Parallel Twin VGT's

[kidturbo]

Hey guys I've been reading a little on the advantages / disadvantages of parallel twins vs compounds or a big single in diesels. But who in here has any real world experience or data with parallel VGT's? As you may have guessed this for marine and not sled pulling or drag racing.

Banks has done it I know, but I've never seen any of his marine stuff actually running in a boat. While Mercury Marine is making a name out of doing it lately. Offering 1100, 1350, and 1500hp "QC4v" pump "gas" engines sporting twin VGT's. And demanding the price of a nice house for them I will say. After running beside a couple equipped boats, it's the ticket to marine power. Even the aftermarket custom engine builders like Eickert and Chief are switching away from blowers to parallel twins. Mostly still choosing gated over VGT while they slowly migrate from dominator carbs to higher pressurized fuel systems and controls.

So I'd like to try a nice little set of parallel twin VGT's for my next diesel build. Nothing crazy, just a enough to support 7-800hp. My current single 4094 split scroll has great low/mid range, but you can stick a fork in it at 3900. Go up in size, and so goes the spool. Not acceptable. Since I always have room to got outward, one on each side just looks so much cooler. Just can't decided on sizes, and figured this crowd would have some input.

Tks.

 

[mike diesel]

How would you control both vane actuators?

 

[kidturbo]

Same way Mercury does it, ECM. It's a simple voltage thing. If I recall, didn't someone come out with split controller a while back?

My first choice for turbos was the GT's off the 6.0L Ford, but I'm guessing they might be a bit large.

 

[mike diesel]

I was wondering if the ecm could handle it or if it had auxiliary outputs...basically same as controlling dual cp3's via ecm. I just didnt know if it was possible.

 

[kidturbo]

Unless they have changed it lately, only two wires, so no feedback.

Funny fact: I needed a couple wires to power the IPR valve on my 6leaker for pressure testing the oil rails this week. Found the left overs from my dmax harness job and guess what plug is exactly the same?? Duramax turbo and Ford IPR valve use same plug to a tee...

 

[catman3126]

What is the boat that you are running a diesel in now? I have been looking into a diesel swap in my Bluewater since it is Volvo (gm) power and Volvo makes a diesel engine.

 

[dirty_max]

Unless they have changed it lately, only two wires, so no feedback.

Funny fact: I needed a couple wires to power the IPR valve on my 6leaker for pressure testing the oil rails this week. Found the left overs from my dmax harness job and guess what plug is exactly the same?? Duramax turbo and Ford IPR valve use same plug to a tee...

pretty common plug, I find it on injectors, IVAS, engine brakes, crank/cam sensors. we have bags of them laying around the shop because they are junk and always break.

 

[S Phinney]

Vanes are controlled by ECM so it would need reference from second turbo to control it.

 

[NC-smokinlmm]

Do the Garrett 3794's. They are about the same size as a stock LLY charger with better flow capability. I'd bet they would do well for you...

 

[duratothemax]

I assume you mean separating the intake tract of both left and right banks completely, right?? IE, each turbo feeds each bank only and there is no crossover.

The issue wouldnt be controlling two...its easy enough to split the control (ie, solenoid actuator) signal.

But the feedback from the vane position sensor would be the tricky part. The ECM only knows how to read the feedback from one vane position sensor at a time.

I guess you might be able to use the EGR output/input. It is a second closed-loop feedback system on the stock ECM that would be unused on any modified engine. It would take a lot of trial-and-error tuning to make the EGR % tables sync up with the desired boost tables though...especially since the EGR table (in efilive) is only RPM and fuel rate referenced.

In reality, what would be the thing to do is to build a microcontroller-based circuit for the second bank.

The inputs to the controller would be:

-Boost, bank 1 (the primary duramax-ECM controlled side)
-Turbo vane position sensor reading, bank 1
-Boost, bank 2
-Turbo vane position sensor reading, bank 2

Outputs would be:
-Turbo vane position solenoid, bank 2

The microcontroller would read vane position from Bank 1, and then vary the duty cycle of the Bank 2 solenoid appropriately until the vane position on Bank 2 matches Bank 1. It would use that as a reference "target" point. Then, it would compare Boost from bank 1, and Boost from Bank 2...if Boost from bank 2 is higher or lower than Bank 1, the microcontroller would then add or subtract vane position/solenoid duty cycle from the Bank 2 turbo until it matched Bank 1 boost.

To make it simpler, I guess you wouldnt REALLY need to monitor vane position. Just monitor boost from both banks...and then the microcontroller would vary the duty cycle of Bank 2 solenoid so that actual boost of bank 2 matches that of bank 1. That would actually be pretty simple as far as coding it.

Simple 8-bit micro with 2 analog inputs, and one PWM output driving an appropriately-sized MOSFET to vary duty cycle on the bank 2 vane position control solenoid.

Read ADC 1, read ADC 2, compare, if ADC 1 > ADC 2, than increase PWM-out duty cycle until ADC 1 = ADC 2 .....if ADC 1 < ADC 2, than decrease PWM-out duty cycle until ADC 1 = ADC2

Ben

 

[NC-smokinlmm]

Couldn't you use a stock cummins 6.7 vnt and controll it with springs and vaccum like the guys retrofitting them to GM 6.5's and completely avoid the electronics headache?

 

[S Phinney]

Couldn't you use a stock cummins 6.7 vnt and controll it with springs and vaccum like the guys retrofitting them to GM 6.5's and completely avoid the electronics headache?

You would still need to match vane positions as Ben was saying. His idea probably is the simplest and best way to sync data and make it act the same on independent banks.

 

[kidturbo]

I assume you mean separating the intake tract of both left and right banks completely, right?? IE, each turbo feeds each bank only and there is no crossover.

Ben, I've seen it done both ways on gas. Mercury is using twin drive by wire "electronic" throttle bodies on the QC4v. Their intake looks to be separated, still searching for a cut away view. I believe banks used the same on his parallel diesels? However some of the aftermarket gas I've seen with gated run a cross over or feed both to a single charge cooler setup.

What the general consensus on both scenarios? Open or small cross over would equalize pressures making it less dependent on vane position alignment. Last, lets throw in an electronic crossover idea, maybe putting that old EGR circuit to good use.

Rest of your layout is same as I was thinking. Down stream microprocessor handles in and out feedback to the ECM. Tune it normally and make it believe it's a single.

Here is the QC4v layout. Parallel twin scrolls, 2cyl feeding each.

---

Here is a link to their diesel 4.2L WITH the twin VGT/VNT setup.. http://www.mercurymarine.com/engines/diesel/tier-three/4.2L/

-K

 

[kidturbo]

Catman; my current boat is the 21' Warlock PPE built a few years ago.Single non-VNT turbo. However, I grew up on a Bluewaters and know them well. My brother has a 53 currently. Those were rare with diesel power...

We have talked about switching his from gas, but in your case it wouldn't be hard at all. Probably has the SAE 3 bell housings, or you would need to match up the Dmax plate with with what ever is on the trans. The water cooled exhaust I've sourced, 3k head to turbo. Or second, use a thermal wrap like I have currently and another member on here has done. The rest should be cake, only need the right engine to trans coupler.

:thumb:

EDIT:
Sorry just re-read your post.... Your saying gas Volvo to diesel Volvo? Not Volvo Diesel to GM Diesel swaps. I'd find the motor trans combo cause gearing and props are going to need to be matched up. Biggest difference to consider is the RPM range and how it changes per boat.

 

[catman3126]

Catman; my current boat is the 21' Warlock PPE built a few years ago.Single non-VNT turbo. However, I grew up on a Bluewaters and know them well. My brother has a 53 currently. Those were rare with diesel power...

We have talked about switching his from gas, but in your case it wouldn't be hard at all. Probably has the SAE 3 bell housings, or you would need to match up the Dmax plate with with what ever is on the trans. The water cooled exhaust I've sourced, 3k head to turbo. Or second, use a thermal wrap like I have currently and another member on here has done. The rest should be cake, only need the right engine to trans coupler.

:thumb:

EDIT:
Sorry just re-read your post.... Your saying gas Volvo to diesel Volvo? Not Volvo Diesel to GM Diesel swaps. I'd find the motor trans combo cause gearing and props are going to need to be matched up. Biggest difference to consider is the RPM range and how it changes per boat.

So you were thinking put a duramax in my blue water. mine is an 01' Mirage 20' You think i could put a steeper prop and still be able to run 45 mph with less rpm or would I have to spin the duramax over 4k? I will have a spare LLY soon but no electronics which wouldn't be hard to come up with.

 

[kidturbo]

Drive gearing is the sticker Catman. But since it's relevant to my reason for twins, quick lesson on why performance diesels in performance boats are uncommon.

Typically a gas engine spins 4500 - 6500R's and uses 1.5:1 or 1.75:1 drive gear ratio depending on CID. Your looking to spin the prop 3200-3600 rpms or so wide open optimal. Engine torque curve is key in marine, HP is just a calculated sticker number. When it's done pulling hard, your done accelerating. Manual trans truck in 4th gear, loaded trailer, up a long hill is the comparison. Depending on weight, what drive gearing you have now, a bigger prop alone might work out where ya want.

I run a 1.26:1 gear and a big 37 pitch prop, barely reaching 3000rpm prop speed at 80mph and 3700 on the engine. The Duramax curve would be best suited with 1:1 gear ratio or even .80:1. However you don't find out drives with these gear ratio, they've never existed. Some diesels boats successfully use a 2 speed transmission to overcome this issue, but that's more weight which slows ya back down again and a whole different subject.

So in my case, I'm looking to spin a slightly modified Dmax 4200 Rpms max with a custom 1:1 drive gearing. Totally realistic goal, being I'm now spinning a stock crank and LLY rods up to 36-3900 reliably every weekend. Only problem, needs more air up high, but without sacrificing any spool time down low. She has gotta start spooling up by 12-1400 or will never get on plane. Once lit up, it's all about moving that torque curve up the chart and not running out of air. Reason I'm thinking small T3 variables for best curve.

Sorry for the lengthy off topic reply, but the design requires a bit different thought logic from normal. Ultimately I'd love to do a 1000+hp/2500lb torque Dmax setup and show all the gassers what it's about. But a chat some years ago with a very wise member on here who built a couple for a boat has kept me in check with reality...

-K

 

[catman3126]

Very good information, Do you have any pictures of your setup?

 

[kidturbo]

Look under garage sale for Ultimate Duramax Toy. Pics and links on it there.

Here is a unique spin on the parallel twins that I had missed. From: http://www.autozine.org/technical_school/engine/Forced_Induction_3.html

"Nissan VG30DETT engine on the last generation 300ZX had each turbo feed the opposite cylinder bank. This formed a feedback loop and automatically balance the power between the two banks. Most early twin-turbo engines, like Ferrari F40's and Lotus Esprit V8, had the same design. Modern engine management system can do the balance job by altering ignition, so the cross-feed arrangement is no longer necessary."

So if one turbo gets a bit behind, the pressure from the other turbo is feeding those cylinders more air which should bring it back to even... Interesting older concept I don't recall seeing on a diesel. Also looks like the racers prefer to feed a single plunim from both.

In theory I like the ecm controlled crossover idea because you should be able to feed more air per cylinder on the big end than from a single charger. Thoughts?

 

[kidturbo]

Ok leave it to Audi / VW to master it first. The 4.2L V8 twin VGT that Mercury marine uses is actually the Audi 4.2L TDI marinized. Same diesel that's stock in the VW Touareg and other German offerings. That little sucker makes some power, 370hp stock. Here is one I found in a A8 mildly tuned and DPF deleted.

[YOUTUBE]jy9ReE5ktcE[/YOUTUBE]

Anyways it's not only possible, but done with Bosch Common Rail, even using the same Bosch ECM as a late model Duramax. Gonna take a little more digging, but it shouldn't be to hard to size this up.

Now to go test drive a Touareg, and pull the engine covers...