up single would make much more power just due to efficiency

 

You're drawing air through the 80mm, then compressing it and forcing the volume through a 64mm, which then intercools and enters the engine.

The exhaust gas goes from the engine, through the smaller turbo/wastege, then enters the larger turbo.

The smaller turbo doesn't concern itself with volume, moreso pressure ratios.

 

did you also run a turbo feeding a maggie? i'd love to see pics of these set ups if you have a link!

 

Not sure if anyone is aware but the original 2jz-gte twin turbo is a sequential setup through 95 I think until 02. An actuator opens at the command of the computer (solenoid)to allow the second turbo to come online. The old trick is to put pressure in that line and tie it shut so the valve is always open, made it more like a true twin setup.

I dont think Sequential is the same thing as a 'compound', isnt compound when there are two different size turbos?

 

Im going to speak from diesel experience, but it will still cross over.

Typically what happens if the Exhaust goes from the engine, to the small turbo, then into the large turbo. The Intake goes from the large turbo, into the small turbo, into the engine. What happens is the high pressure (smaller) turbo spools up and the engine starts accelerating. At this point the low pressure (larger) turbo is not a restriction. If it is, its very minor. Then the low pressure turbo spools up and starts making boost. Instead of the high pressure turbo sucking air in by itself, its being crammed in, making the turbo drastically more efficient.

You have the spoolup of a stock turbo, but the mid range and top end of a much larger turbo. Can you make more power with a larger single as opposed to a S475/stock? Yes. But you lose towing ability and drivability.

Hope that info helps.

 

Wouldn't infinite turbos be best, having more of them in general is excellent as each is able to recover some portion of whatever is coming out of what the engine is burning. problem isn't "is turbos more better" the problem is "is the total cost of plumbing/running as many perfectly as close to infinite turbos as possible acceptable" from zero to infinity

The zero mark helps you see the entire graph. Going from zero to just one turbo does something to the curve- it may both reduces and increases it as rpm increases, sometime dramatically, depending on the size of that single turbo. A turbo can be small enough that there is barely any, or never any "reduced areas (lag)" from the original curve. And it can be large enough to give you only one small raised portion at the upper region of rpm on a graph.

 

Im going to leave this here http://www.yellowbullet.com/forum/sh...d.php?t=216811

you can read till you drool.

 

I saw that a while ago. Good Read.

 

Did he go any faster / quicker than with the turbo / n2o combo? I thought he didn't!...

In my opinion, sequential turbos are for BMW Diesel engines in cars! Far too manny valves needed to get them working correctly. Take a look at the various attempts on Perrier motors back in the 80s and 90s. Everyone ditched them and went back to normal turbo.