3SGTE/Turbo: twin charged

[feral4mr2]

you'll find the ones that say the twincharge system is soo hard and expensive etc. are those that have never tried it for themselves and read it somewhere... haha..

looking forward to hearing how the present TC projects in this thread go.

[rsfire]

i've done my research, i've read about it done both ways, it's just much more common to do turbo>s/c. The VW that comes stock twincharged is the same as my method too.

[Kevin mr2 1985]

so i had another idea for a twin charged system

go air fliter > turbo > throttle body > supercharger > IC > to block.

now i would replace blow off valve with one with springs that could be changed, so then i would get a 20 psi spring and maybey move up later. Other than that is that all the stuff needed to make the system run.

[div0]

Originally Posted by Kevin mr2 1985

go air fliter > turbo > throttle body > supercharger > IC > to block.

That is the easiest way to put together a twincharger system, and I believe that is the method feral4mr2 described using earlier. You will want to setup your tubo's wastegate control based off the total combined boost of the turbo+supercharger at the manifold, and regulate it for your desired 20psi boost pressure.

I decided to go more complicated and intercool the charge between the turbo and the supercharger, and also bypass out the supercharger in the higher RPM range. Both steps are intended to help preserve the life of the supercharger as well as improve performance.

[Kevin mr2 1985]

nice its sounds like it is very complicated

[4G63T-SC]

Hi divO & everybody. Interesting to read your setup. Just so happens that I'm
gong to use a GT30 > I/C > SC-14 > water/meth > T/B. My project isn't an
MR2, even tho I do likum ! Mine is a 92 Lancer 4G63 auto awd locked 50/50.
Always been keen of the Lancia Delta S4 setup, so it inspired me copy it.
To fit the SC-14 where my A/C was, I have to cave in my firewall. No biggy.
The Lancia S4 had a very short bypass-t/b pipeline. My idea is to branch
down off the SC intake > 90deg bend > T/B (bypass) under the SC > 90deg
bend up > branch back into the SC output spigot. Idea from this Lancia S4.

I'll use adj VDO elec switch boxeS to kill the clutch & open the t/b-bypass.
I see my switching points need to be per gear rpm to lessen bearing ware.
The Lancia killed the clutch at 5k & bypassed to free up the turbo output.
My clutch off guess without testing is 4k 1st, 3.5k 2nd, 3.5k 3rd (av load)
*divO what's your drive ratio guess to match the SC-14 with the GT30 ?
Keen to see how your setup goes >>>>
Cheers !

[div0]

Originally Posted by 4G63T-SC

*divO what's your drive ratio guess to match the SC-14 with the GT30 ?

Hello Anthony. Here is my best guess for the drive to supercharger pulley ratio for the setup you described. First, when you say GT30 turbo, I'm assuming you are referring to the Garrett GT3076R. According to the Garrett website, this turbo is good for applications between 2.0L - 3.0L displacement engines. A 2.0L engine won't fully spool this turbo till late in the RPM range, while a 3.0L engine should spool it fairly quickly. Since one of the primary goals of twincharging is to gain a wide torque curve, we want the turbo to spool quickly and should target an equivalent displacement near the maximum 3.0L.

I'm also going to assume that your SC14 supercharger is rather old. My SC12 supercharger has just over 100k miles on it, and based on the pressure ratios I was seeing before it was ported, it has an unported volumetric efficiency of about 77% (post porting it increased to about 82%). I'll assume 77% for this calculation.

So you want to target a pulley ratio that gives you an equivalent displacement of about 3.9L when you include the efficiency reduction.

The SC14 displaces 1.4L per revolution. A 4 stroke 3.9L engine displaces 1.95L per revolution. So I would target a pulley ratio of about 1.4:1 crank pulley to SC pulley to give you a final equivalent displacement of a 3.0L engine.

You may want to see if you can find the specs on the SC14. With a 1.4:1 ratio, with the engine at 6000 RPM, the SC14 will be spinning at 8400 RPM. The max spec for the SC14 RPMs may factor into your choice of what RPM to start bypassing the SC.

So that is my best guess. I Hope it helps. Good luck!

[4G63T-SC]

Removed graph, not needed.
Cheers !

[M-r2d2]

kevin the guys that did your wiring DR tweek have done a TC setup on a corolla with the 4agze you can call them to see what they did Josh is very helpful.
and Div0 if you are going for longer life of your components then not bypassing the SC would be better. This is how dr tweek explained it to me basically just add a turbo. the SC is a positive displacement SC so any air that is passed through it will be compressed. so if you add a turbo that is compressing air the the compressed air from the turbo will then be compressed again by the SC. So say you won't 20psi of boost TC'ed then set your turbo out put to something like 4psi and then with the stock 10psi from the SC it will multiply to a much bigger boost result (just example not hard fact nubers). so for more reliability this is the way to go your SC runs at stock boost all the time just the way it was designed to. the turbo will run at a much lower boost than it was designed for so it will last much longer. If you decide you need more boost then all you have to do is adjust the wastgate to up the turbos boost and there you have it long lasting TC engine set up.

Oh and the idea is to get a turbo that will kick in at 4K rpm cus that is where the SC is at max boost. So you will definitely feel the kick of the turbo jumping from 10psi to 18-20psi

that's what I've gotten out of everything i have read about TC hope this help

jason

[Kevin mr2 1985]

i really like the idea of twin charged but i want to find an inexpensive adjustible turbo to use. cause that is the only thing right now that is stopping me from doing it... well there is that money thing. or lack of lol.

will this turbo and stock pulley on sc be good? with about 20psi blow off valve be good?

here is the manifold i will use: cxracing.com: Turbo Exhaust Manifold For Toyota Corolla with 4AGE Engine with T25 Turbo Flange

here is the turbo: cxracing.com: T28 Turbo Turbocharger Civic S13 S14 Internal Wastegate 8Psi, .86 A/R Compressor , .42 A/R Turbine

here is the blow off valve: cxracing.com: Blow Off Valve and 2.5" BOV PIPE Adapter Welded, Matching Silicon Hoses and Clamps

so will that be good for around 200 hp? or how much hp?

[M-r2d2]

well i don't know that much about turboing yet i just understand the TC set up.
there are turbo headers on ebay that will set the turbo alot lower than that one and I think thats where you wont it. just search for like AE86 there is alot of Corolla stuff just take a peek. I know the tweek set up used a garret turbo and I think its like $500 give or take cant remember.

I'm going to TC sooner or later I just need to get the dang thing on the road first. I would start small first I would be trying to find a good water to air innercooler. I'm going to use frozenboost.com set up. Then maybe suspension stuff so this rocket will fly straight.Then move up to more power.

But i do know you cant just jump up to 20psi right out of the shoot. I think injectors,ECU,stock fuel pump will only hold you up to 18psi if that much. then you have to start upgrading everything. but there are plenty of people on here to get the right turbo and header just search and wait don't act on impulse.

[Kevin mr2 1985]

lol im not going to buy those just found the site and the very inexpesive parts and i thought i would post but my car is done with susepension and brakes now im focusing on power, i also bought a 255lph walbro fuel pump it can handle up to 550hp and the injectors are already oversized for a 4agze, and my ecu is from a 94 levin gtz its a little better than the stock mr2 one thats for sure, but ill wait and see what i do thats for sure.

this is probably a better choice of turbos i read somewhere it was at 10psi around 3700 rpms Holset HY35 turbo.

anyone have any other good suggestions for a turbo that spools at 4000 rpms?

[4G63T-SC]

divO did you get my PM ?
Cheers !

[div0]

Originally Posted by M-r2d2

and Div0 if you are going for longer life of your components then not bypassing the SC would be better. This is how dr tweek explained it to me basically just add a turbo. the SC is a positive displacement SC so any air that is passed through it will be compressed. so if you add a turbo that is compressing air the the compressed air from the turbo will then be compressed again by the SC. So say you won't 20psi of boost TC'ed then set your turbo out put to something like 4psi and then with the stock 10psi from the SC it will multiply to a much bigger boost result (just example not hard fact nubers). so for more reliability this is the way to go your SC runs at stock boost all the time just the way it was designed to. the turbo will run at a much lower boost than it was designed for so it will last much longer. If you decide you need more boost then all you have to do is adjust the wastgate to up the turbos boost and there you have it long lasting TC engine set up.

jason

Well, I guess I'll have to respectfully disagree with Dr Tweek. One thing to remember is that the stock SC12 setup already includes a bypass. It was not designed to be a 100% duty cycle supercharger. It was designed to kick in and out using the supercharger clutch and only engage when needed. The time the supercharger is off, it is bypassed.

One minor correction to your post is that the SC12 positive displacement supercharger doesn't actually compress anything. It actually just moves a fixed volume of air per revolution. Compression occurs at the outlet of the supercharger, where the supercharger is forcing a larger volume of air into the intake than the engine can swallow at atmospheric pressure. The result is that the pressure in the intake rises until the engine is forced to swallow the same volume that the supercharger is feeding it.

When you add a turbo to this mix, the volume of air that the supercharger is moving is higher than atmospheric pressure to begin with, and it now takes a lot more effort for the supercharger to force pre-compressed gas into the intake manifold. So twincharging does create a substantially higher load on the supercharger. At the higher RPMs, a lot more power is being consumed by the supercharger, and I'm concerned on how it will hold up. I consider it better to bypass the supercharger at the higher RPMs, eliminate the parasitic drag from the supercharger, and size the turbo such that it is running in an efficient zone for the flow seen in the higher RPM band. With the turbo sized correctly, it should be most efficient running solo in the upper RPMs and providing all the boost. Based on the compressor map, it would actually be less efficient at running lower boost levels.

I should also add that I'm running an oversized pulley. In the twincharge setup, I'm hoping this will help the turbo spool at even an earlier RPM range. I've also read some concerns about the SC12 rotor coatings starting to melt at higher RPMs with oversized pulleys. Certainly pumping hot compressed gas from the turbo compressor outlet into the supercharger could only make this situation worse. So limiting the supercharger to the lower and cooler running RPM range makes sense from this perspective as well.

These are the things I considered when deciding to bypass the supercharger at the upper RPM range. The most difficult trick will be making this transition smooth. But having both the bypass and the clutch engagement both individually under computer control should allow me to experiment until I have it set nice and smooth.

And who knows, maybe Dr. Tweek is correct and I'll find my SC12 blowing apart someday when it gets bypassed in the upper RPM range.


-div0

[M-r2d2]

well that is a nice over view. Everything did make seance but the part that the supercharger was made to be turned on and off cus it was designed that way might be off, I think that toyota who is know for long life and good gas millage made it that way to help with the gas millage it could run constant but then it would use gas and well cut down on SC life. I don't thing that compressed air going into the SC would make it work harder its already being forced through at that point. the SC just pack it all in the same as if it has to pull the air in or if it is being forced in. the only down side would be that the air is hot but an innercooler fixes that.
I know its not going to change your mind and it looks like you have done a lot of work and if you can get it all to work and work really well then more power to ya. Your idea is very good just a lot more complicated and just more things to brake if anything gos wrong. The way I see it is that my way is simple and I have herd the testimonials of the setup and I'm sure there are tons for your setup that I haven't come across.
but good luck with it and I hope to see a video of you car ripping it up.
I have gotten so that I can drive my 4agze DLI just plain stock w/ NA exhaust and with copper plugs (for now) and DAMN so TC in anyway will make any one go oooooooh

[4G63T-SC]

Advancing the inlet cam will allow more time to push more compressed air in.
Creating more cam separation = more air passing threw the same engine.
More exhaust speeds up the spool time for the same engine/turbo combo.
I agree that the turbo should be allowed to outperform the SC up in the high
rpm range by bypassing the SC completely at it's peak torque. divO also the
hotest engine rpm is between 3k & 4.5k. This heat creates knocks & can be
lessened by richening the fuel trims during those revs. You will be bypassing
somewhere between those rpms. When you do bypass, your inlet temp will
drop because your SC will no longer be heating the air & less hp drain tooo.
Cheers !

[div0]

Originally Posted by M-r2d2

I don't thing that compressed air going into the SC would make it work harder its already being forced through at that point. the SC just pack it all in the same as if it has to pull the air in or if it is being forced in. the only down side would be that the air is hot but an innercooler fixes that.

Actually having to move denser pre-compressed air will make the supercharger work harder. As long as the engine is driving the superchager, there is no period of time where is it a restriction to the flow of compressed air from the turbo charger... the pressure from the turbo doesn't help move the supercharger. Rather, the (positive displacement) supercharger will take the denser compressed air, move it through the supercharger and introduce it to the intake manifold with a fixed compression ratio that is determined by the fixed supercharger RPM vs. the engine RPM.

Even though the pulley ratios cause a fixed compression ratio (~1.68 measured for my 178mm pulley), the amount of torque required to drive the supercharger is proportional to the pressure differential between the intake and exhaust. If the supercharger is driving atmospheric pressure to boost, for my supercharger it would go from 14.7psia to 24.7psia (~10psi boost pressure). The supercharger requires the amount of torque necessary to drive this 10psi pressure differential.

Now if I'm feeding the supercharger 9psi of boost from a turbo, the supercharger will take 23.7psia and raise it to 39.8psia (25.1 psi boost pressure). The pressure differential is 16.1 psi, so it will take 1.6x more torque to drive the supercharger while moving the 9 psi boosted air compared to atmospheric.

The torque required to maintain this relatively constant pressure differential across the RPM range should be approximately constant. However, the power required to drive the supercharger will be proportional to the torque x RPM, so more power will be taken to drive the supercharger at the higher RPMs.

Originally Posted by 4G63T-SC

divO also the
hotest engine rpm is between 3k & 4.5k. This heat creates knocks & can be
lessened by richening the fuel trims during those revs. You will be bypassing
somewhere between those rpms. When you do bypass, your inlet temp will
drop because your SC will no longer be heating the air & less hp drain too.

That is really interesting information. Is that measured data for the intake air temperature between 3000 - 4500 RPMs? I know the volumetric efficiency of the engine peaks between 3000 - 4500 RPM, and would require more fuel in this region to not run lean. You can see this in my torque curves on this link:

1988 MR2 Supercharged Twincharger project stage 0 to stage 3 dyno plots - div0’s Photo Gallery

But I would have expected the maximum air intake temperatures to be in the highest RPM range, with more friction dissipating more heat, and the supercharger consuming more power in the higher RPM ranges. Unfortunately I don't have the intake temperature data with the dyno plots to confirm this peak temperature trend. However, in the final twincharge setup, I'll have this data realtime, as I'll be using a PLX digital gauge cluster that includes measuring the air intake temperature in the intake manifold, and also a second air temperature reading right before the supercharger intake. It will be interesting to see how the temperatures behave over the full RPM range.


-div0

[4G63T-SC]

Hi divO, The hotter period between 3k & 4.5k is combustion chamber temp.
This applies to a turbo'd engine during the spike boost higher temp.
I'm expecting the same higher temp between 3k & 4.5k with twin charging
because the turbo spike boost higher temp air is being forced into the SC
input side. The higher temp between 3k & 4.5k is best solved in the fuel
trims to avoid engine knocks. This way the ecu maintains the timing rather
than retarding it. A lot of dyno graph results show a hesitation in hp climb
& it is because of the ecu pulling timing back because of the above. I road
adjust my safc compensation up a hill in 2nd & 3rd to come up with the
best a/f graph that suits both gears. Evo Scan with my 02 graphed in it.
My a/f varies from 12:1 to 10.5:1 & my highest knock is a huge (4)
My timing maps are very agressive & the auto box loves it.
Cheers !

[Kevin mr2 1985]

so what im getting from this is its a ton easier just to turbo the car then to even try twincharging it? also how much power could i get out of a 4agze block with a turbo running 18psi?

[div0]

No, I don't think it has to be very complicated to twincharge. It just depends on your goals for the project. I have very high goals which were inspired by Gerald San Agustin's original HKS twincharger project from so long ago:

Ken Tokowitz's 88 Twincharger

But it sounds like feral4mr2 had excellent success with a simple twincharge project running 18psi on lil feral from just slapping on a turbo to directly feed the throttle body, bumping up the fuel delivery, and leaving most everything else stock. So if you want to go for an easier twincharged project, I recommend you talk directly with feral4mr2 and find out everything you can about his setup and then copy it, once you have your supercharged project fully up and running well.


-div0