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[Ecotec] Factory L67 TwinCharged Plans

azza77

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As ive wanted to do something out of the original for the ecotec, im contempt to heading down the twincharged track. Ive only seen it done once on the L67 engine in America but im sure there is a few getting around somewhere in oz. Just so i don't have to explain it in text, i done up a few diagrams in the mighty old MS Paint. Let me know what you guys think and what would be the best suited. Ive used a A2A Intercooler to integrate the turbo. Im thinking Design 5 will probably be the best pick. Also i have forgotten to put on all diagrams is the MAF. It will be on the A2A IC intake after the turbo.

All (helpful) comments welcome.
 

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VN_Luke

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The simplest, and most effective way to do this would be to have the turbo upstream of the charger.

If you put the turbo downstream of the supercharger, you will find the supercharger will be restricting the amount of air the turbo can flow. (Hence your bypass valve in designs 4&5) - while this might work, i reckon a direct air intake for a turbo is best, since it will want to breathe HEAPS at big rpm and big boost. - a wastegate as a bypass to allow the turbo to breathe just seems really restrictive.

also, with a supercharger that is always on, you would want your throttle body 'upstream' of the supercharger. otherwise the thing is going to make some serious noise. Although, you'd want it to be as close to the intake valves as possible :p, to avoid issues with compressed air left over in the piping entering th emotor after you've backed off.

so, ultimately your intake path would go something like:

Filter -> AFM -> turbo-> intercooler -> original throttle body -> supercharger -> intercooler -> engine.

if two coolers are technically unfeasible, just skip the cooler between the turbo and supercharger.

Then you want just a single wastegate in the exhaust like on a normal turbo setup. The boost reference for the wastegate should be sourced from AFTER the supercharger (i.e. the combined total boost from the turbo and the supercharger).

Common misconception is that the supercharger is a 'restriction' on the flow path of the turbo, but in reality, this is rubbish.

The supercharger just moves X volume of air from one side of the charger to another. It doesn't care about the density of the air it moves.

It's a fine balance between charger pulley, rear turbo housing, and total boost level.

The theory to get the most out of this, is you run a turbo with a massive rear housing as to remove as much back-pressure as possible, and consequentally be able to run more timing (meaning more power) than you would with a regular turbo setup.

Usually a turbo with that big-a-rear housing would be laggy - but not when you have a supercharger providing extra exhaust gasses to spool that puppy up real quick :)

say you want to run 20psi - you set the supercharger to run (for example) 6psi by it's self, plumb the wastegate reference to AFTER the charger, and the turbo will just work as much (or little) as it needs to to make whatever amount of boost it needs to, so that once compounded by the charger, the total is 20psi!

hope that makes some kind of sense :) it's a real interesting topic.
 

VN_Luke

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Here's a pretty picture. - While the pipes look more complicated, basically you are only ADDING the intercooler and turbo piping.... and everything supercharger related (other than the cooler) stays exactly as it is.

note the airflow meter is in a non-boosted area... while it might work with it in the boost side piping, i dunno how comfortable i'd be winding up the boost in a plastic tube :p

ultimately you'd run a MAP based ecu/tune to avoid any issues with the crazy airflow and potential reversion you might get under particular circumstances.
 

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azza77

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Common misconception is that the supercharger is a 'restriction' on the flow path of the turbo, but in reality, this is rubbish.
That is the exact reason for the turbo after the supercharger! From my knowledge, I was under the impression that all superchargers would be restrictive to pressure with the exception of a roots type charger. So is there enough clearance through the rotors for the turbo to pass upto say 20PSI while the supercharger is running at a mild 6-7psi? Im thinking that due to the fact that the supercharger will be under almost no stress there would be little or no heat generated in the supercharger, so the only heat i would have to worry about is from the turbo? Im only asking the question is because would it be better to run a W2A IC plate after the SC or a A2A IC after the turbo but before the SC? (makes it a real IC then doesnt it!) The ultimate cooling system would be to have a liquid cooled turbo linked to a liquid cooled SC plate (like you said). Thinking ive got some new plans...

Just in regards to the bypass been to restrictive for the turbo, i was thinking a 60mm wastegate? Surely that would be plenty?

Then you want just a single wastegate in the exhaust like on a normal turbo setup. The boost reference for the wastegate should be sourced from AFTER the supercharger (i.e. the combined total boost from the turbo and the supercharger).
And that would just be the reading on the boost gauge from the SC wouldnt it?

Usually a turbo with that big-a-rear housing would be laggy - but not when you have a supercharger providing extra exhaust gasses to spool that puppy up real quick :)
My thoughts exactly! :yeah:

Great information mate. Very informative!
 

VN_Luke

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That is the exact reason for the turbo after the supercharger! From my knowledge, I was under the impression that all superchargers would be restrictive to pressure with the exception of a roots type charger. So is there enough clearance through the rotors for the turbo to pass upto say 20PSI while the supercharger is running at a mild 6-7psi? Im thinking that due to the fact that the supercharger will be under almost no stress there would be little or no heat generated in the supercharger, so the only heat i would have to worry about is from the turbo? Im only asking the question is because would it be better to run a W2A IC plate after the SC or a A2A IC after the turbo but before the SC? (makes it a real IC then doesnt it!) The ultimate cooling system would be to have a liquid cooled turbo linked to a liquid cooled SC plate (like you said). Thinking ive got some new plans...
yeah ultimate cooling would be something like a PWR barrell cooler after the turbo, and a intercooled plate under the blower - both linked up to the same water system, with a massive radiator/etc :)

as for the supercharger restriction:

it's easiest to think about the supercharger and the motor as simply air pumps.

your motor can 'pump' say 1.9 litres of air per revolution (half of 3.8 cause it's a 4 stroke, so two revs for a full cycle) .. anyway

your supercharger can 'pump' say 1.4 litres per revolution.

turn the blower at 2x the crank speed, then you are pumping 2.8 litres of air, into an area not big enough for it - and the engine is a 'restriction' for that air. Therefore you get positive pressure (boost) after the blower.

now, insert the turbo into this equation;

say the turbo is upstream of the blower; Once the turbo spools up enough to 'outflow' the supercharger's air requirements, it will generate positive pressure between the turbo and the supercharger. So it is kind of true that the supercharger is a 'restriction'... - BUT
what happens now, is the supercharger simply gets 1.4 litres of already compressed air, and pumps that air into the engine... - the result is 'comounded' boost. (i.e you are not adding the 6psi from the charger, and the boost from the turbo. Instead it kind of 'multiplies') - google about 'compound charging' - there'll be someone a bit better with words that has already explained the theory and maths behind it.

Unfortunately, the fact the charger is moving much DENSER air, means that it is working a lot harder. - thus it will probably be also working a bit hotter... - but that's why they invented intercoolers :)

The beautiful thing here is that your turbo is only working hard enough to say 'by itsself' provide say 10psi - but by the time this goes through the blower that has a pulley size that makes say 6psi by itsself - the 'comounded' boost is up to 20psi!!

which is perfect - because you have 20psi total boost, and a turbo that's not very restrictive in the exhaust! - the less restrictive the exhaust, the better - so BIG rear housings and BIG wastegates are a winner in that departament.

At the end of the day, it's a matter of measuring pre/post supercharger pressure, and exhaust backpressure - while monitoring power output, and fiddling with different size pulleys and turbo housings and boost levels etc.

Just in regards to the bypass been to restrictive for the turbo, i was thinking a 60mm wastegate? Surely that would be plenty?
how big is the turbo inlet? remember just because a gate valve is 60mm wide, it doesn't mean it'll flow as good as 60mm pipe :) - it has bends and angles etc etc. - either way, if the turbo is before the supercharger (how most systems are done) - you don't need to worry about these bypass valves.

And that would just be the reading on the boost gauge from the SC wouldnt it?
Your boost gauge would be hooked up to your intake manifold - reading the boost pressure the motor is running.

You can hook your wastegate up to the same source - this will ensure that your engine boost pressure never exceeds what the wastegate is set at (so long as your gate spring is set higher than the supercharger pressure, of course)
 

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VN Luke is right it is the pressure ratio that makes the boost so to get 20psi at the SC outlet with the SC running 6psi you would need the TC to be making about 10psi boost plus any IC losses. here is a really great article on an MR2 Project MR6 Toyota MR2 - Compound Forced Induction - Map Sensor - Turbo Magazine. I am already planning to go down this route with my VT I just need to sell some of my other toys first.

You can run quite a large TC because the SC will make boost from the goget and the additional exhaust flow will spool the TC quite quickly. I was thinking a 1.06 AR turbine with a .70 AR compressor, with about a 54 Trim.

I would definitely go TC into SC this is the setup that Lancia used on their Delta S4 rally car
 

HoldenManDan

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I'm getting a 4.2 litre L67 stroker built and it should be finished real soon. It's going into my VS with a Mal Wood T56 6 speed behind it. Plan is to enjoy the M90's low end torque for a while before converting to turbo. However, i wonder if i'll miss the added punch the M90 would have provided after going turbo! Unless of course i could have the best of both worlds without too much headache!

The M90 has a 10psi pulley on it atm, and the 5% overdriven balancer will bump it up to around 12-13psi. Perhaps add a GT35R with the 1.06 housing (the biggest) and run 20-ish psi in the intake will get me in the vicinity of 350rwkw, with bucketloads of torque! Ultimate goal is to make an effortless cruiser that i can run 10's in down the quarter. I'm not all that clued up in regards to turbos, so any guidance would be great!

I think it should be able to run such a time with the turbo alone, but running the M90 too would be awesome as long as it wasnt too hard to accomplish, that and the fact that it would be quite unique. Perhaps i'm being too greedy for low down torque, and should just let the extra torque provided by the stroker take care of things. I just imagine the intake setup, tuning and getting a nice linear power curve will be the main challenges. I hope VN_Luke will be able to add some more insight, as that's where my thoughts on twincharging really began :bow:.

Looking forward to hearing peoples' thoughts :thumbsup:
 

warrjon

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The M90 has a 10psi pulley on it atm, and the 5% overdriven balancer will bump it up to around 12-13psi. Perhaps add a GT35R with the 1.06 housing (the biggest) and run 20-ish psi in the intake will get me in the vicinity of 350rwkw, with bucketloads of torque! Ultimate goal is to make an effortless cruiser that i can run 10's in down the quarter. I'm not all that clued up in regards to turbos, so any guidance would be great!:
You want to run the minimum boost on the SC 6psi is more than enough. If you run more the SC will rob more power from the engine, also if you have the SC at 10psi to get 20psi at the SC outlet the TC will be pumping 6psi with a large TC and that flow rate the TC will be very inefficient. You can also IC between the TC and SC with the SC only running 6psi no need to IC

I would run a large TC and use the TC to provide the bulk of the boost. The large TC will spool very quickly due to the exhaust flow created by the SC.
 

VN_Luke

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You want to run the minimum boost on the SC 6psi is more than enough. If you run more the SC will rob more power from the engine, also if you have the SC at 10psi to get 20psi at the SC outlet the TC will be pumping 6psi with a large TC and that flow rate the TC will be very inefficient. You can also IC between the TC and SC with the SC only running 6psi no need to IC

I would run a large TC and use the TC to provide the bulk of the boost. The large TC will spool very quickly due to the exhaust flow created by the SC.
Yeah it's like a scale - SC boost vs turbo boost - but it's SO hard to say what's best to run without actually just trying combinations and monitoring boost pressures.

at one end of the scale you have:

Most boost through the SC:
Advantages:
- turbo doesn't need to spin as fast, and hence is not a restriction in the exhaust as much..
- run lots more timing and make more power due to above reason
- keeps exhaust temps a lot cooler
- *probably* spools the turbo a bit quicker
- if the engine takes more timing, it might not need to be pushed as far towards det. in order to make same/more power than most boost through TC. - this means a 'safer' state of tune

Disadvantages:
- more power draw on the motor
- more strain on the charger, belt, etc.
- potentially high intake air temps (pending cooler efficiency etc - would want to monitor these)


Most Boost through the TC
Advantages:
- supercharger doesn't rob the engine of power as much
- less strain on supercharger

Disadvantages
- more exhaust backpressure & temperature
- potentially longer spool time




So you need to find a point somewhere between all those two, by experimenting with pulley size, and monitoring all the pressures, while being able to monitor power output, and see how much more timing the engine will take. - Only then can you really get a clear picture of how it all works :)

On my setup, I've used a bypass valve which essentially allows compound boosting, until the turbo is ready to make more boost than the blower, in which case the boost 'adds' - until the blower switches off, and the turbo takes care of the rest of the work. I have been thinking about keeping the SC on for the whole run, but I don't know how much more power I can make on pump fuel, and whether my magnetic clutch pulley would hold at those pressures (unlikely) - I have gone with the bypass for now because the charger would be bloody loud if on all the time, and I doubt the pulley would hold at the boost pressures i'm aiming for - so really, I've essentially just used the charger to spool the turbo up (and not taken advantage of the whole backpressure thing :p). The fact that the charger is electronically switchable is what makes my setup able to pick and choose where and when i want the charger to engage (via ECU) without serious side effects on drivability, or complex valve setups.

Regardless, once the car is back together, i will try book a dyno for a whole day, and experiment with (all of the aforementioned params), until i have dyno proven power, torque and boost curves, and some more (maybe new?) theories.

And having said that - even without having found the optimal charger pulley size, etc - check out the difference in boost curve PRE and POST charger! - If i use compound boostage (the next plan) all the way through till full boost, I predict full boost can be achieved by like.... 2500-3000 rpm.... watch out rods!

 

warrjon

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Yeah it's like a scale - SC boost vs turbo boost - but it's SO hard to say what's best to run without actually just trying combinations and monitoring boost pressures.
Check out the link in my last post for the Twincharged MR2. These guys did a lot of dyno work, monitoring boost pressure in a number of different configurations, real interesting read.

I was originally leaning towards bypassing the SC at higher engine RPM but the testing they did showed the SC is NOT a restriction to flow. And this kinda makes sense. In theory flow (CFM) is related to pressure, as the pressure increases so will the flow.

My plan is to add the TC without IC straight into the SC and run 10psi at the manifold, at this point have it dynoed to get a comparison with a 10psi pulley.

From here develop the system to run 16psi and see what happens.

So what's your setup? sounds interesting.. cheers
 
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