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Hi guys,

You may remember me from my ridiculous posts about 7 years ago regarding putting 2x T88 turbos under the bonnet of a stock block mk4.. Well 7 years later I've gained a lot more experience, both hands on and theoretical, and I'm here to ask some real questions, and start this build.

The Plan:

I got ahold of a 1986 MK3 aerotop, 1g-ge and auto box (it was cheap and only 129,000 kms). I also have a s2 GS300 with a vvti 2jz-ge, and also an auto box. What I want to do is use the motor from my gs and build it, then drop it into the mk3. At the same time, depending on difficulty, drop the 1g into the gs, and being able to sell it as a driving car to recouperate funds (info on that will be great but for now, back to the Supra). This differs from regular posts and the ability to "use the search bar" when I get onto saying that I will be combining the difficulty of an na-t conversion on a vvti motor, WITH a supercharger in the mix as well, in a car that wasn't designed to house either.

So now you know I have a vvti na 2j. Id say in very good health. I have an Eaton M62 from a Mercedes c230/320 with low kms, it has an electronic clutch. I will say that I am looking to spend as least as possible, without doing this in any way that could cause detrimental problems later. I don't want to 'cheap out' as such, and I have no problem doing head studs, bearings, etc. That is all work I can do myself. I am trying to avoid the extra expense of buying a gte head, as a mate of mine is adamant that using my vvti na head is going to cause headache throughout the build. I need some pro advice, where is the problem he is talking about?

The Setup:

I have designed and drawn a twincharged setup that makes sense to myself, I will attach a photo in a separate post as I keep getting a security error here. I know that compressing air that is already compressed gains an efficiency, meaning, if a turbo pushes 10psi worth of boost through a supercharger that would compress null pressure air to 10psi, you will get 28psi (ish), not 20. This appears to be a useful gain at whichever point in the rev range it will occur, and I wish to use it.

The designs I have drawn show the direction of air as follows:

Intake,
Turbo,
FMIC,
Y pipe, (leads to some TB/WG/valve**)
BOV,
SC,
WCIC,
BOV,
TB,
Intake.
** The Y pipe that leads to the valve is designed to bypass the SC once it has surpassed it's useable rpm/boost range, and feeds the turbo boost directly to the intake. Also when this valve is closed the air being pulled through the SC is getting pulled through the turbo, helping it to spool (slightly, but it makes a difference).

The extra BOV between turbo and SC is there to serve it's standard purpose, although there is no throttle body directly after it, if the engine suddenly decreases rpm so will the SC, creating excess pressure. The BOV directly before the TB will work no differently.

The process of compressing air creates heat, when compressing that air again it temperature increases drastically. Pair that with the fact that the turbo air is hot naturally due to passing exhaust turbing, and you can run into potential danger inside the engine. This is where the water cooled IC comes into play.

I will leave the info at this as to not go too far before we get first things first. Please comment away and let me know any problems with my design of the setup. Things I need comment on, I don't know the following:

Recommended compression ratio,
Recommended boost values to reach desired psi,
Turbo sizes & designs to fit the setup,
Other necessary info I am missing out.

Peace
 

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If any of this was easy, much more well funded, technically astute, and motivated people would have done it already and you'd be able to copy their setups. As it is, the only serial twincharged setup that worked well on a street gasoline engine was the HKS turbo kit for the AW11 SC MR2. This is because the MR2 SC started off with a nicely engineered and elaborate setup that would clutch the SC on and off, and open a bypass valve when the SC wasn't going. The HKS piggyback would control that so the SC ran hard through the midrange, and then the bypass valve would open and bypass the SC while the SC disengaged. This allowed the turbo to bypass the restriction of the SC running and also avoided the very real and massively elevated intake air temps from compounding boost from the turbo through the SC.

There's no easy way to duplicate those kind of control features into an aftermarket SC setup, which is why that setup was so unique and not duplicated effectively in any other setup I've seen regardless of the expertise and the budgets that have tried in the past - they all resulted in show cars that look cool but never run well (or at all).


Cheaply as possible means follow the beaten path. Doing things differently than everyone else requires money and a lot of experience and knowledge to be successful. None of those things seem to be in your favor, based on your admitted focus on budget and the questions you're asking.

Far, far too many car builds start out like this with a really sweet kick ass different idea, and a bunch of parts get pulled off of a running car, and shit gets tinkered with, more parts get bought, and after a few years it gets sold for a third of what they have in it and they buy a boring normal car.

Personally, a 1G narrowbody aerotop MK3 isn't a great start as far as Supras go, so personally I'd clean that up nicely and sell it to try to get your money back out of it.

Enjoy the GS300 stock as a daily driver, and save money up for a JZA70 or JZZ30 with a manual trans. Having been down this road of wanting to build a car $300 or $500 at a time for years, I'd have gotten a lot further just saving the money until I had enough to buy a car that starts off a hell of a lot closer to what I want in the end.

Different means downtime, and downtime sucks. It's 1000x better to drive something even if it's a 'normal' setup. Hell, keep the 1G-GE car and find a cheap 1G-GTE engine set from another Supra. Or a JZA70 engine set. The GS300's 2JZ-GE is about the least ideal JZ and trans setup for swapping into a MK3 between the oil man, mounts, ECU, harness, etc.

Keep it simple.

Just speaking from 20 years of playing these games.
 
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Not sure what supercharger you are planning on using, but I'd not recommend a split twin charged setup like that. Just have one feed the other.
Large sized turbo feeding a roots type blower mounted on a custom intake manifold.

Edit: Thinking about it more, I doubt the second way I mentioned would save much room or be easy to implement.
 

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Yes, in series would be best, in parallel would be a valving nightmare.
Use one BOV after the turbo to protect it when the throttle is chopped, and another to bypass the supercharger when the turbo comes online to act as a wastegate. You can do this with a GReddy due to them having a vacuum/pressure connection on both sides of the diaphragm.

But there are way more little problems, that I don't remember, and the complexity of controlling engine management.
I had/have a GReddy twin pressure gauge, and an HKS twin temp gauge to watch pressures and charge temp independently. My intercooler was mounted inside the intake plenum.

Coupe of points,
First, to make 10 psi with a blower, it will take 35 HP. Not something you can do with a 6 or 8 rib serpentine belt, or run through a clutch, both of which are reasons why so many MR2s fail to make real HP, one or both are slipping.
An Eaton M90 supercharger is boarder line to make 15 psi on a 3 liter., as to get there you will exceed the rpm limits of the blower (14,000 rpm).
So to have any type of blower life, you will either need something larger.

You really are better off finding one of the Toyota twin charged 1G engines, they re out there if you look.
I have an image of the under hood emission sticker that came on them, and was going to duplicate it for when I put my twin charged 7M in the car.
 

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^lol, reminds me of a rotary with all those vacuum lines.
An Eaton M90 supercharger is boarder line to make 15 psi on a 3 liter
The M90 is probably the largest I would go on a 3 liter, no need to try to wrangle everything out of it either, it's just for the low RPM grunt until the turbo starts taking over. This is what I'm planning on doing with a 3.2L on another project.
Your engine setup looks great, didn't think the supercharger would fit under the hood that well.
 

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An M90 is the smallest you can go on a 3 liter.
90 cu in per rev blower turning 1:1 will supply almost enough air to do ZERO boost into a 183 cu in (3-liter) engine.
You will have to turn it roughly at a 1.3:1 over drive just to do 5 psi boost.
If that is all you want, you could get by with a 6-rib serpentine belt, like the OEM applications use.
(they are all low pressure)

Any smaller of a blower, you would exceed the blower's max rpm by the time you reached red line of the engine. The M60 is just too small. An M60 would have to be turned 2:1 to do just 5 psi.
You may be able to get away with this for a while, but the Eatons have a weak rear bearing design on the rotors. The only way around this is to machine the back out, and put on a billet rear body that takes sealed ball bearings.

Believe me, or not, but I have been working with compressed gas (air) and flow formulas for 35-ish years, used to be a dealer for AISIN superchargers for after market applications, and have been making blower dives, and helping customers for doing their own for at least 15 years.

The setup in the picture was done many years ago, and I just kept running into little annoying problems, and shelved the project. I wasn't going to accept a mediocre boost level, and when I started to see other Eaton blowers loose their rear bearings, said 'fuck-it'. It may come out of retirement down the line for a low boost supercharged daily..........Na, all out, all the time.
 

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How high are people spinning the 7M? My application is going to probably see 7500 RPM max. 5 psi from the M90 is fine, it's just there to get a little more area under the curve in the lower RPMs, help spool up the turbo, and force fresh air into the cylinders during overlap. It's not the primary power maker, and I don't want it to negate any of the gains by heating up IATs.
 

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An M90 is the smallest you can go on a 3 liter.
90 cu in per rev blower turning 1:1 will supply almost enough air to do ZERO boost into a 183 cu in (3-liter) engine.
You will have to turn it roughly at a 1.3:1 over drive just to do 5 psi boost.
If that is all you want, you could get by with a 6-rib serpentine belt, like the OEM applications use.
(they are all low pressure)

Any smaller of a blower, you would exceed the blower's max rpm by the time you reached red line of the engine. The M60 is just too small. An M60 would have to be turned 2:1 to do just 5 psi.
Thank you to everyone for your inputs, didn't think I would get this much help without getting ridiculed!

Sixpack (and others), I am not sure what sort of psi numbers I need to be running (I am aware it depends on size of turbo also). I am only trying to achieve 400hp on the 3 liter engine. I did not think that power goal would require high psi numbers? I am wanting a relatively smoothe/even power and throughout the rpm. I thought that with a low power goal, the vvti engine and small supercharger size would not be an issue?

Can you comment further on this?

1. Would my sc be able to provide somewhat efficient boost? Or is it really going to be pushed to it's limit no matter what power I am trying to achieve?

2. What type and size turbo would I be wanting to get 400hp, and make sure the power doesn't come on too late but also doesn't fall away at higher rpms?

3. I would assume a W58 would handle the power I am looking at? I may be doing the odd burnout here and there but I will not be raping the car on track days 24/7. Do you recommend the R154 to guarantee longevity?

4. Am I actually going to run into issues using the vvti na 2jz from my gs300 or is that only one you start pushing 500hp+?

5. Is there benefits tuning wise using the vvti?

Cheers again!
 

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The setup in the picture was done many years ago, and I just kept running into little annoying problems, and shelved the project. I wasn't going to accept a mediocre boost level, and when I started to see other Eaton blowers loose their rear bearings, said 'fuck-it'. It may come out of retirement down the line for a low boost supercharged daily..........Na, all out, all the time.
Can you expand on that part? What issues were you running into?

The motor I am using it on is a V6, and the M90 will be modified to be similar to the Guppe-M variant after the motor is baselined with the unmodified version first at a couple different boost levels to get IATs on the dyno and see how it reacts to varying degrees of meth. Same tests after the modification.

The engine already has headers and exhaust, so the SC PSI will be higher trying to push through the turbo. The plan is to select the largest exhaust housing available that would work best based on its map. End goal is to use the turbo against itself to raise SC PSI down low, and use the SC to force exhaust out of the cylinder to prevent detonation. Running both charging setups at a lower PSI to keep temps low and prevent heat soak.

Turbo -> FMIC -> TB -> SC -> Engine
Meth before and after the FMIC if needed.
 

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To my knowledge, there has never been a successful 'compound twincharged' gasoline engine setup built that did not bypass the SC at high RPM. Twincharged MR2's, the Twincharged 1G-GZE, The Lancia Delta S4, etc all had systems like this.
If there has been a straight compound boost twincharged setup on a gasoline engine that was successful, I'd love to learn from it and see more details on how that was done.

On a diesel it is simple, and compound boost is no issue as typically the SC is massive and the turbo is massive and the only concern is EGT's, and one simply needs to dump more fuel to lower the EGT's. I've worked on many twin charged Detroit diesels set up like that.
 
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Enjoy the GS300 stock as a daily driver, and save money up for a JZA70 or JZZ30 with a manual trans. Having been down this road of wanting to build a car $300 or $500 at a time for years, I'd have gotten a lot further just saving the money until I had enough to buy a car that starts off a hell of a lot closer to what I want in the end.
I'm a prime example of building a car $300 or $500 at a time, and while the car I have to show for it is pretty cool as far as Mk3's go, it's truly best described as a mostly functional nugget.

Wanna know what you wouldn't call a nugget? The F430 I could have bought with the same money I've spent over the years... food for thought.

2. What type and size turbo would I be wanting to get 400hp, and make sure the power doesn't come on too late but also doesn't fall away at higher rpms?

5. Is there benefits tuning wise using the vvti?

Cheers again!
I think you're overthinking this one bud. What is your elevation like where you're at? I would highly recommend a Garrett G25 turbo for your 400hp goal. I run the G25-660 0.92 on my 1jz, and made peak numbers of 371 whp and 350 wtq, but get this... the average numbers were 291 whp and 278 wtq if my memory serves me correctly. Spools up super fast, even at 6500' altitude, and holds power all the way to redline. You can get even quicker spool if you go with the G25-550 variant.

Best of all? You avoid the plumbing nightmare that would be a twin charged setup. Will it deliver the exact same level of performance? You might lose out on a couple hundred rpm down way low, but... honestly, for the simplicity of a modern single turbo, you won't miss it much.

Tuning vvti will net you more torque down low, and also help with spool if done right, I recommend it after seeing more than a handful of graphs over the years.
 
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How is it a plumbing nightmare? You're just putting a supercharger on the intake manifold.
It's like two separate systems due to the throttle body being between them. Reference the turbo wastegate to the intake manifold, done. No need to worry about the insane design Toyota did with the MR2, where both chargers are before the TB and you have an increased risk of grenading the SC if a valve in their vacuum/boost system fails.

What's the point of bypassing a roots or screw blower? It's still moving more volume than what the turbo alone would, it's just a much more dense volume due to the turbo compressing it. It's being used to get much more power under the curve and to help evacuate the cylinders during blowdown, forcing the hot exhaust out and past the exducer.
 

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How is it a plumbing nightmare? You're just putting a supercharger on the intake manifold.
It's like two separate systems due to the throttle body being between them. Reference the turbo wastegate to the intake manifold, done. No need to worry about the insane design Toyota did with the MR2, where both chargers are before the TB and you have an increased risk of grenading the SC if a valve in their vacuum/boost system fails.

What's the point of bypassing a roots or screw blower? It's still moving more volume than what the turbo alone would, it's just a much more dense volume due to the turbo compressing it. It's being used to get much more power under the curve and to help evacuate the cylinders during blowdown, forcing the hot exhaust out and past the exducer.
There's a very real threshold where a roots supercharger just becomes its own intake blockage to a much larger turbo setup. Ideally one should use a very larger supercharger and have it pullied for pretty low boost. The compounding boost effect dangerously elevates IAT's in a way that is not linear with boost pressure alone, and also unpredictably shifts the pressure ratio as seen by the turbo which can push it over the surge line. That all blows shit up a lot sooner than hypothetical Boost pressure > Backpressure benefits from the SC could be realized. EGT's would elevate from that, too.

Whether a shitload of methanol and modern EMS's could change that, who knows, but I honestly doubt it.
What I do know is this is simply not an experiment for someone on a shoestring budget like the OP, and frankly it's not much of one for rich people either unless they like blowing shit up a few times before figuring something out.
The simple truth is that teams with experienced engineers that built a lot of race engines and had a very seriously kick ass budget, and Toyota (which obviously has a kick ass R&D budget) both chose to bypass the SC once the turbo was up and going.
I have lost count of the number "do something different" projects started like the OP's that ended up a pile of garage parts and eventually ended up parting out, and that is always heartbreaking because simply following a proven path with the budget they had would have resulted in a running, powerful, fun car.

If you've built a few 'Proven' cars already and want to get 'different' at that point, well, that's a different story too - but that is clearly not the OP's situation.
Personally I think encouraging him on a path like this is bad advice, no matter how encouraging or well-meant it may be.
 
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A roots/screw SC will not become an intake blockage. By design this is false.

My questions had nothing to do with OP. I was asking the guy with years of experience why he thought twin charging was so complicated. Sure, the MR2 bs Toyota did was, but that wasn't what I was talking about.

Large block V8 guys have been twincharging for decades. It's not rocket science.
 

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I stopped caring about this thread as soon as I seen "V6".
You know everything, figure out piping on your own.
And what you just said about a positive displacement blower is absolutely false.
 

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It's a drop in engine that mates to the OEM six speed tranmission without modification, and fitting a larger engine in a mid engine platform isn't easy. The OEM V6 is a 90 degree split and takes up a lot of room, the replacement is a 60 degree split and frees up a lot of space for the turbo piping.
Piping is already figured out. No idea what you think I said was false about the supercharger.

The arrangement of pumps has prevented you from replying to a topic of which you have multiple years of experience with and already commented on? I figured the throttle body placement would have made you realise how easy this is, not sure why you brought up the MR2 in the first place. It's the worst twincharging design, sacrificing simplicity and reliability for throttle response.
 
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