Possibly moving to twins, need help understanding them

[NakeDiesel]

I've finally gotten the engine together and in the truck, I'm to the point where I need to make some decisions on what to do for turbo or turbos for the truck. A little about the truck:

I race in 200' mud pits, truck is a full out race truck/toy. Frame is a 96 dodge Ext/LB shortened 3', body is a 46 power wagon and at this point, just the cab and doors are original. Fenders are all carbon fiber, bedsides are CF, hood is steel strap/aluminum with a CF grill. Engine is 18 3/4" back from stock location, cab is back that far as well. 6.13 gears in the diffs, lincoln locked in back and lunchbox locker in front, 47re with full manual vb and factory transfer case in high range. Tires are 38x11x16 fronts and rears are 39.5x18x15 rears

Now to the engine. 5.9 block bored out .45 with CP Carrillo hybrid pistons/rods, fully studded engine, crank girdle. Hamilton Head, ported/polished with larger valves with tube intake. Water to air intercooler with dual pumps fed from bottom out from top with 10 gallon tank. Air shutoff valve on intake. Hamilton 230/240 steel cam. Injection pump was just redone by Seth, 13mm p pump, hamilton 2.75 cam/springs. full cut delivery valves and larger holders, .120 lines. Injectors are IH 5x20 dual feeds. Fuel fed by 2 air dog pumps independantly front and side with check valves set at about 50psi if I remember right with a fuel return external regulator.

I've run a single s475, just not big enough anymore with this setup, tried running an s480 but had issues spooling it, just too much fuel at spool up, worked with Seth to fix that issue.

Exhaust Manifold is a t4 straight steed

Turbos I have sitting around right now:

s366 from ED, billet wheel, comp cover .90ar t4 foot, used many years ago when I was just starting out, needs to be rebuilt after years of 2000 degree + runs

s475 billet wheel, comp cover .90ar t4 foot .87 exhaust side

s480 reg wheel and cover, .96 exhaust side with I believe a 1.0 or 1.1 ar t6 foot

I'm at a crossroads, looking at buying a t6 comp steed manifold and running the s480 and seeing how it spools up with the changes made and getting rid of the adapter I used (t4/t6)

But also interested in possibly twinning the truck, only thing I'm worried about with twinning is I'm very limited under the hood with what I can fit under it.

What would be a workable combination with the s475 I have as the small turbo? Would a t6 foot manifold be better for twins? I've never really looked into twins before because of the classes I've been in with the different orgs, but I'm to the point of pushing out of those classes anyway with the changes I've made so might as well start looking and planning for the future.

Any insights or people I need to talk too about the twins road? Any help would be appreciated.

[Mark Nixon]

Not much help on the technical aspects, but that's a neat truck!
Looks like you like to put a lot of effort in, to make a clean rig.

Mark.

[NakeDiesel]

Thanks, I try. Just a simple farmboy/software engineer who grew up poor and learned to do things for himself. Spent a year researching making carbon fiber parts before I made my first ones. Not a great welder or fabricator but I've enjoyed the challenges of building this toy over the last 9 or so years. I have a 75 page thread in the Dodge Competition and Performance section if you are bored, named Rebirth of Monster Mudder.

[zfaylor]

Honestly the s366 and S480 with the correct hot side housing combo would be a pretty decent setup if you wanted to go compounds.

[MAXX IT OUT]

It would come down to how much power you want. If your planning on using planning on using a S472 as the small turbo, your going to need something pretty big(88mm+) to go along with, which runs into space issues. That goes the same for Triples. I agree with ZFAYLOR, S366 and S480, should be good for up to 1000+HP and is small enough to package in a small space.

[NakeDiesel]

Yes I can see the 366/480 would be a small package, but would it really give me much more air over the s480 alone? I know I could bump the 480 to a 1.32 ar or so to get just a bit more air, but wouldn't the s366 be really restrictive? Noob to twins question.

If it comes down to it, I can always modify my hood and just cut a big area out to fit twins in there, don't really like the idea, but wouldn't be opposed to it either. Could also fab up a power bulge to keep them covered. Before the new engine build I was at somewhere around 1000hp with the old build and would really like to move on up, not stay where I was around.

Truck weight before moving the engine with just the fenders CF 2 seasons ago weighed 4980 with a 60.56 front to 39.44 rear weight bias and balanced side to side. I haven't weighed the truck with all the changes yet from the last major work on it. But hoping its down to about 4500lbs with a 50/50 weight distribution, that was the goal, don't know if I made it yet. I race against 1000+ hp gas trucks that weigh as little as 3000lbs.

Radiator, fuel cell, trans coolers, fuel pumps, battery are all either over the rear axle or behind it to help with weight transfer.

[zfaylor]

Honestly, you will need to buy some things to go much bigger. I read it as you didn't like the 480 as a single because of the spool time and that the 475 was maxed out as a single. Just like Maxx it out said you will need a rather large primary to go with an S475 to really reap the benefits. Given the turbochargers you have I would go 366 and 480. If you are open to buying new turbochargers then obviously there are better options to get more power. You need to decide 100% what you are after in terms of a power goal and how much you want to spend.

[NakeDiesel]

The issue with spooling the s480 was I had a gutted AFC housing which worked ok with the 12mm p pump, but with 13mm, I feel I was dumping too much fuel to get it spooled right, There were other issues as well that have been addressed. Found some air leaks on tearing the truck down that shouldn't have been there but were, as well as issues with my Trans. For this season, I will probably just swap in a T6 steed comp and run and try the 480 and see how it works with all the changes, and start planning for twins.

I just don't know enough about how twins are setup or work to jump right into them. Most definitely not afraid to change out or buy different turbos to get a better working combination. I budget out build changes on the truck and do as much as I can within the budget I set for a season. I've had a few sponsors help me out with parts over the years, but it's been mostly me buying parts and fabbing things up.

I'd like to have enough air to make 1600 hp with the truck, whether that's realistic or not, no idea. Never been able to get the truck Dynod or engines dynod, just seat of the pants testing in my pasture along a half mile straight away. Tried the chassis dyno once, but the truck was so low geared, dyno couldn't load it up with regular tires on it.

[wwentzler]

Biggest start is you need to set a goal of what you want, cramming stuff together at that power level doesnt work so well. Also common misconception, you dont "gain air" from compounds, you can only flow the air volume that the primary can provide (less actually but nother topic). What you wanna do is find an atmospheric charger first, by dividing your HP goal by about 8. That will give you a ballpark mass flow(lb/min) you need (plus or minus depending on setup efficiency and how much room to grow you want). Using a compressor map find a turbo that flows that air mass at 60% efficiency. That's not where the turbo will sit but for easy and simple, it's a great start. From there you can select your secondary, in which theres a fair number of thoughts on. Imo the secondary should flow about 60% mass flow at 60% efficiency as what the primary does. Hope this gives you a decent start.

[NakeDiesel]

Thanks for the info wwentzler, I know you wouldn't gain air, but help with spool up of larger turbos. My question on the s366 as the small one was if it would be too restrictive. Guess that's where you get into waste gates and pipping around the turbo on the hot side to feed the large turbo.

Gives me food for thought and a starting point to start investigating where to move next with the truck.

[MAXX IT OUT]

This is a pretty interesting watch on compounding, I know its a honda, but the info is interesting.
3000HP, 150 PSI Of Boost | What Do YOU Know About Compound Turbo Systems | Shane T [TECH TALK] - YouTube

[wwentzler]

Originally Posted by NakeDiesel

My question on the s366 as the small one was if it would be too restrictive. Guess that's where you get into waste gates and pipping around the turbo on the hot side to feed the large turbo.

Youd be correct, the 66 is going to hit a point where it will be a choke point. This can and does come from both hot and cold sides. On the cold side, you force the atmo to "want" to compress at a higher pressure ratio because just cant move the mass without doing so, but on the flip side the hot side of the 366 becomes a huge choke in flow and the atmo turbine doesnt receive enough energy. Realistically you can use a bigger atmo and gates and whatnot and continue to achieve slightly more peak power, but it's a diminishing returns kinda thing.

[NakeDiesel]

Interesting discussion in that video Maxx.

I forgot to list up above I do have a data logger system on the truck. I have new sensors to hook up and get logging. Once I have them all setup and working, will track RPM, Driveline RPM, EGT at Exhaust Manifold, Inlet air temp, Temp post turbo/pre intercooler, Temp post intercooler/pre intake, back pressure at exhaust manifold, pressure post turbo and pressure post intercooler, trans temp, trans pressure, fuel pressure as well.

Once I get the new sensors setup and start testing probably with the 480, I'll start learning more on any issues the 480 is causing. So I'm not just trying to throw parts at the truck, I used the logger to determine that I'd maxed out the ability of the th400 I was using and breaking converters on, as well as other things with the truck.

[zfaylor]

Are you after 1600hp or do you plan to run it much lower? Putting 1600hp worth of air on a truck and running it at 1200hp isn't very efficient. We get a lot of guys who want a turbo to grow into and more times than not you will be disappointed is why I ask.

1600hp worth of air is a lot on a 12v.

[NakeDiesel]

I guess that's the starting point I need to figure out, what the max power goal is for the engine. I'm really not sure how much my current build will support engine wise.

I know my singles and 2000+ egt's aren't the best on the engine that I've run in the past. I've cut the fuel way back on the pump and when I get it all together I'll start pushing it higher as I gather more results and testing with my current turbo and I can figure out from there I guess where I need to go.

I've tried to logically research and build a competitive engine that would get me up there hp wise, but I don't have all the experience in the world either to know what the limitations are going to be.

[J-Pipes]

I'd think a single would be the way to go. Seems most of the big racers are going single. I mean even the top single turbo sled pullers are past that power level, I know different spool up requirements, but still. Pretty sure the firepunk s10 is single turbo 2k plus hp.

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[DDually]

Subd

[thatguy69]

Your not using a spool jet are you?

[NakeDiesel]

nope, no spool jet, haven't really heard much about them, but have been swamped with stuff for the last year or so as well.

If I can get a big single to work, I'd be all for it. Room is a premium in the truck. I think I was having a series of issues with spooling up that 480 and I may just be annoying people with this thread for nothing.

Dug up an old pic of the s475 sitting in the truck

[SmokeShow]

A good billet wheel s400 (88 or so) is capable of getting up to that power goal. It might need help spooling though. Hell, buy "last year's" 3.0 charger off a sled puller, they're plenty capable of making that kinda power... Trickery will come in how to get it lit ASAP on the hit.

Is n2o allowed? If so, just spool with that. I assume it's not allowed or you'd already be using it?