twincharging prototypes needing constructive critisism (SC14 + turbo)

[Jayem]

Here's my version. Supercharger is Eaton M90 and turbo is Garrett to4. I have throttlebody after the turbo and then there's Y-cross. Another goes to Eaton and another goes to supercharger bypass that opens after the turbo pressure exceeds the pressure produced by Eaton. After that Turbo boost has straight way to intercooler and intake manifold. I consider this as simple system. Sorry I dont have more recent pics.

BTW. What car is your M90 off from. Mine is from Thunderbird. I thought that this was easiest because it has intercooler pipe connection in pressure side. Most M90's bolt to intake manifold directly and those have complicated flange arrangement.

[RAd28]

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

that a 4cyl? from the hilux right?

there was a RA23 running in targa tas this year had one of them turbo'd, sounded pretty sweet... hard to say how it performed though, was running in touring class which means it's driving in a pack with other cars :S

good luck with the project.

[twiztd]

I apologise if this is of no interest but inspiration can be taken from the old group b rally cars... specifically the Lancia Delta S4...
these things easily put out 500hp out of 1.8L engines... back in 1983....

check out the pic of the engine setup

http://www.carsfromitaly.net/lancia/index.html

Basically they have a bypass on the supercharger which allows air to flow down the path of least resistance once the turbo is making boost. as you can see there is really only one more valve than in a standard turbo system. lancia found this to be a reliable system which produced between 450 and 600 hp depending on the requirements for whatever rally they were doing.


twiztd

[brett_celicacoupe]

yeh ive seen their plans. there were bigger pics on PF

[5000gt]

after searching for research, i found this thread... very good read... because i am using a twin screw, i need a clutch setup as it will still have a massive paralytic drain even at idle (internal compression)... the setup i have chosen has already been posted... few changes can be made as need be but will be done during testing stage... for now, this is just research...

Something else to note, i am not doing this on a toyota engine. 12a rotary is the target... charger being used is an IHI twin screw unit off a eunos 800 (mazda millenia) miller cycle engine with internal compression to about 20psi....

Clutch will be engaged when charger no longer supplies enough air and turbo has spooled sufficiently. Design chosen sees charger before turbo to help in turbo spooling... positions of BOV's have yet to be chosen....

comments? advice?

[brett_celicacoupe]

the best way to do it from my research is to have the turbo feed the supercharger then into the manifold. there will be a bypass valve in parallel with the SC to relieve pressure if you have the throttle body after the PD blower.

Design chosen sees charger before turbo to help in turbo spooling

'turbo spooling' should be no different whether SC is post or pre turbo. X amount of air flows through the compressor housing regardless.

the 'paralytic drain' of the supercharger is a function of the pressure difference across it. so remove any pressure difference across it (open the bypass) and it wont put any noticable load on the engine.

with a turbo>SC>engine setup, the SC wont become a restriction like many people think. the SC pumps a fixed volume (NOT MASS) which is always higher then engine's consumption. regardless of the air density, the supercharger will pump the same volume. if we want to get a higher mass of air into the engine, remembering that more air mass = more power then you can either increase the air density at the SC inlet, or pump more volume (change SC pulley ratio). the turbo feeding air into the SC is essentially increasing air density.


if you setup the system so SC>turbo>engine then the supercharger will become a restriction. the max air mass flow and consequently max HP is dependant on SC inlet temps, pulley ratio and SC volumetric efficiency. you could probably even work this out on paper.


ill try explain it with perfect world/theoretical numbers....with the turbo>SC>engine setup, the turbo may initially double the air density. this means you effectivly have 2L of atmosphere air in a 1L space. if the engine displaces 0.5L of air per rev then you would expect it to have 1L of atmosphere air in the cylinder before combustion (2x0.5). if you place a supercharger in series that may displace 1L of air per revolution then things will change again. the supercharger now displaces 2L of atmosphere air in the same engine revolution as the engine is consuming 0.5L. so your now trying to force 2L of air into a 0.5L space with a supercharger in series.

it probably makes no sense but thats my theory on it

[5000gt]

i think you're forgetting that i am using a twin screw which will drain power regardless of whether the bypass is open or not as it is ALWAYS compressing air while turning. That is where the clutch comes in to stop it turning... which also sees the need for the bypass which is built in anyway. This is the only con of using a twin screw.... will always be ON even at idle or cruise without a clutch.

The pic i posted is only an indication of the setup...not exactly how it is being done... obviously, piping will be shortened where possible etc...

I think you're right about there being no benefit to spooling by having sc pre turbo though.

The problem with having turbo>sc>engine is that the twin screw will then further compress the charge which may be catastrophic for the engine (internal compression to nearly 20psi)...

Unless i am stupid in my understanding of how the twin screw charger works, i think i am right to assume turbo pre charger will be a bad idea if it is ingesting boosted air.

Tan.

[oldcorollas]

the twin screw has internal compression, but the losses may be much less than you think.

power loss comes from both mechanical loss (of just turning the parts) and the compression loss, from compressing air... but it is all relative.

if there was no internal compression, and a bypass valve, then with bypass open, the air pressure on both sides of charger is equal.. regardless if the TB is pre or post SC.. that just changes the amount of air flowing thru the SC. so there is no compression loss.

with compression (you say up to 20psi.. which means internal compression ratio is 2.4:1?), with bypass open, both ends of SC are same pressure. when the rotors are sealing with a pocket of compressed air (lets say just before it opens to the manifold) that is trying to force the rotors to turn backwards.

if the TB is after the SC... then inlet and outlet are at 1bar. the compressed pocket is at 2.4bar and so you have a pressure difference of 1.4bar trying to open the rotors,

if the TB is before the SC, then the amount of air going in is much smaller... ie, say you have 0.4bar pressure in manifold, and both before and after SC.
even if compression takes place in the SC, it is 2.4 ratio of 0.4bar.. ie 0.96bar pressure in the pocket in the rotors...
this leaves you with a pressure difference of 0.92 bar trying to force open the rotors....

but it is a little more complicated than that

because of the rotor geometry required for internal compression, ie the outlet volume of rotors is 1/2.4 = 42% of the inlet volume... when the bypass is open the force trying to turn rotors forward (from manifold pressure) is greater than trying to turn them backwards...

ie.. if before and after SC is 1bar, and inlet area is A (ie, inlet volume of rotors before they close), then the forwards turning force is 1xA.. but the backwards turning force is 0.42xA...

if manifold pressure is 0.4, then you have 0.4A and 0.17A... so this actually DECREASES some of the losses due to internal compression...

or maybe i'm getting comfused

[5000gt]

just finished doing some work...tired... and you just made my brain hurt....

lol, i think i'll try and read that again after a shower and some dinner. I think i understand though.... so it works out the same as a roots type.... with bypass open, the pressure on both sides of the charger should be the same.....

[oldcorollas]

nah, it will be higher than roots.. cos you have the bubble trying to open the rotors.. once the intake end has closed.. but the outlet end hasn't opened.
the increased area open at the inlet end, compared to the outlet end, may (or may not??) have effect of reducing losses (i am not sure on that )

your losses will be smaller if you throttle before the twinscrew, rather than after, as the absolute pressure differences will be smaller..

someone mentioned that the having throttled twinscrew causes them to heat up more, as there is less air going thru to physically remove the heat from the metal.....

what do ya think?

[5000gt]

i can see the possibility of heat soak due to lack of air.... how much? dunno till the charger arrives and i can try out a few tests myself....

i may ask a few people who have had success with twin charging twin screws before i do anything definite...

[feral4mr2]

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.

mine works great in the same way as your set-up (though the s/c is switched on/off by ecu as stock), but i dont get the same boost vs rpm as you. could be the damn large 0.84 a/r ex of my t04..

with a turbo>SC>engine setup, the SC wont become a restriction like many people think. the SC pumps a fixed volume (NOT MASS) which is always higher then engine's consumption. regardless of the air density, the supercharger will pump the same volume. if we want to get a higher mass of air into the engine, remembering that more air mass = more power then you can either increase the air density at the SC inlet, or pump more volume (change SC pulley ratio). the turbo feeding air into the SC is essentially increasing air density.

indeed, my thoughts too.

[5000gt]

did a little digging and found out that VW had a twin charge Golf running around for quite awhile now. Interesting to also find that it has a charger pre turbo..... intake -> roots charger -> turbo -> engine

[MWP]

did a little digging and found out that VW had a twin charge Golf running around for quite awhile now. Interesting to also find that it has a charger pre turbo..... intake -> roots charger -> turbo -> engine

I wonder if there is a simple one-way-valve in parallel with the SC that opens when the turbo is drawing through more air than the SC can supply.
The vacuum caused by the turbo on boost simply could suck the sprung one-way-valve open.
When the valve does open, SC inlet & outlet are at equal pressure, which also = no SC pumping losses when turbo is on boost.

Easy to setup, and would give a very smooth transition.
My likey this idea

[brett_celicacoupe]

I wonder if there is a simple one-way-valve in parallel with the SC that opens when the turbo is drawing through more air than the SC can supply.
The vacuum caused by the turbo on boost simply could suck the sprung one-way-valve open.
When the valve does open, SC inlet & outlet are at equal pressure, which also = no SC pumping losses when turbo is on boost.

Easy to setup, and would give a very smooth transition.
My likey this idea

im still sold on the turbo-SC-engine configuration as it essentially multiplies the power rating of the supercharger. you can take advantage of the fact that a supercharger pumps a volume of air regardless of air density. if you double the pressure (2 bar ABS) at the inlet of the blower and not raise the temperature then your going to pump double the air mass (=double the power). this is why a supercharger wont be a restriction in this arrangement but will if the blower is before the turbo.