Been lookin at some twin setups and I noticed that most people run the air filter on the 2ndary and it feeds the primary(small) charger, wouldn't it work better if the small faster spoolin primary feeds forced air into the larger 2ndary so it will spool faster? I'm probly just overlookin somethin elementary, but I was just courious cause I came across a ht3b today off a road tractor and thought about fabbin up some twins, any insight would be helpful

BC

 

The small turbo cannot move enough air to feed the larger turbo , that's why they are the way they are. either that or i am totally confused.

 

First off, you've got which one is the primary and secondary backwards, but dont worry, its a common mix up, the terminology can indeed get confusing, since technically the primary compressor is the compressor of the large turbo and the secondary compressor is the compressor of the small turbo, while the primary turbine is turbine of the small turbo and the secondary turbine is the turbine of the large turbo BUT>..... We simplify matters and name by the compressor, SO (finally ) the large turbo sucking in air from the air filter is called the primary turbo, and the small one is the secondary.

Now, the reason they work is not a matter of one spooling first, then the other.... Twins setup correctly spool at very nearly the same time. The purpose of twins (or compounds) is to compress the intake charge in two compound series stages, and expand the exhaust gasses in two compound series stages. In this manner massive boost pressures are generated far more efficiently and without crazy heating of the intake charge and also without huge back pressures by allowing the two properly sized compressors and turbines to do approximately the same work. The sizes are dramatically different as a direct result of the drastic density increase and associated volume flow decrease when the air is compressed in the compressors and the drastic density decrease and associated volume flow increase when the exhaust gasses are expanded in the turbines...

I always encourage guys to read about multi-stage high speed centrifugal compressors like those used in natural gas compression and in very large industrial air compressors to learn how the pressure, denisty and volume flow changes through the stages. Also some reading on gas and steam turbines will also explain how the gasses are more efficiency cooled and expanded in twins as well.... Do some technical reading on this information, and you will be far better off then listening to lots of the myths and wives tales that get told about twins.... (hint: the turbos being sized differently to give you different points of spooling is a persistent incorrect one....)

But, in a nut shell, a very nice and proven combo is indeed an HT3b as a primary and your existing HX35 as a secondary.

KP

 

Thanks for clearin that up I'm notorious for jumpin in head first, figured everbody had em that way for a reason, gotcha though just like a 2 stage compressor, oh yea I've got a hybrid 35/40 16cm2 now think I should go back to the old stock hx and 12cm2 housin?

 

a towing twin setup usually has a 35/16 on top while a more performance oriented setup has a 40. i would assume a hybrid with a 16 housing would be an excelent top charger. however that is only an assumption

 

Cool thanks for the input, anybody got anyother suggestions comments, I ain't that bright fella's I'll take all the help I can get.............

BC

 

heres the best advice i can give you. DO NOT fab up a set of twins, instead, ship that ht3b to me and ill get it out of your way

 

Well if you think,............wait a minute

Any suggestions, or really if it can be done, a hx35/ht3b (headgasket friendly) twin setup, as far as wastegate settings on the 2ndary or a wastegate at all?

 

your gonna want an external gate and when it comes to how those are setup I am lost

 

yeah the hx35/ht3b twin set up is known as the towing twins or the cheap twin set up. i am in the process of collecting the parts for this exact set up. ive been told that you can wastegate it down to 50 psi so it wont blow the head gasket. but studs are still a good idea.

 

ya know what a rebuild kit for a b3 runs, forgot to call today.

And where ya gettin your parts from, local or ya orderin em?

Bryan

 

Still a bit slow over here
Umm, what? You talking about the idea that the little turbo spools the big turbo?
Or that the little boosts at sucha such psi and the other at > whatever?

So all 'twins' are set up like you describe in your posts (besides optional IC and such)?:
air filter->bigt->lilt->aftercooler
exhaust manifold->lilt->bigt->downpipe


Ocmechanx- give Olee a call. He sells twin kits with 35's and 35/40 hybrids. Call Piers too. Get some great advice and maybe some parts you'll need too
http://www.powerbypoole.com/turbos.html#dodgezilla
http://www.piersdiesel.com/

 

Actually Phatboy, I was saying that the idea of the turbos spooling at drastically different times and 'one spooling the other' and 'one for low RPM and the other for high RPM' were all INCORRECT myths.... Setup properly, they should spool very close to each other and deliver approximately equal pressure ratios.

And yes, that is the way all twins as we use them on our Cummins are setup, with the option of an intercooler between the stages as you noted. Personally, I wont build mine without the intercooler between the stages. This is next year's project, but I am gonna figure out how to make room for the intercooler or ELSE !! lol

KP

 

I'm fixin to do some r&d on spraying the secondary's compressor section. If I've got my numbers right...and a bunch of them I promise ...the heat latency of a 50/50 mix delivered at 3% of air mass will surpass that of even an efficient air to air. The net would be somewhere in the neighbor hood of 30% increased secondary efficiency, and a temp drop of 200* at the aftercooler inlet. The bugger to work out is getting the mix down to 10 microns, and how to place it in relationship to the compressor wheel. I believe a close proximity and aiming it the wheel center will keep tip wear negligable to non-existant. 35 wheels are cheap to experiment with....and if the results don't pan, I'll break out the pipe and welder. but, as with you, I will be intercooling, there is just too much to be gained not to.

 

got Diesel, Look into Delavan (www.delavan.com) mechanical atomization fuel oil burner nozzles. They are sized in Gallons per Hour and come in many different spray angles. They use strictly the fluid pressure to atomize the droplets into incredibly small particles, essentially a fog, by causing rapid spinning and shearing of the fluid within and then discharging through a very small EDM'd hole. They come with a super fine mesh strainer or a sintered bronze strainer right on the nozzle. They are rated in GPH at 100 Psi, but higher pressures give you even finer mist and the flow will follow the square law. Don't go much under 100 psi though, or the fog quickly breaks down into droplets. I have gone down to 70 Psi, and its still decent but noticably less fine.. By 50 Psi, its a mess... So you need a pump to do about 100 Psi.

There is no doubt these nozzles are the way to go to fog water/meth into an intake or compressor scroll. It is my opinion, that the improvised 'hole-only' nozzles supplied in most kits do not give a fine enough mist.

If you want 3% of mass airflow, figure you need about 100 Lb/hr of water flow or about 12 GPH. So you could try a Delavan 'B' series (solid cone) 12 GPH, 45° angle nozzle run at 100 Psi to start with. They are about $10 each if I recall.... And you will need a nozzle adapter as well, it has either an 1/8" or 1/4" NPT femal on one end and threaded to recieve the nozzle on the other and its about $25.

KP