[Ecotec] Factory L67 TwinCharged Plans

[VN_Luke]

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

I like the sound of your setup - nice and simple to start off with! The main concern I would have is with intake temperatuers providing the supercharger has to move denser air. It's possible that gains from twincharging won't be AS noticable as they should be because of corrections in timing vs intake temp, etc.

However you should be able to monitor intake temperature POST charger(s) - it would be very very interesting to see how this does actually effect temp.

My setup is a gt35 turbo, blowing into electro-magnetically clutched SC14 supercharger, on a 3 litre straight 6 motor.

There's an A2A intercooler located downstream of chargers, and the throttle body is on the intake plenum (downstream of the intercooler).

currently, the supercharger pulley magnet is controlled via an aftermarket ECU, allowing it to engage @ 0 manifold vacuum, and dis-engage once the manifold pressure has hit approx 20psi)

There's also a bypass valve around the charger, letting the turbo blow air around the charger, once the pressure it creates exceeds the pressure created by the supercharger (plus X amount of compound boost).

the wastegate for the turbo was using the boost feed from between the chargers (which ultimately ends up being the total boost level, once the supercharger has switched off).

this setup was designed solely with the intention of spooling the turbo much earlier, and adding a bunch of low-end torque to make the setup nice to drive on the street, and allow it to be much more tractable by trying to make the power curve a bit more linear.

here is the official design document:

and effect on power/torque so far:

I have many things to try in the next few months once the car is back together (currently in pieces), which will test a few of my theories.

I have knocked up a massively more overdriven pulley setup (2.6:1 as opposed to 1.8:1 like in the ^^ graphs), and will be testing the 'bypass supercharger' vs 'supercharger stays on' ideas.

Thanks for the mr2 link - I haven't read this before.

 

[azza77]

This diagram is an official diagram of a TwinCharger VW TSI. Interesting setup to a supercharger before turbo:

Cant see it producing as much power as a turbo before SC setup but..

And below is the new plans of a liquid cooled setup. Take note that for convenience i would opt for a mafless tune and also the BOV would most likley be fed back to the intake pipe. Ill also do up a A2A Intercooler setup tonight with basically the same plans. Now just deciding weather it would be less expensive (but effective) to go for A2A (make my own plate, not FIT's) or maces intermediate liquid cooler and modify it.

 

[warrjon]

My setup is a gt35 turbo, blowing into electro-magnetically clutched SC14 supercharger, on a 3 litre straight 6 motor..

How does it go engaging the clutch at high engine revs, like highway cruising and mashing the throttle. I also have a Mercedes AMG supercharged at it will not engage the SC clutch above 3000rpm as Merc says this could snap the belt.

I like the official design documentation Aussie ingenuity at it greatest.

 

[warrjon]

I like this design

if you IC before the SC with the SC running only 6psi you should not need the W2A IC. Need to investigate this possibility. I have done some preliminary calcs and running the SC at 6psi and TC at 6psi the intake temp should be down 10degC.

I used this calc to estimate the temps. Stealth 316 - Turbo Outlet Temperature

 

[azza77]

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

But if its linked to the same cooling system as the engine, would the fluid be as hot as 90 degrees? Would be awesome though!

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.

Seems to be a relatively easy setup with twincharging, just tuning is the huge dilemma.

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.

Pretty much the same sizes ive been looking at. Just wouldn't be plausible to use anything much smaller. It would have a excellent broad range of power with a large turbo. Just need some good steady figures on an actual l67 now! As everyone knows, the torque is already incredible in an l67

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)

Completely agree.

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

Potentially longer spool time yes, but loss in power? Definitely not. Especially with the supercharger winding it up from go. Supercharger up to 3000rpm and then kicks in the TC.

if you IC before the SC with the SC running only 6psi you should not need the W2A IC. Need to investigate this possibility. I have done some preliminary calcs and running the SC at 6psi and TC at 6psi the intake temp should be down 10degC.

I used this calc to estimate the temps. Stealth 316 - Turbo Outlet Temperature

Very interesting concept... Would make things a heck of alot easier. Would have to test temps after the TC and see how it goes. From there it would decide weather to put on a second cooler under the SC. Generally if the turbo is forcing the air through the SC, the SC will be hardly working so the only heat the SHOULD need cooling is from the TC as you said.

 

[VN_Luke]

Azza - I also approve of your latest design. I think the answer to water or air cooler after the supercharger lies in which one works better on a factory s/c 6 application.

But if its linked to the same cooling system as the engine, would the fluid be as hot as 90 degrees? Would be awesome though!

I meant that it'd be hooked up as part of it's *own* cooling system sorry. i.e. barrel cooler, and under S/c cooler hooked up to their own water supply and pump, etc - like in your latest drawing.

Potentially longer spool time yes, but loss in power? Definitely not. Especially with the supercharger winding it up from go. Supercharger up to 3000rpm and then kicks in the TC.

Generally if the turbo is forcing the air through the SC, the SC will be hardly working so the only heat the SHOULD need cooling is from the TC as you said.

Sorry, more boost through TC should say:
"- Advantage: Less strain on supercharger, up until the turbo comes on boost."

The turbo never helps the SC turn. - the SC's rotors are basically sealed against the housing, and it doesn't let any more air through than what it's suppsoed to when it turns.

The SC is spinning at a fixed rate with the motor. if the turbo is supplying more air than the SC is supplying to the motor with atmospheric pressure on the intake, it doesn't 'help' the sc turn and somehow magically drive the SC or engine. - rather, it creates a point of restriction for the T/C air, and there is a build up of pressure against the supercharger rotors. - the rotors continue to turn, and simply move the *pressurized* air from one side of the blower to the other - into the same volume. so you get that whole 'compound boost' effect. (so, the blower is not a restriction for *power*, but it is a restriction for the turbo->engine air path, obviously)

Since the now pressurized air that you are moving with the SC is denser than air at atmospheric pressure, the supercharger has to work MUCH harder. (hence taking more power to drive, and getting hotter, etc) - the resulting power should more than make up for this, though

- think about turning the supercharger by hand, and using it to pump water. Imagine what it'd feel like to turn it

- now imagine the same again, except with honey

Very interesting concept... Would make things a heck of alot easier. Would have to test temps after the TC and see how it goes. From there it would decide weather to put on a second cooler under the SC. Generally if the turbo is forcing the air through the SC, the SC will be hardly working so the only heat the SHOULD need cooling is from the TC as you said.

- i'd put the cooler after each, or after both as already stated... (refer to above honey example for reasoning)

Having said all that, though - if you take a different approach I'd be very keen to see results!

How does it go engaging the clutch at high engine revs, like highway cruising and mashing the throttle. I also have a Mercedes AMG supercharged at it will not engage the SC clutch above 3000rpm as Merc says this could snap the belt.

I've not yet noticed an issue. I suspect the clutch on the pulley would slip before the belt breaks, though. If it wears over the next few years - it's no big deal. If I was building 100,000 of these cars for mass market, I would definitely review the design more thoroughly. - but I could limit engagement RPM by ECU if it ever becomes an issue.

 

[azza77]

In regards to the vac lines on diagram 6, would it be fine to attach it before the SC after the throttle body?

 

[VN_Luke]

In regards to the vac lines on diagram 6, would it be fine to attach it before the SC after the throttle body?

diagram 6 being the one I drew?

the wastegate line should see the combined boost of both chargers - so downstream of charger.

the BOV should be hooked between the throttle and supercharger - my apologies.

 

[azza77]

diagram 6 being the one I drew?

the wastegate line should see the combined boost of both chargers - so downstream of charger.

the BOV should be hooked between the throttle and supercharger - my apologies.

Sorry about that, i meant my diagram 6 with the liquid cooled.

Yeah that was my main thought. I could possibly link in a vac line fitting for the wastegate through the liquid cooler plate.

Ill have to get an extension pipe to put between the throttle body and the metal intake from the charger so i dont have to drill/weld the original intake pipe for the vac line.

 

[VN_Luke]

Sorry about that, i meant my diagram 6 with the liquid cooled.

Yeah that was my main thought. I could possibly link in a vac line fitting for the wastegate through the liquid cooler plate.

Ill have to get an extension pipe to put between the throttle body and the metal intake from the charger so i dont have to drill/weld the original intake pipe for the vac line.

your throttle body should already have some vac lines to it? - for charcoal canister, etc?

your fuel pressure reg should be hooked up to a boost source AFTER the blower already - simply T piece the wastegate into this line.

where does the brake booster plumb into at the moment?