twincharging prototypes needing constructive critisism (SC14 + turbo)

[Esteban]

Interesting and long read, I doubt I took it all in...

Brett re: concerns cooling SC charge ... inline water to air setups are relatively cheap nowadays? dont have to increase the length of your inlet tract anywhere near as much. They may not be as efficient as A->A, but it might be better than nothing?

[Jorrs]

okay, so im thinking something along the lines of;
whether "TB 1." is mechanically driven or electronically is something ill need to look into. if it is mechanically driven, the butterfly will probly have a flat filed into it so that it can never close 100%




thoughts/opinions?

thats a good setup there, much like the Nissan Super Turbo, nice diagram mate it helps explain it alot better !

[Drew]

silly question,
why turn the blower off ??

i understand the bypass idea around the blower if it becomes a restriction but the turbo can not flow more air by itself than the blower & turbo combined.

[Esteban]

The blower will not be creating any usable boost when the turbo matches and out puffs it. The turbo is creating boost for free, whereas the blower is not, it has a large parasitic drag.

Also, one of the benefits of using the supercharger at lower RPMs is you can gear it (or belt it) to run to it's maximum efficiency lower in the rev range, and produce more boost at lower RPM. This does however have its disadvantages, as beyond that RPM range, the blowers simply produce more heat. This is always bad in a heat engine where the relative difference in heat in and out is our power factor. Also anecdotal evidence suggests our SC12's and 14's rotors start to melt themselves or their teflon coating at these higher temperatures.

And that's your bloomin' lot

edit: i kant spel

[Bored?]

I think this setup is needlessly complicated.

I haven't read the whole thread so sorry if this has already been covered, but there are some smart comments and some dumb comments in the last few posts. I'll leave it to the reader to figure that out.

By definition, a fixed displacement supercharger like the sc14 being suggested here can't "run out off puff" because it is geared at a fixed ratio with the engine.

Therefore, if you ditch TB1, and never disconnect the supercharger, airflow through TB3 (usually called a bypass valve) must always flow away from the engine, and back towards the turbo. Moreover, the pressure between the supercharger and the throttle body must always be greater than the pressure between the turbo and the supercharger.

Therefore, to simplify your solution, you should ditch TB1, use an off-the-shelf wastegate in place of TB3, and control it off the pressure differential across the single remaining throttle body.

[Jorrs]

i see where your coming from it would make the process alot simpliar running the one TB before the intercooler and keep the SC running as well as the Turbo making boost ?

PS, i would love to see some pics of someone who has actualy done one of these..

[Drew]

the blower is just an air pump it does not care if air is being pushed into or around it, it still pumps air.

for 2 years my 4agze has been running a stock pulley sc12 & a vg30det t03,
the blower has been running switched on constantly for 5 years all up in a daily driver.
the setup is
air filter > turbo > t/body > blower > intercooler > manifold.
bov between turbo & t/body

simple, smooth transition, reliable
the blower makes boost as soon as you mash the throttle, the turbo starts to make boost at 1500rpm & it has 18 psi in the manifold at 2500rpm.
i haven't increased turbo boost yet as i was trying to preserve the now broken t50 box,

in my exp when you gear the blower up it will fail quickly, i have replaced the blower 3 times in 18months on another gze with a bigger crank pulley.(12 psi boost)
i think it is rpm rather than heat that damages sc12 blowers.

[thechuckster]

stockymcstock on Performance Forums has twin-charged (on the cheap) a VL. Includes pics and vids.
http://www.performanceforums.com/for...php?t=67207968
and
http://www.performanceforums.com/for...php?t=67210218

[Esteban]

Well, okay, i'm terribly sorry to offend you with my out of puff comment, but superchargers have their efficiency ranges just as do turbos, and that is all I was referring to.

[Drew]

i'm not offended ,
i know what you meant about efficiency ranges of superchargers but that changes when you force air into them trust me.

[DeftAnesthetik]

well, i have read the entire thing. while here i grabbed some really usefull info. as i have been thinking about this for about a year, I too will be jumping into building one of these things. something that is recurring in the discussion here is that all setups seem to come back to some type of compound setup ie. SC feeds Turbo or Turbo feed SC with some sort of bypass for when the turbo is approaching higher boosts. The only real parallel system i have seen is this one.



while it does have its issues they can be solved and (IMHO) offer better flow and more powerful outcome.

On my project I am planning on taking the next step an going for a twin turbo, twincharged 4a. so a 4A-GTTZE! This will be going into an AW11 so room for pumbing should not be an issue.

I am planning on drawing something up and crunching the numbers on this to see what i can come up with. I will post when I am close to get some feedback.

[brett_celicacoupe]

everyone with a working setup just feed the turbo through the SC full-time.

the model above will not work since a turbo cant produce 10psi (say) a 0 flow

ie, the turbo one way valve will never open

[RAd28]

hows progress going brett?? any updates?

[mic*]

i'm not offended ,
i know what you meant about efficiency ranges of superchargers but that changes when you force air into them trust me.

Bestest most concise statement on this thread yet!!!!

Its all conjecture about how the SC responds to a turbo pumping into it, and the whole thread is really dedicated to various opinions, and means to eliminate problems based on conjecture...

There are two things that affect the SC's efficiency;
-RPM's
-Pressure ratio

The parasitic drag on the crank is determined by the acceleration of engine rpm's & the pressure ratio across the SC.

Eg. Accelerate from 1500 to 5000rpm's at 2:1pr (14.7psi-ish boost) in 5 seconds = X drag
Accelerate from 1500 to 5000rpm's at 1.5:1pr in 5 seconds = <X drag
Accelerate from 1500 to 5000rpm's at 2:1pr in 3 seconds = >X drag
Hold engine speed at 5000rpms at ~0 pressure ratio (bypass open) = ~little drag
Decelerate from 5000 to 1500rpms at ~0 pr = <X neg drag (forward spinning inertia)

So when the turbo is actually boosting against the SC, the pressure will be trying to accelerate the lobes, negating all drag inherrent with the SC making the boost because the pr is pushing forward, and negating some of the drag caused by accelerating the engine for the same reason...

There would actually be more drag on the crank as a result of a bypassed unclutched SC than there would with an un-bypassed unclutched SC (bypass is still there for vac, just cloed under boost). HOWEVER, the "boost bypass" might allow the turbo to see a lower pr and be more efficient... Who cares??? Get a bigger turbo...

I think iv said this somewhere within this thread, but my conjecture is it all comes down to your intercooling & turbo sizing, not intricate/elaborate bypasses etc.

Lets stop splitting hairs about where to scavenge tiny little bits of efficiency out of an inherently inefficient concept. This idea for me is about making power! Keep it cool and stuff the fuel...

[brett_celicacoupe]

hows progress going brett?? any updates?

bought a 3RZFE
am buying a eaton M90(waiting for clint to get back to me ). i think the SC14 i already have will be too small for a 2.7L

the turbo will be something like a GT35 or GT40 series