[Ecotec] Factory L67 TwinCharged Plans

[warrjon]

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)

Kinda but not exactly. What the SC will do is take the inlet pressure and pressurise it via its pressure ratio.

The pressure ratio is set by
SC rotational speed (pulley size)
receiver volume (the engine)

The SC wont restrict the TC all it will do is compress what it sees at the inlet.

To give an extreme example lets take a 6psi SC pulley. This is 6psi at sea level if you take your car to 15000ft this same pulley will only give you 3.3psi boost. this is because at sea level atmospheric is 14.7 psi but at 15000 atmospheric is only 8.3psi. This same will apply if the inlet pressure rises either by being below sea level or by adding boost pressure to the SC inlet.

This is why the Spitfire used a 2 stage supercharger it basically had a 2 speed gearbox to increase its speed at altitude to maintain boost.

Hope this helps with the design.

Just remember flow through the SC will increase as SC inlet pressure increases or the air temperature drops. So IC prior to the SC.

 

[VN_Luke]

Kinda but not exactly. What the SC will do is take the inlet pressure and pressurise it via its pressure ratio.

The pressure ratio is set by
SC rotational speed (pulley size)
receiver volume (the engine)

The SC wont restrict the TC all it will do is compress what it sees at the inlet.

To give an extreme example lets take a 6psi SC pulley. This is 6psi at sea level if you take your car to 15000ft this same pulley will only give you 3.3psi boost. this is because at sea level atmospheric is 14.7 psi but at 15000 atmospheric is only 8.3psi. This same will apply if the inlet pressure rises either by being below sea level or by adding boost pressure to the SC inlet.

This is why the Spitfire used a 2 stage supercharger it basically had a 2 speed gearbox to increase its speed at altitude to maintain boost.

Hope this helps with the design.

Just remember flow through the SC will increase as SC inlet pressure increases or the air temperature drops. So IC prior to the SC.

I think we're saying the same thing ?

I agree the SC will not 'restrict' the provision of vast amounts of air to the motor. - everything that is output by the TC will go into the engine - pumped in via the blower.

I also agree with your atmospheric pressure example (and very cool spitfire example!!)

however, to see higher than atmospheric pressure on the inlet side of the blower means that the blower has to be some kind of 'restriction', since pressure is caused by restriction to flow, right?

either way, the engine still gets all the air that extra air goodness that the turbocharger provides!

taking your atmospheric example a bit further - do you envision the blower working any harder (i.e. more resistant to pumping all that extra air in) when working in denser air @ a higher pressure, as opposed to thinner air, @ a lower pressure?

 

[warrjon]

I think we're saying the same thing ?

I agree the SC will not 'restrict' the provision of vast amounts of air to the motor. - everything that is output by the TC will go into the engine - pumped in via the blower.

I also agree with your atmospheric pressure example (and very cool spitfire example!!)

Agreed:thumbsup:

Yeah the poms had SCing down pat in the 1940's Meth injection for take off to increase the octane of the fuel, pretty cool stuff for the time.

taking your atmospheric example a bit further - do you envision the blower working any harder (i.e. more resistant to pumping all that extra air in) when working in denser air @ a higher pressure, as opposed to thinner air, @ a lower pressure?

My pumping theory is very rusty but I would say the SC does not work any harder with pressurised air at the inlet. It will only work harder if it is required to pressurise the air more (more boost smaller pulley)

What will happen is the flow that the SC is capable of at Atmospheric will increase. Let say the SC has a max flow of 700CFM this is at 14.7 psi as the inlet pressure rises the SC will flow more CFM, reduced temp will also flow more air. So the SC effectively increases its flow capacity as turbo boost rises.

One last question

How does yours 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.

cheers

 

[VN_Luke]

One last question

How does yours 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.

cheers

I covered this a few posts back, but here it is again anyway;

I've not yet noticed an issue. I suspect the clutch on the pulley would slip before the belt breaks (it doesn't have a 'positive engagement' with dog teeth or anything like that, although that does give me an idea!)... - I haven't yet measured how much slip there potentially is. This will likely be more of an issue now that I have a much more aggressive overdrive ratio, but i'll see how it goes when everything is back together.

If the clutch faces wear over the next few years - it's no big deal, being a once-off car. If I was building 100,000 of these cars for mass market, I would definitely review the design more thoroughly. - Seeing as the engagement is ECU controlled, I could also take the Mercedes approach and limit engagement by RPM as well if I wanted to.

 

[warrjon]

I covered this a few posts back, but here it is again anyway;

OOPS sorry missed it.

I am definitely going to twincharge my VT. The director of finance says I have sell some of my other toys first. So hopefully will start on the build in the next month or so.

I have already decided on the initial parts.

Manifolds will be log style I think these will be more than adequate as I am not to worried about TC spool time. This can be shortened by turbine housing size and larger wastegate.

TC one of those cheap Chinese off Ebay will do. Something with enough flow for 500-600hp. Initially running 3psi boost.

The MAF will stay where it is between the TC and SC but maybe move it closer to the TB (need to research this). I want to do this without a tune running 10psi to start with.

From there we will develop it with FMIC for TC up the boost and Roller rockers.

 

[VN_Luke]

OOPS sorry missed it.

I am definitely going to twincharge my VT. The director of finance says I have sell some of my other toys first. So hopefully will start on the build in the next month or so.

I have already decided on the initial parts.

Manifolds will be log style I think these will be more than adequate as I am not to worried about TC spool time. This can be shortened by turbine housing size and larger wastegate.

TC one of those cheap Chinese off Ebay will do. Something with enough flow for 500-600hp. Initially running 3psi boost.

The MAF will stay where it is between the TC and SC but maybe move it closer to the TB (need to research this). I want to do this without a tune running 10psi to start with.

From there we will develop it with FMIC for TC up the boost and Roller rockers.

Be careful with your choice of turbo charger. The ebay ones tend to be hit and miss. The larger ones seem better, because they don't spin as fast so the balance tolerances and clearances (or lack there of) don't seem to affect them as much. - It would just be a shame to see a turbo go through the blower and engine for the sake of a few hundred bucks. - a brand new Garrett GT42 journal bearing turbo is around the $1000 mark. - a second hand one around half that!

As for the MAF - the maf setup is prone to error because (in the case of the nissan ones, anyway)

- It doesn't know which way the air is flowing (i.e. reversion when you snap the throttle is treated the same as air going into the motor - resulting in overfuelling, stalling etc)

- It can only measure so much air before it maxes out - I'm not sure what the limit is on these particular units, but be weary that if you cross it, you are stuck on the 'last known cell' in the fuel and ignition maps.


Also be weary of running this kind of setup without a tune to suit - the engine's requirements for fuel and ignition timing will be vastly different to what they are with just a supercharger... I think the tune is where you can take the most advantage of the setup and see how the car responds to increase in timing advance, particularly in the top end. (as well as making sure the MAF hasn't maxed out, and that you have ample fuel delivery)

... on that note, any particular reason for running the MAF between the TC and SC?

is it possible to do a 'mafless' tune on the delco ECU used in the S/C 6 commodore?

 

[warrjon]

Be careful with your choice of turbo charger.

As for the MAF - the maf setup is prone to error because (in the case of the nissan ones, anyway)

- It doesn't know which way the air is flowing (i.e. reversion when you snap the throttle is treated the same as air going into the motor - resulting in overfuelling, stalling etc)

- It can only measure so much air before it maxes out - I'm not sure what the limit is on these particular units, but be weary that if you cross it, you are stuck on the 'last known cell' in the fuel and ignition maps.


Also be weary of running this kind of setup without a tune to suit - the engine's requirements for fuel and ignition timing will be vastly different to what they are with just a supercharger... I think the tune is where you can take the most advantage of the setup and see how the car responds to increase in timing advance, particularly in the top end. (as well as making sure the MAF hasn't maxed out, and that you have ample fuel delivery)

... on that note, any particular reason for running the MAF between the TC and SC?

is it possible to do a 'mafless' tune on the delco ECU used in the S/C 6 commodore?

Thanks for the input, this is uncharted waters I have had a few turbo cars and SC all factory, but never modded one in this way. My VL turbo was built by someone else for 500hp.

The TC I was looking at was about $600 from the USA

I think 10psi is ok without a tune as most of the 10psi pulleys dont do a tune and I wanted to see how the twincharge setup compared to the 10psi pulley. It will be done on the dyno anyway so we can pickup any issues.

The MAF needs to be as close to the intake as possible and FIT have a MAF relocation kit for their SC FMIC which puts the MAF between the SC and intake manifold. ZZP in the USA said the standard MAF will take up to about 14psi before being maxed out, so we should be safe.

Maybe in the initial setup I can instal the MAF just before the TC??????

I believe there are Super6's around with a MAFless tune, although in the USA they are getting huge HP (5-600 is common and up to 2500hp) from these engines still using the MAF (albeit a larger one usually a Corvette)

 

[delcowizzid]

depends if you go blow through or suction on the maf they tend to run out at 8-10 psi blow through IE in the cooler pipes and really if going cooled it needs to be as close to the engine as possible like the last thing the air goes through before going into the engine.

 

[warrjon]

depends if you go blow through or suction on the maf they tend to run out at 8-10 psi blow through IE in the cooler pipes and really if going cooled it needs to be as close to the engine as possible like the last thing the air goes through before going into the engine.

Can you expand does the MAF max at 10psi blow through or suck??

I know the closer to the LIM the better as there is less delay. So would it be better to put the MAF prior to the TC.

Remember this is a base setup to compare with a 10psi pulley setup. Then we'll go nuts with FMIC more boost MORE POWER (KABOOM) LOL

 

[delcowizzid]

blow through.you could put it before the turbo if its not running a long length of pipe to get it too the engine and the maf needs to be far enough away from the turbo so it doesnt sence air being pushed out the turbo inlet .its going to make an extremely hot lot of air thats for sure :whistling intercooler is going to be a must in my opinion